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petcock diaphragm

Old 01-19-2013, 12:50 PM
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petcock diaphragm

I have been looking for information about the petcock diaphragm in the forum and the manual. Specifically diagnosing a torn or malfunctioning diaphragm. What are the symptoms of a torn/damaged diaphragm?

I am getting a little gas in the vacuum lines I put in to sync the carburetors. I don't want to replace a part that isn't broken. Advice?
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Old 01-19-2013, 02:55 PM
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Seeing as how I have had to replace two of them, my experience both times involved fuel starvation to the engine. It would start to lose power and misfire while cruising down the highway. It often started slowly, a quick pull of the clutch and some revs would clean it out and you'd keep going. Over time it gets worse, to the point that the engine cuts out (not a good thing when you're in the process of passing a rig!!!!!). It would idle ok but misfire and bog when trying to give it gas. It had me stumped the first time (thought I had bad gas initially) but I quickly diagnosed it the second. IN the end, very erratic running that gets progressively worse.

Hope this helps
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Old 01-19-2013, 05:30 PM
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Originally Posted by mikstr View Post
Seeing as how I have had to replace two of them, my experience both times involved fuel starvation to the engine. It would start to lose power and misfire while cruising down the highway. It often started slowly, a quick pull of the clutch and some revs would clean it out and you'd keep going. Over time it gets worse, to the point that the engine cuts out (not a good thing when you're in the process of passing a rig!!!!!). It would idle ok but misfire and bog when trying to give it gas. It had me stumped the first time (thought I had bad gas initially) but I quickly diagnosed it the second. IN the end, very erratic running that gets progressively worse.

Hope this helps
thanks for the reply and help! I think it was hawk who mentioned the failing diaphragm in relation to fuel in the vacuum lines used for syncing the carbs. I've also been experiencing the bike just dying when cold at stop lights and stop signs. It's like using the kill switch, the bike just stops. It starts up again easily enough but it's got me wondering what the hell is going on.
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Old 01-19-2013, 06:08 PM
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could just be your idle speed is set too low (re: stalling at lights)
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Old 01-19-2013, 07:34 PM
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Originally Posted by mikstr View Post
could just be your idle speed is set too low (re: stalling at lights)
idle speed at operating temp is 1300rpm.

If the choke/enricher is malfunctioning can it cause this?

this started happening after I synced the carburetors. I synchronized the carburetors because the bike was farting/coughing in 1st and 2nd gear at 3500 to 4000 rpm. constant speed.

Could be coincidence.
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