Tired Combat Wombat

[RichardMott]

I am in the Mike Perrett camp. Since my 03 motor has a limited source of pistons, I run 20:1 or even 16:1 Pennsoil. I do not race. Just trail and trials. Plus I do not foul plugs. My smoke is not high so as long as I feel that my motors are getting the best fuel/air mixture and lube, I will continue to use high amounts of lube. Just my 2 cents.

[taber hodaka]

Well shorty I don't think you are leaving the beginners with sound advice. peanut oil olive oil , Pistons bigger than the bore. Any oil is fine for racing old or new 'peanut oil olive oil?? old or modern oil makes no difference. We are leaving information for beginners here as seasoned riders will ignore the information. Ask a logger that has to run his saw all day and a breakdown is not a lost race but a days pay plus the repairs, In the 50's with poor oils we ran 16:00-1, in the late 60's I used 40;00 to 50;00--1 with over 60+ races motor cross and cross country 60 + finishes and 60 plus trophies no burned up engines . one bit of advice one bit important to all TUNE and JET your motorcycle for whatever oil you are using but use a proven oil. Watching the races at Hodaka Days they were flat running but not on peanut oil. Shorty you have the tech side on many issues with valuable information for us but I think you missed on oil and the importance of tuning ---Clarence

[taber hodaka]

If I used pennsoil I would be mixing 12:1 ------------Clarence

[dcooke007]

Max,
See what you started...run run as fast as you can

Danny

[hodakamax]

Danny, I'm trying to get the lid back on! What was I thinking? At least AZ kept it fairly short. Just kidding again!

Maxie

PS--A lecture on synthetic oils and 2-stroke tuning is forthcoming of course but I must be semi-responsible today and put out other fires. Perhaps later today! Stay tuned!

PSPS--Thanks Clarence, for your valued opinion!

[racerclam]

Just thought I would continue the pump priming . Why not go even further into synthetics ,? Cheep synthetic hydro carbons compared to Di ester to polyol ester base stocks . Which is best ? Why ? Not all synthetics are equal . Now do your home work.

Ok Im running away now

Rich

[Zyx]

Any debate about oil and ratios is bound to remain contested from now to the foreseeable future. There is no consensus. Frankly, I was not intending my remarks about oils for the beginners in the crowd, and I doubt either the builder or the racer here are beginners. I thought we were discussing what might have gone wrong with this engine during a flat out run during a race. That's not a discussion for beginners, and no one mentioned peanut oil.

Read Jennings 2-stroke Tuners Handbook. It discusses most of the issues involved in this single incident, with the exception of a discussion on why to mix richer oil for high speed use. If we are looking for a reason the engine failed when it did, I think you will find it under Jennings discourse on piston speeds and ring flutter. I won't paraphrase his observations here. Best read them for yourself, but it isn't a book for beginners. Frankly, it takes a lot of background to follow some of the discussion on engine theory, but is worth staying with it until it makes sense, because the guy has it right. If the failure here started with ring flutter caused by excessive piston speed, or exceeding the design limit of the piston and ring, no oil would save the day. But that doesn't mean that for racing purposes we can disregard the reasons to use more oil in the premix.

[Charlie R]

Ahemmm......Ahemmmmm.....That's me clearing my throat while taking my position behind the podium for a lecture...

Just kiddin! This could be it's own topic (actually has been about 10,000 times). Harry Klemm is the guy I most respect as far as building/tuning the 2 cycle engine. I would recommend reading his information several times to fully digest the info. Harry writes in a manner that most folks can grasp. If you want technical engineering info that will dull your senses and glaze your eyes over, well, he can provide that as well. Harry engineered and built some of the most competitive engines used by the top riders in the 70'S AND 80'S. Google klemmvintage.com.

Sorry Max, I'm not gonna play with this one.....

[hodakamax]

Wow, we're off course again blaming engine seizure on ring flutter, cracked frames and low rear tire pressure when it just got too hot. Peanut oil was good after we ran out of whales. Time to use the latest developments in oil technology and jet from there as Clarence said in his "real world" statements of experience and testing. I have the same story as Clarence in that after years of team racing with four bikes and hundreds of wins that seizing engines was never a problem at 20:1 ratios and using the best lubricants of the day. Jetting was the key. Gorden Jennings book is in my library and well used but Clarence and I also went to the "School of Hard Knocks" which proved much more useful in the long run as shown by our successes of the day.

