I am trying to get this bike running after putting 150/40's in.

I have a clear fuel filter hooked to the lower hard nipple between the carbs. When I first turn to petcock to prime - it filled with gas. Now when I started the bike - the filter slowly ran empty. Plenty of gas is coming out of the petcock outlet on all settings (apply vac for run and reserve of course). What would cause this?

Also one of the carbs seems to be spitting fuel out of front of when I rev the motor (no air filter on right now).

Thanks!!!!
Dylan

I recently noticed the same thing w/ mine.  Fuel goes through, but just sort of dribbles through.  Normal?  Bike runs fine... although I'm trying to troubleshoot some idle mixture / warm up issues after rejetting... not sure if it's related...

I had a carb that was spitting back some.  Turned out to be a bend left exhaust valve.  Pressure from the right cylinder's exhaust was blowing back in through the left's exhaust valve when the left's intake was opening, causing a kind of popping sound along with some fuel spitting back out.

Do a compression check.

I also test bench motors with my compressed air hose (w/rubber tip on it) by inserting it into the spark plug hole and pressureing up the cylinder while rotating the crank with a wrench.  When both valves are closed, there should be pressure built up in the cylinder.  I listen for leaking air.  If I don't hear any, it's a good sign the valves are seating good.

A word of caution:  The air will put enough pressure on the piston to rib the wrench right out of your hand.  USE CARE!

Paul

By bench testing I mean the motor with the carbs and exhaust removed.  This way I can get my ear right up to the ports to listen for escaping air.

Sounds like a leaking tire - Hsssss

Otherwise, a compression testing tool is the best bet for motors in the bike.

you mean a leak down tester...  that is a good idea but;

I think if he had a bad vavle it would noticably run bad and he would be able to see/feel the carb running "backwards".

Which carb is leaking fuel? If its the left one I would suspect an bad air leak in the intake boot. This would explain why its not drawing fuel/air into the carb and why it isn't pulling enough vaccumm to open the fuel vavle.

Quote from: 90GS500rehabWhen I first turn to petcock to prime - it filled with gas. Now when I started the bike - the filter slowly ran empty.

It sounds like he's seeing this happen even on PRIme, which should clear bad vacuum, I think (?). There's always the possibility of pinched fuel hose from when the tank got put back.  But I've also read posts from others with clear fuel lines or filter, that even healthy bikes show "bubbles" in the fuel line.

Quote from: JamesGyou mean a leak down tester...  that is a good idea but;

I think if he had a bad vavle it would noticably run bad and he would be able to see/feel the carb running "backwards".

Which carb is leaking fuel? If its the left one I would suspect an bad air leak in the intake boot. This would explain why its not drawing fuel/air into the carb and why it isn't pulling enough vaccumm to open the fuel vavle.

Yea, if the valve is just slightly bent or worn, it won't show up with a compression tester, your right.  The compression tester will tell you if you have a supstantial leak on one of the valves or bad rings.

Quote from: Rema1000

Quote from: 90GS500rehabWhen I first turn to petcock to prime - it filled with gas. Now when I started the bike - the filter slowly ran empty.

It sounds like he's seeing this happen even on PRIme, which should clear bad vacuum, I think (?). There's always the possibility of pinched fuel hose from when the tank got put back.  But I've also read posts from others with clear fuel lines or filter, that even healthy bikes show "bubbles" in the fuel line.

Yes it happens on prime too and there is plenty of fuel coming out of the valve when I unhook the outlet.

Quote from: JamesGyou mean a leak down tester...  that is a good idea but;

I think if he had a bad vavle it would noticably run bad and he would be able to see/feel the carb running "backwards".

Which carb is leaking fuel? If its the left one I would suspect an bad air leak in the intake boot. This would explain why its not drawing fuel/air into the carb and why it isn't pulling enough vaccumm to open the fuel vavle.

If you are sitting on the bike it is the right carb. Before I had the carbs apart the bike ran great so I am hoping for "operator error" but I will check the compression as well. What does a healthy 500 produce psi wise?

Thanks!!!

Ok, I was out tinkering with the bike tonight. There still seems to be some air kick back out of the carbs. I adjusted the ign timing back and forth through about 10 degrees with no real help.

I noticed the right header is hotter than the left while knelt down messing with the timing.

I pulled the right side spark plug - engine quits.
I pulled the left side spark plug - the engine keeps running

If I pull the left side off just enough for the spark to still jump to the plug, the bike runs a lot better. Doing that would increase the voltage of the spark slightly. I guess I will try swapping coils and see if the right coil works any better.

Anyone have similar experiences?

Thanks!!

Your bike is wierd.  

Good luck and let us know, these are kinda like soap operas.  You always wannna know how they turn out.

Funny thing is it ran like a champ before I pulled it apart and I am far from mechanically uninclined. All I can figure is:

A. Some of the o-rings are leaking in the carb
B. The coil or wire crapped out when I took the harness off the bike.

Swapped out coil - did the same thing on left side.

Today I checked the float levels and they seem pretty close to being right on with the gasket level.

I tried to synch the carbs but I need an intermediate valve as they are too far apart to do with out since one side will try to swallow water as soon as you start it. So I took out one spark plug and set each to about 1000rpm w/ one cylinder running.


Tomorrow I will try taking out one washer or putting a slip on since I think its too rich just yet. The only bad thing about the slip on its Erion Racing can and its a straight through 2" design. I think it will deafen the neighborhood. Anyone ever run a straight through can?

Thanks!
Dylan