'84 Tecate Crank Stuffing and Rebuild w/ pics

[81Rmachine]

So my Kawi chewed up a crank and when I went to rebuild it I thought I'd try to bring it up to date with some of the newer dirt bike engines I've had apart. Just about everything made since late 80's early 90's has some sort of nylon stuffers in the lightening holes. Honda has the whole counterweights wrapped in sheet metal all in an effort to decrease crankcase volume. I realize this has all been discussed but I hadnt heard of anyone actually trying it so Ill see what this does. In theory a decreased crankcase volume should create a greater vacuum as the piston travels up to pull more air through the reeds. It should also build more pressure as the piston travels down to shove more air through the transfers thus making the engine more powerful and giving it more throttle response.
So... Heres the pics!
Heres the crank fresh outta the engine, as you can see in the 4th pic the one thrust wash was completely shredded.
183832183836183837183838
I started to press it apart with a bearing seperator between the 2 halves but it was taking so much force and no go so in order to prevent distorting my crank webs I cut through the rod and pin, and pushed the pin out of each half.
183839
If you look at each web you can see how the inside of each is hollow and it goes in about 1.5 to 2 inches on each one so before i pressed it back together I took a dremel with a sanding wheel and cleaned out each hole real well and cleaned them out with brake clean and then some soap and water. I heated some JB weld and heated the crank halves and with the epoxy heated it poured like syrup and i filled each hole from the bottom up into the hollow area in the center of each web to take up a decent amount of volume. If you look close at the first pic where the rod pin is in one side you can see the epoxy in the center.
183840183841183842183844
One crank half was slightly bigger dia. then the other so i put that side down and when I was ready to press on the other half i used the press to hold each half square and then used a straight edge and swung the top half side to side until I had the same gap on either side with the straight edge across the counterweights. I got very lucky, I was expecting to do some truing with a brass hammer but when i threw it up on V-blocks I had .0005 runout on the drive side and .0003 on the flywheel side. The Kawi service manual spec is .0011 if you convert it to std so that was plenty good for me as i didnt want to make it worse.
So now that the crank was rebuilt and true the only other thing left to address was the ends of the rod pin and the lightening holes, so I ordered up some nylon round stock, the same thing in OE cranks, and turned it down to a have a .005 press fit in each bore. I pressed them in with red loctite and the gauge on the press read about 1 ton of force so they're not going anywhere. I made each one .050 shorter than each counterweight and put a 45 deg chamfer for adequate rod clearance. You can see how they stick out and while i could've made em shorter I wanted to take up as much volume as possible.
The next question I had before doing this was obviously balance, and I weighed absolutely everything for rotating and reciprocating mass and figured out a bobweight just as if I were balancing a V8 crank and there was a slight difference in weight that I wasnt worried at all about especially seeing as how these singles use a much higher balance factor than the common 50% on a V8. They have very heavy counterweights to cancel more reciprocating mass and reduce up and down vibrations for more front to back. Heres pics of turning and installing...
183859183860183847183848183849183850183853
Questions and comments welcome, sorry if this post got a bit long but atleast there's pics to keep you interested;), Ill post my results once its running here shortly!

[El Camexican]

Way cool project. I admire people who are willing to experiment with their engines.:beer

I do have a couple of questions. The first is about what you call “lightening holes”. I was under the impression that those holes are put there to facilitate aligning the crank halves when pressing the rod pin in at the factory more so than as a method of reducing weight or balancing the crank. If you know more about that please share it.

In photo 15 is that the nylon plugs protruding into the space between the two halves and if so how close does the rod come to them? Looks tight. You mention that most engines come with them and while I agree that they seem to be on a lot of engines, yet my 2002 KTM 300 does not have them. I did a little case stuffing on that engine and was considering filling those holes, but didn’t. Now you have me thinking…

So what else to do have planned for that engine?

