Flat Spot during acceleration

I

imovertheinternet

New Member
I have a 1982 honda cm450e it seems no matter which gear I am in, if i crack the throttle open half way the bike seems to bog and kind of hit a "flat spot" if I continue to open the throttle all the way the bike seems to come alive again and blasts off. Any ideas on where I should start looking? The bike seems to be back firing quite a bit as well. Thanks.
 
Get the carbs apart and give them a thorough cleaning. Ultrasonic is best, but boiling them for 15 minutes in lemon juice often helps, too. Use the high E string from a guitar to clean the jets and passageways and then blow them out with compressed air.

I can't remember if the CMs use rubber or metal diaphragms, but if they're rubber, inspect for any rips, holes, or tears. Also make sure the cap on the top of the carbs forms an air tight seal.
 
Tim said:
Simple - open throttle all the way! VROOOOOM!
Click to expand...

LOL that is how I rode my CM450 everywhere. It sounds like the middle range jets are plugged up or wrong size and until you open the butterflies enough to get to the mains it is starving for fuel or flooding out. I would do a plug chop at that throttle setting and see if it they come out wet (Rich) or white (lean). to do it, put clean plugs in, take bike to a stretch of road where you can open the throttle to the spot it bogs and ride it like that a minute or so (if it will keep running that long) pull clutch and hit the kill switch, pull over and pull the plugs and see what they look like. if they are black and wet it is flooding, if they are white ish and really clean it is lean and either the jets are dirty or they are too small..... now after all that I can't remember which jet is the one doing most of the work, it is either the pilot or pilot and needle.
 
Found the issue. I believe it has to do with the 61a jet needle.
I did the washer mod on the jet needle and completely fixed the problem. Still can't believe it worked.
 
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