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Lil Help with my Lil 391 4mil


DwnSouth

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Lookin for a Lil advice or suggestions on what to expect out of this motor After alky conversion. Kevin Herr ported some stock cylinders for me few months back. The important stuff..

 

1-5 Rudy Kurtz with direct drive lockout

4 mil crank with 795 wiseco's

Chariot cool head with 21cc domes (4 mil cut)

V force 2's

35mm Keihin's

Trinity intakes

Trinity timing plate on +6

CPI inframes

lightened everything..

Flywheel

JJ&A Hillshooter gun drilled axle

Stock frame 35lbs

Metal tech a-arms

Chassis Inc +6 swinger

Drag steering stem. Metal tech

Struted in the rear

12 paddle triple buff extremes (72-74 ro)

Drag cut fronts w 18.5 smooth buffs

R1 clutch

15/41

 

I weigh 180 lbs bike went 4.45-4.49 consistently last trip on race gas. I tried launching in 2nd with the 15/41 in the dirt and it wasn't happnin. Well since then I strutted the front (-6lbs) and put some 38 lectrons , billet bowls, and single power jets by Dennis Packard on methanol. My question is what kind of ET gains can be expected assuming tuned correctly? Should I add a couple teeth in the back to get a 2nd gear launch? (does 2nd really help in 300ft). I would think it should be a Lil stronger on meth maybe 15/43 or 44 would get me out in 2nd?

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Turning 4.45s with stock cylinders on race gas is a pretty good run. As far as the 38 lectrons, thats a lot of carb for that motor. Not saying it can't be done, but you may have trouble getting it tuned in correctly. I'm running 39s on a 68mm bore 10mil stroke on alcohol. Gearing depends on an few things. Your launch rpm, track conditions, weight and engine setup. Go up a couple on the back and see how it reacts. If thats not it, go back to the 41 and drop down one in front.

All of this is speculation and its hard to tell without hearing the motor and watching the performance.

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I would defiantly set it up for a second gear launch.... bike hooks harder and it doesn't blow the tires off near as easy when leaving in second. Start with like 15/44 or 15/45 and see how it leaves.... if it spins alot keep dropping the rear sprocket size till it leaves good and dont bog.

 

make sure ya start out real fat on alky.... best advice I can give ya is take everything ya know about gas tuning and throw it out the window..... alky is a completely different animal.

 

Do you have a pingel valve? did you gut the gas cap and drill the vent hole out bigger? gotta make sure the tank flows good or you will not be able to fill the bowls fast enough and it will suck the bowls dry and burn the motor down.

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Turning 4.45s with stock cylinders on race gas is a pretty good run. As far as the 38 lectrons, thats a lot of carb for that motor. Not saying it can't be done, but you may have trouble getting it tuned in correctly. I'm running 39s on a 68mm bore 10mil stroke on alcohol. Gearing depends on an few things. Your launch rpm, track conditions, weight and engine setup. Go up a couple on the back and see how it reacts. If thats not it, go back to the 41 and drop down one in front.

All of this is speculation and its hard to tell without hearing the motor and watching the performance.

 

 

 

They really 36/38's I guess?? Stamped 36 on intake and 38 on filter side. I'm new to lectrons and alky??

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I would defiantly set it up for a second gear launch.... bike hooks harder and it doesn't blow the tires off near as easy when leaving in second. Start with like 15/44 or 15/45 and see how it leaves.... if it spins alot keep dropping the rear sprocket size till it leaves good and dont bog.

 

make sure ya start out real fat on alky.... best advice I can give ya is take everything ya know about gas tuning and throw it out the window..... alky is a completely different animal.

 

Do you have a pingel valve? did you gut the gas cap and drill the vent hole out bigger? gotta make sure the tank flows good or you will not be able to fill the bowls fast enough and it will suck the bowls dry and burn the motor down.

 

 

I have a dual valve Pingel I put on but haven't fooled with the cap. I have one of the aluminum tusk caps, gonna have to see how it's vented. I haven't fooled with the powerjet at all since I got them from RaineyMotorsports (I think that's screenname). I had to drop the needle a turn all my alky was shootin on the floor! How much alky should spit on your hand when revn in neutral ? After about 3 revs it drips off my hand a Lil.

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I set mine up so it takes like 2-3 raps of the throttle to clean the motor out..... then start with the power jets wide open, make a pass, pull the plugs and look for heat marks on the metal part of the plug above the threads..... Do a search on alky plug reading there are a bunch of good threads on it.

 

http://www.dragstuff.com/techarticles/reading-alcohol-spark-plugs.html

 

http://www.planetsand.com/forums/ubbthreads.php/topics/654196/brown_colored_alky_plugs#Post654196

 

good link for ya... read up

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I set mine up so it takes like 2-3 raps of the throttle to clean the motor out..... then start with the power jets wide open, make a pass, pull the plugs and look for heat marks on the metal part of the plug above the threads..... Do a search on alky plug reading there are a bunch of good threads on it.

 

http://www.dragstuff.com/techarticles/reading-alcohol-spark-plugs.html

 

http://www.planetsand.com/forums/ubbthreads.php/topics/654196/brown_colored_alky_plugs#Post654196

 

good link for ya... read up

 

 

Ya I read all of em... Lot of good stuff

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Theses carbs will be fine my buddy has a set of 44 lectrons on his Titan 4mill stock cylinder motor and he runs 4.1s all day long! It will take some tunning but well worth it!

 

 

Ya, I'm hoping to get this Lil motor in the high 20's or low 30's on alky while keeping the inframes. That's getn it for stock frame bike with a key switch and full back fenders! Sleeper and money maker! ;)

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tune the alky to sound just like gas motor. set the needle a tad rich to rich and it can fool you tuning wise if you stare at the plugs too much.

 

learn to listen to the motor when your tuning it. that alone will make you a much better tuner. i'd leave the gearing alone and play with it iF you need to.

 

4-4's 4-3's shouldnt be hard at all. 36/38's are not anywhere close to being to big motor like that should handle 38'/40 or 40/40's with ease.

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