[81Rmachine]

Thanks El Camexican, What I was referring to as lightening holes I had originally thought were aligning holes too, just as you mentioned. Upon closer inspection i could see they were just rough drilled and they weren't even drilled straight through. One hole in particular measured .785 on one side and .801 on the other. The surface finish in the bore was rough torn steel from a dull drill bit. It wasn't even drilled quite all the way through, there was a lip I had to grind out before I drove in the plugs. The main thing that led me away from believing these were alignment holes was the fact that you could see the edge of the con rod when you looked through them which would require grinding a flat spot in your pin for clearance which would make it loose in the bore and basically obsolete. I actually wanted to turn a pin to make assembly faster before I actually did look at it closely.

"In photo 15 is that the nylon plugs protruding into the space between the two halves and if so how close does the rod come to them? Looks tight."

With the nylon plug pressed flush with the outside of the counterweight, there is .050 clearance to the rod as this is how much shorter I made the plugs, and your right it does look pretty close but nothing to worry about.

"You mention that most engines come with them and while I agree that they seem to be on a lot of engines, yet my 2002 KTM 300 does not have them. I did a little case stuffing on that engine and was considering filling those holes, but didn’t. Now you have me thinking... "

I've never had a KTM apart myself so thats interesting to hear, It may just make a noticeable difference, Im curious to see how much of a difference ill see with the tecate. My main bike is an '03 CR250 which is due for a top end soon, and I've read that bike responds well to crankcase stuffing, but with that bike apparently the extra volume is in the crankcase itself which im guessing is what you had stuffed on your KTM? This Kawi really didn't have any space to fill in the case, everything was tight with room for air to get into the transfers and down for the intake port so really nothing that needed improving.
As far as the engine as a whole, I did some light cleanup porting before I sent it for plating, and I surfaced the head after I fixed the damage in the chamber to get the compression back up. Mainly I wanted to do the crank stuffing as a "Reliable" means to increase power. Increasing plain static compression on a 2-stroke drastically reduces reliability, and I wanted to be able to be on the throttle for a long while riding the ice with this one without detonation. If you haven't already I have a separate thread for this trike called '84 tecate build w/pics, I just wanted this to be a separate topic for discussion.

[El Camexican]

Those holes being rough is a surprize, thanks for the explanation. Here is a link my my attempt if you are interested. It seems to have more snap, but without a dyno or 1/4 slips to compair who knows, still its fun to experiment.
http://www.3wheelerworld.com/showthread.php/150791-2002-300exc-rebuild

[El Camexican]

Here are the only photos I can find of the crank. Nothing special, just doesn't have plugs in it.
183866183867

[81Rmachine]

Very Cool thread and very nice work, I didnt realize the KTMs were case reed motors same as my CR. Glad to hear your outcome was good. I kind of wish I would've CC'd the crankcase before and after just as you mentioned especially with all of the epoxy and nylon that went into it lol:lol:
I guess we'll just see, there's only one way to find out right? Im really anxious to fire it, just have a bit more grinding on the epoxy i used to patch the previous owners hole in the clutch cover and she should be coming together within a week or two, as soon as I have an ounce of time!

[81Rmachine]

The holes on your crankshaft look like they have a much better surface finish and are much further from the rod than mine were. KTM could have very well used those as alignment holes as well. Theres alot of room there to fill.. not trying to somehow inspire you to tear apart your gorgeous bike, but it makes a guy wonder if it would be for better or for worse. See this is why I wanted to start this thread I was hoping some people who had experience with this would come outta the woodwork so thank you for sharing!

[El Camexican]

There is a guy that works at KTM World (I think Paul Wright is his name) He does stroker engines and case stuffing, etc. If you can get him on the phone for a few minutes you may get some good info. There isn't a lot of usefull information on the Internet about this as I'm sure your are realizing.

Regarding case volume here’s something to consider: My 2002 300 engine shares cases with the 250 and the 380. The only difference between the 3 engines is that the 250 has a smaller bore that the 300 and the 380 has a larger bore and a 5mm longer stroke. The cases are all identical, so when you consider that a 380 and 250 share case volume it makes you wonder how important it is to the power-band.

