carbs are killing me!!!

condiakos · Mar 3, 2013

I think I have read every carb post on this site more than once. but I still have not got these tuned. I have a 76 xs 650 with a pamco ignition and a pma from HHB I am running straight header pipes and my carbs are 1978 BS38's is a 160 main jet seem too big? The bike idles good but acts like it is not getting enough fuel when I do the WOT test. It will pull good until it gets over half throttle then it stalls out, shoots flames out the exhaust then starts again. :wtf:

have pics of the carbs from a while back in a post that I started if you need more info. :banghead:

CDNTX650 · Mar 4, 2013

did you try riding with stock jetting?....bs-38 carbs werent lean from the factor like 34's of the 1980's were..

People guess at jetting way to much and just throw in huge mains and expect it run.

bluebikerblan · Mar 4, 2013

If your carburetors are the 2FO variety OEM to the 78' models....where on earth did you get the impression that you should run 160 main jets? Some more time with the carb manual might not hurt including this page (with my notes). Starting out with the stock set up and going from there would be worth considering? But 160's ? :yikes:

Sn34ky · Mar 4, 2013

yeah 160 is way too high for a stock bike... go back to factory specs and start with that... ~135, while you are there pull your plugs and start with a new set!

Paulrxs650 · Mar 4, 2013

Exactly as Sn34ky says. 160 far too big, even 150's. It sounds like its overfuelling when that jet comes on song. Back to stock and take it from there in small increments. Pain in the arse I know but you will get there!!

If you have access to a dyno, it does save an awful lot of time. can often be worth the few quid???

jd750ace · Mar 4, 2013

Damn dude! My Road Star has a 165 in it! My SV has 137.5 mains. Both Mikuni.

condiakos · Mar 4, 2013

Alright I am going back to start and starting over. I had to of missed something. If I don't get this time its going to the dyno. Just so everyone knows I didn't put the 160' in but I sure as hell thought about it! Thanks for the input guys I will keep you posted.

hotrdd · Mar 5, 2013

If it makes you feel any better I also have a '76 and played with my carbs all summer long and am still not convinced that I have them where they need to be. I've read that guide from front to back several times but the symptoms of being too rich or too lean just aren't as obvious as I wish they were. I even bought a dozen plugs and did throttle chops. But couldn't ever tell by the elusive smoke ring :banghead:

I think this spring it's going on a dyno because no matter what I do I think I'll always be second guessing myself. What I need is a mentor that can walk me through this stuff. :doh:

carbs are killing me!!!

condiakos

XS650 Member

CDNTX650

XS650 Guru

bluebikerblan

Geezer

Sn34ky

Farmer's can build bike 2

Paulrxs650

XS650 Enthusiast

jd750ace

Front Toward Enemy

condiakos

XS650 Member

hotrdd

XS650 Junkie

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