wshrdskin, I was thinking that if you could locate the position of the hold in reference to the plug then you could come up with the cause of the problem (Possibly). I've built many engines for racing mostly V--8's. And I've burnt down a few from being too lean and this usually happens around the ring lands on a four stroke. Running like we do on these bikes (Right on the fine line of lean) It would usually show problems in two places. The first is the outer edge of the piston down to the first ring groove. It would almost look as if you tryed to sand blast a small groove from the top of the piston to the ring. If the condition existed and you were runnin to hot of a plug you would find the problem right under the spark plug or toward the exhaust port. Kind of like when a 2 stroke burns a whole in the piston.

There is also the thought of unaudable detonation from lack of octane. This is only detected by very sensitive electrical equip. (ei Knock sensor) like in your car. It won't even show on the plug.[img]i/expressions/face-icon-small-shocked.gif[/img]

I found the best fuel for the 2 raptor motors that I've built is 100 octane unleaded 76 racing fuel for 11:1 motors. I even use this in my 12:1 motor but am in the process of mixing it with some 110 leaded 76 to get the optimum ratio.

The plug I've ran in my 11:1 motors was one stage colder DPR9EA9. and I'm running a JR10B in my 12:1 motor which is two stages colder.

Take this for what its worth and if it makes sense to U. This is just my findings and my opinion and by no means am I a professional ( I can't even spell[img]i/expressions/face-icon-small-wink.gif[/img] . So use this if you can.[img]i/expressions/face-icon-small-smile.gif[/img]

 

???

Please explain. Haven't heard this.

 

How does it not show on the plug, at all??? If you are burning a hole in your piston you should be able to see some aluminum flecs on the plug......right?????



Good post BTW.[img]i/expressions/face-icon-small-cool.gif[/img]
I don't think your required to spell to be a good mech.[img]i/expressions/face-icon-small-wink.gif[/img]

 

Ward, I have a friend that builds street bike motors for a living. The same guy who ported my head. He was telling me about this , he says that its only visible if you can see with a magnifing glass . And it doesn't always show on the plug but look on the stem side of the exhaust valves. It has to do with comp,timing,combustion chamber quench,spark plug heat range, and air fuel ratio. He also told me not to worry about it on my application because the fuel has good octane , the colder plug, also the fact that we didn't change the stock timing. This is why some guys get there bikes on a dyno with a A/F meter for the most power the jet up one size for safty and temp changes. This is probibly not 03's problem.

 

Can I just check something here. If you running an 11:1 compression you should be using 93 to 100 octane fuel? NOT 91 octane. Then the other thing. Would it help to ceramic coat the top of the piston and the inside of the head and valves? This will help keep the piston and head cooler. I know some of the v8 performance guys always ceramic coat the piston, head (combustion chamber) and sometimes even the inside of the exhaust ports to keep the heat away form the motor. The ceramic coating acts as a heat shield and it also gives more power as a result of higher combustion temperatures.

 

Bob recommends that as well. I went with the heat coating to be safe and run cooler.

 

Raptor660Fam, did you coat the piston as well as the head, valves and exhaust ports or just the piston top? Most people only do the piston. Have anyone have a picture of a flowed head. I would like to see if the also polish the inside of the combustion chamber and the valves?

 

Yes Craycraft Racing coated it all; piston and head. Sorry no pics. Hopefully I won't be going into it very soon. Been out about four times. No problems. It does fun much cooler than my dad's but I also have an oil cooler, he does not.

 

The hole is about 7/16 to 1/2 inch away from the plug right next to the center intake valve relief. He's using the stock plug heat range 8 and on previous plug checks it didn't appear to be too cold.
He was running 91 octane and by what he told me it would sometimes ping.
This all happened after alot of long runs up comp at Glamis which is what makes me think the carbs may not have enough flow. It was jetted to a tanish brown color and we went up one size from that so I'm sure that it wasn't jetted lean.

What happened? Detonation and a good chance it ran lean on the big hills

For the fix:
He may get a coated piston
A cooler plug
Higher octane fuel
Craycraft carb mods and probably a pingle dual outlet petcock

 

sixsixT, That should cover it. With those mods he should have no problems.[img]i/expressions/face-icon-small-happy.gif[/img]