Ok my inlaws have an 03 rincon that only goes a top speed of 19/22 mph. It hasnt always ran like this as when I first moved down by them three years ago you could get it up to 55 mph across their field. The next year it wouldnt go up past 30 mph so I brought it in to a shop for them to fix it because I wanted to use it in mn. Anyways shop turned out to be a joke, guy changed oil (told him I was going to do it after he diagnosed the problem, had the filter and oil already bought), said it was fixed, yet problem was not fixed at all of lack of higher rpm power. Well being fed up with the loose connectors on atv upon pickup, oil change that was not requested, and lack of being done when said it would be ready, I brought it back to the farm where it sat for another year.. So this weekend me and the brother-in-law decided that we would try and get it running. I figured it was a fuel related issue that could be fixed with a good carb cleaning. I took it all apart and cleaned it with some cleaner and blowing out the passages/jets with air. Everything looked really clean inside afterwards and the diaphram on top looked pretty good, no cracks that I noticed. But after a test drive, still no dice at getting up past 22 mph. Take off seems good and then acceleration slows after 17 so it takes a couple seconds to gain the extra couple mph. We took the air cleaner off and reved it up while sitting because I expected a leak in the diaphram not going up at all. well It did go up and kind of fluttered up and down but I was still able to reach in and push it up more(didnt force it, just pressed a lil) and noticed it reved a little smoother when holding it up. We kinda gave up because it wasnt what I thought. We did also make sure the tank was clean and the fuel flowed good to the carb. Also checked the oil level and that was good. The spark plug could be replaced, and am thinking this as a possible problem, but the quad only has like 900 some miles and really low hours, under 400 for sure so would it need replacing? Anyways anyone have any ideas or a way to get a diagnostic check to see if something is wrong, cuz Im lost and am in need of help. Thanks.

 

The early Rincons could have an O ring leak off oil pressure, resulting in not enough oil pressure to lock the clutches on the transmission. Usually results in slipping in the higher gears...

There are oil pressure test ports with an odd thread. The dealer should have a three gauge set to check pressure in the transmission.

 

If you put it into manual you can shift it through the gears if thats any info that could help. I thought when I was searching on this site that it was a common problem for the older rincons, was this a recall of some sort, if found faulty? The atv doesnt seem to shift at all in auto mode(thought it was due to lack of power to climb rpms), but if this sounds like the same problem others have had then I guess that must be it....