Please keep posting anything you learn.

PS. Nice shop!

[just ben]

Hmm I just ran across this thread by accident. I can tell you that I have an 84-85 tecate engine that has aluminum slugs in those holes. I can't tell you any difference in performance since I have not run the engine. However it was a national race engine built by JP racing and I have to think they did their homework before putting these engines in the racing circuit.

[81Rmachine]

Ben, thats pretty interesting, I wasn't aware anyone did any stuffing before dirt bikes had it done factory except for old vintage sleds I guess.
Well I just got it running here this past weekend, and I can say it did make a noticeable difference. It didn't seem to make any difference in the lower end, I can lug it and it pulls just as hard as it did before, no worse, no better, but it made a pretty positive difference on the upper end. This engine didn't exactly have a light switch powerband from the factory, It pretty much surged into the powerband like a good powervalve engine does. Now it gets up to the powerband and really hits, I like it alot, It makes it so much more exciting to ride. Its not that its peaky or all top end like alot of engines are with abrupt powerbands, it just gained enough on top that when it does hit the powerband it pulls that much harder and makes it feel more like hitting a switch.
In conclusion, I would definitely recommend it! If you have the time and the ambition go ahead and try it for yourself, I had very good results from it and had fun building the engine, It was a learning experience! I'll have to get some vids of it soon and post them if anyone is interested, Nick.

[Keith Salyer]

On our Cammex motors Calvin used cork plugs with epoxy for strength.

[barnett468]

I wasn't aware anyone did any stuffing before dirt bikes had it done factory except for old vintage sleds I guess.2 stroke crank stuffing has been around since at least 1976.

"Turbo venting" on crankshafts has also been around that long also. A guy brought a stock crank into the shop I worked at which he had cut angled wedges out of. He was offering the process as a service for high perf builds. We passed.

[barnett468]

Hello 81Rmachine;


There's some photos of works cranks and other parts in the links below. How about a set of magnesium engine cases that weight 5 lbs, or a 1 piece clutch basket that probably weighs 1/3 of a of a production one and a shifter machined made from billet aluminum. Anyone want a hand made titanium ex pipe, Suzuki had one.

http://www.mxworksbike.com/Honda%20works%20parts.htm

http://vintageworksbikes.com/zMiscworksparts.html

[just ben]

My crank has had other work done besides being stuffed. It is also turbo veined liked Barnett mentions and the rod was lightened and polished. I have heard mixed thoughts on the veining. I believe the idea is to move more air/fuel, some say that it starves the bearing of oil.

[barnett468]

All I know about "turbo veining" for sure, is that it increases the volume of the crankcase, and that it was never used in any production or works Kawi.

My guess is, Kawai as well as the other mfg's, knew about this technology a long time ago, and would have done some testing on it if it looked good enough on paper. They may have done this, however, we never would have heard of it if it failed their tests in Japan.

Even if it did cause premature bearing failure, they certainly would have used it on the works bikes if the overall benefits in performance outweighed any potential loss in performance caused by the increased crankcase volume the process creates.

They rebuilt the engines after every weekend anyway, so as long as it lasted that long they could care less.

Kawi, as well as most of the other mfg's have a ton of money, the time and the equipment to make "turbo veined" cranks and test them.

When I was testing the 86 prototype T3 in Japan, I Told them it needed 41mm fork tubes. It had the same tubes as the 85, but with longer travel, nice.

They didn't have such a thing, yet somehow, they made the complete fork assemblies AND tripple trees in around 3 days.

Since they could perform that amazing feat, they easily could have popped out as many turbo veined cranks as fast as they wanted if needed.

Anyway, since Just Ben has one, and his bike still runs, it obviously doesn't kill the bearing off instantly.


The name certainly sounds cool at the very least anyway.

[MIK6]

My 87 has a sprock 300 topend and a turbo cut crank.. its an animal on the top end!
w the weight reduction it is harder to ride on the lowend, got to keep the Rs up. But I have never been on a trike that likes to be held wide open like it does! When im running thru the gears I dont lift!

