MOPED ARMY

The throttle and choke are easy enough, you basically just need a bracket with a hole for a cable adjuster and a knarp. The harder part is going to be mounting the motor and routing power from the clutch, to a gear reduction counter shaft to the rear wheel. I think if you mount the motor upside-down with the clutch on the drive side the rotation should be correct. You could also mount it with the cylinder towards the back which shouldn't really be a problem with a cooling shroud.

Good luck on your project. I had considered a chain saw motor but the old Homelite saw I have is only around 30 cc. If memory serves the larger chain saw motors are around three horsepower. If you run into mounting issues you may consider making a cantilever mount on the front forks for the motor and mounting a friction drive wheel onto the clutch . You would end up with a Solex style drive something like this vintage Tanaka bike bug motor...

finally someone has found a solution to the problem of mopeds not running when they are upside down

Luckily this one has both a great top and bottom mount on the body. The top one is simple enough to just put a bar across and it won’t be in the way of anything. My plan is to run a flat bar along the top. And mount to two of the frame mounts. And have a third mount at the very front go to the original bar mount on the side of the engine. That way any torque (ha) will be soaked up by that mount rather then the welds on the top flat bar

To be 100% honest. The whole engine in the jawa is too far gone to fix. There was water sitting in the engine for quite some time that all the parts but a handful are saveable. Replacement engine cost to have shipped to me as I can find them in state side but I live in Canada. So shipping over doubles the price then the conversion is making any engine I can find thats original not worth it to me cost wise. The chain saw I bought for less then $15 cad. I’m not planning on doing anything to convert the frame from original as much as I can do if I do eventually come across a motor in Canada for a reasonable price I’ll totally buy it and put it in instead. But for the mean time I’d like to have a running project thats different then others.

Well, the gearing spreadsheet I was just playing with yesterday showed a ratio of around 12:1 for engine:rear wheel rpm on an E50. In that situation people were shooting for 10,000rpm @ 55 mph.

Not knowing anything about that chainsaw engine you have, I’d assume it will need to turn 10-12K rpm to go 25mph?

If you want to do that in one jump, geared from the crank to the rear wheel, you’ll need a 14 tooth sprocket on the crank and a 336 tooth sproket on the rear wheel.

I don’t know if they make those.

But if you build a jackshaft mount right behind the engine, you could drive a small gear off that to the rear wheel and stay in “normal” parts configurations. (edited)

Frank is withholding comment. A Jawa without its heart is not a Jawa.

I'm intrigued. If the motor is mounted upside down, does the head then get re-mounted upside down so the carb (and exhaust) function correctly?

I’ve seen it yes. But for it to cross the border to me it adds over $200 in duty and shipping fees. And I don’t plan on spending too much on this build as of yet. The jawa cost me $200 (I know I over paid on that) and the chainsaw under $15 and I had it run in about five minutes after getting it home. I’m trying to keep the new wife happy by not spending too much on it for a once and a time riding or at the track for fun kinda thing. If I didn’t have crazy winters in Canada and didn’t have a newer car I’d probably ride mopeds all year round otherwise.

I still plan on trying for the sake of trying. If this engine/clutch set up doesn’t work I’m not out a lot but any means

Will try to get photos once I can open the garage door. Neighbour is parked way too close to the garage door to get inside right now.

I’ve attached the worse of the spots in photos. I have the head which was in surprisingly good shape considering the inside.

Hi frank! Sorry for the very late reply to this. I know the engine is salvageable but it’ll need a new crank as the one end is broken off on the clutch side. And wasn’t too sure how much of a bore out the cylinder would need to be repaired and at which point I could no longer get a piston at.

I have a bit of engine rebuild knowledge. Mostly from small block dodges tbh. I did rebuild a old Peugeot 103 motor that ran once I put it back together. But I don’t count that really as too much knowledge.

The underlining issue to be frank is my wife and I only recently got married and as much as she loves the Batavus Starflite I own she’s not super thrilled with the amount I spend on the bike projects. As a couple we also have a 70’s Goldwing and pair of cb750s in there that I’m trying to thin out.