250sx grinding noise

[cheddarhead]

About 2 weeks ago my 250sx started making a pretty loud grinding noise as I was riding. Had been on it that day about an hour - working it pretty good, making trails and climbing over fallen trees - which I've done a lot of with it. I kind of slowly ran it back to the house - without the noise. I was then testing it out and found when I got on the throttle pretty hard it would make the gringing noise. No noise when idling or going slow. The next day, we fired it up - no noise - I let my son take it and after about 15 min, he said it was grinding again - he was racing around the house, so again, getting on it somewhat. Anyone have any ideas how to start troubleshooting this? I have the manual, but didn't want to just start taking off covers without some direction from you guys. I'm thinking maybe cam chain related? How do I know if the tensioner is working correctly?
Also - maybe this has some connection to this - on this same 250 - after about 15-30 min. of use, when you shift into 1st (the SL gear) it jumps forward pretty hard - when it's cold and you shift into 1st, it just clicks into gear and never moves. Is it normal for the trike to jump into gear like this?
Would appreciate any suggestions. Thanks.

[Tri-ZNate]

it is normall for them to jump like that, or at least my two do. I had the same problem make sure that the kickstart lever isnt pinched between the plastic and the chassie. For some reason it makes it grind. Hope this helps.

[hotroddal]

right when my trikes starts it idles sorta high and sorta jumps when i pop it into gear but i dont know what tyhat grinding noise is possible the shaftdrive???