1982 Honda Magna V45 (750cc) Idles High: Help?

S

Shawn

New member
I just bought a 1982 Honda Magna V45 (750cc). It seems to run ok, it just needs the choke opened all the way to start, and once it does it runs fine. However once you either rev the motorcycle, or give it some gas it revs...and then takes a while for it to idle down to normal. So in essence it idles high, what could be causing the issue? I just bought it yesterday, and it's raining as i type this. So i tried for a min or 2 to find the throttle screw, and couldn't. Can anyone tell me where to look to find it? Can anyone tell me if cleaning/rebuilding the carbs would fix the issue? Or point me in the direction of what it could be?

Thanks.
 
That bike employs a carby design known as Constant Velocity or CV for short. There is a rubber diaphragm on the top of each carb that can deteriorate over time and require replacement. Tuning of these carbs MUST be carried out with the engine at full operating temperature. Failure to do so can result in the symptoms you describe. The specific model on your bike (you have 4 of 'em) is "32mm Keihin CV". Plug that into a search engine and you will find diagrams and tuning tips. A four carb setup can be difficult to nail if you are not equipped / experienced at it. I'm not familiar with that bikes ignition but if it does use a mechanical advance mechanism for the spark it could be sticking in the fully advanced position. This would also produce your trouble. Happy reading on your rainy day.
 
idle adjust screw is on the side of the carb its a screw that hits a stop so its easy to recognise. However you may have an intake leak so spray some W.D.40 around the intake manifods [rubber boots that connect the carb to the head] and if it gets sucked in then theres your problem.Inspect the manifolds for cracks as well.
 
Possible vacuum leak- to test spray carb cleaner around manifold/fittings: if idle changes while doing this, investigate that spot. Carb cleaner evaporates quickly, but be careful of what you spray it on.
The Magna's carbs are buried between the V-4's banks and you might need to remove the tank and set up a "I V" Stand (like in a hospital room) for a temp tank while you run/diagnose issue and to get at idle/adjustment screws. Good luck.
 
Possible vacuum leak- to test spray carb cleaner around manifold/fittings: if idle changes while doing this, investigate that spot. Carb cleaner evaporates quickly, but be careful of what you spray it on.
The Magna's carbs are buried between the V-4's banks and you might need to remove the tank and set up a "I V" Stand (like in a hospital room) for a temp tank while you run/diagnose issue and to get at idle/adjustment screws. Good luck.
 
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