Tri Z Engine Build

[El Camexican]

A lot of people have died or been injured producing and refining that fuel. Pemex safety policy is like that of the Panama Canal trenchers.

I believe you guys refine a lot of it. Fortunately you save all the ethanol for yourselves It's dirty as all heck due to the storage systems here, but as long as you run a filter it burns great. I always topped my street bike up with it before trailering it the Hill Country to ride the Twisted Sisters up north. Seemed to run much better than on TX premium with 10% ethanol.

[El Camexican]

And then you don't get any tire testing done

No worries, I don't drink till the sun sets. I love to drink and I love to drive, but I hate doing both at the same time. Hope to see you there. We can talk about your Sabers

[barnett468]

No worries, I don't drink till the sun sets.

Yes but I think that not stopping until it rises again might make racing a little bit challenging.

[El Camexican]

Yes but I think that not stopping until it rises again might make racing a little bit challenging.

It does! I crashed one morning doing a burnout in front of a large crowd once while my liver was still working on cleaning my blood up. Loosened my steering head bearings (guess the races weren't properly seated) Next pass ended up being a 110mph tank slapper. That one sobered me up!

[onformula1]

Might want to get this-

http://www.scottsonline.com/Stabiliz...os.php?ID=1191

[keister]

Yea, it's a 99.99% done deal........... Planning to bring 2 trikes, 1 big bottle of rum and a 1/2 dozen cigars. Food, shelter and other luxuries I'll figure out when I get there......

Stop the presses!! That is awesome news!!

Most of the heavy hitters in open are running 4 snows.

Actually, I think they are called '3-Snows'.

..........3) a couple hangovers of epic proportion ........ And don't be the last person at the Choo tree

If we're gonna be best friends, you're gonna need to man up

[barnett468]

On a 2 stroke-

Retarded timing= more upper mid, top end & over rev

Advanced timing= more low end and mid

This statement is a little vague to me at least and therefore would be more helpful if a more detailed explanation or a link to the source of the info is posted so I and others that might not understand it could better understand it.

I am definitely not as knowledgeable about ignition timing as many people, but in general, part of my experience and understanding of it is that it is not completely accurate that "advanced timing" timing increases bottom end power but "retarded timing" increases top end power etc, however, it is certain that each individual engine determines exactly how much timing it wants and at what rpm it wants it, at least this is the way it has always been in the past.

The ideal time to have the spark occur is when it is timed to cause the combustion to create the most pressure in the cylinder . . This is referred to as the location of peak pressure or LPP . . The point at which the combustion makes peak pressure will always be after top dead center, however, it will not always be at the same point relative to the crank angle/piston location . . The more the ignition timing is advanced towards its optimum point for a particular engine, the higher the cylinder pressure becomes and the closer to top dead center the LPP becomes . . None of the people whom have done the LPP test and wrote articles I read by them regarding their findings are certain just why this location changes.

Unless one has the sensors to determine the exact LPP of every engine vs the point at with the spark plug fires relative to the crank angle/position of the piston, one has to resort to alternative methods to determine it as closely as possible . . One of the options to determine the LPP, which will also get the engine to produce the maximum hp and tq throughout the entire rpm range, is to test different timing settings at different rpm's on a dyno and then modify the computer program on engines that have computer controlled ignition, or modify the mechanical advance unit and change the distributor or timing plates position on engines that don't have computer controlled ignition timing so they provide timing settings that are close to the best dyno test settings found as possible . . The timing curve can be set more accurately with computer controlled ignitions than it can on ignitions that only use a mechanical advance unit to control them.

Another one of the options to achieve maximum power is to advance the timing until the engine begins to detonate slightly then retard it a little so there is a safety margin . . I add the safety margin because the greater the load on the engine, the greater the potential there is for it to have detonation, and there may be times when an engine is subjected to greater loads and/or ambient temperatures during actual use than it was when the timing test was done . . It is better to have a little less timing than what is optimal than it is to have a little more than what is optimal because a little more may cause the engine to hurl.

