detonation with 110?

[Elkwagn]

So I took the sled out for a maiden voyage and it worked good for a while, then it just flat quit. After it cooled for a few it fired right up and ran fine for about another mile and shut down again. Got it home and tore it apart, and one piston looks like it had a sandblaster just eating it away, but the other one is still perfect? Why would only one look like that? The engine is about 18:1, and I was running 110 purple, but maybe not enough. Time to de-tune this unit I think. Gets expensive at $9 a gallon especially when I used five gallons to put on about 15 miles!

 

[sledsrock]

So I took the sled out for a maiden voyage and it worked good for a while, then it just flat quit. After it cooled for a few it fired right up and ran fine for about another mile and shut down again. Got it home and tore it apart, and one piston looks like it had a sandblaster just eating it away, but the other one is still perfect? Why would only one look like that? The engine is about 18:1, and I was running 110 purple, but maybe not enough. Time to de-tune this unit I think. Gets expensive at $9 a gallon especially when I used five gallons to put on about 15 miles!

18:1 with 110?

 

[mastertech]

18:1 Holy hell.. And I thought I was at the breaking point.

I think you need to do some more figuring on your sled set up!

 

[zx800x]

Really doubt you are at 18.1 at that compression you dont need spark plugs maybe you should be running it on "DIESEL"

 

[Elkwagn]

It is seriously at 18:1, Custom cheater head with domes, done by SLP. Massively ported cylinders, no dpm, custom computer tune by Skidoo raceshop, SLP twin pipes etc., etc. Looks like i will be replacing pistons, different head, re-map the computer, single SLP pipe, re-do carbs. Still dont get why only one piston went?

 

[xpspenziv]

VP FUEL --Q 16/ if it really is 18-1 is to much for 110...that much detonation!!!you probably pounded the bearings right out of that thing.What psi on comp test?is there any porcelain left of the plugs?

 

[Elkwagn]

180 psi on comp test, and plugs still look perfect

 

[PTE800]

Could be many things such as a bad crank seal , base gasket leaking , but I would definately look at the carbs. Sounds like one of them might have something in it. Also; 110 is not enough for 18:1....
One word of advice, back the compression down to around 13:1 and it'll run better. Been there and done all that high compression stuff. It just doesn't work like on 4 strokes...

 

[mastertech]

15:1 is the sweet spot on 100LL.. 18:1 C16 might not be enough!