Questionmy 76 cb550k has been backfiring since i took apart the top end to replace gaskets.i reset everything bach to where it was, timing,valves,etc. i cleaned the carbs and found 2 floats off.reset them all to 22 mil.now bike stumbles around turns .mixture screws are 2 turns out, seems better that way as backfire happens at higher rpm.also have a hotter plug in cylinder 2 due to minute oil leak by valve.also have mac 4 into 1 exayst since last year with no problems.should i jet the carbs up since the floats are now where they should be? any advice would be great.
AnswerCarl.... check the compression first to see that you don't have any mechanical issues. If you put the cam in a tooth off incorrectly, it won't run well and the compression will be low across all cylinders. Normal readings are in the 160-175 psi range.
When you had the head off you should have replaced the valve stem seals and checked the sealing of all valves.
When checking float adjustments, be sure that the floats are NOT compressing the spring loaded needle tips.
Take the point cover off and watch the points to see if there is excessive arcing due to weak condenser. The points should be nice and shiny, gapped to .012-.014" and set to open at the 1-4 and 2-3 F marks. The mechanical spark advancers can stick, so remove the point plate and check the advancer for free weights and proper return spring function.
Check the spark plug caps for excessive resistance. Should be around 5k ohms. Be sure that they are screwed on tight to the ends of the wires. Stock plugs are D7ES and you should stay with that.
Be sure that all exhaust leaks around the head flanges and muffler connections are tight and leak-free.
Bill Silver
