SOHC.co.uk Forums > CB500/550

Advice appreciated

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Fairview:
Hi, I have recently acquired a CB550 k1 as a rolling (light) renovation project. Initial impressions of the bike have been good but I hoped to benefit from the combined wisdom of forum members regarding a couple of pressing issues, I'm not hugely mechanically knowledgeable.

The first is a running problem which I think is a misfire noticeable from about 3000 revs up. Having just returned from a 120 mile round trip the problem was most noticeable on the motorway where max possible speed was about 60mph (speedo wavering between 40 and 80mph), engine sounded lumpy especially up-hill where lack of power was very noticeable, you know things aren't going well when you re overtaken by a string of artics. Fuel consumption was poor (30 odd mpg). At low revs performance isn't noticeably effected and she can be coxed up to red line without too much trouble in low gears. Starting is always great, single kick hot or cold, tick over isn't bad but engine has to be fully warm for it to settle. I'm not sure if it's relevent but it only needs choke for a few seconds when cold, and on inspection this evening the plugs are a little sooty. I put some premium unleaded in it and for a while it seemed to run a bit better but soon went back to it's bad ways. I know it could be a hundred things but if anyone has got any suggestions of where I should start I'd be grateful. It has had a recent service, still waiting for a new air filter bu the existing one has had a blow through.

The second less important problem (if anyone's still reading) is the throttle control. Despite being free moving, gripping and holding the throttle open for more than five minutes at a time is cramp inducing agony. Not sure if its down to the shiny hard grip or if there is any other means of improving things. It doesn't sound much of a problem but I'm not exaggerating when I say it made the long ride flipping hard work, especially coupled with the lack of power.

Thanks

LesterPiglet:
Who did the service and what was serviced? It may be running rich by your description and the fact that it's an old air filter. Try running it without the filter and see if it improves any.
Remove the second (closing) throttle cable if it is still there, it isn't needed.

Bryanj:
Done a full 6,000 service with new plugs, plug caps and possibly points? or just a 1500 oil change?

What exhaust system is it running?

K1 and 2 don't need much choke it's the K3 thats cold blooded.

Sorry Lester but both cables ARE needed (Try stopping one with the throttle stuck open!!) but new cables and grips will probably help

SteveD CB500K0:
The throttle spring is very heavy on the 500. We just lived with it...

Easy starts, quick off choke, lack of top-end power sounds like rich running.
Do a plug chop on full throttle and see what colour they are. Plenty of instructions for how-too if you search on here.

Steve

florence:
Rich running definitely.  Check that one or more of your carbs isn't flooding; this would give the all symptoms you describe. 

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