1972 Jawa 250 Californian - Rust Machine

damiansd

Been Around the Block
Hey all,

Build Newbie alert!

I scored a seriously rusty Jawa off eBay Australia and have opened up the money pit that you guys call a restoration. Two of the key things that attracted this newbie to this bike are a) it's a single and b) it's a two stroke. Mechanically it doesn't get much simpler.

The bike is complete except for electricals. Whilst that's a real pain, I've got a good opportunity to convert this thing from a 6 volt to a 12 volt system. I figure a bit more juice and better spares availability are good arguments for the 12v conversion.

You'll note that in the title I've called it "Rust Machine". That isn't quite true as this is a Czech bike after all. So from here on in this Czech beauty is known as Rez Stroj.


A few before pics...

Rusty trailer picking up the beast.
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At home in the drive way.
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and
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and
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The traditional workmanship shows in the stamped plate. And the frame and engine are a matched pair.
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A feature I love is the speedo and key in the headlight. Classic!
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And while I've painted a rosy picture, there is plenty of work to come. Here is a shot of the exhaust. I'm sure there are critters living in there...
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So where to start?
My priorities are to get the engine sorted first, then start on the beautification. While I'd like to go pure restoration, there may be a few little changes. Things like indicators for example where I can't get them unless I raid some poor Czech farmers barn...


Cheers,
Damian.
 
Some background on what started this journey.

I've been talking about doing a build for a while. My son wants to get into the engine and get it going with me. My daughter wants to make it look awesome again, and being 18 months from getting a bike license thinks this bike is for her.

Here she is on 'her bike'. Good luck with that kid...

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She is into photographer and took this next shot.

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That picture is the inspiration for the bikes name - Rez Stroj (Rust Machine).

Cheers,
D
 
Tear down starts.

Tank removal was simple enough. My can of penetrant got a good workout.

Removing the seat was a bit more fun. The previous owner didn't have the seat key. After some inspection we found that the lock holding the seat wasn't a big problem.

Here is the seat pan and seat top after a little persuasion. Maybe time for a new seat pan.

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You'll have to forgive me but so much of the craftmanship catches my eye. Here is the right hand engine cover.

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Exhaust came off simply enough, this it was time for the engine. Then was easier that expected as the engine wasn't bolted into the frame. It was just sitting there. Thankfully years of dust and rust kept it from falling out. Here it is up on the work bench.

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Side panels, exhaust brackets, pegs and brackets, tank and exhaust all start to fill up my shelving.

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And here is where I got to by the end of the day.

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Next up - engine teardown and condition check.

D.
 
As suspected, the engine is siezed.

After undoing the top end screws I wanted to find whether the problem was top end (piston) or bottom end. I attempted to lift the barrel and the piston came with it. OK, so the piston is the problem and the bottom looks ok. That's at least a small victory.

After much reading, here is the unseize protocol I'm going to follow:

1. Fill top of chamber with penetrant and a little brake transmission fluid and let it soak. Every day as I pass by, hit the barrel with a rubber mallet and turn the wrench on the drive shaft. The intent is for the occasional knock to cause a mechanical vibration, breaking the link the rusted rings have on the bore. The transmission fluid is thin and should leak through. Do this for a week.

2. At end of week it get's the fire treatment. Fill the top of the chamber with 50% petrol and 50% ATF. Put a small piece of rag in too and light it up. The rag will function as a wick. Let is burn out and cool it over night. In the morning, put the end on its side and hit with the rubber mallet.

3. Repeat 1 and 2. If still stuck after a few weeks, fashion up a puller to drive the piston down.

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Hammer, dangerous fluids and fire. What could possibly go wrong?

D.
 
What a great and unusual project! In the 70s, I knew a guy who had one with a sidecar. If I remember correctly, the shifter and kick start lever are the same.
Rider
 
Hey Rider,

Yeah, you push the shifter in towards the engine, flip it towards the back of the bike and it is the kick starter.

A bit freaky, but cool too.

Cheers,
D.
 
Using scrap from around the garage I made up an engine stand

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Maybe not as sturdy as it could be, but it is better than what I had.

The front and rear fenders came off and the piston is still soaking in my penetrant home brew.

Damian.
 
Another quick update.

Got the wheels off. Need new tubes and tyres. Spokes and rims need a spruce up.

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Headlight came up. Yes, I love it.

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Front forks and triple tree also came of. They will clean up ok.

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So after much demolition works, here is what the frame looks like. You'll note that the rear shocks are still in place as they didn't want to play ball...

