So the guy that bought my superlite blew the motor (( Internal Combustion Engine ? )). He was on 93 octane pump gas. The 360CC water cooled Leckich racing motor (( Internal Combustion Engine ? )) had always been run on VP race gas and 100:1 HPS synthetic oil. I never had any motor (( Internal Combustion Engine ? )) issues and of course I ran it hard. The piston melted out the top exhaust side of the piston, and started to melt the dome. It was REALLY hot and looks like it was really lean. But also looks like detonation (not surprising) The new owner wants to run it on pump gas so it will have to be detuned. It was setup to use a stock three piece head gasket and normal base gasket. The head was cut to the race compression. I don't remember exactly what the compression used to be but I am thinking around 180 PSI at sea level. He tested it when he got it and said it pumped 160 which seems low.

Anyway, I think it will likely need a thicker base gasket or thicker head gasket. Not sure if there is a specific squish gap to set it to or not. What is a good reliable compression to aim for? And what is the best way to get there? It does not need more port timing so a thick base gasket is not a great way to go, but I am not sure about thicker head gaskets either.

Also, he does not have a local shop that he works with to fit the piston. For Seadoos, people use Full Bore for rebuilding, but is there a suggested shop for 25 year old race motors? LoL.

I would like to help him out with some information if possible. Thanks for your brain cells. All of mine are failing me.

Here is the piston. It was way lean. Not sure what jetting he has in it. It is a 38 Mikuni flat slide that is bored.

Rather than trying to detune the motor (( Internal Combustion Engine ? )), it seems like the easiest way to overcome this situation would be to just run av fuel. I went through 5 pistons with break in done on two of them running race fuel. Those two lasted longer than the other two running on 93 which melted within minutes of easy break in driving after completing heat cycles. Piston number 5 is still runnning strong on the 5th tank of av fuel and the really amazing thing is how easily it starts now. Sits for over a week and with no choke or throttle, starts and idles within the first few turns. While av fuel is more expensive than 93, it’s cheaper than race fuel (and as effective) and much cheaper than another rebuild.
Also note that while there may still be jetting issues to work out, at least you can remove the factor of $h!tty gas.
Anyone else (Can Oddy ) want to chime in on this?

Good luck!

Well that looks like a very clear case of detonation to me.
I have a piston collection of my own as proof.
We have been down this road many times on this site. No sense to bring up old wounds.

I think max compression for pump gas is 165 ish.

But there is another consideration here. An oddy type machine has the Engine behind the seat so cooling is an issue if the Engine is not liquid cooled. That elevated Engine temp makes a big difference to detonation.
I second dipnadactyl comment on the Avgas. I run it too, and it solved my piston melting issues.
If this guy don't want to run Avgas or race gas because of the money then I think the best solution is to get another stock oddy Engine from a member here. Your old Engine was mod-ed to the max probably, and by the time he figures it out he will have melted several pistons and probably destroy a very nice high mod Engine. I say this because it requires some Engine math and Engine skills. How does he know how much squish he is suppose to have will all of the other mods ?? Base gasket change is out of the question in my opinion because it will change port timing -- No ??
I hope he don't fkup a nice Engine that has history because he is cheap.
Cheapest solution is Avgas.
Permanent solution is another stock Engine.
Amen.

Here are some old posts and good reading:
viewtopic.php?f=1&t=13570&hilit=max+compression+on+pump+gas
another one (sick read - horror novel): viewtopic.php?t=17367

For a moment there I lost my mind. But I found it again.
The best solution here is to send that Engine to me and I will trade him for one of my spares, pic below.
Please note the liquid cooled head and cylinder made by "Northern Skillbilly".

Haha! Yes, that second one is quite a novel and a horror story to boot! Seems like a real shame for another person to waste as much time and money as either of us already has (and others here, I’m sure) when the clear and easy fix is on these pages...

Army's don't learn from other army's. They have to learn by them selves.

His squish band shouldn't be any smaller than around .050". The stock squish band is around .120"!

Compression shouldn't be any higher than 160psi. I Modified one of the Nature's Recipe Stadium Lite engines for Ridindirty and we wound up installing a thicker base basket.

Rand

Thanks for the comments. This thing was built as a 10500 RPM short course screamer. Fat Bill's pipe, and high stall speed. Not the best starting spot as a play motor (( Internal Combustion Engine ? )). As you have said, a thicker base gasket is not a great solution since the exhaust ports is so high already. Honestly on this motor (( Internal Combustion Engine ? )) as designed, it won't live on AV gas. It needs 104 or better. I think it was already hurt when he pumped it at 160. I think I will suggest a thicker head gasket and then the use of AV gas. I think he said he could get it. I doubt he is up to testing squish but I will ask. Is there a source for thicker head gaskets?

