I have a 1999 honda recon 250. It doesnt smoke when i start it in the morning or after i let it set for some time but when i get it warmed up and say go in a swampy area if im revving high it spits out gray smoke. I recently got a whole new clutch (Drum including) air filter, oil change, valves adjusted, cam chain and oil chain. It hasnt been ran for over a month because it was in the shop being fixed. The smoke comes out for quite some time at times then none at others. If im in second gear going in swampy areas its fine but when revving high it smokes, alos this is the first time i've driven it hard since the fix.
If i give a lot of torque at one time it seems like a grinding noise in the rear diff area then it goes but not instant it takes a second or 2 to get going and it doesnt have much torque at all. Is this just bearrings in my diff or could it be something worse. I dont want to have to put much more money in it because i just put a lot into it. Any response helps thanks!

 

Grey smoke would indicate unburnt fuel, you can tell by the smell if it is oil or an excessively rich mixture. Also the nose of the plug will be black, though excessive oil burning will cause a black plug too.

The most common fault with the rear axle is the LH wheel bearings but the RH bearing and swinging arm bearings can go too. Jack the rear end up and see if there is any lift in all these bearings. The wheel bearings need doing right away as they can lead to wear in the diff splines which will end up a lot more expensive. The LH bearing set up has a design fault which leads to the shaft turning round in the bearings, so a bit of lift can be a worn shaft, but the only way to find out is to remove the shaft and check the bearings by hand. Either the rear prop shaft UJ or diff could be failing, but this is rare on 250s.