One issue is that the point at which an engine detonates is not necessarily the LPP for that particular engine, and in cases where it is not the LPP when an engine detonates, additional power can be gained by doing things to reduce detonation like running a colder plug than stock, however, this is typically only done when the static compression is more than around 10.5:1 . . A plug of the same heat range but which has a retracted tip can also be tried . . Also, installing a cold air induction unit on it [if it is a car etc] so the engine can get air that is the same temp as the outdoor ambient temp instead the air from under the hood, which can sometimes be around 180 degrees, will also reduce the potential for detonation plus it will increase power because the colder the inlet air temp, the denser the air will be and the denser the air is, the more oxygen it will contain.

Detonation, or the potential for detonation can also be reduced by improving cylinder cooling . . One way this can done on air cooled engines is by adding additional size to the cylinder fins . . These fins are designed to keep the cylinder from overheating even with the maximum factory overbore, however they can be insufficient when big bore kits and/or stroker kits are added and/or when compression is increased etc.

The potential for detonation can also be reduced in a 2 stroke by improving the quench band in a cylinder head that has a poorly shaped one, and it can be reduced in a naturally aspirated 4 stroke that has quench pads in the combustion chamber by reducing the distance from the top of the piston to the cylinder head to around .034 to .043 inches with closer to .034 being better . . Detonation/preignition potential can also obviously be reduced with race fuels and part of the reason these fuels reduce it is because they actually burn cooler than pump gasoline. ?

To get the most power at all rpms, variable ignition timing must be used . . Some engines that operate within a very narrow rpm range like professional drag cars and weed eaters and lawn mowers etc don't have a variable timing system because that type is not "required" for those particular apps, however, engines used in transportation vehicles use a much wider rpm range, benefit greatly from having a variable timing system.

Inaccurate timing can cost up to around 10% of an engines potential hp and tq, and I have seen less than optimal power from inaccurate timing literally hundreds of times, however, the driver often doesn't know the engines timing is not optimized because it sill runs "ok" . . Incorrect timing will also reduce mileage and can increase the engines cooling requirements and actually cause it overheat if the cooling system is marginal.

Setting the timing to the mfg's recommended setting does not always mean that this will be the best setting for power and mileage, even if the engine is stock . . Mid 1960's thru around 1984 automotive engines which were non computer controlled, almost always had less total timing and/or a timing curve than was optimum . . This was intentionally done by the mfg's to meet emissions requirements . . Because of this, modifying the timing on many of these stock engines will increase mileage and power and will also reduce the engines cooling requirements.

Setting the timing to the mfg's recommended setting if an engine has been modified is not always the best setting either, and a modified engine will often benefit from a timing setting that is different than the stock one, which is another reason it is important to do timing tests on any engine to see what setting will produce the most power if that is ones goal.


...........
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[barnett468]

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El, I saw the steering damper posted which is a very nice unit, and if you were interested in one for any of your bikes but didn't want to spend $450.00 or more for one, you could buy a universal one for as little as $50.00 which I can attest will work quite well because I have run them before, however, I have not run the particular [probably Chinese] brand below,

That being said, since the company has the same name that Michael Jackson gave his ranch, I'm confident their products will provide a similar level of safety and pleasure to that which was provided by Michael to others at his ranch.


http://www.neverland-motor.com/contr...ng-damper.html


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[El Camexican]

I have a Scotts damper and mounts on both my dirt bikes. I don't expect to need one on my trike (I wish it could go so fast as to shake!) but the mount On F1 posted was cool as hell. For drag racing a $30 unit like the style you posted would be plenty. Track racing is another story. I imagine a Scotts would feel great on an MX trike.

[El Camexican]

This statement is a little vague to me at least and therefore would be more helpful if a more detailed explanation or a link to the source of the info is posted so I and others that might not understand it could better understand it.

http://www.macdizzy.com/update82.html

[barnett468]

http://www.macdizzy.com/update82.html

Xlnt, thanks for the link El.


"The ignition timing has to be set somewhere between 1.8 mm's BTDC and 2.2 mm's BTDC."

From what I can tell, the spec recommended is for a TRX 250 Honda . . Either way, just to clarify, it is not a spec that is going to be the best setting on all two strokes . . Two examples are the the 1970's Kawi H1, which most years has a factory spec of 2.94 mm [or 23 degrees] before top dead center and the 1985 Tri Z is 1.66 mm btdc.


"Obviously, the least amount of initial advance is best Always."