[just ben]

My 87 has a sprock 300 topend and a turbo cut crank.. its an animal on the top end!
w the weight reduction it is harder to ride on the lowend, got to keep the Rs up. That's the silly little kx flywheel that you run LOL. I got rid of my kx ignitions because of that. I still have a motoplat that uses an even smaller flywheel but It will be used on the engine with the modded crank. since it only has a 60.5mm stroke it should work better than it did on a stock engine. I hope anyway

[xrider]

RPM out of Toledo used to stuff cranks back in the 80's. They were known for their "Turbo Cranks". There is a dirtwheels project 82 250r where they had RPM balance and stuff the crank and perform the turbo modifications.


Ben, thats pretty interesting, I wasn't aware anyone did any stuffing before dirt bikes had it done factory except for old vintage sleds I guess.
Well I just got it running here this past weekend, and I can say it did make a noticeable difference. It didn't seem to make any difference in the lower end, I can lug it and it pulls just as hard as it did before, no worse, no better, but it made a pretty positive difference on the upper end. This engine didn't exactly have a light switch powerband from the factory, It pretty much surged into the powerband like a good powervalve engine does. Now it gets up to the powerband and really hits, I like it alot, It makes it so much more exciting to ride. Its not that its peaky or all top end like alot of engines are with abrupt powerbands, it just gained enough on top that when it does hit the powerband it pulls that much harder and makes it feel more like hitting a switch.
In conclusion, I would definitely recommend it! If you have the time and the ambition go ahead and try it for yourself, I had very good results from it and had fun building the engine, It was a learning experience! I'll have to get some vids of it soon and post them if anyone is interested, Nick.

[81Rmachine]

barnett468, Thanks for posting those links. I've heard of "turbo veining" just haven't heard it called that until now and honestly when I heard someone mention it I had to laugh at the idea, I guess the only thing I could see it doing is creating windage in the crancase. Those works bike pics had me wondering why they spent so much time polishing connecting rods. On a 4 stroke V8, just for example, rod failures are fairly common compared to motorcycles and the two main reasons for polishing or the term I'm more familiar with is "beaming" rods, is that it removes any stress risers to eliminate the formation of cracks, and it reduces crankcase windage by reducing wind resistance and by shedding oil from the rod. However any rod failure I've seen at work happens at the big end of a rod with through bolts instead of cap screws and on an application requiring a less than adequate rod by rules and even in that application we dont polish any rods as it wouldn't keep the rod from breaking at the big end anyway. Motorcycle engines are just a bit different, especially 2-strokes. While 4 strokes benefit from running a vacuum pump or a dry sump oil system that pulls vacuum on the crankcase a 2-stroke is pressurizing air for the induction phase. I can't say I've ever seen a 1-piece motorcycle rod ever break either. Seems like alot of work for nothing. Its kind of funny how much theory has changed in engine building. I have a friend that builds factory Arctic Cat Snocross engines and im sure if veining worked they would be doing it.

[barnett468]

Hello 81Rmachine;


I figured you were a car guy after reading your first post. I’ve done a lot of old Ford 289's, 390's, Boss's, CJ’s and Chev’s, like Z28’s etc., and I too have seen a lot of those 2 piece rods you mentioned, lol. Most guys I know simply shot peen them instead of polish them. I always stuff in ARP cap screws.

You might have heard of the latest fad/technology called “chryo freezing” for engine parts. Below is a link in case you haven’t. I’ve never had it done simply because I buy rods I know will work for my app, like Chinese Eagles, Crowers or of course Carillo’s etc.. I also know very little about the process.

http://www.300below.com/motorsports/


TURBO VEINING – Your “windage” comment brought up something I forgot to mention. The turbulence created by the veining will atomize the fuel better, which as you probably know, makes it burn better which creates a more powerful explosion in the combustion process which in turns creates more power.

