550 J cylinder misfire solved

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550 J cylinder misfire solved

Postby barney01 » Tue Oct 02, 2018 6:15 pm

Just want to share my experience when my right hand cylinder began misfiring.
Went out yesterday after about a mile bike felt down on power and was making that funny sound when I cracked the throttle. Bike wouldn't idle. Did the licked finger test on the downpipes right one was lukewarm. Went back home changed plug no change. Did the unscrew plug cap and nip off the end of HT lead thing. On test ride seemed okay to start but then began spluttering. Checked timing with strobe light which confirmed coils were firing okay.
Plug was wet so fuel was getting through so removed choke piston from right carb found that it had stuck mid bore and was therefore flooding cylinder and killing the spark. Gave the choke piston a quick clean with carb cleaner a smidgen of grease and problem solved bike restored to full power!
Last edited by barney01 on Wed Oct 03, 2018 9:28 am, edited 1 time in total.

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Re: 550 J cylinder misfire solved

Postby JOHNJENKS66 » Tue Oct 02, 2018 10:17 pm

Good save Barney, and a cheap fix too :D 8-)
what the fuck was that ????

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Roger Ackery
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Re: 550 J cylinder misfire solved

Postby Roger Ackery » Tue Oct 02, 2018 10:41 pm

Just read your PM Barney, good you fixed the problem ;)

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Re: 550 J cylinder misfire solved

Postby teazer » Wed Oct 03, 2018 1:32 am

Good catch. Another thing to check on our old bikes is to see if the choke plunger is sealing. I have found quite a few that go down and appear to seat but still leak past the hardened rubber insert. A MityVac or similar is an easy tool to use to check for leaks

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Alan H
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Re: 550 J cylinder misfire solved

Postby Alan H » Wed Oct 03, 2018 9:03 am

I had exactly the same back in about 1974 with my 550J. Started well and 'lost' a cylinder after a few seconds as the engine got warm. A bit of tarnishing in the choke plunger tube was soon cleaned and ran fine afterwards. I don't think it would happen on a linked carb set up as they have solid connections, where the separate carbs have individual cables of course.
Proof that four strokes are over complicated

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Re: 550 J cylinder misfire solved

Postby es2GT550 » Thu Oct 04, 2018 5:33 pm

Good stuff -thanks for sharing the info :)


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