79 GS550(former L)--Only runs in PRIME, dies with ON, dies without CHOKE

[tbrand69]

Title says it all. Test ride yesterday revealed bike won't run unless it's set to PRIME. ON will run if I'm at speed above 2500 RPM, dies as soon as I come to a stop. CHOKE needs to be open a little while it's on PRIME as well.

Previous Work:

Carbs were fully disassembled and dipped, rebuilt, bench synched, then synched with vacuum gauge, new rubber all around for intake system.

Refurbished fuel tank (sealed) and new petcock from Z1.

Bike has sat alone for a while. Unable to ride since I bought a house. Would start it every now and then and it would run fine.

After test ride found oily drops on case right beneath the carbs. Looks like they dripped down the carb bodies as I found no oil leak around head, valve cover, etc.

Idle adjuster works fine. Noticeable change in RPM when turned either direction.

Yes, the gas tank is full.

Possible Causes:

Need for PRIME and CHOKE indicate possible lean condition. Petcock filter is clogged around ON opening? Carb passages are clogged from sitting?

Oily drops could be from air filter, maybe oil is blowing out of the carbs from somewhere or clogging it up?

Only running 1 throttle cable. Put on superbike bars, both stock cables were too long, would crunch and bind. Was able to run 1 cable around to where it would not bind or stick. Throttle snaps closed when released.



What do you guys think?

 

[tkent02]

Carb passages are clogged from sitting?

This would be my guess, how long has it sat and where?

 

[tbrand69]

This would be my guess, how long has it sat and where?

I would guess almost two months, unfortunately. Petcock was set to ON to prevent fuel seepage into the carbs, but the bowls were not drained.

Bike was stored inside a garage completely tucked away from the elements, aside from the Central Valley heat.

I was really hoping varnish and gunk wouldn't have built up that quickly. I'll drain the bowls and see if I can pop them off to check. Other wise I'm gonna have to pull the carbs, which I absolutely detest.

 

[gustovh]

I bought my 1100L from a guy in Fresno and rode it home, but that is another story.

Start by checking to see if your gas valve is working. Remove the fuel line and attach another, disconnect the vacume line at the carb and give it a suck, gas should flow, if not that is the place to start. Be sure that the vacume line is correct on the gas valve as well.

The pri position does not flow fuel as fast as the on position, just a note.

 

[tbrand69]

I bought my 1100L from a guy in Fresno and rode it home, but that is another story.

Start by checking to see if your gas valve is working. Remove the fuel line and attach another, disconnect the vacume line at the carb and give it a suck, gas should flow, if not that is the place to start. Be sure that the vacume line is correct on the gas valve as well.

The pri position does not flow fuel as fast as the on position, just a note.

I will double check those points as well. And that's good to know about the PRIME position. When I would switch to PRIME the bike would have this great surge in power, so I can only imagine how it would feel with ON operating correctly.

 

[tbrand69]

Delayed update:

Petcock flows well in PRIME and ON, I sucked on the vacuum line and flowed out real nice.

I popped the carbs off and took off the bowls. No varnish, no gunk, nothing obvious. I pulled out the jets and found nothing clogging them as well.

I pulled out the air filter and noticed that a lot of oil had collected near the bottom of it. No pooling at the bottom of the air box itself. I wrung out the filter a bit and put it back in. No signs of oil in the intake side of the carbs nor in the air box where they seat.

I've run out of ideas about what could be wrong. Carbs not synched or adjested properly? Even though I bench synched and then used the carbtune on it?

 

[tbrand69]

Alright, well it looks like I'm just gonna try and retune it using the carbtune and seeing if that helps.

 

[LarryA_Texas]

This sounds a little like a problem I had with a 650 a while back. The carbs were well cleaned but what I forgot was to clean the bowls themselves. There is a tiny passage at the bottom of the bowl and opens up at the top of the bowl. When I dipped the carbs I hadn't dipped the bowls themselves. The cure was to use carb cleaning spray and blow out those passages. It's worth a look.

 

[chuck hahn]

Poke out the hole he is talking about with a piece of welding wire..go from inside the bowl and down the hole from the top. Scrub the wire around and then rinse and air.

 

[tbrand69]

This sounds a little like a problem I had with a 650 a while back. The carbs were well cleaned but what I forgot was to clean the bowls themselves. There is a tiny passage at the bottom of the bowl and opens up at the top of the bowl. When I dipped the carbs I hadn't dipped the bowls themselves. The cure was to use carb cleaning spray and blow out those passages. It's worth a look.

Poke out the hole he is talking about with a piece of welding wire..go from inside the bowl and down the hole from the top. Scrub the wire around and then rinse and air.

I dipped the bowls when I originally cleaned the carbs, but just in case I jetted some carb cleaner and air through those passages. I checked for air flow in all of the passages with the air hose, and they all passed.

It looks like the vacuum hose is a little loose-fitting, so I'm gonna replace that one with a tighter fit, too. I got everything mounted back on the bike, so when I get it started up I'm gonna check for leaks around the engine and air box boots.

 

[bradranderson]

this might be really dumb, but put a new battery on it. i have a 83 gs1100, would not idle at all. but with new battery it works great. that bike is very picky when it comes to batteries. just give it a try

 

[Steve]

Somehow, I doubt the original poster will see your reply. His status is listed as "guest", and the thread is four years old. :-\\\

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