Sabertooth 500R completed...but

[fyi]

I don't know if anyone remembers or not, but for a while now I have been working on the completion of my 1986 250R conversion to the Sabertooth 500cc engine package in my spare time from running the shop around here. Well it's done...sort of and here's what I've learned...

The Sabertooth 500cc engine conversion package is a real MONSTER and the build quality and workmanship from those folks is superb...couldn't ask for better. The power this thing makes is just silly and to be quite honest...far too much torque for this machine in the trim it's in, even with a +1" longer swingarm. I just can't keep the nose down, so riding it at full throttle is a huge lesson learned in throttle modulation to the point where I just can't pin the gas anymore where the tires will hook like I used to with the stock engine, otherwise~ I'm on my back.. I guess a high HP engine like this might be better suited for a full-tilt drag machine, rather than on a standard (and even mildy modified) ATC.

Now for the bad part.... I can't keep the transmission alive in this thing!!! Burning clutches, broken trans. gear teeth...everything and it's getting old. I'm a 230 lb. 5'-10" guy, so maybe that has something to do with it and a lighter guy might have better luck...but not me. The damn thing's transmission is broken again and this time, I think it hurt the case internally when it broke. I'm done with it for a while and I think I'm going to pull that engine and shelf it until I get the motivation to take the thing apart all-over again...

I can't begin to tell you the insane amount of money I've got in this engine with all its trick parts and that's why it makes me ill to see her down again. The engine wants to run hard, but the trans won't take it for very long...

Anyone have any ideas on who produces HD transmission parts for the 250R? What about ESR's engine stuff? If I have to build another engine, I'm going to do it a bit tamer this time so the trans. will hold together for more than a couple of weeks at a time...

Thanks for the vent time...carry on!

john p

[250r'en +TCB]

That is the drawback to this kit, your doubling the displacement and you expect the bottom and and tranny to last????

These kits are meant for drags and hill shooters, not to be driven around on your everyday machine...... What is your geearing at??? Just gear it for top end and that may save tranny's and sprockets in the future. I'd go with either 14/33 or even 15/33.........

[fyi]

The gearing is stock and I knew the transmisison would be approaching it's capacity limit. I had already had everything in the trans. dry-film lubricated, cryogenically treated and micro-polished and it still wasn't enough, so I didn't go at it blindly as you infer...

One of the facits to my business is that we manufacture high performance gearing for race cars, so maybe if I get the ambition this winter, I'll tear it down again to see if I can replicate those gears using our HD materials to see if I can correct the weak areas of the thing before I move on.

It still hurts to see that thing down again after all this effort to making it go faster. As they say however, it's not the end of the project that matters, but rather the journey to get there.

john p

[Dammit!]

How did you fit it into the frame? Did you notch it out above the spark plug? Got any pics?

[Billy Golightly]

Something must be wrong, cause I've honestly never really heard of a 250R transmission grenading as much as this. Theres guys running EFI Turbo setups on the Sabertooths making over 120hp and I don't even think they are having these problems. I think your already familiar with www.planetsand.com but you might make a thread there and see if anyone has some advice for you...

[3Razors]

I have heard that rumor about those kits. Did you get it from Neil at saberracing.com? Sounds like you've gone through all the steps they do for the tranny. I guess it just might be the nature of the beast! Most of the jockeys I see racing them at glamis are 140 pound guys, so that might have something to do with it. Those kits are very $$$ and it is not fun seeing your machine down like that.

[fyi]

Nothing on this machine is stock anymore...at least not the original configuration. Custom counter-weights, custom fram mounts, custom pipe, custom larger radiators, (the thing wouldn't stay cool) the list goes on-and-on.....

Unfortunately, we're usually do busy at the shop, that I don't have the time that's needed to devote to the machine when something like this happens and it becomes a real PITA to fuss with. I work on these machines mostly for the fun and love of what they are, but that leads to them taking a back-burner to my business...which pays the bills and feeds my family, my employees, etc.

Hey Billy- Does your 500R conversion vibrate very bad in the handle bars or thoughout the chassis?

Intially, I didn't want to go the 500cc motorcycle engine route because everyone said that it would vibrate too much to work right, crack frame parts, shake things loose, etc. I listened and went this route instead, but now I'm beginning to re-think that decision.

john p

[deathman53]

I would go with a baldwin tranny if I ever go with a kit like that. I might even get a baldwin tanny for the next motor build of mine. How did you ever get that clear the frame on a the atc, I had a 330 and it was real tight for acces to the spark plug.

[Billy Golightly]

It does shake, I've gotten use to it though and I think most anyone else can too. I'm still running the stock unbalanced crankshaft, so if that was done I know it would make a difference also. There was talk at one time on another forum I visited of possibly finding a way to weight the flywheel in certain places to make it act as a counter balancer. Good idea and theory but probably pretty hard to implement unless you had a small engine dyno and something like a a wheel balancer to figure out where to put the weight.

