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VM26SS Troubles

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I recently replaced the float bowl gaskets and adjusted the float height on my 78' GS750 because the bowls were leaking profusely, following this the bike ran lean so I took the carburetors back off to reset the float heights. After I did this the bike did not want to stay running when cold, It would rev to about 3000 rpm and then immediately drop down and stall no matter what I did until it was warmed up. I replaced the intake O-rings that seal the carburetor boots to the head and it runs good now except I now have to give it a little throttle until it warms up and the plugs are still white. I reset the float heights so I don't know why it would still be running lean and better yet it runs fine, could it be that I still don't have the floats set right? Or is it something else, it never ran lean before so I'm struggling. Thanks everyone, this site and everyone's wisdom is much appreciated.
 
Turn the air screws on the side of the venturis all thee way in then back out 1 1/4 turns. Turning screws IN makes the cylinder RICHER. OUT makes it LEAN. Also the big knob between carbs 2 and 3 is the idle adjusment
 
ok, I wasn't sure if I should mess with the air screws or not because I know how finicky it can be to get these carburetors in sync. Ill mark where they are now just in case that doesnt help so I can get back to the factory settings. Thanks!
 
I put new plugs in and took it for a ride and its running good and the plugs read good, however would anyone happen to know why I have to give it throttle until its warm now, could it be another vacuum leak?
 
The choke works, but after it starts up the revs slowly start dropping and it dies unless you give it a little throttle. I'm going to put new O-rings in the carburetors and run new fuel and vacuum lines and see if that takes care of it.
 
Have you adjusted the valves?

Also, you say it ran good before you worked on it? Tell us exactly what you did
 
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Ok so ill start from the beginning. My GS750 was running good but the carburetor float bowl gaskets were really old and leaking like a siv, I put new float bowl gaskets in it and mildly adjusted the float height to be a little lower based on my manual's specifications. After this the leaks were fixed and the bike ran well however I checked the plugs and they we're white. Because the bike ran perfectly fine before this it was safe to assume it was a result of my float adjustment. I took my carbs back off and adjusted the floats to where they were originally and this fixed my problem however a new problem arose, when cold the bike would immediately start choking down and die, but once warmed up would start and run good, just setting it out in the sun on a warm day would warm it up enough for it to start good. I reasoned this was a vacuum leak somewhere so my first bet was to change the O-rings between the head and the carburetor boots, I ordered some from cycle O-rings along with the stainless allen head screws for the boots and replaced the old ones, the old ones were probably originally as they were very brittle and one had a gaping crack. This helped significantly with starting but it now acts as if its receiving to much fuel when cold starting with the choke on. When I start it, it revs to about 3,000 rpm like it used to when cold starting with the choke but then starts to bog unless I hold the throttle open a little bit. I'm thinking it could be another vacuum leak so I'm thinking I should put new O-rings in the carbs and run all new hoses for good measure as the ones on it are fairly old. My bike is completely stock and I've had it 3 years with no troubles, all I've done to it so far is regular maintenance like replacing the weak clutch springs because the clutch was slipping, updating the regulator rectifier with a ricks motorsports one (I know sh775 is recommended but I liked the simplicity of ricks option), new gaskets, a new paint job, etc. I haven't adjusted the valves though, the bike is sitting at just over 50,000 miles so I'm sure thats probably due but I don't have any noise coming from the valve train and it didn't have any trouble starting before so I don't believe valve adjustment is my problem but I have far less experience than many of you. Thanks for all of your help, this community is really nice.
 
No noise from the valve train is a bad thing
After 3 years, you're overdue
Get yourself a valve cover gasket before you start
It does sound like you have a carb issue. You need to check the pilot air and fuel settings, and maybe clean the carbs
 
I'll check the valves and proceed with the orings and hoses from there, thanks
 
Did you use OEM float bowl gaskets? Some aftermarket ones are a poor fit and can cause the float to snag up on them and not move up and down as freely as they should.
Worth dropping the bowls off and checking the floats dont bind on the new gaskets.
 
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