I just put a new cam and exhaust rocker in my 02 sportsman. The old one went flat on the exhaust lobe. I started it up and there is a ticking coming from the valve cover at idel speed, it goes away with more RPM. I set the valves according to specs, .004 for intake and .006 for exhaust I think it was. When I pulled the new cam out of the bag it came in, the decompression valve was pulled out a little bit and the spring was loose, no tension on it. Before I installed the cam I preloaded the spring with one revolution to have just a little tension holding the counter weight toward the center of the cam and thereby holding the ball on the exhaust lobe out. I am wondering if I have to much tension on the counter weight and that decompression ball is not releasing at low RPM when the engine starts. If that is the case that ball will tear up the rocker arm and that will in turn eat my new camshaft. I haven't run it for more than 30 seconds yet. Anybody have any ideas about this? I have never worked on anything with this sort of compression relief.

 

How is your oil pressure? Sounds like a car with the oil pressure low at idle and when the rpms' are increased the oil pressure is high enough to cut out the valve noise. I'm guessing that if the engine has that many hours on it that the valves are flat, possibly the oil pump is worn too? Or maybe the oil and filter just need changed.
Hope this helps,
Tom

 

I pulled the valve cover off and started it up and it was pumping lots of oil at idle. I then took the cover off of the cam decompression valve and decreased the preload on the spring one turn, it dosen't even seem to hold the counter weight firmly but I put it back together like that and it sounds great and runs great.

 

Iaangus,

According to the book the spring is not supposed to have any pre-load on it. You will hear some noise from your valves if there set right. I have been working on a 2000 sportsman 500 and both intakes and exaust valves are supposed to be set at .006, your must be different.

How did you time everything when you put it back together? Not that you did anything wrong I am just putting this one together and want to make sure I get it right. The flywheel has the T mark on it for Piston at TDC on the compression stroke, The timing chain with the two plated links line up with the two dots on driven sprocket and camshaft drive sprocket pin straight up, cam lobes facing down. Or did you just put the motor at TDC and change out the cam right away?

 

It sounds like you have the right idea with the timing, I just lined up the T mark on the fly wheel I didn't have a book or anything so I had the two dots on the sprocket and the dowl pin nearly straight down and I was sure not to turn the crank. I guess it was a top dead center on the exhaust stroke. I didn't pay any attention to the silver link because once the cam sprocket was off and the chain was loose I could'nt be sure it was indexed to the lower sprocket. I was just kind of winging it. The last time I changed a cam on an ATV was around 1980 on my ATC 185. I was about 13 years old. Good luck, Oh the sportsman is still running good, Just in time because I had cows out all over the place Saturday morning and it would have been a nightmare without a fourwheeler.