Since as Just Ben mentioned, there is some talk about this process possibly “starving” the rod bearing of oil, if I had a turbo veined bike, I would simply run a rich oil/fuel mix. This will at least help compensate for any potential loss of oil to the bearing created by the veining process.

If one runs at high rpm’s frequently, it would be beneficial to run a rich mix anyway due to the increased rate of oil migration created by the higher rpm’s.


As far as motorcycle rods go you must be young, lol. There were plenty of snapped 2 stroke rods back in the 70’s, especially on the 125’s, and especially on the pro bikes like DG and FMF etc. I have also read several threads about ATC250r’s breaking rods. Not being there, there is no way to tell why. The rod breaking issue seemed to be much less prevalent after the 70’s.

As far as 4 stroke bikes go, yes I too have seen fewer rod failures with them, however [short irrelevant story], while I was at Kawi, Rob Muzzy was testing a Super Bike [1000 cc road race engine] on the dyno. The dyno was 75 feet from me. He spun it up to max rpm at which point it literally shook the concrete floor a little, then after around 20 seconds, it grenaded, which sounded like a bomb going off and I could hear Muzzy mutter some colorful words as he turned and slowly walked away from the carnage.

I don’t remember if Kawi polished the rods on the works bikes. All I can say is that race wins and season championships were their only goal despite the costs back then, so if they simply thought it was added insurance against breakage or that it might gain a rider half a second at the end of a 30 minute race, they would do it irregardless of the cost.

From Steve Wise interview.

“The Daytona 200 - I rode the 1982 200 on a 1981, in-line, four-stroke, while my Honda teammates Freddie Spencer and Mike Baldwin got the new V-4 FWS. That bike [the FWS] was a huge deal because Honda quietly told all of us that it was a true $1 million dollar motorcycle.”

http://www.motorsportretro.com/2010/12/legends-steve-wise/

[81Rmachine]

barnett468,
I have heard of cyrofreezing as you mentioned, there seems to be a few companies every year at PRI and IMIS advertising cryogenic freezing for everything from valve guides to, as you mentioned, connecting rods. Mondellos promotes cyro freezing as well as stress relief shaking for any part most specifically blocks because of how much the bores can shift from relieving residual stress. This process is basically a shortcut and perhaps a more effective means of "seasoning" a block from repeated heating cycles as im sure your familiar with. While I was working for Brzezinski's just last year we were contemplating using these processes to eliminate premature guide wear in iron guides near the top from the old non roller stamped rockers required by many circle track rules, but ended up using liners with very good results. I see many different brands of rods with the company im with now. Eagle, Scat, Carrilo, Crower, Oliver, and Callies are a few of them we use in engines all with pretty good success and no freezing.

The turbo cut cranks make much more sense in creating turbulence to promote mixture motion as you mentioned over the theory I was told. Keep in mind I've never seen a crank like this in person, but someone had told me it was to act like a fan and throw air and fuel into the transfers which I didn't buy because the only way that would work is if the air and fuel entered at the center of the crank, which who knows maybe that theory might work on a rotary valve then??

As far as your assumption of me being young... You hit the nail on the head LOL I haven't heard or seen many motorcycle rods break in my lifetime, but then I've only been around since '91! I can see the additional expense for a little added insurance as you mentioned, it certainly can't hurt!

[MIK6]

Here is the only pict of my crank I could find.. I forgot to take before picts.. lol
I added green arrows to point out the cutting..

[MIK6]

I run 40/1 klots in 110 octane fuel.. the motor has 40 or so hours on it mostly wide open.. lol
idk about changing fuel mixture.. she runs great!!
I let anyone that looks at it at TF take it for a rip! Makes me smile to hear what people think of the old girl!

[86T3]

Ben, do you have a pic of your crank? Idk why but i think i remember the veins being much more subtle on ben's crank. I love this thread btw, maybe ill do a little stuffin sin im planning on tearing apart my show motor

[barnett468]

Here is the only pict of my crank I could find.. I forgot to take before picts.. lol
I added green arrows to point out the cutting..Wow, cool photo. Looks like they only did the inside 1/3rd of the crank. The crank I saw in 76 was done the full width of the flywheel surface. This was before CNC machines or computer operated mills were on virtually every street corner. On the crank I saw, the guy likely cut the crank on a mill with a rotary table. Had to take a long time, lol.

