Questions about making 66cc more reliable,

Discussion in '2-Stroke Engines' started by JeffHWV, Jan 7, 2017.

  1. JeffHWV

    JeffHWV New Member


    My first post, have been lurking for past few weeks getting info before I bought anything and just signed up.

    I bought a 66cc kit on eBay and a new Schwinn Drifter. The engine castings look better than I expected although they have been bead blasted. I did some light disassembly after I got it. The first thing I noticed is intake is complete junk, no way that thing will ever stay tight on a vibrator like this as there is not room for fastener head to contact anything more than edge of weld and weld itself is pathetic, protruding well into the port. Definitely going to need revamped. Next thing I noticed is clutch shaft is quite loose in bore, like maybe 1/16" undersized. Is this common to these engines and is it a problem area? Other than random torque if any on fasteners engine looks okay.

    I have substantial experience with Husqvarna chain saws and have done several complete rebuilds. My intention is go through the entire engine before I mount it to the bike. I did some research on crank bearings and I see them advertised with a single metal shield on a 6202 bearing. I keep a set of SKF 6202C3 as 372 Huskys take them but they are open bearings. Does anyone know if these engines are supposed to use a shielded bearing and if so why? Crank bearings are the most important component in a two stoke engine longevity wise and I want them to be right. I figure if the crank balance is near right and the SKF bearings will make the bottom end trouble free for more than the life of the engine. Also, wouldn't it be better to use rubber sealed bearings on the jackshaft bearings? I know from experience that the bearings with metal seals rust pretty fast and don't seal that great either.

    I have seen some posts about the poor quality of the crank seals. Are there better ones available? Do they have problems staying in?

    I noticed the gaskets are very poor quality. Are decent gaskets available or is it better to go with Threebond if thickness isn't an issue? I have a mountain of used socket head bolts from saws so I will use them where I can and buy any fasteners that look iffy.

    Also, I bought a rope starter separate from the kit but didn't realize how wide they make the engine. Can you run one on the bike and still be able to pedal it, or is it even practical? I thought it would make it a lot easier to warm up the engine and do any tuning.

    Any comments or suggestions on this will be appreciated. Thanks

  2. butre

    butre Well-Known Member

    I've never heard of any issues with the clutch shaft other than people losing the pin that holds it in place.

    there's no need for a shielded bearing since the crank seals hold all the oil in. the wrist pin bearing is a bigger concern, you probably have some Stihl 028 wrist pin bearings laying around too if you keep the 6202s as well. the big end bearing likes to go out too sometimes but it's a bear to replace so I just swap the whole crank when they go out.

    the crank seals aren't really that bad, they just have a tendency to blow out when people leave the fuel on and all the gas ends up in the case. any 15mm x 27mm x 7mm seal will work

    there aren't decent gaskets available, but the shape is simple and gasket paper is cheap, plus you already have a template if you make the gaskets before ruining the originals. shoot for about 3mm on the base gasket and as thin as you can get a hold of for the head gasket. the thicker base gasket significantly improves the port timing.

    you need offset cranks to run the pull start and still be able to pedal. the easy way to do tuning is to start it with a drill.
  3. Jonj57

    Jonj57 Active Member

    I currently use the pull starter setup and the thing pedals just as easy as anything else, though I only use one of the offset crank arms and the regular mountainbike style right side crank arm that comes with the jackshaft kit. After just one ride you immediately get used to the slight offset and don't even feel it anymore. I'd also recommend lightening the wrist pin and piston by boring and drilling them out a bit as per Jaguar's website. Makes the vibrations a non issue unless you've got a 9000 RPM rip-roarer. I'd also recommend to EVERYONE that they use the jackshaft mounting plate even if they don't use a jackshaft, having 3 points of contact to the frame with firm muffler clamps creates an absurdly strong mount compared to the weak 2 point system that comes stock.
  4. crassius

    crassius Well-Known Member

    Are you confusing the bucking bar with the clutch shaft? It is a loose fit inside the shaft.
  5. JeffHWV

    JeffHWV New Member

    Thanks for the replies. I'm thinking maybe doing a total tear down might not be worth it if I am just as likely to have trouble with the rod bearings. They are virtually trouble free on Electrolux saws. I have reused the cranks on multiple rebuilds and have only had one lower rod bearing cage failure in almost 25 years of working on them and it was a factory build. Never had a problem with a wrist pin bearing and I reuse the oem ones if I use an aftermarket top end. You wouldn't think you'd have problems considering they are running considerably lower rpm but with Chinese stuff you never know. I mostly only work on my own stuff and haven't had a Stihl since the eighties but I can probably get my hands on one if I decide to do it. Probably an equivalent Electrolux as I think the top ends are made by Mahle on both brands.

    What I called the "clutch shaft" is the shaft the lever arm hooks to and has the notch the ball sets in to push on the rod that disengages the clutch. I had seen some references to "bucking bar" but was confused as the same term is used for the lump of steel used to back up aircraft rivets. It is very loose in the housing.

    Might not be worth it to me to go with the rope starter. I'll have to wait and see. Thanks again.
  6. Frankenstein

    Frankenstein Well-Known Member

    I dare you to install a pull start. Some of the best hunks of crap money can buy. Sorry I meant worst and wasted on.

    If you have a standard set-up then in nearly every case you'll find it easier to pedal start, it really takes no effort and has zero complications or aggravations. You're also using your body weight to start once you get moving, if the motor is in good condition it should start very easily (after break in.)