I have a 1999 polaris scrambler 500 4x4. I ran it too hard one day and bent a valve, so I resurfaced the head and had a valve job done with 3 degree angle. After putting it back together I rode it hard for another full day, it ran great but the electric start wasn't enough to get it going. I would have to pull the recoil to get it going fast enough. After a day of abuse I garaged it for a week or two. Now I can get it to start ok and it revs fine but when the engine is under load it sputters immediately after taking off. I then replaced the cam and had the carb cleaned. Still no change. Any ideas? If not I'm going to part it out.

 

by any chance did you change your plug... i mean by sounds of all the work that you put into it that sounds kinda small but that can have that effect....

 

If electric start wouldn't work or soon dies (Assuming the battery and starter are both working properly), you could have a valve that needs adjusted. If a valve is stuck open or adjusted so that it will not close, it can cause your problem. Check the clearances on all of the valves (Engine cold, of course).

When you had the carb cleaned, did you replace both the pilot and the main jet? I worked on a 97 Polaris that sounded exactly the same. It seemed to rev up just fine in neutral, but wouldn't perform at all under a load. I cleaned both jets about 3 different times with the same results. I then tried simply replacing them both and voila! It came immediately back to life.

If the above suggestions do not cure the issue, then you need to make sure that the cam and chain are perfectly aligned. Being a tooth off in either direction (Opening or closing the valves at the wrong time) can also cause your issue.

 

I installed a new plug when the head work was done. I checked the gap a few times since just to make sure there was no detination and all was well

 

Electric start works but I need to sometimes pull the manual starter cord to give it enough speed to kick up. The battery and starter we both replaced last year. The machine shop said the valves were fine but the seats were warn. I had them regrind the seats as well as angle the valve. They also resurfaced the head, after getting it running I beat it up the following week and it hasn't ran right since. Did I possibly bend a valve? I didn't replace them when I had the head work done.

I did not replace anything on the carb when i had it cleaned. I've looked into jet kits but I didn't want to make a bunch of changes at once because of this situation, something is wrong and not sure what I changed that caused it.

I also know what you meant about the timing chain because I've messed with that a dozen times to no avail. I think I'll get a jet kit and see what happens [img]i/expressions/face-icon-small-smile.gif[/img]

Thanks for all the help

 

you said you bent a valve in your first post, but then you said you didnt replace any valves in your last post. did you straiten the bent valve....

 

im not sure on the 500 motors but if the stator plate has moved position it will change when the ignition sparks. would run fine with no load but with a load it fires too late and cant burn the compressed fuel. flywheel woodruff key could have sheared also making a pre/late spark.

 

Are you sure it is time correctly?And are the secondary clutch buttons good?