Schwinn/Predator 99cc Build Thread

You have made some of the best choices in parts...keep us posted on your build...I have used that jack-shaft setup also...let me know if you have any questions...

Waiting for photos to see if the Schwinn is a straight bar or cantilever.
SB

Waiting for photos to see if the Schwinn is a straight bar or cantilever.
SB

Looks to be a perfect fit in there with the motor...

Keep us updated with pictures and build info

You should do what the manual sez about oil weight. Common consensus from expert engine builders is that synthetic oil is not good to use for break-in. Keeps the rings from seating soon and well .

I broke mine on Castrol 10-30, and still use it . Almost 750 hard miles so far.

Cool bike. Don't mean to sound like a buzz kill but your exhaust is gonna
melt apart and hurt you. Unless that's brazed and not soldered those joints will melt apart and splatter molten globs on you.. I did it once and learned the hard way...just sayin... Not too sure about the rubber coupling either

TiM

Yes, a normal good tuned engine running in it's power band has around 1200 degrees exhaust gas temp. I think solder melts around 800 or so?
If that is silicone hose, it'll hold up for a while.

I've never tried with copper but I know you can use brasing rod to gas weld steel tubing exhausts sucessfully.

BeaverRat said:

Ok,
No buzzkill at all... I want this thing perfect, and I have time to switch stuff up before the jackshaft and clutch get here anyway. How would I go about making an airtight exhaust without solder? I have no access to welding, pipe bending, brazing...

And yes, it is the silicone hose from SBP.

Thanks

Click to expand...

I made mine air tight . If you take the time with a bench grinder and file and dial caliper, as I did, you can work the stock manifold pipe into a tight fit inside of 3/4 EMT conduit, which can be hand bent with a "hickey". No clamp needed and no leakage at all.

I used opti 4 30 wt in my new motor. Are you a plumber by any chance? That exhaust looks like the feed to my water heater that needs to be changed...lol. Listen to the last post and change it up a bit

Pictured below is a 1953 Schwinn with the 79cc Greyhound engine. I no longer have the bike, having sold it on ebay this past fall. Initially I had the exhaust routed under the rear rack with flexible exhaust pipe and wrapped it with asbestos header wrap. Worked fine for one winter, but the wrap trapped moisture and by spring the exhaust failed due to rust.

While rebuilding the bike and after making an in frame gas tank with much help from Tinsmith, I decided to run the exhaust forwards and down under, avoiding the need for header wrap. I bought this stainless steel pipe at a plumbing and air conditioning shop. As I recall, at the exhaust manifold I used the stub from the original exhaust which I cut off. I manged to fit the flex pipe over the stub and secured it with a seat post clamp... one from another old Schwinn. I reefed down on that and then wrapped it a bit with muffler patch. It is like a plastic or fiberglass ribbon that you wrap and then hold in place with wire or a hose clamp and when you fire up the engine it melts more or less and seals up the union. Worked fine.

I had tried making an exhaust for another Schwinn out of copper pipe, soldered it up with silver solder... thought it looked very cool and rode the bike about a hundred feet before the solder melted and the pipe came all apart. Back to the drawing board.

I like the exhaust in the photo. It is simple and works, contributing to the lines of the bike, in my opinion. I kind of wish I still had it. The EZ transmission was smooth and even the 79cc pulled pretty well on hills. I'd give it the 99 like you have and think it would make a very nice rider. Maybe I'll build another one sometime.
SB

Maybe you could adapt some curved tubing from something else. Kitchen chair? Mower handle/ generator roll cage? bicycle handlebars ect.

You could prolly get a local electrician to bend a 90 in a longish piece of conduit then you could cut it to fit at home.

They sell pre-bent 3/4 and 1 inch 90s at my local Lowes. They're not a very tight radius though.

MHF