Sands Posted September 6, 2011 Report Posted September 6, 2011 What do you think about these pictures? Could it be detonation? The right spark plug is damaged. Quote
252wheelieking Posted September 6, 2011 Report Posted September 6, 2011 Looks like detonation to me. Whats your set-up? Quote
Sands Posted September 6, 2011 Author Report Posted September 6, 2011 Looks like detonation to me. Whats your set-up? 421 Cheetah Cub, 22cc domes ( live at sea level ), PWK39 178 jetted, VForce 3, +5º timming, Shearer SBIF. Quote
252wheelieking Posted September 6, 2011 Report Posted September 6, 2011 (edited) What fuel are you using? Do a compression test to make sure your fuel has enough octane. Edited September 6, 2011 by 252wheelieking Quote
Sands Posted September 6, 2011 Author Report Posted September 6, 2011 What fuel are you using? Do a compression test to make sure your fuel has enough octane. 98 octane. I didn't measure que compression after building the engine... It it happens to you, what would you do? New domes? New pistons? Quote
Pasi S. Posted September 6, 2011 Report Posted September 6, 2011 Because you live here in Europe, I´m allmost 100% sure that your gas is not 98. Our Neste 98 is 87,2 to 87,7 MO and AKI is 93,2-> -Pasi S. Quote
Rotax Raptor Posted September 6, 2011 Report Posted September 6, 2011 Take a magnet and check to see if you have any pieces of steel embedded in the top of your damaged piston. That almost looks like something is coming from your lower end and up through your transfers. Quote
EvilBanshee Posted September 6, 2011 Report Posted September 6, 2011 Well it sure as hell aint lean! lol 22cc domes is more then enough for 98 octaine? I think it might be something eles. 91 pump fuel would do 22cc domes. Look like a piece of bearing or metal of some sort got in their and bounced around a few times. See if your rod bearing it getting loose or worn out. Quote
pabansheematt Posted September 6, 2011 Report Posted September 6, 2011 Your running it out of fuel. Thats why the spark plug broke. It's to lean. Quote
Sands Posted September 6, 2011 Author Report Posted September 6, 2011 Because you live here in Europe, I´m allmost 100% sure that your gas is not 98. Our Neste 98 is 87,2 to 87,7 MO and AKI is 93,2-> -Pasi S. In Portugal we have 95 and 98 octanes. Quote
Sands Posted September 6, 2011 Author Report Posted September 6, 2011 Take a magnet and check to see if you have any pieces of steel embedded in the top of your damaged piston. That almost looks like something is coming from your lower end and up through your transfers. OK. Tomorrow I'll do that. Thanks for the help. Quote
Sands Posted September 6, 2011 Author Report Posted September 6, 2011 Well it sure as hell aint lean! lol 22cc domes is more then enough for 98 octaine? I think it might be something eles. 91 pump fuel would do 22cc domes. Look like a piece of bearing or metal of some sort got in their and bounced around a few times. See if your rod bearing it getting loose or worn out. On both pistons? I would believe on it if it only happend on one cylinder... Quote
Sands Posted September 6, 2011 Author Report Posted September 6, 2011 Your running it out of fuel. Thats why the spark plug broke. It's to lean. Maybe... If you were me, what would you do? New pistons or just tore it a little on the top? About the domes, I will certainly buy a new set. Quote
252wheelieking Posted September 7, 2011 Report Posted September 7, 2011 I could be wrong but with 22cc domes for a 421 is suppose to be ran on race fuel. To be on the safe side, if I was you I would buy 24cc domes & run the pump gas that your getting from your local gas station. From the looks of it, it looks like your detonation from low octane. If your going to buy new domes try the 24cc domes. I dont think that your crank is shot from the looks of the piston & domes. You could pull the cylinder off & inspect the crank for piece of mind. Good Luck Quote
EvilBanshee Posted September 7, 2011 Report Posted September 7, 2011 On both pistons? I would believe on it if it only happend on one cylinder... I dont think both sides are damaged? I Think hes just talking about one side. I know what lean looks like. Judging by those plugs she is FAAAATT. Quote
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.