TOO MUCH CARB/for drag racing

[stroking]

How you know when you have too much carb for your motor ?

 

what would be one of the signs of too much ? bogging/no bottomend/no topend

 

would these be goodfor a

 

4mil cub=37-39mm

 

4mil stock cylinder=33-35mm

 

or can you just throw some 41mm on a stockcylinder and be good to go ?

[NYUK]

drag racing you leave wide open and finish wide open. i have run 38mm tmx on a stock stroke 350 on alky, amd 39mm pwk on gas on a 400 stock stroke cheetah. they both worked very well.

[sheefreak]

It is going to be hard to tell w/o either track or dyno numbers. From experience, I and many others can get you where you wanna be. Wether you run gas or alky will also make a difference in selection. A 4 mill cub will for sure want the 39 on alky. It will be up in the air a little on gas for the cub. Most will tell you a 39 PWK on gas as well, but some respected builders may disagree. On a stock cyl 4 mill, I have used a set of 39 PWK's on alky and they worked great. I would definately stick w/ the 35 for gas and you can get away w/the 35 on alky and make very similar power to the 39. Remember that twice as much liquid(when running alky as opposed to gas) will take away some of the available space for oxegyn.

[stroking]

i tried some pwk 39mm on alky on a 4mil cub vs 37mm flatslide mik and you could clearly feel the 37mm were faster and accelarated hard

 

maybe it the flatslide affect that i was feeling

[dajogejr]

Smaller motors, especially non-triple port motors, lack the intake signal to effectively pull fuel out of the larger carbs.

 

As said, you're flowing much more alky than you would be gas, 2:1 as a matter of fact.

That's why the larger carbs work ok on small motors.

 

stroking, I'd bet the 37s mikunis were jetted cleaner for that particular motor than the 39s were.

I doubt you'd see too much of a difference between the two, properly tuned. Maybe 1-3 HP...

[stroking]

Smaller motors, especially non-triple port motors, lack the intake signal to effectively pull fuel out of the larger carbs.

 

As said, you're flowing much more alky than you would be gas, 2:1 as a matter of fact.

That's why the larger carbs work ok on small motors.

 

stroking, I'd bet the 37s mikunis were jetted cleaner for that particular motor than the 39s were.

I doubt you'd see too much of a difference between the two, properly tuned. Maybe 1-3 HP...

 

the 39mm's rev'ed much cleaner but the power was not there

 

the 37mm's would blow alky out the pipes when you rev'ed it and you could only make two full pass on almost a gallon of alky and make 4-5 with the 39mm's

 

seems like the 37 were dumping way more fuel but both have the same size main and dump tubes with power jets wide open

[stroking]

. On a stock cyl 4 mill, I have used a set of 39 PWK's on alky and they worked great.

 

im thinking about test out some 39mm on a stock cylinder stock stroke motor and see how it does against some 34mm

[Darthwall]

sounds more of a tuning deal than anything Ive had 39 pwk,s 98% of the people on here swear by them to be the best even those who dump the money into lectrons come back to them the way I see it huge carbs on alky and smaller on gas

[dajogejr]

even those who dump the money into lectrons come back to them the way I see it huge carbs on alky and smaller on gas

 

I could not disagree with you any more in that statement. I ran 39PWKs, have 41.3 Lectrons now...and if I sold my bike I would really, really think about buying a set of PWKs just so I could keep these carbs.

 

I would say most people that give up on them have the wrong needle or don't take the time to learn how to tune them.

 

To the OP...revving clean and revving lean are two different things.

I'd like to see the alky plugs after a couple passes on each carb.

 

On a 4 mil cub, it will handle 39PWKs on gas or alky all day long.

 

On a stock cylinder, stock stroke without triple exhaust, Dan Hull sets up 34PJs without a power jet on them....