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SOHC.co.uk Forums => CB500/550 => Topic started by: peterengland on May 19, 2019, 12:15:53 PM

Title: Engine misfire
Post by: peterengland on May 19, 2019, 12:15:53 PM
550 seems to be msfiring at lowish revs in 1st and 2nd when pulling away slowish, once opened up in higher gears all trace of the miss disappears totally. New plugs and points fitted and timing done statically. Please someone tell me its not the carbs...(46A) not tried new leads or caps.
Title: Re: Engine misfire
Post by: Nurse Julie on May 19, 2019, 12:24:05 PM
Just a thought. If you gave fitted new plugs, just make sure they are not the resisted ones.
Title: Re: Engine misfire
Post by: peterengland on May 19, 2019, 12:29:17 PM
no they are D8EA , fitted them because of the miss
Title: Re: Engine misfire
Post by: Bryanj on May 19, 2019, 01:01:00 PM
Sorry mate if its PD type, clean the pilots again!!!
Title: Re: Engine misfire
Post by: peterengland on May 19, 2019, 03:04:43 PM
oh god, carbs off then. Where are the pilots exactly?, not sure not disassembled them before.
Title: Re: Engine misfire
Post by: Bryanj on May 19, 2019, 03:28:49 PM
Inside the float bowls and they are pressed in not sçrewed in. You need to grip with vice grips and pull and turn at same time, to refit tap with soft metal small hammer
Title: Re: Engine misfire
Post by: peterengland on May 19, 2019, 03:42:34 PM
Thanks fr that, god I hate taking the carbs off, 30 mins to get off and 3 hours putting them back :(  (if I do it quickly!)
Title: Re: Engine misfire
Post by: K2-K6 on May 19, 2019, 03:54:59 PM
Get everything warm to work on them as it'll give you an easier time with non metal bits.  :)
Title: Re: Engine misfire
Post by: paulbaker1954 on May 20, 2019, 09:03:30 AM
Thanks fr that, god I hate taking the carbs off, 30 mins to get off and 3 hours putting them back :(  (if I do it quickly!)

On my 500 I can get them off and back on in 15 minutes.

I push the rubbers between the carbs and airbox back in to the airbox. The two inners I actually push all the way back  so they are off and inside the airbox and the two outers not quite off. This gives enough clearance to easily pull the carbs out.

May be different on the 550 but just thought I'd share my tip.

Yes a bit fiddly to pull them back through but not too bad and I have even found now I can do it with the airbox still bolted up. Admittedly my rubbers are newish and pretty pliable.

Don't get me started on carbs though They are the bane of my life mine have been off an d on more times than I can remember
Title: Re: Engine misfire
Post by: peterengland on May 21, 2019, 05:49:55 PM
is there a diagram of the 46A's anywhere?
Title: Re: Engine misfire
Post by: Rob62 on May 21, 2019, 09:22:28 PM
Have you tried new condensers before tackling the carbs? Are you sure th inlet stubbs are fully sealed? Worth checking first
Title: Re: Engine misfire
Post by: peterengland on May 22, 2019, 10:36:45 AM
not tried condensers, if it were them would it not affect it at all revs and not just at low?
Title: Re: Engine misfire
Post by: Rob62 on May 22, 2019, 12:58:26 PM
Never rule out simple solutions, always try the simple stuff first before tackling the bigger / more expensive jobs..
Title: Re: Engine misfire
Post by: peterengland on May 22, 2019, 01:10:56 PM
true
Title: Re: Engine misfire
Post by: Ashdowner on May 23, 2019, 05:36:21 PM
Don't worry Peterengland.. With PD46 carbs you'll get plenty of practice at pulling and dismantling and putting them back and those times you quote will soon come down. I've just taken less than an hour to put mine in and everything back together. There are little tricks you learn on how to make it easier.  ;D ;D ;D
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Title: Re: Engine misfire
Post by: Ashdowner on May 23, 2019, 10:06:56 PM
Brian Louis Barnes has written a detailed step by step strip and rebuild of PD46 carbs which is stored in the files section of this website. At first it seems a bit daunting and complicated but if you're methodical and follow what he says you'll get an understanding of the carbs and realise that actually there isn't that much to it. Take lots of pictures, and especially of the spring between 2 & 3 that works the chokes on 3 & 4 so you know how it goes back when you rebuild them. I've just had to strip mine and at the same time I've helicoiled all the screwholes for the float bowls. Another slightly nervy task which with care has ended up a complete success.
Title: Re: Engine misfire
Post by: paulbaker1954 on May 24, 2019, 03:16:37 PM
Brian Louis Barnes has written a detailed step by step strip and rebuild of PD46 carbs which is stored in the files section of this website. At first it seems a bit daunting and complicated but if you're methodical and follow what he says you'll get an understanding of the carbs and realise that actually there isn't that much to it. Take lots of pictures, and especially of the spring between 2 & 3 that works the chokes on 3 & 4 so you know how it goes back when you rebuild them. I've just had to strip mine and at the same time I've helicoiled all the screwholes for the float bowls. Another slightly nervy task which with care has ended up a complete success.

What Helicoil kit did you use, I just sourced a V-Coil kit that gets good reviews
Title: Re: Engine misfire
Post by: peterengland on May 25, 2019, 10:20:43 AM
Yeah I'm sure that's right Ashdowner! carbs back on and bike running good but No 4 carb is overflowing...
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