Also, as Just Ben implied, changing the weight of the crank and/or ign flywheel will affect the engines characterics.

I have done quite a bit of this type of testing. In 76, I had a Paul Nyland, pro ported Bultaco 250. The Tacos had two or three different interchangeable bolt on flywheel weights. It came with the heaviest one and I installed the lightest one. Well, it basically gave it the feel of a 125 on steroids with around 50 hp, lol. It would stall easy while braking in gear, and just spun the tire wildly under hard acceleration unless the track was super sticky, in which case, you better hold on to your hats cause you're goin fer a ride.

[barnett468]

barnett468,

I have heard of cyrofreezing as you mentioned, there seems to be a few companies every year at PRI and IMIS advertising cryogenic freezing for everything from valve guides to, as you mentioned, connecting rods.I wonder how its working for ole' Walt Disney? This might be before your time though, lol.





The turbo cut cranks make much more sense in creating turbulence to promote mixture motion as you mentioned over the theory I was told. Keep in mind I've never seen a crank like this in person, but someone had told me it was to act like a fan and throw air and fuel into the transfers which I didn't buy because the only way that would work is if the air and fuel entered at the center of the crank, which who knows maybe that theory might work on a rotary valve then??Well, dynos don't lie providing one is using the same dyno under the same weather conditions. Some dynos are in climate controlled rooms. It's very simple to do a back to back test with and without a turbo veined crank.

One could also easily compensate for any difference in perf caused by the different weight of both cranks by simply calculating how much weight they needed and add it to the ignition flywheel in the form of a press on outer ring to the turboed crank eng.

I would love to see this because I love testing and hard "factual" numbers.

I also know from my previous testing, that the biggest dyno numbers are not always going to give the best overall perf. This is easy to see of one watches pro funny cars etc., drag racing on tv. They actually have too much hp, so they have to reduce it some so the car hooks up better. Around 1000 hp per cylinder, insane.

While I was doing the development testing on the 86' T3 prototype at Kawi, one of the tests we did was an ex pipe test. We tested around 4 different ones and we said "not good enough", so the engine engineers went back to the drawing board, made some new pipes, dynoed them and gave them to us. Well, the pipe that had the most mid range on the dyno lost, mainly because it had so much that all it did was spin the tires when it came on the pipe, but it was also a bit short on peak rpm as well.

When we told the engineers that we wanted the pipe with "less" power, they didn't understand why until we explained it. I actually felt bad for them because they worked very hard on these designs and testing and I'm sure they were a bit disappointed to some degree. The consolation for them was that the other new pipe they designed was the one that was used on the production bike.

If one simply installs a bigger Mikuni, and throws away the stock "silencer"/muffler and installs ANY non spark arrester type, the 86 T3 will be WAY faster than it already is for around $100.00 in used parts.





As far as your assumption of me being young... You hit the nail on the head LOL I haven't heard or seen many motorcycle rods break in my lifetime, but then I've only been around since '91! I can see the additional expense for a little added insurance as you mentioned, it certainly can't hurt!Well, it sounds to me, that for any age, you are an extremely sharp guy that thinks about a lot of different angles/possibilities and knows a lot of stuff. Considering you think this way and know so much, at what an old guy would consider a "young" age, I think you should do very well.

:beer

[just ben]

Here is the only pict of my crank I could find.. I forgot to take before picts.. lol
I added green arrows to point out the cutting..my crank looks nothing like that. I will try to dig up a pic but I have been having issues posting pics lately.

[barnett468]

my crank looks nothing like that. I will try to dig up a pic but I have been having issues posting pics lately.Hello Just Ben;

I am FAR from a computer expert, however, I think if you turn the photo into a URL and then put [IMG] in front and [/QUOTE] in the back, it should work. Include the “brackets”. I think this MIGHT bypass the systems auto feature, however, I could be very WRONG, lol.

