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Discussion Starter #1
My bike will idle but when revved up a cylinder shuts down. this started happening right after filling up with new tank of gas.

Now I have cleaned the carbs tried seafoam new plugs wires everyting.

When I went to drain the tank. I pulled the hoses of carbs and turned petcock on and nothing would come out... I didnt think much about it for some reason and drained throught the top. But after taking carbs off to clean and new plugs and wires the more I thought about that not allowing fuel through... That should have worked right? My local shop said there is a filter in there... Any chance this is my only problem????
 

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the petcock has a valve that is opened by a vaccuum that is fed by one of the hoses that connect to the carb. to get gas to flow out of the petcock without this vaccuum, you must turn it to RES. that bypasses the valve and lets the gas free flow.
 

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I'm not sure RES will operate without a vacuum either. PRI will on older bikes but I'm thinking RES is still vacuum operated valve. You can attach a vacuum hose to the vacuum port on the petcock and draw a vacuum on it to see if the petcock is operating right...
 

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Linkmeister Supreme
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I'm not sure RES will operate without a vacuum either. PRI will on older bikes but I'm thinking RES is still vacuum operated valve. You can attach a vacuum hose to the vacuum port on the petcock and draw a vacuum on it to see if the petcock is operating right...
You are right fergy, RES requires vacuum to the middle nipple on the petcock the same as the RUN position does, in order for fuel to flow.

PRI (prime) on the older bikes is the only position where fuel will flow without vacuum applied.
 

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Do it to it
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If you figure out the problem before i figure out mine post it up man.Cause mines doing the exact same thing.
 

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Mines a 95 and starting acting that way after I made a sharp u-turn down and then up a hill and dropped my bike over a curb into the grass. I ended up pulling the carbs and cleaned them without splitting. I think I knocked varnish loose that periodically got sucked into the jets. The petcock does need vacuum. I do not recommend this, but I hooked up a hose to the vacuum port and then created a vacuum by mouth. If I ever drain the tank again I'll buy a vacuum pump.
 

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Do it to it
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Ordered a fuel pump diaphram (side of carb) for mine today.pulled the cover off the carb (side that doesnt run well) and diaphram is dry rotted.you can hold it up to light and see through it lol..maybe this will fix mine.
 

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Old Truck Junkie
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Mines a 95 and starting acting that way after I made a sharp u-turn down and then up a hill and dropped my bike over a curb into the grass. I ended up pulling the carbs and cleaned them without splitting. I think I knocked varnish loose that periodically got sucked into the jets. The petcock does need vacuum. I do not recommend this, but I hooked up a hose to the vacuum port and then created a vacuum by mouth. If I ever drain the tank again I'll buy a vacuum pump.
A surange will work to draw vaccuum.
 

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Do it to it
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Well i replaced my fuel pump diaphram in the rear cylinder carb ( diaphram on side of carb)and it runs now ALOT better..has a little dead spot when riding but if you give it gas it picks back up.
 

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another good trick to clean carbs and petcocks and tanks is put a bottle of injector cleaner in with a full tank of fuel and let it run thru as you ride cleans it all nice and you dont need to take anything apart
i have done this on my kawasaki el 250 when the needle and flaot got stuck and fuel kept flowing and also just done it to my kawasaki vn 750 when i sucked some crap thru from the tank and has worked a treat
hope this helps you out
 
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