There is actually nothing obvious about this statement at all, and if it is meant to apply to all 2 strokes only or both 2 and 4 strokes, it is in fact very wrong, and basically defies the applicable laws of physics . . To prove this to some degree, one can simply adjust the timing on ANY 2 stroke, [or even a 4 stroke engine they have if they want but that is not what the op is referring to] so it fires at top dead center at idle, then tell us just how much "better" it runs . . Or better yet, set it to fire after top dead center since this will help insure it has close to "the least amount of initial advance possible".

Another way to test this to some degree is to let an engine idle, then slowly retard the timing . . Unless one is hard of hearing, they will EASILY hear the engine rpms reduce, and if they retard the timing far enough, the engine will simply die, I personally guarantee it, and I for one don't see how an engine that is no longer running because it has "the least amount of initial advance" will accelerate any better than one that is actually running even though the running one does not have "the least amount of initial advance" . This same test can then be performed at around 4000 rpm.

The technique mentioned in the paragraph immediately above is actually part of a process referred to as "timing by ear", which I learned when I was around 14 and which countless numbers of others have also used, and when properly done, the timing setting will be very close to results that can be achieved by setting the timing with the engine on a dyno or by having a distributor sent in to be "recurved" to match a particular engine build etc.

This being said, if they instead mean that it is best to have a head design that performs equally well with a lower timing setting than a head that performs the same with more timing, it is a completely different deal altogether, and in this case, it is a far more accurate statement, but again, even in this case, "less timing is better", is not technically correct, because again, the engine is the one that determines the best timing, it is never, ever, the engine builder . . In other words, if the engine runs best with the timing at 30 degrees btdc, but the engine builder says, "Hey, I am going to set the timing at 20 or maybe 40 degrees btdc simply because I am the engine builder and I say that this should be the best setting.", the engine will have less power . . If one wants to run a timing setting that is uncommonly low, they must build the engine so it performs well with that setting, and although this is possible, it is way outside the norm of how engines are typically built . . It might be a good idea in concept, but is a bit difficult in execution.

As far as heads that do require less advance than many others, there is such a thing, and for 4 strokes, these are ones that have a heart shaped combustion chamber and this shape typically locates the spark plug closer to the center of the combustion chamber and it also creates a quench pad which are all good things for naturally aspirated engines which means a carbureted engine with no power adders like a supercharger etc . . On engines with superchargers, the fuel mixture is turbulent enough that the heart shape and quench pad are less critical..


"For tuning purposes you might find it helpful to know that more advance (moving toward 2.0 to 2.2 mm's BTDC) will favor bottom end power..."

See reply above


"...and less advance (1.9 to 1.8 or less) will favor top end power."

One can try the same test as mentioned above to test this statement also.


As with jetting, there is no one ideal timing setting for all engines, it just doesn't work that way, and as I mentioned in my previous post, each particular engine will determine the amount of timing it wants and where it wants it.

The main objective to any engines performance is to set it to have the most overall power within the rpm range it will be operated in . . This is means that at least some amount of sacrifice in power outside that operating range will likely have to be made . . I think posted a couple examples of this in my previous post.


As far as the ignition timing post in that link is concerned, imo, it was written by someone that appears to have good intentions and is definitely very knowledgeable in many areas, but unfortunately, with regards to ignition timing, they didn't post sufficient details and write that post in a way that their message is unquestionably clear and understandable . . The most helpful posts are the ones that are the least vague and ambiguous.

[onformula1]

Yea, it's a 99.99% done deal ( I hate saying 100% in case something comes up). I had planned to go this year, but totally screwed up the date when coordinating a trip my wife was planning and told her to buy her tickets for the day TF 2015 was ending Given the rain I guess I was lucky. Anyway, I won't make that mistake for 2016. Really looking forward to it Planning to bring 2 trikes, 1 big bottle of rum and a 1/2 dozen cigars. Food, shelter and other luxuries I'll figure out when I get there. Slept in my truck cab for three seasons of drag racing, I can do it again for one week.

26 hours one way is a bit far for me, I plan on flying into the closest airport and renting a SUV that I can sleep in, Mike Oscar Mayer is planning on going so I can stay with him in the toy hauler.

[El Camexican]

As with jetting, there is no one ideal timing setting for all engines, it just doesn't work that way, and as I mentioned in my previous post, each particular engine will determine the amount of timing it wants and where it wants it.

