Fuel delivery problem.

[dobyns]

So heres the deal, i bought a 1979 gs550L it had been sitting for about 4 months with fuel in it, i changed the plugs drained the tank, ran seafoam through it and it ran fine. i then made the pipes straight pipes... it still ran fine for 450 miles and now it is sputtering and backfiring when it is at a cruising pace... when the bike is wide open it is fine but when i slow down to speedlimit poce (like 30 to 40) it does the backfire sputter thing... i would have said it needed rejetting, but i rode it for 450 miles before it became an issue which leads me to believe the carbs could need rebuilt, like i said it sat 4 months with fuel in it...... any help?

[ScrumDown]

I'd say yes, you need to do some rejetting (adjusting) because there needs to proper back pressure & when you go to straight it throws things out of whack.
I do not know to what extent you'll need to adjust, but there are other who have done exactly what you have done & posted almost step-by-step instructions.

Good luck & Have fun!

[tom203]

Wide open , you don't need slow speed circuits. Cruising, you do- they got to be clean. Maybe after 450 miles, some gunk dislodged from gas tank and is stuck in these low speed circuits. Straight pipes complicate things. Seafoam is not a cure-all.
Are these VM carbs?

[dobyns]

I think so, not 100% sure, the part that throws me off is the fact that it rode fine for 450 miles with straight pipes... im sure it would have complicated things a bit more soon than that.. i think your right about the gunk coming loose though... i got a quote at a local bike shop for complete carb rebuild and rejetting for 400 bucks.

[Agemax]

yep, sounds like crap has found its way into your carbs, $400 for a rebuild??????

follow the links on your mega welcome and do it yourself. its easier than you think.....

[dobyns]

Sounds like a good idea... i like my money and a rebuild would be super cheap if i did it... could someone post a link in the reply because when i search it gives me an error code on these government computers?

[dobyns]

And thank you guys for the replys, i really appreciate it.

[Agemax]

have a looky here........

http://members.dslextreme.com/users/bikecliff/

you should find what you need in here, if you do attempt it yourself (recommended), follow the tutorials exactly but if you ever get stuck, do not be afraid to ask