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Cheers,
D.
 
Another update

Left peg bracket is now off. Right bracket is stuck. So time and penetrant are doing their work.

I figured it was time to go back and attempt to get the left hand engine cover off. It was still stuck good. After much reading on here, I went and purchased a manual impact driver. Man, these things are good. A few minutes and I had all of the screws out.

There was still oil in the case and I caught that in a bucket (well mostly). Once the cover was fully off I was greeted with black caramel oozing and sloshing around in there. Yuk!

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The kick starter shaft and spring came out and both looked in good condition.

Next up was the clutch.

I used a spanner to press down the springs and the pins came ok. Thankfully none of them pinged around the room. The plates definitely need replacing. In some places the friction pieces had totally come out. I kind of expected this, so that's cool.

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Jawa in their wisdom have a number of specialty tools to remove nuts, bolts, gears, and the like. Getting the clutch nut and crank sprocket nut off both need a tool. After a good think I came up with my own solution.

I got the angle grinder and made this tool shown below. It slips over the clutch plate holder bolt and the clutch basket. This enabled me to take the clutch and crank sprocket nuts off with not too much trouble.

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So current status:
- Piston still soaking and is due for some flame attention soon
- Right hand peg braking is soaking and will get some multi grip action soon
- PLUS swing arm bolt is out, but I need to get the bush pressed out

Fun times.
Damian.
 
OK. The piston has had a week of soaking. So I thought I'd try the heat/cool trick to release the piston rings. I filled the top of the cylinder with 50% petrol and 50% ATF, ripped up some rag then set it alight.

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Black smoke billowed everywhere and she burned for 25 minutes. After that I turned it on its side and let is cool for the night.

In the morning I gave it a whack with my rubber mallet. No joy, so far. So I refilled my own penetrant mix into the top and started the next week cycle.

I finally got the rear shocks off. The rubber bushes were holding the bolts tight and didn't want to let go. In the end I drilled the bolts out, even then the rubber bushes were stubborn. All good now though.

The right peg bracket is still stuck. Nearly time for the multigrips and my clawed 'persuader' to help it out.

Cheers,
Damian.
 
Nice build Damian, I have not seen a Jawa for a long time. Should be a great little bike once you are done with it.
I too am having stuck engine problems, we are following the same procedures and having the same results. I can share your frustration.

Keep it up mate, looking good so far.
 
All right. Waiting time is done. At this stage I've assumed that a rebore, new pistons and rings are needed.

So, I rigged up a pusher to drive the piston out of the barrel.

I got a little exuberant with my rubber mallet. I broke off a fin on the barrel. Cest la vie. Time to practise my welding skills.

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Here is the piston all jammed up.
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After much adjusting, twisting, driving, ... the piston came out. Gudgeon pin came out clean enough.
Two long gouges are left in the piston from me not driving out dead straight.
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Thankfully the bore looks good although the piston has no intent of fitting in. So a bore it is. The rings are totally fused to the piston so I'll be putting both on a shelf as a momento.

Next up - remove the dynamo and split the case.
 
The kids wanted to be involved in this build too, so I sent my youngest out with:
  • All the cases
  • A spray bottle of truck wash
  • A power washer

Needless to say he had fun. And the parts cleaned up ok too :p

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Cheers,
Damian
 
Getting the dynamo off proved a challenge, until I spoke to the guys on a Jawa specific forum - http://groups.yahoo.com/neo/groups/Jawachat/conversations/topics

Find the right bolt, chamfer off 1.5cm at the end and it worked great.

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Next up came the real fun, splitting the case. As this is my first rebuild I was a bit scared of this piece. I had visions of the gear box spilling all over the floor. I contemplated not shining up the cases and just getting it going with grit and all. But the wife is all excited about making the rest of it beautiful, so I bit the bullet.

My harmonc balancer puller came into its own and functioned very nicely as a case splitter. My rubber mullet also assisted in persuading the case to came open. And a bonus - the mallet didn't break anything this time.

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I was quite relieved when the case was open as all looked good. Gear box all moved nicely and the teeth looked fine. Excellent!

Here are shots of both halves. Not too shabby.

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I had hoped to get the crankshaft out too. But it is proving stubborn. More on that in the next update hopefully.

Cheers,
Damian.
 
Today was an early Christmas.

My new clutch plates and gaskets arrived.

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I know, I know. Small things amuse small minds.

D.
 
It's actually a strange one with two exhaust ports out of the one head. Never heard of it before. Let's see how she goes.
 
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