QuestionHey Bill! Love your posts, very complete answers. Thanks.
I've got a pair of CB360t bikes. I've been working them into daily riders. I'm having some trouble with one in particular. I've Got the standard stuff finished (carbs cleaned and maintained, timed, points adjusted, tappets adjusted, tank cleaned, petcock cleaned etc.# I ride this bike 2 or 3 days a week and it'll rip down the road to about 75 with no issue, but here's the problem: first, the valves a quite loud #compared to the other one I own# and the bike bogs down around 7000 RPMs when I wind it out. The engine pulls hard right up through the bottom end, it just won't wind all the way out. Already went down the jetting road. I upped the mains to 110, which gave me a little more juice, but didn't fix the problem. I did have this bike in a shop and the mech overtightened the tappets #pita) I'm pretty handy but am hopping for some direction.... I'm thinking cam chain issues, or damaged valves. it occasionally backfires a tiny bit through the carb on the right side. not really a detonation, just sort of snorts. I am totally willing to crack open the top end as the head gasket has a bit of a leak anyway. Got any magic for me? Thanks in advance
AnswerLarry, I'm glad that I am amusing everyone out there with my hopefully helpful comments... I have no idea of who is really reading it all, after I have answered a specific question.
Gotta start with the basics first... Compression test.. should be about 175 psi. Pull the spark advancer off and check the weights and springs for proper advance/retard function. If the valves are loud, either they are not adjusted properly (set on wrong stroke?) or it may be suffering from the apparently common camchain tensioner/guide issues. Take the points cover off and then the dyno cover to access the rotor bolt. Turn motor back and forth about 30 degrees and watch the end of the camshaft bolt. If it doesn't follow the motion of the crankshaft, then the tensioner is frozen up or the guide/tensioner is broken, assuming that you have tried to make the camchain adjustment previously.
Backfiring through the carbs is generally a lean condition and/or inaccurate ignition timing. Weak condenser(s) could be causing some issues. Look at the points while the engine is running and look for big arcs across the points. Small, random ones are normal, but constant arcing is generally a condenser issue. Make sure that the condensers are grounded properly to the chassis. That was a problem with older 350-450s in some instances.
Make sure that the gas cap is venting properly. If that is all good, check carbs for bad diaphragms or intake manifolds for air leaks.
Hope that gives you something to work with...
Bill Silver