[just ben]

It's hard to see but both crank halves are veined but they are alot smaller on the one half.Also a pic of the aluminum slugs in the crank.I tried to show how the rod is modified also.185020185021185022185023

[MIK6]

Wow ben.. that is alot different!
I got a smoking deal on mine, thats why im running it.. lol
I got it w a new rod for less than I could have had a new rod pressed into my crank.

[barnett468]

I have not seen it done that way before. I can't see it well but it looks like there are some lines going in both directions near the crankcase. It almost looks like knurling in stead of directinal wedges. Wonder why they only put it on one crank half.

[atc007]

Wow Mik.. I have seen a lot of "Turbo Whirling" we called it around here lol. MUCH Like Bens. YOURS,,,,,WOW, That thing would damn near diesel itself for 6 revolutions on it's own once up to RPM. That thing is just,wow. Are you sure they don't have that crank interlocked with another set of gears down in there!! lol. I honestly don't see any advantage to that deal lol. Pretty cool though. Great thread 81 R !

[MIK6]

I dont know how it works either.. lol
im not a motor builder, never claimed to be. I wish someone could tell me more about it..
All I can say is that it runs good! Alot if people have ridden that trike shes definitely a runner! Most guys that hace ridden it cant believe the Rs it turns, another member at TF said hed never ridden a trike that likes to be held wide open and shifted w/o lifting like it does.
I picked that crank up w a new rod pressed in for $50 and a rod kit. So I figured id have more than that into rebuilding my crank. And I didnt have shop turnaround time. If it works I am all set, if not id rebuildtmy stock crank and swap it on next rebuild.
so far the only downfall has been low end lugging thru trails.. but w all the miles I have on that old T3 im use to that! Lmao

[barnett468]

Wow Mik.. I have seen a lot of "Turbo Whirling" we called it around here lol. MUCH Like Bens. YOURS,,,,,WOW, That thing would damn near diesel itself for 6 revolutions on it's own once up to RPM.The first one I saw in 76 was about half as deep as Mk's dual saw blade model but it was all away across on both halves.

Since the transfer ports are on the outer parts of the crank i would think that if anything at least do it there. Perhaps mk's turbo fins are actually connecting rod coiling fins?

Inner piston cooling fins?

An additional gear for the trans?

Certainly looks nasty and pretty cool to me at the very least.

[just ben]

I have not seen it done that way before. I can't see it well but it looks like there are some lines going in both directions near the crankcase. It almost looks like knurling in stead of directinal wedges. Wonder why they only put it on one crank half.all the lines go the same way, looks like knurling but without the crossed lines. It is done on both halves but the lines aren't as deep on one half.I have seen several done this way and was the only way I have seen it done until I seen mikes pic.

[barnett468]

Here's 2 photos in the link below of a totally different approach to turbo veining. It is done on mini 2 stroke engines designed for rc toys etc.

http://www.beatyourtruck.com/prodreview-SUREFIRE32.html

http://www.scooterinvasion.net/forum/viewtopic.php?t=18&sid=110b1c04f6ca7e483a6f89cf9300f007

[Xowner]

185025

This is another version of the turbo crank

[JasonB]

really interesting thread, this is all new info for me. I went through the crank stuffing idea with the 250/500 honda motors. I have seen people swear up and down that putting a big bore top end on a 250r bottom end merritts pulling the tin cans off the crank to increase crank case volume for better operation. I have seen people swear that removing those will increase turbulence in the cases and decrease power. Interesting concept overall, nice work with the install of your nylon filler thanks for the detailed write up on your work. pretty neat

[El Camexican]

It's hard to see but both crank halves are veined but they are alot smaller on the one half.Also a pic of the aluminum slugs in the crank.I tried to show how the rod is modified also.185020185021185022185023
That crank looks like it is meant to give the throws more surface area to pick up pooled oil and throw it back up to where it could drip into the crank bearing holes. Never heard of that before, but what else could it be?

