Jaystre Posted September 29, 2012 Report Share Posted September 29, 2012 So here's the problem ive been having since i had the motor rebuilt . detonation on the right side , so here what is done to the bike . 4 mill ,dune port , +4 timing ,k&n pods , fmf sst pipes ,stock carbs , 350 mains ,27.5 pilot , needle middle clip , sea level ,22cc domes ,160 psi ,.035-.038 squish , leak down test is good . Ive put brand new fuel lines ,brand new plugs ,fresh gas but cant figure it out. i gotta get this bike working correctly . any input would be apreciated thx Quote Link to comment Share on other sites More sharing options...
Dicklez Posted September 29, 2012 Report Share Posted September 29, 2012 So here's the problem ive been having since i had the motor rebuilt . detonation on the right side , so here what is done to the bike . 4 mill ,dune port , +4 timing ,k&n pods , fmf sst pipes ,stock carbs , 350 mains ,27.5 pilot , needle middle clip , sea level ,22cc domes ,160 psi ,.035-.038 squish , leak down test is good . Ive put brand new fuel lines ,brand new plugs ,fresh gas but cant figure it out. i gotta get this bike working correctly . any input would be apreciated thx I would bump your octane up if your just runnin pump fuel. Or bring your comp down. Your squish seems a little on the tight side. Were your domes cut at all? Quote Link to comment Share on other sites More sharing options...
Jaystre Posted September 29, 2012 Author Report Share Posted September 29, 2012 domes were bought from same builder who did the porting ,which is a reputable builder and sponsor here on bhq . so 160 psi and pump fuel would be pretty much borderline to be running? Quote Link to comment Share on other sites More sharing options...
Dicklez Posted September 29, 2012 Report Share Posted September 29, 2012 I personally dont take any chances and run straight race fuel. At 160 i would atleast mix it 50/50. But the thing is, you never really know the quality of the pump fuel. I like to bring the squish in around .040-.050. Quote Link to comment Share on other sites More sharing options...
Jaystre Posted September 29, 2012 Author Report Share Posted September 29, 2012 Well race fuel would be a last resort because its expensive and not readily available . would a thicker base gasket be an option or would mess with port timing? or just larger domes . We have a local airport nearby maybe they would sell some avgas . Quote Link to comment Share on other sites More sharing options...
Dicklez Posted September 29, 2012 Report Share Posted September 29, 2012 Well race fuel would be a last resort because its expensive and not readily available . would a thicker base gasket be an option or would mess with port timing? or just larger domes . We have a local airport nearby maybe they would sell some avgas . Do you know where your port timings are at? I'm not really sure where a dune port actually falls in degree wise but if the builder set it up for a dune port, I wouldnt touch your base gasket. I dont wanna give you wrong info, but almost every 4mill stock cly ive been involved with, we had to cut the domes. Best bet is to talk to your builder, tell him where your at with comp and squish, and inform him of your deto issues. See what he has to say. You might be able to send him your domes, and he can hog them out alil. Quote Link to comment Share on other sites More sharing options...
Jaystre Posted September 29, 2012 Author Report Share Posted September 29, 2012 Alright thx! Quote Link to comment Share on other sites More sharing options...
possum Posted September 30, 2012 Report Share Posted September 30, 2012 whos this reputable builder? Quote Link to comment Share on other sites More sharing options...
Jaystre Posted September 30, 2012 Author Report Share Posted September 30, 2012 jeff at Farm and sand Toys. Quote Link to comment Share on other sites More sharing options...
Redline Racing Posted September 30, 2012 Report Share Posted September 30, 2012 That squish with that psi needs better octane than pump fuel. Have you talked to Jeff? Quote Link to comment Share on other sites More sharing options...
Jereme6655 Posted September 30, 2012 Report Share Posted September 30, 2012 Definitely need more than just pump.....especially if it's lower quality.... Quote Link to comment Share on other sites More sharing options...
Jaystre Posted September 30, 2012 Author Report Share Posted September 30, 2012 yes i did . Quote Link to comment Share on other sites More sharing options...
possum Posted September 30, 2012 Report Share Posted September 30, 2012 this is why its so important to understand this area on the motor. even tho u or me might not know everything. its important to understand whats going on inside these motors. i hear horror storys all day long from people whos setup is what there builder said. no knock on anyone builder. but it is our job to research and learn the numbers and specs to make a motor live. Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted October 1, 2012 Report Share Posted October 1, 2012 this is why its so important to understand this area on the motor. even tho u or me might not know everything. its important to understand whats going on inside these motors. i hear horror storys all day long from people whos setup is what there builder said. no knock on anyone builder. but it is our job to research and learn the numbers and specs to make a motor live. Agreed, so many people think that just because a builder reccomended something that it is impossible to be wrong. Thats why we need to know what we are looking at and what to check on assembly. The only absolute sure fire way for them to be flawless is to have the cases, crank & piston combo, and the cylinders in hand. Quote Link to comment Share on other sites More sharing options...
mopar1rules Posted October 1, 2012 Report Share Posted October 1, 2012 This ain't the first time i heard jeff at FAST give a setup that he said was suppose to be pump gas worthy when it really ain't. That squish is far too tight for pump gas and you can't use your comp tester to dictate what octane of fuel to run. You go off of comp ratio and not a cranking psi reading from a gauge. I had to machine 22cc domes to be in 110 octane fuel range, for my 64.5mm bore 4 mill build. There is no way unmachined 22cc domes will work on pump gas in a 4 mill build. Adding another base gasket will help the squish issue and not jack with the port timings enough to notice by seat of the pants. Quote Link to comment Share on other sites More sharing options...
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