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350 twin (new)

Right cylinder runs rough
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Brent Dugan

Joined:
2009-07-10 03:17:31

Posts: 4

Posted:Friday 10 July, 2009 3:32 AM

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Subject: Right cylinder runs rough

I've been doing bikes for years (but new to Honda twins) and this one has me stumped. I rebuilt the carbs on a '72 350 twin and the right carb rev's on the low speed jet but goes blahhh at higher RPMs. I put on a known good carb and it did the same. I checked the compression, checked the valve clearances, replaced the intake boot, installed new plugs, etc. I caught a blurb in another forum discussion about the 'timing being off for that cylinder'. Are they timed independently? This bike sat since 1984 but is in general overall excellent condition. Any thoughts? Thanks.
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tom costello

Joined:
2009-01-09 02:06:51

Posts: 25

Posted:Monday 13 July, 2009 2:37 AM

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Subject: Re: Right cylinder runs rough

Hi Brent,
Check to make sure the vacuum slide is working properly if you haven't already. An easy way to do this is to remove the air cleaner then look down the throat of the carburetor as you open the throttle wide open with the engine running, you should see the vacuum slide start to rise at about 5000 RPM. It should come back down as you close the throttle. If not the diaphragm is bad or the slide could be sticking in the carb body. If it checks OK the next thing I would suspect would be a bad ignition coil.Also the ignition timing is set separately on each cylinder. I am assuming that this has been checked.
Good Luck emoticon
Tom
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Brent Dugan

Joined:
2009-07-10 03:17:31

Posts: 4

Posted:Monday 13 July, 2009 2:58 PM

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Subject: Re: Right cylinder runs rough

Tom, Thanks for the response. I did everything you mentioned (thank God for a spare parts bike)to no avail. I finally hit on the solution this weekend. The o-rings on the jet retainers in the float bowl weren't sealing! The vacuum on the primary and secondary jets just wasn't happening like it should. I found out I had the same problem on my "known good carb"! The bike runs great now :-)
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