superfastyfz450driver Posted May 3, 2010 Report Share Posted May 3, 2010 ran in to some problems today tuning the bike on methanol, i bought a set of mikuni tmx 36mm's , the bike starts and runs pretty good, a tad on the rich side on the low end but nothing too bad, runs real crisp at 1/4 - 1/2 throttle, but after that just before your about to shift it coughs and just about dies, if you let off the throttle for a split second and get back on the throttle pull pretty good again, the plugs are still brand new looking clean, just the cross over strap is turning the galvanized color a darker gray to the timming is right on at 4.5 degrees advanced, do you guys think its just too rich or possibly running low on fuel in the float bowl, if its running low on fuel i will have to add a fuel pump, but i guess i can try and pressurize the tank slightly to feed a bit more fuel to the engine and see if it goes away but maybe its just rich so i will see what you guys say Quote Link to comment Share on other sites More sharing options...
blanco25 Posted May 3, 2010 Report Share Posted May 3, 2010 show us a picture of the plugs. Let us know what your main is drilled out to as well as all your mods. You may want to look in the directions of oversized bowls and make sure you drill out your vent cap. Quote Link to comment Share on other sites More sharing options...
firebanshee Posted May 3, 2010 Report Share Posted May 3, 2010 Are you running a dual feed pingal and a drilled out gas cap? Quote Link to comment Share on other sites More sharing options...
superfastyfz450driver Posted May 3, 2010 Author Report Share Posted May 3, 2010 i am running a stock gas cap with all the internals removed from it and all the passageways are drilled out to 3/16ths, the fuel valve was removed and i built a billet aluminum block with 5/16ths tubes where i clamp the fuel lines directly on so there is zero restriction, then instead of a fuel valve i used the motion pro single quick disconnects as a shut off, i tested before running and if you just let the lines run into a 1 galolon measuring jug the 5/16ths fuel lines run full stream the plug is a br9eix by ngk, the strap is a darker shade of galvanized then original and the ring around the base of the threads is perfectly clean and slightly wet looking, main jet is a .112'' or as the mikuni number said a 720, the pilot is a 30, im also running klotz super techniplate at 32:1, v force 3 reeds, port matched base, cpi inframes Quote Link to comment Share on other sites More sharing options...
dajogejr Posted May 3, 2010 Report Share Posted May 3, 2010 What is your compression ratio and cranking compression? What is your squish? Ditch those plugs and get some BR9ES and gap them at .018. What are your plugs currently gapped at now? Did you do a leakdown test on the bike? Quote Link to comment Share on other sites More sharing options...
J-Madd Posted May 4, 2010 Report Share Posted May 4, 2010 I'm gonna say that's pretty lean. You have a dual feed powerjet on those carbs I assume? Nothing wrong with those plugs per se; but they may not read the same as the "es" plugs because the plating on them may be different (I think.) They cost 3 times as much and do resist fouling better; but won't net any hp increase though. Quote Link to comment Share on other sites More sharing options...
RadarRacing Posted May 5, 2010 Report Share Posted May 5, 2010 When they act like they die or just die after WOT and you let off the gas and let the fuel catch back up and then they act fine and start back up, that for me has been bowls running out of fuel, that can be a problem as you describe. Quote Link to comment Share on other sites More sharing options...
quaddad817 Posted May 5, 2010 Report Share Posted May 5, 2010 When they act like they die or just die after WOT and you let off the gas and let the fuel catch back up and then they act fine and start back up, that for me has been bowls running out of fuel, that can be a problem as you describe. X2 Quote Link to comment Share on other sites More sharing options...
