1981 gs750l misfire(great spark)

[Broady01]

Hi all. I'm an auto mech working on a customer 1981 gs750 to help him out. He got screwed by a motorcycle shop and will never go back. Anyways. It came in leaking gas and oil and running bad. I took carbs off. Cleaned em up. Fixed oil leak. It's still missing on cyl number 2. Plug soaked in gas. Plenty of spark. I don't have access to my comp gauge till Monday when I get back to work. My thought is ex valves not opening. Just wondering if I'm heading in right direction? Are these bikes bad for valves etc? One odd thing I noticed in carbs was rubber plugs over pilot jets. They don't seal well. But all carbs are basically the same. Thanks guys/gals.

[cowboyup3371]

Welcome to the site. Those plugs over the pilot jets must be there as they keep fuel from coming from the wrong place.

[Broady01]

Thanks. Yea I kept em there. Just don't remember seeing those on other carbs I've done. Makes me really appreciate my rc51 with fuel inj haha. But I do wanna get this bike running mint for this guy. He spent 550 last summer. Sat at a shop for 5 months. Got it back with a dent in the tank. No oil in engine. Almost fried his clutch. All bowls leaking and an oil plug ****ing oil. I dunno. Just wanna make things right for the guy and get him rolling with a dependable bike !!!

[cowboyup3371]

Start by reading these two pieces of great information and then go spend time at Basscliff's website:

Top Ten Newbie Mistakes - http://www.thegsresources.com/_forum...d.php?t=171846

Carb Cleaning Tutorial -

http://www.mtsac.edu/~cliff/storage/gs/Mikuni_BS-CV_Carburetor_Rebuild_Tutorial.pdf

Basscliff's website - http://members.dslextreme.com/users/bikecliff

[haggisbasher]

Hi there

You should check the petcock, on the 80-81 GSs they use a vacuum operated petcock which draws vacuum from carb 2. The petcock is notorious for failing and dumping gas into cylinder 2 down the vacuum line.

Good luck

Tom

[Broady01]

Tom you hit the nail on the head!!! So I guess I can put petcock on prime and plug the vac line and make sure bike runs proper and get a petcock if all is well. If they are still available???

[haggisbasher]

I believe they are still available new although a lot of people consider replacing them with Pingels for peace of mind. If you leave it on prime and its not working properly I would clamp the hose if your going to leave it for any time otherwise you might find gas leaking int in the crankcase.

Tom

[Chris lee]

You'll notice the float bowls have a seat that presses the rubber plugs in tightly when installed check the petcock vaccume line for raw fuel and that the diaphram isn't leaking also if the diaphram on the needle to your main jet doesn't operate smoothly or leaks vaccume it won't raise andcan also cause a flooding condition at part to full throttle