Pitting on piston crown
- Thread starter EricP
- Start date
roostafish
Gold Level Site Supporter
This is caused by detonation. Higher octane fuel would help, Non ethanol fuel would help. Even sending the head to RB Designs for the squish band mod, and discussing with Ron your issues would be a low cost helpful mod. Very simnply it could be that your jetting is too lean!
Detonation, or engine "ping". You made need to use higher octane fuel. Or you may be jetted a little lean. You may be able to retard the ignition timing a little too if you are already using good gas and are jetted correctly.
There really is a bunch of ways to cure it using one or a combination of all. Bikes run leaner in the summer. And as they warm up (get hot) it also causes a lean affect. Plus elevation.
The guys that are serious about how they ride jet according to elevation and temperature almost every time they go out.
I try to just take it easy when it's hot out and I'm working the bike hard. But I don't race either.
There really is a bunch of ways to cure it using one or a combination of all. Bikes run leaner in the summer. And as they warm up (get hot) it also causes a lean affect. Plus elevation.
The guys that are serious about how they ride jet according to elevation and temperature almost every time they go out.
I try to just take it easy when it's hot out and I'm working the bike hard. But I don't race either.
GMP
Active member
If it were detonation, I would think the plug would be burned white with aluminum specs fused on it. Also, its usually in the center of the piston. Do you see this? Did you notice any pinging or rattle? If not, I'll take a guess and say it ingested something, or something is coming apart in the lower end, and getting pinched in the squish band area. I've seen this from a rod bearing cage that fragmented.
It would be helpful to see the piston in question. I don't think it would be caused by a head gasket leak but stranger things have happend. Old gas that has lost some if its vapor pressure is just as harmful as low octane gas. It's kind of like splitting hairs. Best general rule of thumb is damage/ deterioration on the top of the piston is low octane/ too much ignition advance, or a chip, chisel mark or some type of irregularity that causes a hot spot. Damage on the side of the piston is from (incorrect) jetting or poor/ no oil in the gas. Let us know how things turn out.
