Alright, i am going out on a limb here since i haven't torn it apart yet.....

While riding a sportsman 500 project i have been working on, the motor died on me. It was almost like it was starving for fuel, the motor just bogged down and shut completely off in a matter of a seconds. My initial thought was fuel, but it had plenty. After checking the fuel i cranked it back up and it ran for another 100 or so yards and the motor bogged down and died again, it's almost like you were stopping up the exhaust and compression was building to the point it just bogged the motor completely to a stop. Then when trying to crank i could here a scraping sound, almost like metal to metal....after letting it sit overnight I tried again to crank it and it felt like there was enormous amount of compression or something, the starter could barely get the motor to turn over fast enough to start, it's was almost like the battery was low but it wasn't. I can get it to start with some effort including playing with the choke/throttle, but once it starts there is a loud ticking sound which appears to be coming from the top end of the motor.

It sounds like a valve train problem to me, but i am no guru, so any suggestions or similiar cases here on the board???

I'll be tearing it apart to see what i can find, but was looking for some insight prior to doing so.

Your help is greatly appreciated.

Thanks,

 

i would gues internal seizeure of some kind as well. time to tear it apart.

 

I would have to agree with stendori on this one...seizure=bad news!

 

Could be a blown gasket is causing water to get into the cyl and hydralicing the engine. Remember, a liquid will only compress so far. What level is the coolant at?

 

yea i can see the water hydrolicing it but when you got it started did it smoke at all? maby some white or gray smoke? check the water like mongrol said and also check the oil levle if it is high than water might have got in and maby over night it drained into teh crankcase into the oil and thats y it started.

 

sounds like a dropped valve or spring

 

either way plan on pulling the head for sure as you have to start there any ways.

 

Ok, i worked a little last night on it....

It will now crank and idle without much effort, with the exception of the abnormally loud ticking coming from what seems like the top end. I pulled the valve train cover off the top of the head and everything appears to be in place, but.....I have never worked on valves before and i noticed that the rocker arms seem to be loose, you can move the intake rocker arms back and forth along the rocker shaft +/- 1/8" probably. Also there is +/- 1/32" play between the end of the little adjustment screws and the top of the valve spring retainers. Does this sound normal? I was hoping to find something obviously broken, but other than what i have stated above everything appears to be in place with the valve train.

Before i take the valves/head apart, what should i be looking for?

Also, i did check the water level and it was full, the oil doesn't appear to have any water in it and it is full as well, i don't remember it smoking any the other day and it was not smoking last night.....

Thanks!

 

Before going to the effort to remove the cylinder head, take a good look at the exhaust valve system. The 425/500 engines are prone to the exhaust lobe on the camshaft to wear drastically, especially on machines that have not been run with a "thin" motor oil like the 0W40 specified by Polaris. This wear is also transferred to the exhaust rocker arm, causing it to "dish", which will open up the valve clearance and could cause loud ticking noises - AND a noticeable loss of power at higher RPMs.

Your other description of being "hard" to start is another symptom of camshaft failure as the exhaust valves are not opening enough to expel the exhaust gases.

If you are having difficulties "seeing" what is going on, there are only 4 bolts holding the rocker assembly to the top of the head - remove the valve cover and pull the rocker assembly, then you will be able to inspect the rocker as well as have a clear view of the camshaft lobes. A service manual will go a long way in helping you with these tasks.

IF you are dealing with camshaft failure - there is no need to remove the cylinder head as all the components can be replaced without removing the head.

 

Ujoint has the most reasonable expl. so far.