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wont rev till hot

3K views 30 replies 7 participants last post by  jdavis61 
#1 ·
I have a 1996 sportsman 500 rebuilt top end new carb new starter. all levels good. but it idles perfect and wont rev up till full temp on radiator. any ideas why?
 
#10 ·
It takes 15 to 20 minutes of run time to accurately get a plug reading at the speed the problem occurs at and with no lead oxygenated fuel, the plug will stay white longer. The only plug reading will be for an overly rich condition. Black and fluffy is too rich and wet black is extremely over rich.
 
#13 ·
latebird is a very knowledgeable person.
what i'm going by is I have a similar situation going on and I put a black plug in and my machine turned it white in a couple of minutes just off idle. Yes it was dying and backfiring. I dropped the clip and it made it better but I don't know if that was a ''cure''.
 
#17 ·
Hose clamps can introduce a problem!

I can assure you that as long as the clamp that is on there is not damaged and is the proper size, no other clamp is going to improve whatever problem you might have.

You can over-tighten a hose clamp and cause an air leak! If the carb fits tight enough with the clamp you have that you can't pull the carb out as easy as with the clamp loosened, there is no need to change clamps. If you need to install a new clamp, get a narrow band hose clamp so the clamp will not be exerting pressure beyond the spigot of the carb.
 
#20 ·
ok carb reset someone asked about cables they are great and set right....runs a little better now when cold if I apply choke it will rev....guess need to adjust again
its almost positive to be the fuel air mix on the set screw on the front of carb
also should there be a clamp on the air filter in the box? I dont see one on parts diagram?
 
#28 ·
The fuel screw only has an INITIAL setting to get the engine started and warmed up - when the engine is at normal operating temperature, the fuel screw is adjusted to achieve the smoothest idle - the final setting can be anything from 1/2 to 4 turns dependent on the condition of the engine, valve adjustment, fuel used, air density and carburetor calibration.
 
#30 ·
How the F was a brand new carb needle corroded?
 
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