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Hi and thank you all for posting such great information. Although I am a do it-yourselfer, my knowledge of 4 wheelers is minimal. I understand the carburetor basics and and things like that but having trouble diagnosing my issue here.

I have read a lot of info but still looking for help with my 2003 Rincon 650. It starts and idles well (however when hot and been putting it under load, it would sometimes kill at idle). But for the most part it idles but when I go between 1/2 to full throttle, it has no additional power. At full throttle it only goes 12 miles per hour. When in neutral, 1/2 to full throttle also only provides minimal additional rpm's.
-I have removed the gas tank, checked gas flow and replaced the fuel line so I feel it getting gas.
-I will replace the spark plug (just bought one today)

Any thoughts about what might be happening before I buy a Carb Kit, take the carburetor out and try to clean/rebuild it? I became worried when someone in a post spoke about oil rings, oil pump...or something????

Brad
 

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You should check the diaphragm on top of the carb throttle slide. I and others have run into this before. All it takes is a pin hole in the diaphragm and you will not get full throttle. You can remove the seat and see the top of the carb. Remove the 4 screws and lift out the cap, diaphragm and slide. Check the Diaphragm very closely with a strong light to look for pin holes or tears.
 

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Discussion Starter #3
You should check the diaphragm on top of the carb throttle slide. I and others have run into this before. All it takes is a pin hole in the diaphragm and you will not get full throttle. You can remove the seat and see the top of the carb. Remove the 4 screws and lift out the cap, diaphragm and slide. Check the Diaphragm very closely with a strong light to look for pin holes or tears.
Thanks Harley Dog!
I will inspect the diaphragm as suggested. Since the machine idles, and since my issue is in the upper end of the throttle, is it a lack of gas and running lean?
 

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HD made a good first suggestion.

A CV carb works differently than a typical cable connected to slide carb. On a CV carb, the diaphragm uses engine vacuum to open the slide. So, if the diaphragm has a pin hole, then the vacuum will only open the slide part way. It is lack of air and without the air going through the carb, the jets do not spray enough fuel into the venturi.
 

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As like Corndog said, if there is a leak in the diaphragm the throttle slide will not open fully. It will idle just fine but when you open the throttle the slide will only rise part way. It is like have a throttle stop. Check the diaphragm first. This condition will not set any codes that I know of.
 

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Discussion Starter #6
As like Corndog said, if there is a leak in the diaphragm the throttle slide will not open fully. It will idle just fine but when you open the throttle the slide will only rise part way. It is like have a throttle stop. Check the diaphragm first. This condition will not set any codes that I know of.
I did a careful inspection and couldn't find any pin holes in the diaphragm. next steps....? Carburetor rebuild kit and give it a good cleaning? Is there a jet within the carb that might be causing the lower power at the upper throttle. (I turned the brass screw that is on the underside of the carburetor that faces down, which I assumed was the jet on the engines side.) It didn't seem to run any different with 1/2 turn out vs 3 turns out.
 

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Time to get the service manual. If the idle/air screw has no effect you probably have a bunch of debris inside the carb, When you removed the tank, did you clean the screen at the petcock? The only time I have ever heard of diaphragm damage was when someone was in there messing with the spring... It is sealed and unless you were in there, a long shot at best.
 

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I have a 2003 Rincon. Have worked on the carb quite a few times.
This comment:
It didn't seem to run any different with 1/2 turn out vs 3 turns out. Tells me there's a problem.
If you want the best performance IMO get a manual and start over with the carb. I would take it apart checking everything according to the manual. Order OEM parts that need replaced.
Or buy a new OEM carb.
 
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