For some reason when i first start up my sportsman there is a load knock coming from engine . This knock has never been there before. After it warms up and is ridden for 5-10 minutes knocking goes away completly until next time I start it again. Any ideas. Do the heads need to be adjusted?? Any info would be great. Thanks

 

I have also been driving very slow in low gear for last 100 miles or so.. Anyone else have this problem and what was it thanks for any help you can give

 

Can't hear noises over the net, but what you're describing sounds alot like piston slap. This happens when the piston to bore clearance is too great. It will usually shut up when it warms up as you describe. Unto itself it won't really hurt anything, it will just get louder or more frequent as the engine ages. Just about every engine General Motors builds these days has a cold piston knock, if you want a good example of what this sounds like listen to a 00' or newer chevy p/u with the 6.0l. These thing are LOUD when they are cold, some of them even when they are warm.

 

You did not mention age or miles but yes it does sound like piston slap. With wear of the cylinder the piston will have more clearance but as it warms up things start to expand and decrease the clearance.

 

Sorry the mach is only 21/2 years old and has just under 1300 miles on it

 

Just a thought but maybe it's your automatic decompressor failing to disengage. It engages to start the engine and as soon as the rpm picks up it is supposed to disengage. It can be heard every time you start but after a few seconds knocking disappears. If this is the case I would imagine a loss of power when accelerating.
Like I said just a thought.

 

my atv had the same problem i adjusted the idle on the carb and it went away

 

My 2000 sportsman 500 has been doing the same thing, a noise from the shifter side of the engine, and I also have been using low gear alot, any ideas?