[just ben]

That crank looks like it is meant to give the throws more surface area to pick up pooled oil and throw it back up to where it could drip into the crank bearing holes. Never heard of that before, but what else could it be?I was thinking mik6's looked more like oil slingers. Although I am 98% sure who the engine builder was there is NO way to contact him to pick his brain for the reasons they modded these engines the way they did.

[El Camexican]

I was thinking mik6's looked more like oil slingers. Although I am 98% sure who the engine builder was there is NO way to contact him to pick his brain for the reasons they modded these engines the way they did.

I’ve seen photos of one like Mik6’s before (I don’t remember where) and seem to recall reading that the idea was that you got a lighter crank that created more turbulence in the cases. I guess if you were curious enough you could send a photo to these guys http://www.faliconcranks.com/ and ask them if they might know what the theory behind yours is. As far as I know Falicon is the be all end all of motorcycle cranks (at least for 4cyl engines) and they’ve got some guys working there that have been around a long time.

I typed “2-stroke turbo crankshaft” into Google images and a lot of wild looking cranks come up, but nothing like yours, thats a keeper!

[just ben]

I know Raffa's 490 was/is running a crank that looks just like mine. I'm sure there is a build thread on here for that bike maybe there is a pic showing the crank. I have also seen this in a air cooled R engine.

[barnett468]

Just found the following online, thought it might be interesting for some.


“I've been going back to some old Dirtwheels mags and came across an interesting article on a Factory Honda 250r for Stadium cross... Dean Sundahls Atc. Anyway, here's what was interesting:


Excerpt from article in Dirt Wheels, Oct 1982."

"...after the crankcases are matched, RPM (Racing Products for Motocross in Toledo Ohio) cuts a small boost port into the front transfers. This allows the fuel/air charge to start its trip to the top a little sooner..."

The crankshaft receives RPM's unique "turbo" modification. The crank is full-circled, stuffed, and balanced. With this balancing, the 250r counter balancer can be removed, allowing the engine to rev move freely because it has less weight to turn."

Special "veining" is then cut into the outer circumference of the flywheels. This machining, when used with the small boost port (from above) cut into the cases, actually forces the charge into the transfer ports and up to the combustion chamber, giving the engine a sort of "two-stroke turbo" effect, as well as fully atomizing the fuel/air mix for better burn. This is the most expensive mod done by RPM, as well as, being an exclusive in the engine-building field."



CYLINDER HEAD “TURBO” CUTTING

“Trinity tried to think outside the box for a while with cranks and their heads as well.....They still to this day turbo cut the head. I have a head on my bench that is an early model done by JD i believe when they were doing the R&D.

In THEORY it was to create a funnel reaction that would focus the fuel to the spark plug.....Notice how the cuts turn and angle to the plug. Trinity still does this I believe but they have perfected it by using the CNC or another type of non-human method.”

[TecateDan]

This is good as I'm just about to build a new motor for my tecate.

[81Rmachine]

x

Well, it sounds to me, that for any age, you are an extremely sharp guy that thinks about a lot of different angles/possibilities and knows a lot of stuff. Considering you think this way and know so much, at what an old guy would consider a "young" age, I think you should do very well.

:beer

Thank you for the kind words, I sure appreciate it! I try to do as much R&D and flow testing as the boss will possibly let me get away with, but in reality you have to get engines out the door to make money. I have a passion for 2-strokes even more so and being able to talk with gurus such as the guys in this thread is very interesting to me!

atc007, Thanks, Im sure glad this thread got the attention I was hoping for. Anytime you post some of your own work on a forum you always suspect some criticism which is expected and constructive criticism, such as it all has been so far, can be very helpful. Of course some other forums are full of guys that just love to tear your work apart and I'm glad to be able to talk with you guys who are open minded and were around when they were actually making 3-wheelers yet and not too young like me LOL:lol:! This thread has been full of interesting pics and I've learned alot already so thanks to everyone who has contributed and KEEP POSTING!!