1979 GS1000L Problem backfiring

[outlawfox13]

First off let me introduce myself. I am a proud owner of a 1981 GS750L that I am putting a GS1000 motor on, and my parts/donor bike 79 GS1000L. I am new to this forum and to the Biker world. I am a very handy mechanic so I do all work my self(aside from tires). I am at Ft. Meade MD and I absolutely love my Bike. Now back to why I am here. I am having serious backfiring issues with my GS1000 The carbs are backfiring as well as flames out the exhaust. Now the bike has 25,XXX miles on it, and will idle kind of fine, I got it to run After I cleaned out the carbs. I took off the float bowl and float needle cleaned the ports and the jets, I also cleaned and regapped the plugs to .040 If any one can give me Ideas on whats wrong would help. Also I have an extreme amount of gas comming out of the drain lines on the carbs, it leaks any time the bike sits or runs. I acctually have to use a shut off valve to keep it from leaking.

[Larry D]

Welcome !!
How did you clean out the carbs ? They need to completely disassembled, dipped and reassembled using new o-rings.
The leaking sounds like you could use a new petcock.

[outlawfox13]

Thanks, I will look into a new petcock diaphram, also I took the float bowls off dunked them and the carb, I did not disassemble them, but I did blow air through all passages. Should the whole thing be broken apart? Also I did notice I may be sucking air in after the carb, but before the engine. Any more help would be appriciated.

[DanTheMan]

The carburetor boots have o-rings that may be bad, which would cause it suck air. Most likely since you did not disassmble your carbs and just dunked them, they're a mess inside now too. The o-rings and needle valve seating surfaces don't stand up to well to dipping in carb cleaner.
Buy a whole new petcock, not just the diaphragm. The little it costs for a whole new petcock is worth it, most diapragm kits are an excercise in frustration.

[Nessism]

Thanks, I will look into a new petcock diaphram, also I took the float bowls off dunked them and the carb, I did not disassemble them, but I did blow air through all passages. Should the whole thing be broken apart? Also I did notice I may be sucking air in after the carb, but before the engine. Any more help would be appriciated.

Short cut carb cleaning jobs are long cuts in the end. I suggest you pull the carbs back off and perform a full teardown including replacing all the O-rings with a kit from cycleorings.com

[outlawfox13]

Cool, thanks for the advice. I will start working on the bike again this weekend. I will repost as I go along.

[Nessism]

Cool, thanks for the advice. I will start working on the bike again this weekend. I will repost as I go along.

http://www.thegsresources.com/files/vm_carb_rebuild.pdf

Good luck and watch those fuel screw tips.