GrayRacing Posted May 6, 2010 Report Share Posted May 6, 2010 ran in to some problems today tuning the bike on methanol, i bought a set of mikuni tmx 36mm's , the bike starts and runs pretty good, a tad on the rich side on the low end but nothing too bad, runs real crisp at 1/4 - 1/2 throttle, but after that just before your about to shift it coughs and just about dies, if you let off the throttle for a split second and get back on the throttle pull pretty good again, the plugs are still brand new looking clean, just the cross over strap is turning the galvanized color a darker gray to the timming is right on at 4.5 degrees advanced, do you guys think its just too rich or possibly running low on fuel in the float bowl, if its running low on fuel i will have to add a fuel pump, but i guess i can try and pressurize the tank slightly to feed a bit more fuel to the engine and see if it goes away but maybe its just rich so i will see what you guys say i run consistant 3.17s in 200ft from tuning my carbs, for 1, i would go to a set of 38-39mm airstrykers, go to a size 52 on your pilot jet, and drill ur main jet out. set your timing to +7 degrees, and what i did on my 1st race was that i raised my needles all the way up, and if it was too fat, then id drop them, i kept dropping them until i got it lean but yet fat. and i usually run ngk spark plugs, i use a BR9ES, and if its not hot enough, go to a BR7ES. Quote Link to comment Share on other sites More sharing options...
dajogejr Posted May 6, 2010 Report Share Posted May 6, 2010 \i kept dropping them until i got it lean but yet fat. and i usually run ngk spark plugs, i use a BR9ES, and if its not hot enough, go to a BR7ES. Lean yet fat? You should never need a 7 range plug for methanol....9s' work most of the time, if not...throw an 8 in....7 is too much. Quote Link to comment Share on other sites More sharing options...
GrayRacing Posted May 6, 2010 Report Share Posted May 6, 2010 Lean yet fat? You should never need a 7 range plug for methanol....9s' work most of the time, if not...throw an 8 in....7 is too much. thats what you think but i was at full throttle one night, i had 9s in as usual, and it was prolly 75 degrees outside, i couldnt get the alky to burn then i went to a 8, it was a little better then i went to a 7. its like my bike wouldnt run warm. Quote Link to comment Share on other sites More sharing options...
dajogejr Posted May 6, 2010 Report Share Posted May 6, 2010 If you throw too much at it...it won't burn. Quote Link to comment Share on other sites More sharing options...
badassbanshee479 Posted May 7, 2010 Report Share Posted May 7, 2010 (edited) my 4 mill cub loves fuel! I ended up running billet bowels and cutting one float off of each carb so it would not run out of fuel...... just some fuel for thought I would also consider bumping the main and dump tube up a bit...... mines somewhere in the .120-.125 range Edited May 7, 2010 by badassbanshee479 Quote Link to comment Share on other sites More sharing options...
camatv Posted May 7, 2010 Report Share Posted May 7, 2010 yep i think thats your problem is that the dumps are not big enough you need around a 120 -125 main drill and dump. also need a powerjet the carbs DO have a power jet on them? i would also go with the cutting the one float off but you may need to make sure the float will still shut of the fuel with the alky you are using. 421's with some porting will SUCK up about as much fuel as you can give them escpecially with mikuni's/ you'd probably have to pump both mik's and keihn's. the lectrons are a lil better in the fuel department.. AND easier to jet.. you want to have more than enough fuel for the motor urn your pj's ALL the way out OR at least 4-5? turns out if they are clippards. just not to far some of them will turn out and fall out might check that also. gap the plugs at .18 and start with a b8 bla bla bla i prefer the b8eix myself. the mikuni's are VERY prone to run out of fuel on a long run just make sure you set up the lower end as lean as you can that will keep more fuel in the bowls on the run. pig rich and blowing alky out the pipes is NOT ok.. is the alky NEW!!! not that stuff your buddy had in the back garage? Quote Link to comment Share on other sites More sharing options...
GrayRacing Posted May 8, 2010 Report Share Posted May 8, 2010 finally got my bike in the low 3.2s tonight, close to 3.1s, and im running outta fuel too aswell, i need a set of billet bowls, anyone got any for sale ? Quote Link to comment Share on other sites More sharing options...
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