I expect swapping motors is off the table. Too bad these things were not stock water cooled so he could just drop on a stock barrel and head. But stock ported Leckich water cooled barrels and heads are a little rare........... Maybe I just have him run it at 7000 feet above sea level and that will drop the compression ;) Lol.

Thinking about it, maybe a little thicker on the base and on the head gasket as well. Sources for thick gaskets?

Sorry I don't know.
I make my own out of copper shim stock I bought.
Maybe several stock metal gaskets with red high temp silicon for sure sealing ??

Anyone else with an idea on gaskets ??

Try Copper Gaskets Unlimited.

That's who made the spacer for Ridindirty's Ody. Do you know what thickness he is needing for the base gasket? I have one here that is quite thick that can be milled down.

Rand

Is there a good source for the head gaskets? Are the three piece ones available? I see rebuild kits that have a composite/metal gasket, but I know we used to use the three piece gasket. Would it be a horrible idea to stack two head gaskets of either style? Worried about detonation from hot spots. What about base gaskets? Stacking them would be easiest so he can assemble, check compression, and add more if he needs to adjust the compression. If I had the motor (( Internal Combustion Engine ? )), it would be easier, but I just want to help him with a more or less simple solution.

Copper Gaskets Unlimited will make any thickness of base gasket you request.

I would check and see if they can scan a head gasket and make them to his specifications.

Rand

I know I used one thin layer of gasket to bump my compression doing one of my 350 builds. I peeled it from the layered base gasket I had, I think it had 3 layers in total, prior to me peeling.
Might keep laying base gasket until compression drops then test drive, if it still runs and pulls hard order what you need (one thick gasket) as Rand suggested. At least then you know what to order. Side note, if it doesn't pull but does run well clutching can/might be massaged to bring it back/lessen the performance loss.
Too bad he can't run race fuel. That is a piece of history not many of us will ever get to experience.
Regards

Hey Rand- Thanks for all the information. Do you have any idea of how thick you used on the Natures Recipe motor (( Internal Combustion Engine ? ))? I just realized the way the Leckich head is that the oring for the water wont seal if you go with a thick head gasket. So kind of stuck with doing the base. Just not sure where to have him start. Without head chamber CC numbers I have no clue besides trial and error.

Does anyone know a stock FL350 chamber volume?

Here is the head. Got beat up pretty bad with the failure. I told him to smooth it out with a dremel so there will not be hot spots. And it will add a few cc's to the chamber. I found that a stock FL350 head is 36CC, but is flat. And this one protrudes into the head gasket. So that makes it harder to compare. I guess that is how Jerry Leckich got the higher compression.

Don,

He's gong to have to do a squish band check in order to find how much base gasket he is going to need. I want to say the gasket I wound up using was around .050" but I can remember for sure. I believe the one I have hanging in the garage is around .090".

Rand

I will see what he can do. Good news is that I talked to the copper gasket guy (nice guy) and he will make what ever he wants for a base gasket for around $20-25. Seems like a good price for a custom gasket. Is there a standard squish test for one of these? I know how to do it on a Seadoo... Ill search the forum. I also may be able to back calculate it in.

I simply use a piece of soft solder laid on top of the piston, long enough to get to the outside of the cylinder walls where the squish band is the narrowest. I then slowly rotate the Engine one full revolution.

If you have to you can twist several pieces solder together to make a thicker solder wire.

PS, make sure you lay the solder sideways across the top of the piston parallel with the wrist pin.

Rand

OK, probably gonna get myself in trouble for saying this but here goes:

Seems like an awful lot of thought is going into trying to detune a very modified buggy (and a very cool piece of history) that someone has already spent a lot of money to bring back to original spec, just to be able to run it on cheap gas. As stated above, original spec had it running on race fuel. It just seems that if you put that much time and effort into bringing a classic race buggy back, the last thing you should be concerned about is spending the extra dough for good fuel. Really not trying to be argumentative and please give me a verbal reprimand if I am missing something or out of line. It just seems like the potential for another meltdown and possibly very expensive additional repairs to really hard to find parts are being risked instead of upgrading the gas. That thing is a classic and it deserves to be treated to the finer things in life. Like race gas/av fuel.

