QuestionHi, Jan. I have a 1981 CB1100RB, with low mileage. I've developed a problem that is only costing me damn money, and I can't seem to get a mechanic to fix it, although they know how to fix my bank balance! The carb's been cleaned, or ''cleaned'', by two ''experts'', but still the engine loses power after about 5km, and then I have to sand the blackened plugs clean. the bike then goes great for another 5 - 10 km, and the problem starts again. Is there a screw I must toggle, or what can I do? the floats are plastic, cannot be adjusted, and I'm getting so frustrated I'm gonna cable tie a hairdryer to the carburetor next! What can I do??
AnswerHi Quinton, nice bike you have! If you have checked the basics, which I am sure you have, black and fouling plugs can either be too rich of a gasoline mixture or burning oil, as a result of excessive ring leakage at the pistons. Since you mention the bike has low mileage I assume it has been treated well and that the engine does not produce blue smoke. When the bike runs, do you see blue smoke or black smoke? If blue, would suggest oil. Black is fuel mixture. If we assume fuel mixture, then cleaning the carbs is the obvious choice but you have already done that. Next thing to check is that the jets are the correct size, not by reading the marks, because I have seen many jets that have been drilled out. Also verify that the carb needles are stock. Was the bike running right when you got it, or did this problem gradually start? Verify with the people that cleaned the carbs they did not use a drill to clean the jets. Also on the CB1100RB, the two inner carb main jets are a different size than the outer ones, so make sure they were put back correctly.
Hope this helps, let me know how you get on,
Jan