There's no doubt that more lubrication is better but only up to a point. Once you have met the lubrication requirements of the engine why replace fuel (which is where the power comes from) with more oil or worse yet, with inferior oils of the past? At 1:8 ratio your fuel is 12.5% mostly non-combustible oil but at 1:32 ratio you only have about 3.1% oil. This means you are missing out on about 9.4% more fuel to create more horsepower. If it's not a race engine it's OK to put in more oil, it does add protection but at a cost of horsepower. There's certainly no harm in being cautious particularly during break-in and severe service. I personally would up the main jet to provide more cooling AND lubrication.

OK, I'm being the Devil's Advocate again so don't take me too seriously! All for fun--

Maxie

PS--ah c'mon Charlie, It'll keep you entertained! Good to see you typing again--I might need your help!

[dcooke007]

Well, in this case since you found me out. It wasn't the rear tire pressure that was low but the front.

Danny

[hodakamax]

Maxie

[hodakamax]

Well, in this case since you found me out. It wasn't the rear tire pressure that was low but the front.

Danny

Danny, Why didn't you tell us earlier? Everyone knows that low front tire pressures causes piston seizures even more than ring flutter. Now I have offended my good friend AZ because of the incomplete story. Actually AZ is not fooling about ring flutter, It is probably a factor in some cases according to Gorden Jennings but not Max. In this case I think she just got too hot.

Maxie

[dcooke007]

Ok bike arrived today and attached are pictures of the piston. No time for comments at this time. Lets see what you think.

Danny

[bchappy]

I am still going with the main jet being to small for conditions. That sucker got really hot to melt the aluminum like it did. As I said, I had a bushel basket full similar to this one back in the day. I thought I was the speed king but soon learned how important jetting for conditions was.

[hodakamax]

I'm with Bill, It looks like a typical lean seizure complicated by new clearances and some early big demands. When we put in a new piston in the old short tracker we went up on the main and tried to get an easy hour on the engine by running it up and down the road at different speeds using some full throttle but at lower RPMs than race speed. The engine was disassembled and checked for wear spots on both cylinder and piston. Usually there were not any. Any wear points on the piston were sanded lightly and cleaned. Another series of easy runs for several minutes and we were ready to go. At the track we started rich and worked our way back to the original jetting. More time would have been nice on the engine, but it always seemed to work.

More oil in the mix could have been another approach (and not a bad one) but we had already added more lubricant through larger jetting. This engine was a race engine and needed all the fuel it could get. After the early work on the engine (I had some pistons just like Clarence's and Danny's), the engine was raced for years with no seizures at 20:1 oil mix ratio and was a consistent winner in three states for a long period of time with either my teammate or me driving it.

Wow, I started out to just agree with Bill and got carried away!

Maxie

PS--I don't know if anyone is noticing but the three Musketeers from the past, Clarence, Bill and Max seem to all be on the same page. Maybe it's because we all raced for years and hundreds of hours in the development stage of the Hodaka. We've experienced this type of disaster and learned from it. It's not about us but I think we are all just telling the story of a remarkable time in motorcycle history!

[taber hodaka]

Looking forward to hearing and seeing this machine back on the Track! Yes we can discuss the many wins without melting down. And I like the others had the tray of melted pistons. There are oils that are better than others, they will run cooler,can be run with less oil and may have to be jetted leaner. Run with a cold heat range plug mix use a proven quality oil and tune to whatever you are using. Even the ace 90 book covers tuning very well ------------Clarence

[hodakamax]

Thanks Clarence, I always respect the opinions of the other two Musketeers.-- or maybe

Maxie

[Zyx]

The metal displacement here is not from lean heat, but from friction caused by contact between piston and cylinder wall. Lean heat would have attacked the piston crown. From the video, the bike did not sound lean. Actually, it sounded very good. Sorry to disagree, but running today's fuels in yesterday's bikes is more likely the cause of failure than jetting.