The main objective to any engines performance is to set it to have the most overall power within the rpm range it will be operated in . . This is means that at least some amount of sacrifice in power outside that operating range will likely have to be made . . I think posted a couple examples of this in my previous post.


As far as the ignition timing post in that link is concerned, imo, it was written by someone that appears to have good intentions and is definitely very knowledgeable in many areas, but unfortunately, with regards to ignition timing, they didn't post sufficient details and write that post in a way that their message is unquestionably clear and understandable . . The most helpful posts are the ones that are the least vague and ambiguous.

I’ve found that when it comes to things that can’t possibly be determined with hard math good info can be short and sweet “Here’s the current school of thought, start here and figure out what works for your application by testing and tuning” There simply is no substitute. Books and some advice will get you close, but unless every single component, tolerance and other variable is identical you still need to test and tune. I would say ignition timing is a perfect example. On F1’s post was exactly that, good advice. All he left off was the “results may vary" disclaimer that should follow everyone’s advice, although I personally prefer “You get what you pay for and this advice was free”.

Timing (ignition or cam) could be broken down to one simple sentence; “For best performance, set your timing to where the vehicle runs best and does not self-destruct”. Reading about all the theory behind what causes one setting to be better than another is all good an well on a cold and rainy afternoon, and great info to have when wondering which what to turn screws first, but at some point one must go outside, pull the covers and start testing.

Yea, Macdizzy is a Honda guy and most of his experience seems to apply to them, but he seems to have a great grasp of the whole 2 stroke thing. I’ve enjoyed reading his stuff.

Connecting rod length/bore width ratios is something else that seems vary greatly from application to application. In my case the Tri-Z uses a 130mm center to center rod. From what I’ve read a 7mm longer YZ490 rod and a spacer plate is bolt on power due to the longer dwell. I’ve never seen one run, yet alone driven one, but the former Yamaha rider that posted on here said all his engines had them and a friend back home said the local dealer had the mod done on their quad conversion. He claims that it pulled away from everything else on the ice straights.

So if a 137mm con rod is the hot ticket on one 68/70mm bore 2 stroke why are the Honda’s, Kawi’s, KTM’s and newer Yamaha’s all running rods shorter than 130mm? Then consider that a 250 and 300 KTM share the same bottom end and both seem to have linier power in abundance. I’m not planning to do this mod, but I find it interesting that I seem to have the longest 250 rod of the three Japanese trikes and yet it’s “too short” for Yamaha’s factory trike. The short answer may be that one can overcome most any small design compromise by making changes in other areas.

[onformula1]

I’ve found that when it comes to things that can’t possibly be determined with hard math good info can be short and sweet “Here’s the current school of thought, start here and figure out what works for your application by testing and tuning” There simply is no substitute. Books and some advice will get you close, but unless every single component, tolerance and other variable is identical you still need to test and tune. I would say ignition timing is a perfect example. On F1’s post was exactly that, good advice. All he left off was the “results may vary" disclaimer that should follow everyone’s advice, although I personally prefer “You get what you pay for and this advice was free”.

Timing (ignition or cam) could be broken down to one simple sentence; “For best performance, set your timing to where the vehicle runs best and does not self-destruct”. Reading about all the theory behind what causes one setting to be better than another is all good an well on a cold and rainy afternoon, and great info to have when wondering which what to turn screws first, but at some point one must go outside, pull the covers and start testing.

Yea, Macdizzy is a Honda guy and most of his experience seems to apply to them, but he seems to have a great grasp of the whole 2 stroke thing. I’ve enjoyed reading his stuff.

Connecting rod length/bore width ratios is something else that seems vary greatly from application to application. In my case the Tri-Z uses a 130mm center to center rod. From what I’ve read a 7mm longer YZ490 rod and a spacer plate is bolt on power due to the longer dwell. I’ve never seen one run, yet alone driven one, but the former Yamaha rider that posted on here said all his engines had them and a friend back home said the local dealer had the mod done on their quad conversion. He claims that it pulled away from everything else on the ice straights.

