bigdaddy69 Posted June 17, 2008 Report Share Posted June 17, 2008 Hey guys I need help with my buddys bike. He has stock cylinders 100 over coolhead 19cc domes t5 pipes +4 timing vf2's and the trinity 2 into 1 with a 33 pwk at around 3000 ft temp is 80-100. If it helps any, right now we have a 190 main and a 78 pilot clip on the needle is all the way up airscrew is at 1.5 turns. He just bought the cool head, when he went to put in on took the stocker off and one piston was all pitted up. so he went ahead and replaced pistons and put the cool head on. Now at mid to high rpm it will backfire out the left cylinder. Need help quick he is goin to LS on thursday. Quote Link to comment Share on other sites More sharing options...
SAVAGE420 Posted June 17, 2008 Report Share Posted June 17, 2008 MOFO thats sounds lean as all hell. +100 i dont know about that man..you sure! Quote Link to comment Share on other sites More sharing options...
bigdaddy69 Posted June 17, 2008 Author Report Share Posted June 17, 2008 lol Im not sure at all thats why we are seeking help. with the stock head it ran forever and damn good with that jetting. Until he went to put the coolhead on and found the pitted up piston and dome in the stock head. I went over there ran it for awhile in the shop and it does backfire I pull the plugs and couldnt tell much from the color because they had maybe 10 minutes on them but they looked a little bit wet. He told me tonight they they threw in a 195 main and it seemed worse. So at this point i am lost. keep the info coming please, we have to get this thing fixed. Quote Link to comment Share on other sites More sharing options...
slc_hillshooter Posted June 17, 2008 Report Share Posted June 17, 2008 if you didn't then put new plugs in it. The reeds were fine right? Quote Link to comment Share on other sites More sharing options...
SAVAGE420 Posted June 17, 2008 Report Share Posted June 17, 2008 Huck the stock head on there and see what happends...mabey your getting pre detonation running that small of dome at your alt! Worth a try! :thumbsup: Quote Link to comment Share on other sites More sharing options...
slc_hillshooter Posted June 17, 2008 Report Share Posted June 17, 2008 Huck the stock head on there and see what happends...mabey your getting pre detonation running that small of dome at your alt! Worth a try! :thumbsup: thats a great point 19cc at 3000 feet could need race gas. Back the timing back to zero and see if it clears up the pop. Quote Link to comment Share on other sites More sharing options...
bigdaddy69 Posted June 17, 2008 Author Report Share Posted June 17, 2008 I was sctually thinkin about putting the timing back to zero so we will try that. as far as the stock head goes we threw that shit in the trash, most everyone in our area runs 19cc domes so it shoudlnt be a problem but we will do a compression check just to make sure. oh and the reeds are fine actually he just replaced the petals on them. Anyone have any pointers on the jetting? does the 190 main 78pilot sound anywhere close? Quote Link to comment Share on other sites More sharing options...
Erwin8r Posted June 17, 2008 Report Share Posted June 17, 2008 I was sctually thinkin about putting the timing back to zero so we will try that. as far as the stock head goes we threw that shit in the trash, most everyone in our area runs 19cc domes so it shoudlnt be a problem but we will do a compression check just to make sure. oh and the reeds are fine actually he just replaced the petals on them. Anyone have any pointers on the jetting? does the 190 main 78pilot sound anywhere close? Everyone I asked that knew has told me that 20cc domes require 50/50 mix (race/pump) most of the time, and 19cc domes definitely require race gas. I would start there as that is the "new" variable you introduced. Backing off the timing is addressing a symptom, not the problem... Quote Link to comment Share on other sites More sharing options...
Snopczynski Posted June 18, 2008 Report Share Posted June 18, 2008 19cc domes at 3,000 feet will make less compression than at sea level. 19cc at 3k is like 158 psi compression on a stock bore, stock port bike.You cant gauge octane off dome size, its got to be gauged off squish and compression actuals. Your pilot jet is way to huge, you never said what needle is in it, I would think that main at 3,000 ft would be too rich. Did you try swapping the plug wires side to side to see if the problem changed cylinders? Exhaust port height will also change the compression reading. Quote Link to comment Share on other sites More sharing options...
bigdaddy69 Posted June 18, 2008 Author Report Share Posted June 18, 2008 They pulled the head tonight, they didnt realize when they put it together but aparently whoever they bought the pistons from accidentally sent blaster pistons so that should be our problem on the backfire right there. As far as the domes go I agree with you 100% snop that is almost exact to the compression I had on my last motor here with 19cc domes. I figured the pilot was too big you can tell that from the slight bog on the bottom and the needle is either CEL of CGL I didnt pay close attention to that the other day when I messed with it. We really need to do a plug chop on this thing. In the meantime please let me know what jets you suggest. Quote Link to comment Share on other sites More sharing options...
Snopczynski Posted June 18, 2008 Report Share Posted June 18, 2008 Where they both blaster pistons? That needle is a twin carb needle, sounds way too lean. Needle selection for that is tough because of the elevation. I would think it would run like shit with a c series needle all the way lean in it. I would have probably tried a dek or a del needle in center clip. 40 pilot jet, 180-190 main and airscrew 1.5 turns out. You basically dial in main, then needle, then when its warm, adjust the airscrew for best idle quality and sound. Quote Link to comment Share on other sites More sharing options...
bigdaddy69 Posted June 19, 2008 Author Report Share Posted June 19, 2008 Are you serious about the pilot? I have no clue on this 2 into1 setup but that seems small to me. With dual 33 pwk's on my FAST dune ported motor I had 42 pilots. We will try a different pilot and get back to you. I appreciate the help. Quote Link to comment Share on other sites More sharing options...
Snopczynski Posted June 19, 2008 Report Share Posted June 19, 2008 I put a 40 pilot in a 4mill dune port motor at sea level on memorial day weekend. Quote Link to comment Share on other sites More sharing options...
sredish Posted June 20, 2008 Report Share Posted June 20, 2008 I ran a 45 at sea level on my 2-1 setup. yea, a DEK needle should work well. has a compression test been done on this motor after the install? +4 timing is pretty mild, although if your at the race gas line and running pump, it could be just enough to make the difference. get a compression check first and get ahold of carbparts.com for a needle. I'd also say hold on to the 190 until you make the needle change. don't want to be making a lot of changes at one time, otherwise you won't know what caused what. Quote Link to comment Share on other sites More sharing options...
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