My '92 EVO CV carb spits gas out the ventura under a load, ie. 70mph in 5th gear. when running easy it doesn't happen. I have tried 3 dif. carbs and they all do the same thing. I have set the float by the book and reduced the float level down a little a couple of times, no change. Any Ideas?

 

You could have an small air leak aound manifold if this is happening with other carbs. Get some starte fluid, start the bike and sray starter fluid around intake, if you hear a change in ideal speed, you have leak. Keep it away from the air intake when doing the test.

 

Did air leak test and had leak, replaced o-rings and it got better ( less response to start fluid), thought that fluid was migrating to air intake. I now have new filter (K&N) and air box. I'll try it again today. after I finish my coffee. Thanks!

 

can also be reversion which is influenced by cam, intake tract and exhaust tract tuning

( basically a pulse of exhaust gasses is coming back up the pipe and through the head in the time that the intake and exhaust valves are open)

this phenomena will be rpm specific

and can be tuned out by changing any part of the exhaust- length, restriction etc.

could also by a leaking accel pump on the carb...this will be less rpm specific

Mike

 

As I said before about the exhaust was shortened about 4" I will check into a set of drag pipes today. Thanks for the help, I think this my be my problem,(I HOPE) any way Thanks.

 

drag pipes ?

hmm.

do you ride closer to 3000 rpms or 6000 rpms.

drag pipes give up low end for high end power.

base your build and tuning choices on the anticipated use.... I know I spend alot of time near 3000. Not much above 5000

mike

 

Well I guess drag pipes aren't what I should think about, my problem is cash I'm trying to survive on SS so I'm limited on funds, I was looking at exhaust systems and every thing is pretty pricie, guess I'll do a little looking around on craigslist and such. I think you might be right, I've tried every thing else that I could think of. THANKS again, we'll get it figured out. :-)>

 

What if I eliminated the cross over pipe between the front and rear pipes?

 

The crossover pipe helps balance the exhaust and you will lose a little power if you get rid of it. The power you lose is on the top end.

This is what was explained to me by a couple of mechanics when I asked the same question.

 

If you did that, you would be better off with longer pipes so the 2 cylinders can get some balance.
Where is your compression? if it's too low, you will get fuel coming back out the venturi. If your main jet is too big, you could also get this effect.
Hatch.