I haven't found any cracks in my frame or suspension parts but I've had one hell of a time keeping a pipe together on it. I think I welded the mounts back on my old pipe 5 or 6 times, even though it was rubber mounted. I'm running a pro circuit now that seems to be holding up better.

[fyi]

It does shake, I've gotten use to it though and I think most anyone else can too. I'm still running the stock unbalanced crankshaft, so if that was done I know it would make a difference also. There was talk at one time on another forum I visited of possibly finding a way to weight the flywheel in certain places to make it act as a counter balancer. Good idea and theory but probably pretty hard to implement unless you had a small engine dyno and something like a a wheel balancer to figure out where to put the weight.

I haven't found any cracks in my frame or suspension parts but I've had one hell of a time keeping a pipe together on it. I think I welded the mounts back on my old pipe 5 or 6 times, even though it was rubber mounted. I'm running a pro circuit now that seems to be holding up better.

Do you think a company like Falicon Crankshaft or the like would have the capability of internally balancing that crankshaft? I don't think our automotive crank balancers we use here would work right for such a small crank like that...

I'm going to keep my eyes open on Ebay for a complete, late model 500cc 2-stroke engine to maybe use- at least it's transmission would be better suited to handle the power I'd guess.

john petrossi

[250r'en +TCB]

Ever tried rubber engine mounts??? Even just really thin ones??? Maybe that would help........

[fyi]

I would go with a baldwin tranny if I ever go with a kit like that. I might even get a baldwin tanny for the next motor build of mine. How did you ever get that clear the frame on a the atc, I had a 330 and it was real tight for acces to the spark plug.

The frame was modified by on of our fabricaters here and the engine sets down lower in the chassis by about 9/16" than it did before (basically as far as one can go to allow chain clearance) and the original gusset tube that used to connect the underside of the backbone to the front down tube was removed. Small plate-type gusstes were used in it's place to maintain chassis strength at that area. Mike, our fabricater is quite good and I wish I had half the talents he does in doing such things...

BTW- Do you have a link to these Baldwin Trans folks? Thank you.

john p

[Billy Golightly]

You know what I would do (Here goes my big secret I had planned ) Destroke the CR500 crank, and make the sabertooth cylinder fit the CR500 bottom end. You gain a far far better clutch and transmission setup. Hell I guess if you could get away using a spacer plate you could use the CR crankshaft with a custom rod to fit the 95mm piston. The CR motor will make a ton of power on the stock componets if you work it, but it wont rev like the sabertooth. The CR redlines around 6500 I think which is actually pretty slow. The easiest horsepower is RPMs.

Falicon says they can balance the crank, but I think theres a caveat. From what I've read and understood, on a single cylinder it is impossible to totally balance the harmonics. You can only change their direction, from up and down to side to side unless you use an actual counter balancer like the 250Rs have stock.

[fyi]

You know what I would do (Here goes my big secret I had planned ) Destroke the CR500 crank, and make the sabertooth cylinder fit the CR500 bottom end. You gain a far far better clutch and transmission setup. Hell I guess if you could get away using a spacer plate you could use the CR crankshaft with a custom rod to fit the 95mm piston. The CR motor will make a ton of power on the stock componets if you work it, but it wont rev like the sabertooth. The CR redlines around 6500 I think which is actually pretty slow. The easiest horsepower is RPMs.

Falicon says they can balance the crank, but I think theres a caveat. From what I've read and understood, on a single cylinder it is impossible to totally balance the harmonics. You can only change their direction, from up and down to side to side unless you use an actual counter balancer like the 250Rs have stock.

So the CR500 engine must use a smaller bore than the ST, but have a huge stroke that makes big torque and limits engine RPM? Damn Billy....I can feel my wallet crying again... Sounds like a good idea and maybe we can chat on the phone sometime to throw ideas back and forth. Heck, if I get your idea to work on my sickly machine, maybe we can use what is learned on yours?

I'm going to have to get some books and poke around online to learn more about the CR500 engine.

[Billy Golightly]

Yeah...the CR500 motor is 79mm stroke, 89mm bore stock that goes to 91mm max oversize if I remember correctly, might be 92mm. The stock 250R stroke is of course only 72mm. The normal sabertooth crank is a shorter stroke then the 250R one for easier revving. The connecting rod is quite longer ratio wise also. Normally you have a 1:2 stroke-rod length ratio. The sabertooth rod is longer and from the posts on planet sand I've read from Calvin Pollet (the guy that designed and casts the sabertooth cylinders) the reason is its less leverage and friction on the side of the piston during travel.

You would be looking at some serious work to make the saber cylinder fit the CR cases, but everyone knows that anything is possible with a welder and a 3 axis milling machine