BigRed350x Posted November 17, 2008 Author Report Share Posted November 17, 2008 then it sounds like a jetting issue. If its not dome configuration and its not fuel supply..... any air leaks? was a leak down done? if all things check out.. then its gotta be jetting. Did you try drilling the jets bigger? I've checked for leaks many many times. Even in behind the flywheel. Also did a leakdown test on it a week or so ago and held 10lbs for 15min. I've gone from a .120 main with powerjets all the way open and it running like total shit down to .112's with no powerjet at all. Doesn't seem to matter. Still backs them out. No matter how much this happens, there is never any damage to pistons or domes. No pitting, discoloration, anything. Could it possibly be hydro-locking inside the cylinder or could vibration cause this?? I've done everything else I knwo of that will generally cure this issue with no luck. I'm not new to methanol by any means, but this one has me stumped. The bike runs hard, but has more in it if we can get past this issue. Quote Link to comment Share on other sites More sharing options...
gregrob Posted November 17, 2008 Report Share Posted November 17, 2008 Wonder if your port for the fuel pump on that left cylinder could be leaking air Jared. You've probably checked it but just something I thought about. Maybe the little piece of hose on there is cracked? We could epoxy that thing up and see if it helps... Quote Link to comment Share on other sites More sharing options...
Wildcardracing Posted November 17, 2008 Report Share Posted November 17, 2008 Calvin may have a point, it was the left cylinder backing out if I remember right. You could just use a pipe plug in it instead of the fitting. Quote Link to comment Share on other sites More sharing options...
AKheathen Posted November 17, 2008 Report Share Posted November 17, 2008 Calvin may have a point, it was the left cylinder backing out if I remember right. You could just use a pipe plug in it instead of the fitting. all this talk about meth cracks me up :yelrotflmao: maybey i'm outa my league here, but i would just try a colder plug? it may niether like the pipes and cooler temp combo on the low end and the plug might be harder to read on meth :woot: maybey 50-60 degrees is the fine line that diferentiates between changing plugs and jetting. up here, i know it's around 20-30 degrees and you almost have to run cans and switch plugs. Quote Link to comment Share on other sites More sharing options...
moneybags Posted November 17, 2008 Report Share Posted November 17, 2008 (edited) What are you gapping your plugs and pickup at? Edited November 17, 2008 by moneybags Quote Link to comment Share on other sites More sharing options...
dajogejr Posted November 17, 2008 Report Share Posted November 17, 2008 Get the right domes. What is your squish and squish band? My 10 mil backed 'em out and burned a strapped, and I had pumper carbs feeding it plenty of fuel for 300 to 500 foot dune racing. Your timing is way conservative as is your compression for a methanol motor. You should be able to run 7degrees all day, unless this is a HUGE bore and stroke motor... Been there, done that...get the correct domes. Have a shop machine you a set of alky domes...a competent shop... Quote Link to comment Share on other sites More sharing options...
BigRed350x Posted November 18, 2008 Author Report Share Posted November 18, 2008 What are you gapping your plugs and pickup at? .018" Good point calvin, I will double check that pump pickup and probably just put a threaded plug in there instead of the hose barb. - jared Quote Link to comment Share on other sites More sharing options...
BigRed350x Posted November 18, 2008 Author Report Share Posted November 18, 2008 Get the right domes. What is your squish and squish band? My 10 mil backed 'em out and burned a strapped, and I had pumper carbs feeding it plenty of fuel for 300 to 500 foot dune racing. Your timing is way conservative as is your compression for a methanol motor. You should be able to run 7degrees all day, unless this is a HUGE bore and stroke motor... Been there, done that...get the correct domes. Have a shop machine you a set of alky domes...a competent shop... I've tried two sets of domes from dave at noss machine and a set from patriot racing. 19cc and 18cc domes. I have an experimental set from dave with a really wide squish that work really well with this setup, but still back the plugs out. Then another standard 18cc 4mil domes from dave at noss and it still backs them out. When I give it a lot of timing like I would expect to run well with methanol it makes it a LOT worse. Same with the compression. I've also tried different thickness base gaskets, and had squish at .028, .035, .042, and .056. Same thing with all of them. Backs the plugs out. It doesn't burn any straps. Ever. The plugs are soaking wet every time, and no signs of detonation on the pistons or domes. I've actually never had it burn a strap since I've been messing with this top end. Its got me stumped. Quote Link to comment Share on other sites More sharing options...
dajogejr Posted November 18, 2008 Report Share Posted November 18, 2008 (edited) Try different carbs.. checked to see if the crank is out of phase? Edited November 18, 2008 by dajogejr Quote Link to comment Share on other sites More sharing options...
desertdeweller Posted November 18, 2008 Report Share Posted November 18, 2008 Anyone know what it takes to detonate meth? I had some issues at sand mountain backing plugs out on meth. Was curious what it takes compression-wise to do it. Had .116 mains and powerjets open all the way up. Had another bike with .109 mains and powerjets off and it wasn't detonating, but he had 19cc domes and I had 18's. Both 4mil bikes. This may seem weird but I have heard of people having problems with meth detonating in their exhaust from being to fat, but it was in a oval track car. You mentioned above a similar bike running leaner and running ok. And another post about the plugs being wet. you might be getting excessive fuel in your pipes causing the detonation to happpen in there. I told you it sounds weird but hot spots like carbon could be the source of ignition in the pipes. but you might try to close off your power jets like the other bike and maybe lean it out a tad. or just the powerjets first and see if it improves, seems like you covered everything else. Quote Link to comment Share on other sites More sharing options...
J-Madd Posted November 18, 2008 Report Share Posted November 18, 2008 Maybe your CDI box is fried and not retarding the timing at upper rpms. Quote Link to comment Share on other sites More sharing options...
dajogejr Posted November 18, 2008 Report Share Posted November 18, 2008 Good call Jarid.... It is always a possibility...or other weak ignition component not able to burn fuel causing it to near hydrolock and push the plug out... Quote Link to comment Share on other sites More sharing options...
BigRed350x Posted November 19, 2008 Author Report Share Posted November 19, 2008 Try different carbs.. checked to see if the crank is out of phase? I've tried three sets of carbs: 35.5 Mikuni's set up by K&T, a set of 35 PWK's and 38 air strykers both that I set up. the 35's have .116 dumps and the 38's have .118 mains. Crank is good. Checked that not too long ago. Quote Link to comment Share on other sites More sharing options...
BigRed350x Posted November 19, 2008 Author Report Share Posted November 19, 2008 Good call Jarid....It is always a possibility...or other weak ignition component not able to burn fuel causing it to near hydrolock and push the plug out... I'll nab some eletrical parts off one of my other banshees and try it out and see what happens. That CDI is pretty old. Quote Link to comment Share on other sites More sharing options...
Tim Potteiger Posted November 19, 2008 Report Share Posted November 19, 2008 I'll nab some eletrical parts off one of my other banshees and try it out and see what happens. That CDI is pretty old. CDIs are mostly bad or good, in my experience there is rarely an in between for stock CDIs. Quote Link to comment Share on other sites More sharing options...
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