stang007 Posted January 29, 2011 Report Share Posted January 29, 2011 I'm having a problem with the plug backing out of my left cylinder only...it's done it 3 times now and happens after about 20-40 minutes of riding. I run my timing at +7, have 20 cc domes, and run straight 110 octane at 32:1. Ive run this same setup for 3 dune trips now and 2 seasons and never had an issue, but took it out the first time this year and it happened at the end of my first ride. At that time, I also noticed some extra oil build up on the right exhaust pipe and so I took the motor out and split the cases to replace the crank seal...that problem solved. I leakdown tested it and it held all 6psi for the 6 minutes. When putting it back together, I bought a fresh 4 mil cheetah cylinder and pistons as well as 19 cc domes this time. I also turned the timing down to +5 degrees. I've been breaking it in the last couple of days and tonight it popped out of the cylinder twice...again only on the left side, again after about 20-40 minutes of vigorous riding. The bike is running super strong and I'd say the jetting is pretty much spot on by looking at the plugs and just listening to the bike through different phases of riding it.. I can't hear any detonation whatsoever. Both carbs are adjusted identically and so I am baffled. I know people say that plugs typically back out because of detonation or preignition or even running lean...but on one side only? Oh, and yes I am tightening them correctly. Any suggestions or tips would be greatly appreciated... Quote Link to comment Share on other sites More sharing options...
jbooker82 Posted January 29, 2011 Report Share Posted January 29, 2011 I'm having a problem with the plug backing out of my left cylinder only...it's done it 3 times now and happens after about 20-40 minutes of riding. I run my timing at +7, have 20 cc domes, and run straight 110 octane at 32:1. Ive run this same setup for 3 dune trips now and 2 seasons and never had an issue, but took it out the first time this year and it happened at the end of my first ride. At that time, I also noticed some extra oil build up on the right exhaust pipe and so I took the motor out and split the cases to replace the crank seal...that problem solved. I leakdown tested it and it held all 6psi for the 6 minutes. When putting it back together, I bought a fresh 4 mil cheetah cylinder and pistons as well as 19 cc domes this time. I also turned the timing down to +5 degrees. I've been breaking it in the last couple of days and tonight it popped out of the cylinder twice...again only on the left side, again after about 20-40 minutes of vigorous riding. The bike is running super strong and I'd say the jetting is pretty much spot on by looking at the plugs and just listening to the bike through different phases of riding it.. I can't hear any detonation whatsoever. Both carbs are adjusted identically and so I am baffled. I know people say that plugs typically back out because of detonation or preignition or even running lean...but on one side only? Oh, and yes I am tightening them correctly. Any suggestions or tips would be greatly appreciated... What is the squish clearance? Quote Link to comment Share on other sites More sharing options...
BluBanshee98 Posted January 29, 2011 Report Share Posted January 29, 2011 I had one cylinder that also did this. Leaned it out and trashed the piston first ride after I built my first stock cylinder 4 mil. It squished on the money but who knows. How fresh is your gas? I would either back your timing off or go to some bigger domes. I doubt you will hear detonation over a screaming banshee. It might not be detonating horribly but with heat and expansion over your 45 mins of riding seems like what I had if I remember correctly. Quote Link to comment Share on other sites More sharing options...
dajogejr Posted January 29, 2011 Report Share Posted January 29, 2011 Take off the carbs and exhaust and do a leak down test on it. Quote Link to comment Share on other sites More sharing options...
stang007 Posted January 29, 2011 Author Report Share Posted January 29, 2011 I leakdown tested it after building it earlier this week and it held the full 6psi for 6 minutes and the gas I'm using is fresh as well. I didn't check my squish...will have to do that, just assumed since it worked before that it would work now since all the parts are the same except for the domes and I wouldnt be going through this.will try turning the timing down to +3 and go for a ride and see what happens. Quote Link to comment Share on other sites More sharing options...
gotta_goatsfast Posted January 29, 2011 Report Share Posted January 29, 2011 I leakdown tested it after building it earlier this week and it held the full 6psi for 6 minutes and the gas I'm using is fresh as well. I didn't check my squish...will have to do that, just assumed since it worked before that it would work now since all the parts are the same except for the domes and I wouldnt be going through this.will try turning the timing down to +3 and go for a ride and see what happens. Checking for squish clearance involves measuring the distance between piston at TDC and the dome, I'd say changing a dome should warrant a quick squish band test. Quote Link to comment Share on other sites More sharing options...
BigRed350x Posted January 29, 2011 Report Share Posted January 29, 2011 Check your stator side crank seal. If the little spring gets loose or comes off it will do stuff like you're describing. I'd do like daj suggested and do a leak-down test. You can also spray carb cleaner around the crank seal, and gasket surfaces and head while its idling... if the engine bogs or dies, you have a leak in that area. A leak-down test & check your domes would be where I would start. Also clean your carbs. If you have a jet getting plugged up it can lean you out a little up on top and cause detonation. - Jared Quote Link to comment Share on other sites More sharing options...
WINDYCITYJOHN400 Posted January 30, 2011 Report Share Posted January 30, 2011 Cheetah or Cheetah Cub? If it's a full Cheetah your problem is your domes. Nothing in life is ever perfectly balanced, so one plug is going to back out first. (You ever burn out both headlights at the same time? No.) So when detonation kicks in the weekest link in the set-up is the plug. Just be glad your not blowing O-rings. You might have less packing in one pipe or the other, crank could be out of phase, carbs pulling different, one filter cleaner than the other.....either way, the backing of a plug means "Stop riding till you figure it out before something very pricey happens." Quote Link to comment Share on other sites More sharing options...
sleeper06 Posted January 30, 2011 Report Share Posted January 30, 2011 Well put i have seen many variables come into play,all seem coinsidental.Did you check the crank for trueness ,and did you put the rite domes in for the blaster pistons Quote Link to comment Share on other sites More sharing options...
tedd1 Posted January 31, 2011 Report Share Posted January 31, 2011 ...did you put the rite domes in for the blaster pistons x2, 19cc domes seem small for blaster pistons? Quote Link to comment Share on other sites More sharing options...
J-Madd Posted January 31, 2011 Report Share Posted January 31, 2011 x2, 19cc domes seem small for blaster pistons? For gas for sure. Unless it's 5000 ft asl. Quote Link to comment Share on other sites More sharing options...
WINDYCITYJOHN400 Posted February 1, 2011 Report Share Posted February 1, 2011 He said it was a cheetah cylinder.....still need to know if we're talking "Cheetah" or "Cub". Quote Link to comment Share on other sites More sharing options...
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