BigRed350x Posted November 16, 2008 Report Share Posted November 16, 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. Quote Link to comment Share on other sites More sharing options...
alcoholbanshee Posted November 16, 2008 Report Share Posted November 16, 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. What was your timing at....what carbs/needles?????? Quote Link to comment Share on other sites More sharing options...
BigRed350x Posted November 16, 2008 Author Report Share Posted November 16, 2008 What was your timing at....what carbs/needles?????? Timing at 2 degrees. Keihin 38 PWK Airstrykers. 55 pilots, EGN Needles on middle clip. These are some experimental cylinders of sorts. Had a builder try some different ideas I had with them. Any chance the porting could make it do this, or do you think its a timing / fuel issue? Quote Link to comment Share on other sites More sharing options...
alcoholbanshee Posted November 16, 2008 Report Share Posted November 16, 2008 What are the dump tubes drilled to? The most common causes of detonation are fuel, compression, timing. Quote Link to comment Share on other sites More sharing options...
gregrob Posted November 16, 2008 Report Share Posted November 16, 2008 His dumps are drilled to .118 and it only had 150lbs of compression. When you say "fuel", compression and timing, on the "fuel" part what do you mean. Quality of the fuel? Quote Link to comment Share on other sites More sharing options...
alcoholbanshee Posted November 16, 2008 Report Share Posted November 16, 2008 (edited) His dumps are drilled to .118 and it only had 150lbs of compression. When you say "fuel", compression and timing, on the "fuel" part what do you mean. Quality of the fuel? How much fuel the engine is getting is what I mean. Was this on long pulls that the engine was detonating? Does the bike have a pingel valve? The engine has to be starving for fuel. The compression and timing are very conservative IMO. You may need big bowls on the carbs or delete one of the floats in each carb. Edited November 16, 2008 by alcoholbanshee Quote Link to comment Share on other sites More sharing options...
shanYE west Posted November 16, 2008 Report Share Posted November 16, 2008 I agree with Roger.. Sounds like a fuel issue... What temps are you guys riding in over there? Quote Link to comment Share on other sites More sharing options...
Bansh-eman Posted November 16, 2008 Report Share Posted November 16, 2008 I'm still learning about meth myself, but doesnt meth generally run best at around 7 degrees plus or minus ??? As for the quality of meth, all the reading I have seen on meth is that meth is meth. all of it is 99.9 pure. The problem comes when you start putting additives like M3 and M5 blends. Now of course I am no chemical enginerr so I cant say for certain if any of it is true, that just stuff I have been reading when I decided to make the switch. Quote Link to comment Share on other sites More sharing options...
shanYE west Posted November 16, 2008 Report Share Posted November 16, 2008 I'm still learning about meth myself, but doesnt meth generally run best at around 7 degrees plus or minus ??? As for the quality of meth, all the reading I have seen on meth is that meth is meth. all of it is 99.9 pure. The problem comes when you start putting additives like M3 and M5 blends. Now of course I am no chemical enginerr so I cant say for certain if any of it is true, that just stuff I have been reading when I decided to make the switch. "optimal timing" is going to vary from motor to motor depending on dome design... Quote Link to comment Share on other sites More sharing options...
Wildcardracing Posted November 17, 2008 Report Share Posted November 17, 2008 I agree with Roger.. Sounds like a fuel issue... What temps are you guys riding in over there? He's got billet bowls and a pingel valve. The air temps were in the mid 50's. It was doing it at low speeds most of the time. We acctually switched to a dome with a more conservative squish band and it still did it. Backing out plugs all day and it never showed any damage to the piston or domes :shrug: Quote Link to comment Share on other sites More sharing options...
shanYE west Posted November 17, 2008 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? Quote Link to comment Share on other sites More sharing options...
firebanshee Posted November 17, 2008 Report Share Posted November 17, 2008 I had the same problem with my bike,i ran my bike a few weekends with 18cc domes and +8 timing and everything was ok then i went back and kept rattling plugs out and popping dome orings so i switched to 19cc and left everthing else the same and it ran perfect i was told that 18cc is on that fine line were everthing has to be just right to run them without much room for error. Quote Link to comment Share on other sites More sharing options...
BigRed350x Posted November 17, 2008 Author Report Share Posted November 17, 2008 How much fuel the engine is getting is what I mean. Was this on long pulls that the engine was detonating? Does the bike have a pingel valve? The engine has to be starving for fuel. The compression and timing are very conservative IMO. You may need big bowls on the carbs or delete one of the floats in each carb. Plenty of fuel.. Those carbs have billet bowls, one float removed and fed by a pingle. Quote Link to comment Share on other sites More sharing options...
BigRed350x Posted November 17, 2008 Author Report Share Posted November 17, 2008 I agree with Roger.. Sounds like a fuel issue... What temps are you guys riding in over there? It was 55-60 degrees all weekend. The problems with the plugs backing out happened at all hours of the day. Morning, afternoon and evening. Quote Link to comment Share on other sites More sharing options...
BigRed350x Posted November 17, 2008 Author Report Share Posted November 17, 2008 "optimal timing" is going to vary from motor to motor depending on dome design... Anything more than 4 degrees timing on this bike will back the plugs out even more. Went from 4 degrees retarded to 7 degrees advanced. The more timing I throw at it the worse it gets. Quote Link to comment Share on other sites More sharing options...
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