Hello. I was wondering what the motor/kit options are for my bike. It is a 1979 Schwinn Varsity, 27 inch frame, 15 speed. I was trying get a high cruising speed, probably around 40 mph, for use in rural Texas. Any advice is appreciated. 
79 Schwinn Varsity
- Thread starter TorrentIV
- Start date
You're going to have to do bar work, I'd suggest a straight bar with bolt on horns, so you can have your throttle on the inside of the horns.
As far as clearance, you're set - a motor will take to that size tube frame well, but, without knowing measurements of the intersecting tubes at the cranks, I can't say if you'll have clearance for the sprockets.
As well, I'd try to figure something out for alternative driven sprocket mounting, either disc brake mount, dual threaded hub, or clamshell adapter. With the longer spokes on the larger wheel, they will flex more and your wheel won't last so long.
As far as clearance, you're set - a motor will take to that size tube frame well, but, without knowing measurements of the intersecting tubes at the cranks, I can't say if you'll have clearance for the sprockets.
As well, I'd try to figure something out for alternative driven sprocket mounting, either disc brake mount, dual threaded hub, or clamshell adapter. With the longer spokes on the larger wheel, they will flex more and your wheel won't last so long.
Measure the outside diameter of your old bars at the point they go into the headset.
I was 235 last year, and I got around fine on a 48cc china girl 2stroke.
I was 235 last year, and I got around fine on a 48cc china girl 2stroke.
I have a '67 Collegiate, similar frame/smaller size, with 26" wheels. I had to spread the rear chainstays of the bike to make room for the drive gear in the back. I spread it to 135mm or so from the 120mm it is stock and used spacers as well. This gave it enough clearance.
My bike is the smaller frame, and it is super heavy, I'm at least 220. It's hilly here so I went with the 66cc. The starts are where the bigger engine really helps. Obviously the size 48cc is the most legal way to go.
The old schwinns work really well to absorb the shock due to the weight. And the steel spreads easy for the clearance. The problem I've been having is that I keep breaking the back wheel. First it was the spokes, due to the rag joint that comes with the kit. So I upgraded to 12 gauge spokes. Then a pot hole blew out the hub. So expect for some problems to arise with the rear wheel. If this is a regular form of transportation for you you should be looking into a better solution to mount the rear sprocket as these folks have suggested. You probably want a hardier wheel in the back. I haven't found a good solution yet. I was hoping that sportscarpat's new adapter could be used with a multi speed bike, but it will require some modifications. Also Staton Inc has a hub that can have a multi speed cog on one side, and a drive gear on the other. Not sure about the price.
The kit should work with the stock china girls, as long as you spread the rear. But yeah, that back wheel will take a beating.
My bike is the smaller frame, and it is super heavy, I'm at least 220. It's hilly here so I went with the 66cc. The starts are where the bigger engine really helps. Obviously the size 48cc is the most legal way to go.
The old schwinns work really well to absorb the shock due to the weight. And the steel spreads easy for the clearance. The problem I've been having is that I keep breaking the back wheel. First it was the spokes, due to the rag joint that comes with the kit. So I upgraded to 12 gauge spokes. Then a pot hole blew out the hub. So expect for some problems to arise with the rear wheel. If this is a regular form of transportation for you you should be looking into a better solution to mount the rear sprocket as these folks have suggested. You probably want a hardier wheel in the back. I haven't found a good solution yet. I was hoping that sportscarpat's new adapter could be used with a multi speed bike, but it will require some modifications. Also Staton Inc has a hub that can have a multi speed cog on one side, and a drive gear on the other. Not sure about the price.
The kit should work with the stock china girls, as long as you spread the rear. But yeah, that back wheel will take a beating.
Oh, also, I did have to get a one piece crank that was wider, as the stock schwinn one did hit the motor. The one I got I believe was made by pyramid, and only slightly wider, but it worked. I bought it from spooky tooth, I'm not sure they are still in biz. The other must have upgrades are the dual pull brake leaver from Sick Bike Parts, and if you use the chain tensioner that comes with the kit, then you have have have to replace the bolts with grade 8 hardware so that the thing is tightened down so that it won't bend into your wheel. Most folks here recommend drilling through the chainstay, or finding a way to go without the tensioner. For my collegiate I found that I had to use the tensioner, the first bolts stripped thankfully alerting me to their shoddiness. With good bolts you should be able to clamp that sucker down so you can kick it without it moving. After I clamped it down I used a plumbers wrench to put a slight twist in it so it was better aligned with the drive chain. It took a while to get that right. If the chain derails, then the rear wheel locks.
DuctTaped Goat's got it right, you want an upright bar, straight or even curved like the collegiates and some varsitys come with.
Upgrade's I'd recommend for first install:
grade 8 bolts for chain tensioner
wider one piece crank
upright bar or flip your current handle bar
dual pull brake lever from Sick Bike Parts
#41 chain, you can get it online the stock chain can be a problem
For Later/Post Break In/going over 15mph:
Replace back wheel with a better hub, drive gear solution, aluminum rims
Better Brakes! This can be accomplished with a V brake and aluminum rim in the front or something fancier like a disc or drum brake.
HD Throttle from Sick Bike Parts
better spark plug
Also, I run the 100:1 ratio Opti 2 oil, I think it's great, there is debate over it though so use at your own risk. There's a mega thread on this board about it.
I so far have had good luck with the Grubee Skyhawk 66cc kit. I have the standard, non Super Rat version. I"m not sure I'd go with the Super Rat in it's current incarnation. For one I am using the White wire for lighting, that is not available on the Super Rat.
Here's a vid of my Collegiate:
YouTube - Back In Business
DuctTaped Goat's got it right, you want an upright bar, straight or even curved like the collegiates and some varsitys come with.
Upgrade's I'd recommend for first install:
grade 8 bolts for chain tensioner
wider one piece crank
upright bar or flip your current handle bar
dual pull brake lever from Sick Bike Parts
#41 chain, you can get it online the stock chain can be a problem
For Later/Post Break In/going over 15mph:
Replace back wheel with a better hub, drive gear solution, aluminum rims
Better Brakes! This can be accomplished with a V brake and aluminum rim in the front or something fancier like a disc or drum brake.
HD Throttle from Sick Bike Parts
better spark plug
Also, I run the 100:1 ratio Opti 2 oil, I think it's great, there is debate over it though so use at your own risk. There's a mega thread on this board about it.
I so far have had good luck with the Grubee Skyhawk 66cc kit. I have the standard, non Super Rat version. I"m not sure I'd go with the Super Rat in it's current incarnation. For one I am using the White wire for lighting, that is not available on the Super Rat.
Here's a vid of my Collegiate:
YouTube - Back In Business
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