Replacing Drive Shaft Bearings???

I am the happy owner if a 66cc G5 and after 4.5 gallons of gas it works great. Today however I tryed to take a link out of the 415 chain because the chain tensioned was at its highest position and the chain was still slipping off the front sprocket. So I took a link out and now the chain is to short (wow amazing really like really???) I was soo short that I was able to take the chain tensioner completely off (really like the look of that) but after rotating the back tire to "pull" the chain on the chain is now so tight that it has almost no flex like almost none.

Here is the question. With the engine off I can coast down a hill and at about 4 to 8 miles an hour the drive shaft on the engine goes into a high frequency vibration and one I accelerate beyond that it’s nonexistent. I think the chain is so tight that it is ruining the bearings in the drive/clutch shaft of the engine.

HOW DO YOU REPLACE THESE BEARING AND WERE DO I GET RELLY GOOD REPLACEMENTS FOR THEM?

Thanks for giving me the reference two tensioners sounds good and I already have a top hat adapter for the rear sprocket and it works great. What makes SKF so expensive??? Are they ceramic?

Well....about my top hat. I started with a rag joint like everyone else and when it started breaking off spokes at the shank i realized that it was no longer going to work for me anymore. I went for the HD wheel kit at first hopeing that it would solve the problem but it was a too much of a pain in the ass even to build. So i went a different route. I bought a rear wheel that had an ISO disk brake adapter and it cost me 60 bucks. Then the rest was easy i just went to kings sales.com bought the tophat adapter with a 1/8th offset and then chose the sprocket i wanted to go with it (39 teeth for me). And as if it was ment to work i bolted it all together and it runs perfectly true. If anyone dosent have the tophat adapter set up there conecting their sprockt to the rear wheel the wrong way.

but about those bearings... were do i buy them online i cant seem to find a sight that sells them. Also if they did have all the bearings that go into this motor in ceramic i would gladly pay 15 to 20 dollars a bearing for them, i think once you do that your "cheap chinese engine" will never break down again. There is just not much to go wrong at that point