Motor swap plans for a locked engine jawa

Hi all!

I’m planning on doing a bit of a fun conversion for myself by converting my jawa (210?) from 1984 into a fun simple ride. By using a 1974 chain saw motor I recently bought from a auction.

I got the general idea figured out. Not exactly sure how I’m going to figure out the throttle and choke lever yet. But that’s a fun adventure that awaits.

Got the chainsaw motor running with about five minutes of work. Only thing I’m not sure on is if the clutch will slip or not with my weight on the bike. Will attach photos in the chat of my bike and my plan

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Re: Motor swap plans for a locked engine jawa

Ian MacKenzie /

Motor I plan on swapping into the jawa

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Re: Motor swap plans for a locked engine jawa

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.

Re: Motor swap plans for a locked engine jawa

Yeah the hard part about those engines is they really don't have any square/regular bolt pattern type faces usually. The older ones can be better but the modern stuff is just chilling in rubber cushions.

Re: Motor swap plans for a locked engine jawa

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...

Re: Motor swap plans for a locked engine jawa

I don’t dig friction drive, but yeah, chainsaws are peaky and will need to be spinning high high revs to pull a moped around.

Direct drive with a tiny roller may get you there easily. Or maybe one of those old-timey leather belts that are on a pulley the same diameter as the rear wheel?

I like weird projects but dont envy the work that has to go into this.

I have been eyeing the ignition on a chainsaw lately…

Re: Motor swap plans for a locked engine jawa

no groms no blasters /

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

Re: Motor swap plans for a locked engine jawa

Ian MacKenzie /

Would swapping on a clutch from a go cart work for better push off power? My grandfather in law had a old go cart he had in the 70’s and mounted a chainsaw motor to with some help of a machinist friend that had modified the original clutch bell to use standard chain drive rather then chainsaw. But he said he had to push it a bit as a stop to start it couldn’t push him off the line

Re: Motor swap plans for a locked engine jawa

Ian MacKenzie /

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

Re: Motor swap plans for a locked engine jawa

Just to be clear, you are doing this because of a masochistic need to put a chainsaw engine on a moped, and not because you don’t want to rebuild or replace the existing engine… right?

Everyone here, maybe everyone, loves to see you experiment. But nobody thinks this is a good idea if you just want to make the moped work. Feel me?

Re: Motor swap plans for a locked engine jawa

Ian MacKenzie /

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.

Re: Motor swap plans for a locked engine jawa

Ian MacKenzie /

The exhaust is going to be needed to be replaced with a smaller version that still flows well but moves outside of where the chain is located. Currently looking into a mini torque converter to replace the one original to the chainsaw motor. After the chain alignment is figured out I’ll get the bar and square tubing cut and bent into shape as well as welded by my wife’s cousin as my personal welding equipment is at my family’s shop over a hour away

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Re: Motor swap plans for a locked engine jawa

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)

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Re: Motor swap plans for a locked engine jawa

Frank will be here soon, frank is everywhere, frank is Jawa, frank is life.

Re: Motor swap plans for a locked engine jawa

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

Re: Motor swap plans for a locked engine jawa

Around 11 min this guy has some cool echo engine jackshaft action. Teapot mufflers… the little lids flap. I like it.

Maybe the jawa engine could be bought for cheap. I dunno good luck mdude.

Re: Motor swap plans for a locked engine 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?

Re: Motor swap plans for a locked engine jawa

> Trent Anderson wrote:

> -------------------------------------------------------

> 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?

Chain saws use a pumper carb and function in any position .

Exhaust can be routed as needed .

Re: Motor swap plans for a locked engine jawa

> Frank Bailey wrote:

> -------------------------------------------------------

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

Re: Motor swap plans for a locked engine jawa

Pavel Rehacek /

Why Are you don't use original engine Jawa 210? One is on Ebay

Re: Motor swap plans for a locked engine jawa

Ian MacKenzie /

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.

Re: Motor swap plans for a locked engine jawa

When I was a kid I took an old homelite or partner chainsaw and tried to power an old schwinn cruiser. I had a sprocket welded to the clutch and had the largest 10 speed front sprocket welded on to the rear. The bike was OK if you could get it going. You are just gonna burn that clutch up. Sorry but you are wasting your time. Prove me wrong? I still have all the bits. I even put the beach cruiser bars upside down for the cafe look. Didn't help

Re: Motor swap plans for a locked engine jawa

Ian MacKenzie /

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

Re: Motor swap plans for a locked engine jawa

Show us pictures of the Jawa engine. I've saved some pretty bad ones.

Re: Motor swap plans for a locked engine jawa

Ian MacKenzie /

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.

Re: Motor swap plans for a locked engine jawa

i would be interested in that Jawa 210 engine

rusty or not

let me know after all is said and done

i am in KCMO USA 64114

Re: Motor swap plans for a locked engine jawa

Ian MacKenzie /

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

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Re: Motor swap plans for a locked engine jawa

That's the two speed engine and definitely rebuildable. All parts are available from The Jawa Shop. What kind of small engine repair experience do you have? From my experience the two speeds are fun but a bit tricky.

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