Edit: and yes, this is coming from the guy who refused to run better gas until he got to the 5th piston. Big Dummy, I am.

Not everyone can afford to run race gas. At 10 bucks a gallon I for one can't.

This Engine can be simply de-tuned to run on regular pump gas with no issues. Ridindirty's Ody Engine was a race Engine and it runs very strong de-tuned on 91 octane with 10% ethanol pump gas. You just need to know what modifications were made to the top end to correct them.

Proper jetting is everything for 2 stroke Engine longevity. Remember spark plugs are cheap! Top ends aren't.

Rand

Looking again at the picture of the piston and that head I see things that are off.
The piston shows clear signs of detonation to me, but most intriguing is that the top ring is not there. Did he remove it before the pic was taken or did it break up ??
I ask this because looking at the pic of the head I see signs that are not caused by detonation in my opinion. Those elongated strikes look like broken ring strikes because they're all the same dimension and size it appears.
So if the ring from this piston is still intact then I say this damage was caused by a previous explosion.
Just my opinion.

Rand- Thanks that is the same squish test we use on the Seadoos. I'll have him put it together and check that out.

CO- Good input. The top ring is there, just hard to see. But looking at it, I think the head damage is old from a previous disaster. Looking at this I think it is my backup motor (( Internal Combustion Engine ? )). At one time the thing broke the top ring locating pin out of a piston so we tried to fix it by pinning it from the top. But then that pin got loose and beat up the head. This thing has a huge exhaust port.... Who knows. Many years ago lol. Back in the day I was racing every other week (sometimes back to back weekends in far away cities) and we fired what ever we thought would live for another race into the car. I am convinced that this issue is pure detonation and lean jetting. I think we can get it to live by getting the compression down and some conservative jetting. I used to run an EGT probe. Not sure what happened to it, but it is not on the car now.

Dip- your input is also good. I totally understand your opinion. When I was ending my racing, I knew the car would be hard to sell since it was a race car and not a play car. It living out its life as a play car did not make sense, but racing was sputtering around SoCal. That is why I did not sell it. I knew the motor (( Internal Combustion Engine ? )) would not live as a trail putter, or even a fire road cruiser. Detuning it makes sense. Still not sure of the longevity of everything after he does it. Not sure if you ever have sat in one of these with a max ported motor (( Internal Combustion Engine ? )). The power is crazy for a 360 motor (( Internal Combustion Engine ? )). It is built to rev to ~10500 RPM and that is a lot for that sized cylinder. 10 minute blasts are fine, but hour long cruises may be an issue. My desert car motors were good, but not as hot as my short track motors. But bottom line is that it is not my car any more. He did an amazing job bringing her back to life. And he deserves to play with her. I will suggest that he stay off the fire roads and build/find a fun track to play on. This is not a Glamis sand toy. But it was built to drive and not sit in a museum. All of this makes me sad that it is not mine anymore. Those were some amazing days....

Quote: "Dip- your input is also good. I totally understand your opinion. When I was ending my racing, I knew the car would be hard to sell since it was a race car and not a play car. It living out its life as a play car did not make sense, but racing was sputtering around SoCal. That is why I did not sell it. I knew the motor (( Internal Combustion Engine ? )) (( Internal Combustion Engine ? )) would not live as a trail putter, or even a fire road cruiser. Detuning it makes sense. Still not sure of the longevity of everything after he does it. Not sure if you ever have sat in one of these with a max ported motor (( Internal Combustion Engine ? )) (( Internal Combustion Engine ? )). The power is crazy for a 360 motor (( Internal Combustion Engine ? )) (( Internal Combustion Engine ? )). It is built to rev to ~10500 RPM and that is a lot for that sized cylinder. 10 minute blasts are fine, but hour long cruises may be an issue. My desert car motors were good, but not as hot as my short track motors. But bottom line is that it is not my car any more. He did an amazing job bringing her back to life. And he deserves to play with her. I will suggest that he stay off the fire roads and build/find a fun track to play on. This is not a Glamis sand toy. But it was built to drive and not sit in a museum. All of this makes me sad that it is not mine anymore. Those were some amazing days...."

Don, i definitely see your (and the new owners) point as well. He bought a race buggy for the cool factor - which BTW, it has a lot of - and it looks like he did a fantastic job of restoring it. Hopefully, the detune will get it to where he can enjoy it! And no, i have never been in one of these and can only imagine - my pilot with the power turned up to 10. It would be a recipe for disaster with my track record!

Good luck!