Ok I am back after forever. I finally got all the parts together to fix my gs. I got the new valve cover gasket on awhile back but then I decided to take apart the carbs to try to fix the issues I was having. Here is new info on what I have done and the behavior of the bike. Hopefully you can help me narrow down the issue.

Things done:

- new float needles
- 1 new float (one side was cracked)
- new o-rings and gaskets (OEM)
- new needles
- new jets
- 1 new plastic top cap (one side was broken)
- all circuits cleaned with 120 psi air pressure
- new spark plugs
- spark is tested and good, problem does not follow spark plug

Behavior:

- Runs on one cylinder (left) when not using choke
- Runs on both cylinders when using the choke (25% or more), but only above about ~2500 rpm
- knocks
- Backfires (sometimes fiery)


What are your thoughts? I have gone through these carbs when a fine tooth comb several times and as far as I can tell they are setup properly. But I could be mistaken.

What about valve clearances and compression numbers? Just getting that out there.....

Being that your right side is only running with the choke (enrichment circuit) on, I would say it's not getting enough gas otherwise. But the fiery backfire makes me think it is getting gas, just not igniting it properly. I would hope it isn't an actual compression problem, just valves being out of spec.....

And you said the jets were blown out with air - what about the actual passageways in the carbs?

Quote from: Big Rich on November 22, 2014, 09:26:10 PM
What about valve clearances and compression numbers? Just getting that out there.....

Being that your right side is only running with the choke (enrichment circuit) on, I would say it's not getting enough gas otherwise. But the fiery backfire makes me think it is getting gas, just not igniting it properly. I would hope it isn't an actual compression problem, just valves being out of spec.....

And you said the jets were blown out with air - what about the actual passageways in the carbs?

Nah the jets were completely replaced, the circuits (the passage ways) were blown out with air. I actually checked the valve clearances when I was replacing the valve cover gasket, the clearances are in spec. I have not checked compression and I don't have the tools to do that but it seems like a fuel problem not a compression problem.

What about float height? And have you tried switching the pilot jets left and right? AutoZone / Advanced has a tool rental program that you can get a compression tester. Just take one of the spark plugs with you to make sure you get the correct adapter.

Not trying to give you a hard time Joe, just covering all the bases.

Quote from: Big Rich on November 22, 2014, 10:48:42 PM
What about float height? And have you tried switching the pilot jets left and right? AutoZone / Advanced has a tool rental program that you can get a compression tester. Just take one of the spark plugs with you to make sure you get the correct adapter.

Not trying to give you a hard time Joe, just covering all the bases.

Oh I know I haven't tried switching the jets but these are brand new mikuni oem jets that I just put in. There shouldn't be anything wrong with the jets. I have also checked the float height, goes right to the top seam of the bowl. I just ran it with it without the air filter for a second and checked to make sure the slides where moving correctly, looks good.

I did however notice something just now. I took out the spark plugs and I noticed there was some oil on them so I shined a flashlight down into the cylinder. I saw what looks to be about a ~2-3mm deep puddle of oil on top of the piston on the side that isn't running. I checked the side that is running and it had a bit of oil on the spark plug too, although not as much. When I checked that side with the flashlight it too had oil but not nearly as much, just a thin layer on top of the piston.

I am going to clean out the cylinders, put new spark plugs in it, and run it again... then check for oil again. Before I panic and start worrying about head gaskets and piston rings, I want to make sure this isn't some leftover bs from the whole valve cover gasket blowing, oil spewing all over the place incident...

Good eye. Did you tip the motor at any time messing around with it? Certain circumstances can allow oil to pour down into the cylinder.

Either way, good luck!

It was a 98 with only 2400 miles on it when purchased, old bikes with very low mileage frequently have dried out seals.  Leaking valve seals might account for the oil leakage into the cylinders.  Hopefully the cylinder bores/rings didn't dry out and rust during long storage periods.  As I recall this bike had running problems when you first got it.  Need compression check, if you can't get a compression gauge the old finger over the hole, crank, and pop would be helpful input.

Choke wont work if pilot is clogged.
The air screw passage could likely be clogged. Or you may have had a air screw over gorilla'ed and you may have set 1 to 3 and the gorilla'ed one compared to stock may be @ -35 or +200. You could inspect both carbs for damage to the air screw seat, and if they are showing any signs of abuse, you may be able to compensate (by setting one different form the other)

I suspect that first, followed by maybe an air inlet passage in the air filter mouth. Look and see if yo ucan chase those with a thin welding supply cleaner.

Or it may just be resenting the fact that you put the tank in the bathtub and it now has mommy issues.

Cool.
Buddha.

Oh I noticed you never answered Big Rich's float level question. Please make sure they are both equal and correct.
Cool.
Buddha.

Ok sorry it took so long to respond. So the oil in the cylinders was definitely the reason why it wasnt running on both cylinders. I cleaned it out and put fresh plugs in it and got it running on both cylinders, I was able to synch the carbs too. Carbs are fine it seems. I took the bike on a ride with the goal of checking for oil in the cylinders again sometime after the ride just to see if the problem came back.

Well... I experienced another catastrophic failure on the test drive lol. I blew the cylinder gasket... I am not really sure why. But the gasket at the very bottom where the cylinder meets the crankcase failed and started leaking oil everywhere. I didn't realize it until I started losing power and I pulled it over and saw the oil and smelled the smoke.

Sigh this bike is a nightmare, so frustrating. So now I need to figure out how to replace that gasket. Or I am considering getting the shop manual and a gasket kit and the right tools and embarking on a complete engine rebuild. I am tired of chasing down little problem after little problem. No more palliative care, its time for surgery...

Replacing that gasket isn't terrible, but it is certainly tougher than a normal gasket. There are a couple specific things you'll want to keep an eye out for - I would start another thread about it though.

Sorry about your bad luck.

With oil leaking both into combustion chambers and out the cylinder base gasket is your head properly torqued down?  Will need new gaskets anyway.

Any chance the crankcase breather filter and hose on top of the valve cover is plugged up causing high crankcase pressure causing leaks?

Quote from: gsJack on November 26, 2014, 01:59:58 PM
With oil leaking both into combustion chambers and out the cylinder base gasket is your head properly torqued down?  Will need new gaskets anyway.

Any chance the crankcase breather filter and hose on top of the valve cover is plugged up causing high crankcase pressure causing leaks?

I cleaned out the breather cover pretty well, i was able to blow through it pretty easily, looked nice and clean so i dont think so. Maybe a clogged oil channel?

If you lose power cos some spot in your bike leaked oil, trust me - your motor is dead. You've lost enough oil to either get cavitation, or to lose oil pressure. That = dead engine.
I would replace the engine, not rebuild one like that.
Cool.
Buddha.