I got my '74 Interstate on the road today for the first time this year. Rather than lay her up over the winter I have been starting her up and running her up to temperature regularly. Today, after the usual three priming kicks, she started straight away as I expected. All seemed well at first but once properly warmed up on the road I realised all was not as it should be. Particularly during acceleration she was missing intermittently. I returned home after five or six miles and pulled out the plugs. The colour on one was perfect, the other was as black as soot and the exhaust pipe had blued more on that side. I checked the operation of the choke slide on the carb and it seems to be operating normally. When I rode her last year the mixture on both cylinders was perfect. Any suggestions as to what might have happened to cause the unexpected rich running?
Regards to all
RichardP
From my very recent…
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Leaking Floats.
I've had an original type Concentric float gain an imperceptible leak on a seam. Just enough to draw in enough fuel to make it a "sink" rather than a "float".
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Thank you both….
...a job for tomorrow if I'm allowed!
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Shake the float beside your…
Shake the float beside your ear or (if it's sufficiently translucent) hold it up to the light, to detect fuel that has leaked into it.
Submerge a hollow float in hot water and any small leak will be betrayed by a stream of bubbles.
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And another thing....
Starting the bike and not riding it anywhere could very easily foul a plug with unburnt mixture. Very short runs will also foul plugs. This doesn't explain why it is rich on the one side though. See above.
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Burning oil on that pot?…
Burning oil on that pot? That can blue the pipe and snuff the spark.
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It never rains it pours!
Following everyone suggestions I stripped the carb down today. Float appeared ok but I thought I'd treat the bike to a new one and service the carb whilst I had it off the bike. Went back into the garage to find a very strong smell of petrol and a large puddle under the fuel tank - it seems to have developed a pin hole!! Will be a while before I get to try the rebuilt carb....
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From my very recent experience I would go straight to the pilot jet circuit and poke the jet with a guitar string, squirt the passageway with brake cleaner and blow out.