Running on half choke

VENICE BOY · #11 (**permalink**) 05-09-2008, 08:40 PM

I just had this same problem with one of my new bikes... It would only run with 1/2 choke!
I sealed up all the air leaks and checked everything I could think of, but had very little change.

Then I got the idea to drill the jet a little bigger.
I went to the LHWS and bought 6 tiny drill bits in the next sizes up.
Every time I drilled it a little bigger, I would test ride it & every time it rode a little better!

I stopped drilling when it was running good.

I thought I would add this to this thread incase anyone ever has this problem in the future.

**CRUISER** · #12 (**permalink**) 05-09-2008, 08:42 PM

55555555555555555555555 high five venice! nice job. nothing feels as good as when we figure out what is making our bicycle motors run bad and fix it. i imagine you are all smiles.

VENICE BOY · #13 (**permalink**) 05-09-2008, 08:49 PM

I was VERY proud of myself!

**Norman** · #14 (**permalink**) 05-09-2008, 09:42 PM

Did you mic the needle to see if it was tapered right?

VENICE BOY · #15 (**permalink**) 05-09-2008, 09:45 PM

No, but I held it next to 2 others & they all looked exactly the same... So I figured that probably wasn't the problem.

**Norman** · #16 (**permalink**) 05-09-2008, 09:56 PM

Pablo had a problem kind of like yours he sent me the carb and I found that the needle was not tapered right. and it was off by only 0.005.
I compaired his to my carbs needle with a mic. I reground it and the carb would then work properly. Before it would start and idle but would not rev up if you put on the choke it would try but would not work very well at all. after I tapered the needle it ran fine. at the top the needle miced 0.070 and at the bottom it miced 0.065 so its not a lot of taper and very hard to see the difference.
check out my carb post for the main jet size as I don't remember it right off

VENICE BOY · #17 (**permalink**) 05-09-2008, 10:03 PM

Well... it's running pretty good now, but I will take out the needle & check it anyways...

I'll post what I find.

VENICE BOY · #18 (**permalink**) 05-09-2008, 10:41 PM

Also... I don't know about Pablo's carb, but mine ran great as long as the choke was 1/2 on!
Put the choke "off" at full speed, & it would die.
What exactly was Pablo's doing?

Pablo · #19 (**permalink**) 05-09-2008, 11:23 PM

Mine didn't run for crap since new, but in some general terms ran like yours, with choke I could and did ride the bike.....but it actually got worse. I almost started to drill the jet, but I would have measured it first (and found it fine!). But I was getting tired of messing with it and coolio Norm volunteered to take a crack at it. Sure enough - he spotted the needle right away. I had no frame of reference...now I know what the proper needle taper is.

**Bikeguy Joe** · #20 (**permalink**) 05-10-2008, 06:10 AM

I haven't drilled any jets yet, but I have "re-tapered" all the needles.

It's worth the effort to "fine tune" the carbs by this means. One bicycle motor I even got to run very well all the way through the rpm range in this manner.