registered user Posted April 17, 2017 Report Share Posted April 17, 2017 if the piston isnt almost kissing the head then its probly to big. another thing that can really cause problems is stinger diam to small. ive burned the bottom of a few pistons from it. when benol scorches to the underside u know shits getting hot Quote Link to comment Share on other sites More sharing options...
J-Madd Posted April 17, 2017 Report Share Posted April 17, 2017 if the piston isnt almost kissing the head then its probly to big. another thing that can really cause problems is stinger diam to small. ive burned the bottom of a few pistons from it. when benol scorches to the underside u know shits getting hotWell I ask that because the theory makes sense. Also, I sold a good 421 top end to a guy that for some reason now has a pretty high squish clearance (0.058", I think) and now he's backing out plugs left and right. It had a tighter clearance when I had it due to different dome and/or base gasket. I've heard of/seen where too little clearance leads to deto due to increased MSV, but not to much on a high clearance causing issues. Sent from my STV100-1 using Tapatalk Quote Link to comment Share on other sites More sharing options...
registered user Posted April 17, 2017 Report Share Posted April 17, 2017 its hard to say man but .058 seems awfully large for any engine. im using far less on my 500cc single fwiw. a wiseman once said that if theres no fuel left in the squish band then theres nothing to detonate so take that for what its worth. what does his piston top look like ? as you probly know, theres a long list of things that can cause combustion problems. does he know any other variables besides the gap is .058 ? maybe hes got a converging band. send it off to a shop for a thorough inspection 1 Quote Link to comment Share on other sites More sharing options...
J-Madd Posted April 18, 2017 Report Share Posted April 18, 2017 its hard to say man but .058 seems awfully large for any engine. im using far less on my 500cc single fwiw. a wiseman once said that if theres no fuel left in the squish band then theres nothing to detonate so take that for what its worth. what does his piston top look like ? as you probly know, theres a long list of things that can cause combustion problems. does he know any other variables besides the gap is .058 ? maybe hes got a converging band. send it off to a shop for a thorough inspectionI know where he got the domes and they should be right, but I haven't seen them. I've guided him the best I can with the information given to me. He said he had a small air leak on 1 intake, but it's backing both plugs out. I told him any air leak is bad, but both sides shouldn't suffer... Sent from my STV100-1 using Tapatalk Quote Link to comment Share on other sites More sharing options...
registered user Posted April 18, 2017 Report Share Posted April 18, 2017 nothing against your buddy but that's what can happen when a good running engine exchanges hands. parts get swapped and it goes down hill from there. reinstall the same gaskets and domes as when you had it , seems to be the easiest fix 2 Quote Link to comment Share on other sites More sharing options...
registered user Posted April 19, 2017 Report Share Posted April 19, 2017 had a Honda while back and stacked two .020 base gaskets then did the port and head work based off that. sold the bike and forgot to tell the guy about the little stuff I did to it. hope he figures it out when he decides to rebuild it. dumd shit like that can make quit a difference if its not put back together how it was before 1 Quote Link to comment Share on other sites More sharing options...
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