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SOHC.co.uk Forums => CB500/550 => Topic started by: peterengland on June 08, 2019, 04:43:52 PM

Title: No 1 Carb?
Post by: peterengland on June 08, 2019, 04:43:52 PM
Recently cleaned carbs out and bike was running fine and dandy, now it is missing, no1 is not firing, plug out and is sparking just fine so has to be carb issue as when i take leads off all other cylinders it then runs like a pig, as it should, but when I disconnect no 1 it doesn't miss a beat, apart from the beat it misses anyway! so what can it be..any ideas?

550 with PD46A
Title: Re: No 1 Carb?
Post by: Johnwebley on June 08, 2019, 05:11:32 PM
Has the PD carbs got drain screws?

Check fuel is in the float bowl.
Is the fuel low in the tank?

Try it on reserve

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Title: Re: No 1 Carb?
Post by: peterengland on June 08, 2019, 06:27:18 PM
yes have drain screws, tank full and flowing to the other 3 fine
Title: Re: No 1 Carb?
Post by: Johnwebley on June 08, 2019, 06:40:50 PM
yes have drain screws, tank full and flowing to the other 3 fine
Could be a sticky float/needle valve.

Try tapping the carb(s) with plastic hammer.

Leave drain out. And fuel on.hopefully it may shake it loose.

When you get it done.
Give it a good dose of Redex.
Then take it for  long run

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Title: Re: No 1 Carb?
Post by: JamesH on June 08, 2019, 09:48:08 PM
Should be able to remove bowl #1 with the carbs in-situ. You can then check the flow through the float valve..
Title: Re: No 1 Carb?
Post by: JezzaPeach on June 09, 2019, 04:25:10 PM
I had this on #2, pulled the cap off while running and no change in running.
Swapped 1&2 plugs over and the fault went to 1
So it turned out to be a faulty plug.
Also take drain plug out of 1 and see if the fuel keeps flowing out.
If not could be jammed float valve.
Several times I’ve taken the bowls off in situ.
Fiddly but used a driver bit in a small reghtangled Torx handle.
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