So if a 137mm con rod is the hot ticket on one 68/70mm bore 2 stroke why are the Honda’s, Kawi’s, KTM’s and newer Yamaha’s all running rods shorter than 130mm? Then consider that a 250 and 300 KTM share the same bottom end and both seem to have linier power in abundance. I’m not planning to do this mod, but I find it interesting that I seem to have the longest 250 rod of the three Japanese trikes and yet it’s “too short” for Yamaha’s factory trike. The short answer may be that one can overcome most any small design compromise by making changes in other areas.

Nico, keep in mind the thread is titled " Tri Z Engine Build" if the title was different my advice maybe different.

I will save my time and opinion on the long rods and why they work on some and not others. (I sense multiple posts of copied and pasted, Googled info posted by one

[barnett468]

Nico, keep in mind the thread is titled " Tri Z Engine Build" if the title was different my advice maybe different.

I will save my time and opinion on the long rods and why they work on some and not others. (I sense multiple posts of copied and pasted, Googled info posted by one

El, at least one person on the site keeps posting very brief comments about certain subjects but they never seem to post details about them even when asked to, and these comments may give the appearance to some whom read them that that they know something about the subject they commented on and therefore, take these comments as fact even though they never, ever, seem to qualify their statements like I and some others try to do, yet they seem to have plenty of off handed comments to make about others whom try to be helpful in this regard even though it has previously been suggested to them on a few occasions and a few different threads that they stop making these types of comments.

Yup, I certainly post links to other sites and copy and post info off the internet on occasion, but this obviously doesn't mean that I have no knowledge of a particular subject when I do this, and it doesn't mean that others that do this don't have knowledge on the subject they are posing on either, however it's obvious to me that at least one person on the site WRONGLY makes a LOT of assumptions . . One of the reasons I do occasionally post things from the internet is so I don't have to type as much, plus it gives people an additional, independent source of information so they don't have to take one persons word for it whether it be mine or someone else's.

I hole shot many races with my Tecate, and the times I didn't, I was still usually near the front, and this didn't happen because I was lucky or because I retarded the timing on my bike to increase top end power . . I also did a LOT of timing tests on the prototype Tecate's I was doing the development testing on, and in every single case, "MORE" timing produced MORE power EVERYWHERE . . This also held true for the Road Race bikes that Rob Muzzy built for Kawi which went around 165 mph.

Even though your engine is far from stock, if you want to know what affect ignition timing has on a Tri Z, then it might be helpful to ask someone whom has far more experience with them than most of us here, and one of those people would be Bryan Raffa and another would be Harry Klemm whom built Bryan Raffas 350 cc Tri Z engine shown in the video below, and whom has possibly built more National and Series Championship Winning engines than ANY other builder to date.

https://www.youtube.com/watch?v=0JTOdFFozYk


Although there may be a couple of people that use the "less advance makes more top end power" theory, I have never once experienced that being the case in my 40 years of setting the timing curves on literally HUNDREDS of various engines, and apparently Kawasaki hasn't either, therefore, based on that alone, imo, comments about retarding the timing to increase top end power are simply incredibly unlikely in ANY engine . . I even posted how one could test this "theory" for themselves so they wouldn't have to take my word for it.

For someone to imply that ignition timing rules are different for a TriZ than they are for other engines simply makes no sense at all to me, especially when they don't offer any proof, anecdotal or otherwise, to support this claim . . It's been a commonly known fact to engine mfg's ever since an ignition advance system was invented around 347 years ago, that in general, running the most advance you can before the engine starts to loose power or detonate is the correct way to achieve the most power at ALL rpms.


PISTON DWELL

I for one am not afraid to post some of my comments about piston dwell and have anyone whom wants to scrutinize them and tell me I'm wrong if they find an error in them or post info that doesn't agree with mine,even though my comments on this subject may have little relevance since I admit I am not one of the foremost authorities on the it, however, I do know a least a little about the subject.

The following is just general info which you might find interesting if your bored and want to read it, and YES, I copied two quotes from the internet.

Piston dwell is a bit complicated because it is tied to rod ratio and rod length and piston speed, and as with most things, one size does not fit all, and there are good and bad aspects to both long and short dwell and long and short rod ratios.

