SOHC.co.uk Forums > CB500/550

Rough running

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Oldbuthopeful:

I'd be glad of some help in curing the rough running on my 550K3.
After a rebuild 12 months ago, she never really ran sweetly and was too big for comfort so I pushed her to the back of the garage and concentrated on a 350Four.  The 350 is now up and running and is a joy to ride (me being only 5'5" and 70+ years old) but the 550 deserves to be enjoyed by someone out there as it's potentially a nice bike.
So, having had the carbs checked over and with new jets and air screws in, there was a definate improvement but still an
infuriating habit of only running/pulling with the choke out.
Timing was suspect, so I took off the camshaft cover today but found all the marks to be in the right places.
Next, I re-set all the tappet clearances and on start-up, she ran as sweet as a nut - never heard her so good.  I thought I'd
cracked it, but when I took her out on the road, she'd still only run with the choke out.
Patience is running a bit thin now, so can one of you more knowlegable guys out there offer any solutions please.
(And for Gawd's sake, don't say take the carbs off, because I think I'd lose the will to live !)
 

Bryanj:
Did you remove the push in pilot jets and clean them when you had them off?

Oldbuthopeful:

When I rebuilt the carbs about a year ago I replaced the push-in pilot jets with new, as well as putting in new main jets.
But the bike's been sitting idle for almost a year so maybe the jets could do with a spot of TLC ?
I didn't suspect the jets because they were new, but will certainly get them out today and have a gentle poke around.
At least dropping the bowls isn't half as bad as taking the whole bank of carbs off !

Thanks for coming back so quickly Bryanj.

Bitsa (Ralph Wright - RIP):
Sound to me like jets are gummed up.I would recommend when you hibernate a bike drain the bowels every time.My xjr1300 idle jets did this gum up in 6 months.
Hope this helps
Bitsa

mickwinf:
all the above plus check the float hight as its different on the k3 carbs, also check the float needles especially the little sprung loaded bit to make sure its not stuck hence cutting off fuel supply when under load. you could spray carb cleaner around the joints when the engine is running to show up any air leaks. You may have to take carbs off again, sorry! regards Mick

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