QuestionHi Wayne, I have a 1984 honda magna v45 vf750c canadian model. I just switched motors out to the proper magna motor that came with it and put everything on correctly. It idles perfect just sounds brand new but then i try to rev it up and it stops reving at 2 and stays at 2 and wont go any farther it sounds like it almost starts back firing. I even have the right jets in that came with the bike? I cleaned the carbs up real nice. I was hoping you could point me in the right direction?? Thanks aggain. P.s. I have a clear fuel line on and can see that there is fuel getting to the carbs.
AnswerHi Reid,
That is an odd problem but I wonder if
you have a stuck valve or something.
Can you check the compression and
see what colors the spark plugs
are running? Check if they are sooty
or clean.
Backfires are usually related to
lean fuel mixtures.
Do both pipes heat up evenly?
The carb float levels okay and
the carb slide diaphragms okay?
Try some starting fluid in the carb mouths as
it speeds up and see if the
rpm's rise.
Does the choke make any difference?
If the compression is okay and the
spark looks good then I suspect
some fuel or vacuum problem
as long as no one has tampered with
cam timing or whatever.
You can try a timing light to confirm
the spark and spark advance.
The off idle to three quarter throttle opening
is controlled by the slide and slide needle and needle jet
in the carb center.
Three quarter to full throttle
is handled by the main jets.
The float levels can affect all higher speeds.
The spark plugs can tell you what is happening
in the engine.
Run it with some clean plugs at the
problem speed and then shut it down quickly.
Check the plug color and condition for clues.
http://verrill.com/moto/sellingguide/sparkplugs/plugcolorchart.htm
Let me know if you notice any other
results or symptoms.
Good luck!
Wayne S.
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