su carb belching gas : V-Twin Forum: Harley Davidson Forums

mark982 · 11-02-2009, 09:43 AM

go a 67 shovel, i run a su carb on it. love the carb,very simple but i can't get it to quit puking gas on my right pant leg. i changed to the cam that rivera said would elimate that,but it didn't,went to a smaller jet same thing. anything else i could do.

claydbal · 11-02-2009, 10:07 AM

is it flooding at idle? do you have straight pipes?

mark982 · 11-02-2009, 04:56 PM

no,it's not flooding at idle, i do run straight pipes. 1-3/4x 38". cant figure this out. bike runs great otherwise. what's also strange is i have to run 2 different heat range plugs colder in the rear. i thought compression might be the problem,checks within 5 pounds of each other.

claydbal · 11-02-2009, 07:17 PM

install mufflers. some old shorties will do the trick.

mark982 · 11-02-2009, 09:24 PM

explain the shorty pipes, don't understand that one. at this point i'll try anything.

claydbal · 11-03-2009, 09:59 AM

slip ons, they are about 6-8 inches in length. still available from paugco i believe. of course you can find any slip ons, they will all help your problem.

BVBOB · 11-03-2009, 04:01 PM

Love the look of that SU carb setup, what is likely causing your problems and what I am guessing that Claydbal is getting at is you are experiencing reversion, the mufflers will help but you might also try the old trick of a couple of bolts crossways in the end of the pipes to break up the exhaust wave if you like the sound now.

mark982 · 11-03-2009, 10:18 PM

bvbob,thanks now that's something i can understand. i really do love the su(it's like me --simple)

stroker93 · 11-04-2009, 10:30 AM

what size of jetting??? what size of motor??? I've SU carbs bout 10 yrs now..I don't have any issues like that and run drag pipes,,2 into 1 homemade set ups,,and now run"thrush" glass papacks for mufflers...What air cleaner????Some cleaners with let the fuel "draft" outta carb when goin down highway,,actually suck out gas onto leg..I would guess jetted to big..these carbs are a constant velocity they pull in fuel from motor vacuum,,,check jets and get back to use with sizes..

dave

Hillside · 11-04-2009, 01:07 PM

You can control the reversion via using a 1/4" bolt, 1 1/2" long, installed 3" from the end of the pipe, and stack as many 5/16", or 3/8" nuts on it as you can.
Still have the sound/look of the open pipe, and the low end torque will come up, and your carb issue should end as well.

Scott