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85 honda shadow 500 missing at high speed or high rpm

4K views 3 replies 3 participants last post by  Dodsfall 
#1 ·
I need some advise, I have a 85 honda shadow vt500, runs great but if you get about 5000rmp between gears or in overdrive ,try to go above 60 mph, it starts missing, is this a carb problem or coils or what??
 
#3 ·
high speed miss

Ive talked to several people and pretty much every one thinks carb issue. So i contacted mechanic and told him order rebuild kit, BUT none exist for that particular motor. I did find small gasket set,so guess we will clean it and adjust best we can and see what happens. will post result, may be awhile cause the rest of this week is riding weather, will wait for breakdown when I can't ride.
 
#4 ·
A couple other things to look at:

Fuel delivery- make sure the fuel volume is flowing fast enough to supply the engine at high demand. Check petcock flow and make sure floats are adjusted to spec.

Vacuum leakage- a small vacuum leak may not be noticed at low rpm, but gets compounded as vacuum pressure rises at high rpm. Check suspect areas for air leaks. A cut-off test of the plugs at high rpm may indicate a lean condition if this is the case.
 
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