[hodakamax]

More oil on a cracked frame will help ease the vibration as well as a larger main. Let's see, where was I? Welcome back AZ, we need you to lead us astray and make us laugh. Just kidding again--

Maxie

PS--Flywheel,Flywheel,Flywheel---Too Lean,Too Lean,Too Lean! Hey, I did read about ring flutter again and concluded that it does happen only after all the oil has cooked out from between the piston and ring (too much heat again). The ring has been scraping oil and storing it until it got too hot, probably from a lean condition. Of course EXTREME piston speed could pump it out but seems unlikely to me if the engine was properly jetted and had the proper amount of oil. I do like discussing technical things because they make us think. We must beware of reading on the internet, magazines and other publications of the past that prevent us from thinking and doing research in the real world. Always fun stirring you up AZ, and am I making any sense on the ring flutter thing?

[Zyx]

What's your point, Max? If you lack confidence in your own opinions, fine, but don't take it out on me.

Look at the photo of the underside of the piston crown, and tell me if you see any signs of excess heat. Those signs would be coke ash. Light coking is normal. Ash isn't. I see no signs of excess heat. Plug is black, piston normal, sounds clean at full throttle. Where are your supporting symptoms of lean condition? Simply because you have always attributed seizure to lean jetting doesn't make it so. Let us know which diagnostic symptoms you are using in support of your conclusions. I have Staed mine, and stand by my conclusions. If lean jetting contributed to this result, it certainly wasn't the principal cause. I doubt jetting is wrong at all. I see no signs of leanness anywhere. All I see is a seized piston. Why it siezed is the question. Lean carb isn't the answer.

[hodakamax]

I don't lack confidence in any of my opinions or I wouldn't be giving them. I do not mean to offend anyone and I apologize if I have. I must say that you seem to have a negative opinion on anything I write. To me this is a clear cut case and I have no doubt that was the cause. I sometimes feel that you're not reading what I say before you post your opinion. I think both of us should work on a consensus rather than an argument. Let's lighten up and work together to solve the problems of the Forum.

Max

PS--Please don't take my weird sense of humor and teasing seriously. I've told you before not to take me seriously because I rarely am. Again I apologize.
I can also explain my position in detail if you would like.

[DGardner]

I'm going to insert my 2 cents on this subject....but you have to remember my 2 cents is worth about 1/2 cent. If you look at the outside edge of the piston there looks to be some detonation going on from maybe to much compression? or is there other things that haven't been talked about. DG

[Zyx]

Detonation, surely, but unless running race gas, it is most likely attributable to running pump gas. Today's fuel, yesterday's bike. Where did I hear that recently. If the bike was detonating on race gas at 97 to 101 octane, timing might need retarding slightly. Otherwise, it's hard to find "high" octane fuel these days, and what we can find detonates readily due to low octane and modern additives.

[hodakamax]

DG, your opinion is worth way more than 2 cents. that's what the forum is about. Keep it up!

Maxie

[Zyx]

Not having a Wiseco piston handy, I would wonder about the difference, if any, in dome height and profile of the Wiseco piston versus a stock Wombat piston. I know folks heavily into modern bikes who won't use Wiseco pistons due to inconsistency in the product. This is hearsay not science, but I would start with a comparison of the replacement piston to stock in terms of dimensions, particularly height above the wrist pin, and overall weight. I can't find any data from Wiseco regarding their maximum recommended piston speeds, and perhaps they don't even have such data. The Wiseco uses a keystone ring I believe, and for high rpm racing, I would prefer a piston with a Dykes as they seal better and are very hard to unseat due to rpm. Compare Ace 100 Pistons to Super Rat Pistons for example. The Hodaka MX bikes all used the single Dykes for a reason, and the Super Combat is rated for 10,000 rpm, which verges on insane imho.

Bottom line here is that the piston shows signs, but not signs of overheating. The erosion around the perimeter does look like detonation to me, but saying so here will lead to a refrain on lean jetting, which for the most part does not cause detonation. Not seeing any signs or hearing any sounds of lean burn, I look elsewhere. Pushing the piston beyond its limits and beyond the limits of pump gas is my suspicion.