Changing Bearings

W

wtwrestling07

New Member
I have quick question. I have a 80cc/66cc engine I bought off of ebay from rose32 about a year or so ago and I ran it on the bike about 2 tanks. I didn't even finished breaking it in yet and ended up taking the bike apart and taking a welder and grinder to the bike. .weld I turned it into a lowrider/cruiser bike. usflg Soon I will be putting the motor back on, except before I do, I am going to be doing some heavy modifications to the motor like Port matching/possibly more grinding depending on how it goes, billet head, billet tapped intake, boost bottle, performance carb, and exhaust from sbp, and some other stuff. My question is should I open up the crank case and change out the clutch/crank case bearing and wrist pin bearing to hd bearings before I do all the modding because I dont want to do all this work and then the bearing mess up because of all the modding. Or do you think because it is basicly brand new it should be alright with the bearing that are in it. The bike is mainly going to be a show/cruising bike. I might take it down the road a few times and see what its got after I do the heavy modding. brnot xct2 After that it will probably be just for taking a cruise every now and then except mainly a show bike. I have seen a few tutorials on how to change out the wrist pin bearing/clutch/crankcase bearings and it seems fairly simple and HD ones are some what cheap. It might also be a pain in my neck and after I get it open I might end up wishing I hadn't opend the damn think and end up needing a new motor. So basicly has anyone ever changed out the bearing and is it alot of work or no? or is it worth the hassle of changing the bearings or do you think it will be fine without. Also I saw a copper casket set for sale somewhere for 66cc and if I open up the motor I will be putting on a new gasket. Do you think the regular gasket or copper gasket set would be better for a med/heavily modd 66cc scratg
 
That was a QUICK question?!? ;)

I suggest breaking her in properly and familiarizing yourself with the China Girl's diverse temperament before modding. I also advise complete disassembly and reassembly of these engines out-of-the-box. Not only is it good for your learnin', it also assures that everything is copacetic. That said; bearing replacement is simple once the case is opened.
 
I will agree with Kioshk here.. best to familiarize yourself with these engines before ripping it apart and dremeling the ports and throwing so called performance parts at it. Get a real good concept on porting first by reading as much as you can... you may find less is more, and you may find certain parts will lose their appeal to you once you learn more about these engines.
things I recommend would be a puch or Fred head, a basic port cleanup ( removing any nnikasil that overhangs the port openings and cleaning up the casting ridge in the transfers) re jetting the carb after break in, and a good expansion chamber pipe either modified from a dirtbike or a sbp pipe. This will get you over 35 mph. Widening the intake and exhaust ports by 1mm on each side will push it closer to 40mph.
You can easily get one of these bikes over 40 with the 44 tooth rear sprocket and stock nt carb just by following a few porting basics... just copy what others have posted and raise the exhaust roof by 1mm, cut 5mm off the bottom of the intake side of the piston, widen the intake and exhaust port by 1mm on each side, use a good cooling head like the puch or Fred head and use a better free flowing exhaust, even a modified stock exhaust will get you past the 40 mark with the stock carb if you follow these porting basics. Don't cut more than I recommended unless you have read all of Gordon Jennings's 2 stroke tuners guide and Graham bells 2 stroke books. There's a lot to gain by porting but go too far and you got a chunk of useless aluminum.
Don't bother with boost bottles or other hype, most of them don't work, the stock nt carb has got me and a lot of others past 40mph, and the stock exhaust is very restrictive, but by adding holes to the end cap and internal baffling can do a lot for better speed. Smaller sprockets also help but at the cost of acceleration, I'm hitting 42mph with the 44 tooth stock sprocket on a 26" wheel with a stock nt carb, a ktm pipe, and some more advanced porting and piston ramping,
read all you can about porting and have a spare jug and piston or 3 before you start in case you do goof up.

Oh yeah... use the better wrist pin bearing on the piston pin,the stocker isn't that good. For the crank and clutch bearings, if you do change them, the skf brand are some of the best made, use the sealed type and take off the seal on the inside on the crank bearings but leave both seals on the clutch bearings for best results.
Be sure to ask before cutting when your ready to port the jug and be sure to have a few spares just in case, ramp the piston at the exhaust and transfers before doing any cutting there,once you are happy with the performance, raise the roof on the exhaust the same amount you ramped the piston and replace the ramped pistonnwith a stock un cut one. Pistons are more expendable than a jug so that's the easiest way to tune the ports.
 
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