I am having the same problem, please let me know what you find

 

I did disconnect the muffler, it didn't help.
I checked the reed valves, they looked ok, but maybe they are too week to close at high speeds ???

 

Well I just tried just about everything with the carb. It is bogging down all of the time now not just when it gets warmed up. I have a new finding though. I put the machine up on a stand and played with the throttle and it had absolutley no problems. It would continuously rev up to max rpm without any problem. As soon as I took that machine off of the stand and sat on it to ride it would bog. So the problem is only when the motor is under a load. Would this be a sign of bad crank seals or blow by in the rings? Like I said before it had 90 psi compression when I initally took the compression test.

 

Could still just be a lack of power or maybe you have some transmission problems?If you can't find anything wrong with the engine I would pull off the transmission cover and take a look.You might have some bad rollers or something going on with the variator that is making it stick in high gear..Our viper has about 125 cranking psi in stock condition.I did once install an incorrect head on it that lowered the compression to about 85 psi and it still started and ran ok but was down a little on power. You shouldn't be too bad with 90 psi but a rebuild is probably in your near future.

 

Thank you for all of the replies. I found out what the main issue was. Do not try and tune the carb without the airbox connected. The airbox restricts the air flow to the point where it creates vacuum for the carb to suck more gas.(kind of like a permanent choke) I was tuning it without the airbox because I was constantly taking the carb off to adjust the float. So in the end the real issues were:

1.) dirty pilot jet
2.) dirty main jet
3.) misaligned float
4.) trying to tune without an airbox.

The machine runs perfect now. I am just glad it is not an electrical problem.

 

My son's 2004 sportsman 90 has been a starting nightmare for three years. In and out of the shop for the first year and a half under warranty and then last summer a new throttle assembly installed and a new stator after I suggested that after reading this forum. I am not the mechanic that most are here but am trying now rather than feeding the dealer service area.

My current problem is it starts initially great off the kick start, not great or at all off the electrical. Once it starts you get about a lap around the house and power is lost and then it dies. Will not re-kick start for about a day and repeats problem.

There was some debris in the intake into the stator and that was cleared away. Plenty of consisten spark so it seems not to be that. I tried taking the stator cover off but that is not an easy task and couldn't get it all the way off. Do you have to take the foot rest off to get it off?

When looking at the stator assembly I noticed a cable going into it. It is the throttle cable that Y's off the throttle with one cable going to the carb adn the other to the stator. I can't seem to get this cable to move by either moving the throttle or the choke. Is this supposed to be an automated movement or could it be my problem?

Thanks for any help. My son is about to turn 15 and is looking for a new machine but I just can't honestly sell this problem to anyone else. ANy ideas?