The number one priority for any engine is engine life since it obviously doesn't matter how much power an engine has if it will hurl before the finish line . . High perf street engines like stroker engines, use rod ratios of around 1.5, and these engines typically spin a max of around 6000 rpm with horsepower that typically ranges from around 300 to 500 . . The drag racers like John Force run their engines for around 4.0 seconds so they can sacrifice long term reliability for a bit more power . . The Nascar guys use rod ratios of around 1.7 [which would be considered extremely long for a street engine] because it is easier on the engine which needs to survive for 4 hours at rpms of around 10,000 instead of 4 seconds with rpms of around 8500 . . If that same Nascar engine only ran at 6000 rpm, they could get away with a shorter rod ratio . . Formula 1 cars spin 20,000 rpm for hours and their rod ratios are in the 2's, so it's fairly easy to see some sort of pattern here.

I actually build high perf automotive engines for the street and built my first one in 1971, so I have been doing it for a little while and am interested in all this engine tech stuff including dwell and rod ratio and air velocity and port cross section etc, and I also know several top engine builders, and they all say the same thing, which is basically that the amount of piston dwell doesn't mean much in application.

I have seen dyno charts and comments from 2 different very good automotive engine builders whom actually tested two different dwells by changing the rod lengths in around a 300 hp engine they had and the difference in power was so small that even they said it was within the margin of error for their dynos . . I have also talked to other high perf engine builders and read lots of "technical' papers and comments from other builders regarding the subject.

One of the issues in the "a long dwell is better" theory lies in simple physics, and this is, the more time the piston dwells/lingers at the top and bottom of the stroke, the less time it spends moving, or moving quickly per se, and when it is not moving, or moving quickly, it can not make as much power . . A longer dwell also increases the load on the piston and rod etc because it can not move away from the top of the stroke as quickly as an engine with shorter dwell can after tdc.

The comment below is from Darin Morgan whom built the 1982 and 1983 NHRA National Championship Pro Stock wining engines for Lee Shepherd, and also the 1983 IHRA National Championship Pro Stock winning engine for Lee Shepherd and he is still at it today.

" We also wanted to point out some of the common myths and misconceptions about high-performance motors. For example, I've seen dozens of magazine articles on supposedly "magic" connecting rod ratios. If you believe these stories, you would think that the ratio of the connecting rod length to the crankshaft stroke is vitally important to performance. Well, in my view, the most important thing about a connecting rod is whether or not the bolts are torqued!

If I had to make a list of the ten most important specifications in a racing engine, connecting rod length would rank about fiftieth. Back in the days when Buddy Morrison and I built dozens of small-block Modified motors, we earnestly believed that an engine needed a 1.9:1 rod/stroke ratio. Today every Pro Stock team uses blocks with super-short deck heights, and we couldn't care less about the rod ratio. There's no magic - a rod's function is to connect the piston to the crankshaft. Period."

People look at what Smokey Yunick said and they take it out of context in my opinion. He said you should put the longest rod YOU CAN not the longest rod YOU CAN CRAM JAM OR MANIPULATE into the engine. I see people all the time screw up the engine combination to facilitate some preconceived ideal rod ratio and they wonder why the thing wont turn up and make power. The difference in the GM 358 NASCAR test engine from 5.250 inch long rods to 6.1 inch long rods was maybe 2ft/lbs and 2 HP. Not much to worry about. That satisfied the GM engineers that there is nothing there. Does a short rod make more TQ? Does a long rod make more top end power? It probably does but its such an insignificant amount, its not even worth messing with! If there was a major advantage or power gain in this, it would have been proven a long time ago and we could all put this to rest but no one has. I wonder why???????????"


COMBUSTION CHAMBER SHAPE VS IGNITION TIMING VS DETONATION VS TOP END POWER

As far as dome and squish band shape goes, I know you already addressed that and got a lot of very good info from others here on it so your good there, and I am far from an expert in that area on 2 strokes so it was fun and informative reading those posts . . I did do some squish band and dome shape testing with Harry Klemm but he came up with the design and also made the heads so I was just the test guinea pig.

