2 cycle problem

I have a 1990 Polaris 500 2 cylinder.
It boggs down until you hit 5000 rpm ,then it runs like a raped ape untill 7000.
It has new plugs, 100-120 psi in both cyl, fresh gas and oil. I would like to know why it is bogging down.

Thanks

Pat

It has oil injection . I havent touched it since I have owned it for 5 years but I suppose it could move from vibration.

Pat

soundslike dirty carbs,remove and clen,dont forget pilot jet.

05 It is a snowmobile .It hasnt been sitting very long , less than a month . I dont know if it happens worse when its cold or hot . I know it does happen when it is hot . I just seemed to notice it this year , maybe after the first couple of rides

92 Where you live at ? I live in northern Il

   If it starts and idles ok,most likely not a pilot jet,but the carbs are a good place to start.Definately not a main jet if it pulls hard on top.Throw some isopropyl in it,just to eliminate water as an issue.This may sound dumb,but is the bog smooth?Most electrical issues will cause a breaking up(unsmooth) condition and will get worse with heat.If one of the clutches is acting up,it will not shift properly,causing a condition very similar to accellerating in a car in "too high of a gear".Two strokes have a very narrow operating range and if not allowed to stay in that range they will do all sorts of funny things.
   You'll also want to check the PTO side crank seal.Start the machine and spray the seal behind the drive clutch with wd40 or brakeclean,if the engine dies or the idle really picks up(either could happen)then the seal is junk.I would check this before doing anything else.
   There are many things it could be,I could probably tell you exactly what it is if I could ride it,but that obviously isn't going to happen.Indy 500's are pretty much bulletproof,so I would think it's something basic causing the problem.
   If you're committed to figuring it out yourself without taking it to a dealer,shoot me an e-mail and I'd be happy to help you through it.Sorry for the long post.

   Mike

How much do you weigh?

its a legitimate question, sometimes you don't notice when you put on an extra 100 or 2 and all of a sudden the sled doesnt go quite as fast,

Well, I've met Pat, and it's definitely not his weight. BKH

   Does the problem occur when the back of the sled is off the ground(ie)no load? The air cleaner puffing back would make me want to look at the reeds.If you pull the carbs out of the intake boots,you should be able to look in at the petals to see if they are sealing/broken.If a reed is bad it could cause the airbox pressure you are describing.Does it idle ok?
    Mike

It starts with 2 pulls and idles fine . I did put it up on a jack stand and the problem still occured briefly . Bogged for a second till it hit 5000 then ripped up to 7000 imediatly. I have not had a chance to check the reed valves.

Scott , it does sound like a great excuse to buy a new sled but I have only gotten 800 miles on it since I bought it about 5 years ago . I cannot justify the price for the amount miles I get per year.

05 210 wrote: .If one of the clutches is acting up,it will not shift properly,causing a condition very similar to accellerating in a car in "too high of a gear".Two strokes have a very narrow operating range and if not allowed to stay in that range they will do all sorts of funny things.          Mike

87 BFN wrote:
You might want to check the clutch it self. MY uncle had a sled that the clutch was stuck in high gear so to speak. It was not backing off, in translation it was like taking of in a car in fifth gear. No matter how much gas you gave it it bogged until it hit the propper rpm range for the placement of the clutch. Just a guess and something to check.

__________________
big blocks only


......... Great minds think alike
    
      Mike

Mike sorry I didnt see or misunderstood the clutch thing .I will look at that tomorrow . Could a worn belt also be a factor ?

Andy Yes the sled is acting like the engine rpms . It moves slow untill 5000 then the track will spin and move fast .


Should I spray the primary clutch with carb cleaner or brake cleaner to maybe free it up a little?

Pat

   87,

   It's a good thing you reposted that advise,looks like it got missed the first time.
   
   Pat,
   
    Like 87 said,you should check the belt.Other than that,look at both clutches carefully,Check the primary sliding post for rust,look at the spring and make sure it is not broken.You should be able to take the belt off and check the operation of the secondary clutch also.It is easy to diassemble,clean,and relube,but it has to go back together exactly as it came apart and is under spring pressure.
    Remember the primary clutch controls mostly upshifting,while the secondary is mainly responsible for backshifting.
    The primary is designed to run without lube.You could spray some on it in the sliding areas to see if it helps temporarliy.If it does,you will need to diassemble the primary and replace the faulty components.

   Mike

I always have a tendency to do that then before tou know it the season is over

I did take a look at the clutches and everything apears to work properly

I sprayed carb cleaner all around carbs while running and didnt notice any varience in rpms. Also sprayed all around engine block with no change.

What is the compression supposed to read ?
when I did a check I pulled one plug at a time and ran it on one cyl while checking other . Engine hot

Pat