i have a 1983 vf750s v45sabre. runs like new when cold,when warm ,won't idle,missfires,loss of power?

Question

not to much oil already checked,sparkplugs not fouled

how do check for weak coil? it has 2 and at $145.00 ea i don't want to waste money if not electrical

Answer 1

Thanks for telling us what kind of bike you have. In your previous question you added that you have to rev the motor to at least 2000rpm to get it to idle. From every thing you've told us, it sounds like the carbs need cleaning.
--Runs like new when cold. That's because the choke circuit is compensating for the idle circuit being clogged.
--Runs OK when rev'ed over 2000. The pilot jet in the carb is used for idle and up to 1/4 throttle opening. The pilot jet is so small, a pin won't fit through it. It's very easy to get colgged.
--When gasoline has been sitting in the carbs for a while without fuel stabiliser, it eveporates and leaves behind a sticky lacquerer and gums up the carb and jets.
--If the problem was electrical, it would occur all the time. Not just at specific rpms.
--Remove the carbs and clean them. Your bike is so old, as an added precaution, look inside the fuel tank and check for rust. (carbs don't like rust).

Answer 2

Is there black/blue smoke coming out of the exh.? Will it run with the choke on or off? Sounds like it's running rich. Make sure that your choke cable is not sticking or that the choke plungers inside the carburetor body are not stuck. Also check to see that your air filter is clean.

If it runs ok with the choke, then shuts off when the choke is turned off then the pilot jets in your carb. are probably clogged with old stale gas. You will need to remove them and soak them in carb. cleaning solution.

Answer 3

the vf's had trouble with the cams/housings wearing prematurely. might pay to take the tappet covers off and inspect.

"The big blow came when MCN's (Motor Cycle News) long term VF750S developed abnormal wear on a rear camshaft. At first it was put down to poor metal hardening, but when they printed the tale other VF owners came forward with their own horror stories. A major row blew up with Honda UK at first refusing to acknowledge the problem before coming clean, claiming they were waiting until they'd located and solved the problem before doing anything about it. "

http://www.math.uwaterloo.ca/~rblander/V4_PB.html

http://www.math.uwaterloo.ca/~rblander/V4_cams.html

Answer 4

Check to see if the choke is stuck on or partially on. You'll have to mess with the carb a bit to be sure. Beware of the spring inside.

Answer 5

Sounds like it's in the ignition
Weak coil or ?

Check your plugs to see which 1 is firing black,that should tell you something

Answer 6

sounds like a weak coil to me. have it checked before tearing carb. apart.