Honda-SOHC

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