The comments below are from Harry Klemm . . He built a killer H1 road racer which another guy rode for him and he used the stock timing which is a lot, and it won every AHRMA race and the Championship . . The CDI equipped H1 actually advances the timing at around 7000 rpm to a level that is above its already "high" static timing level of 23 degrees btdc, so the "theory" that less advance increases top end power in a 2 stroke was not the theory the Kawi engineers used on what was the fastest production bike in the world at the time irregardless of engine size . . In fact, Kawi, still didn't use the "less advance increases top end power" theory by the time they built the H2 a few years later, which was also the fastest bike in the world when it came out . . Harry also used the stock Kawi timing instead of using the theory of retarding the timing to get more top end power which he certainly could have done, and instead of retarding it, he left it as it was and modified the heads and added cooling scoops to help reduce detonation so he could intentionally run a lot of advance.


FROM HARRY KLEMM

Our 1975 H1 test bike had the latest version of the H1 CDI ignition. This ignition maintains the same ignition timing from 0 rpm, up to 7000rpm. At 7000rpm, the ignition timing advances very slightly. Why the !!## would KMC engineers do this?.... Simple. It’s important to remember that the H1 was built as a ¼ mile bike that was expected to be operated at peak rpm in high gear for only a few moments (on 100+ octane pump gas of the day) After just a few moments at peak rpm in high gear at the end of a drag race, the engine was then quickly shut down. Under this operational scenario, a small advance above 7000rpm is actually not a bad idea. Sadly, however, for extended operation above 7000rpm, this added advance a “super bad” idea. Add in the increased detonation risks afforded by today's oxygenated 91-octane pump gas, and sustained 7000+ operation is guaranteed to result in catastrophic levels of detonation ...... in less than 30 operating seconds.

As the fleet of H1 500s aged, and pump-gas octanes plummeted, the poor head-dome designs and excessive squish clearances of stock H1s would swiftly generate lethal detonation, any time the bike was operated for a brief time over 7000rpm (usually resulting in a seized or holed piston)…. And exactly the same applies to anyone riding an H1 today….. So what is an owner to do?

Octane Specific Riding - While running a stock H1 CDI ignition, it is impossible to build ANY high-performance H1 engine format that can be operated reliably at sustained 7000+rpm speeds on today’s 91-octane fuel. .... it's never going to happen. This applies no matter what pipes or carbs you are running on your H1. That said, the lion’s share of "stock-pipe stock-carb" riding scenarios CAN be done with 91-octane, or 91-octane mixes. Here is the background.

During the development of our engine packages, we conducted dyno testing with our real-time detonation sensors hooked up to our H1. Using this deto-sensor on the dyno gave us a clear insight on the specific detonation risks. Our H1 showed virtually no signs of detonation at all until the 6000-6500rpm range. Above 6000 we began to see mild levels of deto on the center cylinder only. Above 6500, the rate of deto on the center cylinder increased visibly, and the ignition side cylinder began light deto. As soon as we passed the 7000rpm threshold where the ignition advanced slightly, the center cylinder went into high level deto, with both the left and right cylinders not far behind. Later tests (with staggered compression and jetting) helped to significantly reduce the deto levels of the center cylinder, however every time we exceeded 7000 rpm there was visible (but now non-lethal) deto taking place on all three cylinders. These dyno tests were all done running 110 octane race fuel. The same 7000+rpm passes on 91-octane would have certainly killed a piston.

After these dyno tests, we filled up with 110-octane, and took the bike to Bonneville where we ran 8100 rpm in high gear for the full 50 seconds of our peak speed pass. A few months later, we took the same setup to an AHRMA road race at Willow Springs Raceway (arguably the highest average speed track in the western USA). At Willow, the H1 was steadily running 7000+rpms in 4th & 5th gear for 80% of the 6 lap race. It is impossible to run an H1 harder than we ran this one at Willow Springs. After each event we removed the heads to check for any visible signs of “destructive levels” of detonation …. There were none.

In between the racing, we ran numerous tests on the street running 91 octane fuel. As long as we never ran sustained rpms above 6000, the temperatures and detonation were very manageable. However if we did some aggressive riding that involved repeated 7000+rpm spurts in the higher gears, the 91 octane could no longer run deto safe. For this kind of riding, we ran a 50/50 mix of race gas and 91-octane to manage the detonation to safe limits. On a practical note, riding the H1 this aggressively on the street will likely get you thrown in jail in all 50 states…. And we are strongly against racing of any kind on public highways. That said, everyone has a different definition of “aggressive” riding, so we did this testing to that end only.

For 90% of the street riding that most H1 owners will do, 91-octane in our engine packages will suit most riding applications.
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