Scuffed original stock piston after pipe,head airfilter, clutch mods.
Replaced with wiseco 20 over , ran 1 1/2 tanks
of gas and scuffed it on Sunday.

Clearance was set at 3k ,dealer thinks this may be too little. Another customer replaced his stock piston with wiseco (xplr400) at same time and he is in the shop with same problemafter three tanks of fuel. Dealer checked with hotseat mechanic and he says clearance should be 5k anything less and piston gets too tight.
Iam well aware of cold seizure problems and warm engine thoroughly before riding and giving it hell. Engine wasn,t lean,in fact on rich side.
Running 30 pilot and 280 main stock carb @600ft asl.just to be safe.
Need to know proper clearance and any other info
to make this setup work.Still a novice at this but learning more all the time ,appreciate any expert input from this excellent forum.

 

Personally, I'd use JE or Arias. Wiseco isn't in the same league!

 

Wiseco says .003 so whats a guy suppose to do?
You didn't mention if you pre mixed the first couple of tanks or so. If not you should have. That may contribute to your problem as well as giving a new piston "hell". Take it easy for a while.

 

Thanks for the replies guy
DieselPro,I've never heard of JE or ARIAS.Do they have web sites or other means of contacting them.

ChopperBill, Dealer disconnected oil injection and I went to premix 20:1 first tank of fuel and ran real easy. Next tank 40:1 quit half way through only wot for few seconds as I was riding in trails then ran country road 1/2 to 3/4 throttle when quit.
Your right whats aguy to do? HSP claims they have seen this problem before and as stated 5k is real min clearance.(according to dealer).Iam torn as to which direction to take from here. Go back to stock piston,go to 5k clearance , change to other brand of piston?Breakin easier?
At wits end any ideas considered.
Thanks again.

 

JE and Arias are the real players. They don't deal with consumers. Powroll uses them, but specializes in 4 stroke Yam/Honda. I'm sure someone is using Arias or JE.

Why did you unhook the injection?

Sure you aren't just jetted too lean? Overbore raises compression even with same deck height/piston top.

 

DieselPro,I am definately not too lean,first scuff when pulled plug it was a nice tan color.
Second scuff pulled plug light black with richer jets.
Unhooked injection and went to premix to eliminate injection failure as cause of piston failure. I understand this is a common practice when modifying stock engines.

Thanks

 

I had a 96 400 with very similar mods. Lost the piston (wiseco .003 clearance) on second tank. Sent everything to RCR. He rebored it, bored my carb and I never looked back. I also premix, HPD pipe, Helix, billet head, delta reeds....Send Rick Ritter an e-mail, I believe he set mine up at .003, but I'm pretty sure he measured the piston someplace different than my local machine shop. His website can be linked from www.atving.com under the dealers section.

 

Good point on the measuring point. ALSO, a guy needs to measure clearances cold, not immediately after honing, or you'll end up small!