My girfriend rides an 03 warrior, this year she decided she wanted more power so I ordered a piston and cam kit from Alba. I also installed a Yoshi pipe and a carb mount K&N and outerwear. Broke it in really easy and put maybe an hour of run time on it before we even rode it. After getting the jetting close (172.5 main and lifted the needle one notch 47.5 pilot),seemed really close. Ran fantastic for the first couple hours out at the dunes then it got a slapping noise in the top end and you could hear it coming out of the pipe as well. It only happened under heavy throttle and mid RPMs. At idle and if you loaded it slowly you could rev it out no noise. Rev it in neutral, no noise. So tonight I took it back apart and looked for something I may have done wrong, everything is assembled ok and the things I thought may be causing it have not been the case( cam chain and guides are good and the valve train shows nosign of problems ) The piston looks as though it may have been hitting the head, if you look at the outer edge it has a clean ring about half way around. this dosen't look normal to me although this is my first venture into a quad engine. Take a look at my pics, That's the 10.75:1 JE that alba sent me, is there a problem with it? opinions

pic will be up soon...

 

I have built the same engine with the same kit from alba. This noise your hearing is detonation try some 100 octane gas and make sure your not lean. I had to go up one size with the pilot jet also. Let me know what you find but I know I had to run atleast 92 and if we went to the sand where you have run harder I used race gas.

 

I almost forgot you need to check the valve lash again. This could be why your hearing it out the exhaust.

 

I origionally had it on race gas (110 K&S) but I couldn't get it to perform right so I switched back to 92 octane. If I jetted it to run good then the plug was white!! Tried to go richer and it stumbled on top.. the 92 gave the plug some color and ran good to peak rpm. problems don't start until it gets hot..

 

The valve lash for the cam had a factory spec of .006. This seemed way too noisy so I backed it down to .004, still some tick but not bad.

 

How much clearence did you give the piston? When it gets hot the valve lash may tighten up a bit and hold a valve open. We sold the bike to get the banshee but if we kept it I was gonna get a oil cooler from Four Stroke Tech.

 

I would try .006 and see if that cures the problem. I think it will.

 

I already have it apart. I'm not sure what I'm going to do. I really think when you see my pics that it looks like it may very well be hitting the head when hot. When it's cold it's good, either way piston design could be the problem. I noticed that the JE piston has some sharp ridges that back in my drag racing days would be smoothed off immediately, I am thinking that I may pull it out for a wiesco piston and try that. I need another beer[img]i/expressions/face-icon-small-sad.gif[/img]

 

I heard that JE pistons where bad about doing this. JE does not spend as much time needed to make them exact. I am not ******* JE but this is what i have heard from riders at the sands i ride at. I am running a 12:5:1 CP piston in my DS and i havent had any problems with it. CP will make any custom piston u want for a little over $200 and from what i have seen and heard this is the best way. Hope this helps you [img]i/expressions/face-icon-small-smile.gif[/img] Lance

 

It sonds like detonation to me also. I'd try some 100 if you put it back together with that piston.