Ok, here we go. Sit down and read carefully. IF your friend got his first bore to .90 over it was because he had serious scareing to the sleeves from the pistons and need to remove it. If he had it done to get power and didn't need to he dosent know $hit about shee. Boreing out stock shee sleeves gives lil to no power increase. The only reason to bore your sleeves is to smooth out damaged cylinders and get good compression. Or to put blaster pistons in and add a stroker. But dont worry about that now.

Now your stock sleeves can be bored to .90 over. After that you need to have the sleeves replaced. This is pretty expensive. If your engine is showing low compression then you need to rebuild. I assume this is what is happening because if your compression is good don't touch the engine. Now when you get your cylinders bored out have the least amout that is needed to get the cylinders smooth. Prefferably .10 if possible. If you blew your engine up and the piston trashed everything you may need more. But dont bore any more then you need to, to get the shee running with good compression.

Now If you get to .90 over, then have to bore more then you have 2 option. Get new stock sleves in it and start over. OR you can get big bore sleeves put in. Either way $$$, This is the only bore that will increase power.

Now hear is a reason that you should leave the stock cylinders. With a good port job and some bolt ons and a STOCK 350CC engine you can get 75HP out of your shee. SO why even bore especially when a .90 bore will do nothing but end up costing you money when you have to resleve later.

As for some great power add ons you could get a good port job of $300 and be pushing 60HP. This shows you dont need a bore. Other bikes need thousands to produce this power. And you could still be on a stock bore and be reliable.

OK, Now if you have the engine apart a mod that I DEFFINATLY recomend is to have your stock crank trued and welded. This is $80 insurance that if you start to add mods you will deffinetly want. If you increase compression and timing your pressed stock crank will start to seperate. THIS IS VERY BAD. $$$$$$$$ if it goes.