HELP¡¡¡¡ DASA 16 mm

[meucarango]

But what fuel are you using?
__________________
98 oc

 

[meucarango]

http://www.jetskilaplata.com.ar/
this is where I compete in Argentina

 

[SUPERTUNE]

CC the engine combustion chamber to figure the mechanical compression ratio and check to find out if your too high for pump fuel AND the Powerfactor dry pipe. Don't go over 14:1 compression ratio for a baseline until you have this problem fixed.
Go up with the jetting in the carbs, and set to 4500 start retard with the MSD-TL.
Go up to a higher octane fuel or AV gas fuel!

P.S. I'm sure the lower part of the exhaust port has to be higher than the piston top @ TDC because of the 16mm stroker crankshaft with using the cr500 piston, the piston skirt would uncover the exhaust port @TDC into the engine if you lowered the exhaust port anymore.

This picture shows to much piston heat to me and WILL cause this problem when using the Powerfactor dry pipe.

 

[meucarango]

comprecion is the ratio of 14:1 (38cc dome 534cc)

 

[wsuwrhr]

comprecion is the ratio of 14:1 (38cc dome 534cc)

If you have 38 domes in that bad boy, I think you are already too high for pump gas.

I thought you typed your cranking compression was 180 PSI(which could still high for certain pump gas setups)

You need some 41-42's if you aren't running racegas/110 oc.

Brian

 

[meucarango]

38cc dome I have 180 psi
42cc domes with respect to psi (160 150 140 ?????)

 

[waxhead]

you could be right there chucky
its hard to tell from the pics and something i seem to be doing is sending me blind

Personally I think this engine needs to be sent home so they can look at it correctly and not in fuzzy pics on the internet

 

[SUPERTUNE]

comprecion is the ratio of 14:1 (38cc dome 534cc)

NO, That is not correct!
90mm bore X 84mm stroke = 534.8cc CORRECT
534cc + 38cc divided by 38cc = 15.0:1 ratio
Here is also where you could be wrong again, normally the combustion chamber cc's are smaller with a domed piston protruding into the combustion chamber and this would make your fill volume even smaller yet!! This would then easily get you up to race gas compression ratio's.

Who said this engine was a pump gas compression and NOT to use racing fuel?
I can clearly see now as to why your having problems...

 

[wsuwrhr]

38cc dome I have 180 psi
42cc domes with respect to psi (160 150 140 ?????)

Yes, probably 160, safer for a pump-gas tuneup.

Something mechanical sure seems wrong to bend the rings upward though.

Brian

 

[SUPERTUNE]

you could be right there chucky
its hard to tell from the pics and something i seem to be doing is sending me blind

Personally I think this engine needs to be sent home so they can look at it correctly and not in fuzzy pics on the internet

I know the reasons why this happens to these engines...been there done that.

 

[SUPERTUNE]

These are some of the issues that are your problem...if the squish is correct, rave valve has to proper clearance, and exhaust port is chamferd enough for the rings not to catch the port.
Compression ratio could be to high, too much timing, not high enough octane fuel, add 1/2 cooling lines, with extra piston clearance.
Carbs are too small and also could be to lean, pump not setup correctly to match engine setup.
This is a common problem when engine is not setup right.

I made mention to look at these issues way back at post #43

 

[waxhead]

I know the reasons why this happens to these engines...been there done that.

I dont doubt it Chucky

 

[meucarango]

domes that came with the 44cc engine are
up with the pistons are 38cc

 

[meucarango]

I understand when the relationship of the pistons comprecion is high overheat and deteriorate by the intense heat
my pistons none are reheated
is a mechanical problem

 

[ATS_Aaron]

They look like the pistons from Scott's failure last year. He had too much compression on too low of octane. Try larger domes or higher octane fuel for the next 5 pistons.

 

[meucarango]

the last four pistons in use with gasoline 98oc + octaneboost
same piston destruction

 

[ATS_Aaron]

Octane boost is a joke. Get real race gas or lower compression. Non-US markets don't use the R+M /2 formula for octane. In other words your 98 octane may not be as good as our 93 octane.

 

[Idok]

http://www.vpracingfuels.com/

 

[Lucaumpits]

U might try Red Bull,

the last four pistons in use with gasoline 98oc + octaneboost
same piston destruction

 

[geraban19]

U might try Red Bull,

It will give U wings for sure.