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I lived in Prague for two years and had a succession of Jawa "Kyvackas" both 250 and 350. The California models were rare there because they were for export. Sometimes I miss my first one - a mint red 1964 250. Every once in a while i see one for sale and I suppose I'll buy another at some point.

I think Californias are still premix. The oil-injection ones were called "oilers" or something like that - I'm sure you can find out on the net.

Remember they're positive ground...
 

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I lived in Prague for two years and had a succession of Jawa "Kyvackas" both 250 and 350. The California models were rare there because they were for export. Sometimes I miss my first one - a mint red 1964 250. Every once in a while i see one for sale and I suppose I'll buy another at some point.

I think Californias are still premix. The oil-injection ones were called "oilers" or something like that - I'm sure you can find out on the net.

Remember they're positive ground...
 

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I actually thought that was kind of a cool feature. Flip that sucker up by the little tab on the back and kick it over... One up four down.

Some of the early ones had an automatic clutch feature too. A little cam inside the shift lever would depress the clutch pushrod a little bit to release the clutch when you shifted. The problem is that it wouldn't release it totally and it would eventually burn out the clutch. The Czech dudes removed the pushrod. Neat bikes that stayed hopelessly outdated because of politics.
 

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I actually thought that was kind of a cool feature. Flip that sucker up by the little tab on the back and kick it over... One up four down.

Some of the early ones had an automatic clutch feature too. A little cam inside the shift lever would depress the clutch pushrod a little bit to release the clutch when you shifted. The problem is that it wouldn't release it totally and it would eventually burn out the clutch. The Czech dudes removed the pushrod. Neat bikes that stayed hopelessly outdated because of politics.
 

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Yeah, all 60s/70s Jawas are pretty cool looking but slow. Perak (pillar suspension) motors are interchangeable with kyvacka (swingarm) motors with a few exceptions (different air intake/air cleaner and slightly different cases. So if a motor fits into a Perak frame, it should also work with a Kyvacka frame - the tank might be an issue, though, since they are different.

Those 2-stroke motors were designed in the 30s and only updated slowly until they stopped making them sometime in the 90s.

There was a Kyvacka that I would see around Prague with some kind of motorcross engine - I never got a good enough look at it to see what it was.

There was a 150cc version with slightly smaller frame that had a CZ motor in it - the 125 & 150cc versions were marketed as "Jawa CZ" bikes since the motors were CZ & the frames were Jawa. The 150cc motor actually felt faster than the 250 version.

I'm sure an RD motor would make a great conversion. The only area I would worry about interference would be the frame backbone - I don't know if you could squeeze the RDs carbs back there.
 

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Yeah, all 60s/70s Jawas are pretty cool looking but slow. Perak (pillar suspension) motors are interchangeable with kyvacka (swingarm) motors with a few exceptions (different air intake/air cleaner and slightly different cases. So if a motor fits into a Perak frame, it should also work with a Kyvacka frame - the tank might be an issue, though, since they are different.

Those 2-stroke motors were designed in the 30s and only updated slowly until they stopped making them sometime in the 90s.

There was a Kyvacka that I would see around Prague with some kind of motorcross engine - I never got a good enough look at it to see what it was.

There was a 150cc version with slightly smaller frame that had a CZ motor in it - the 125 & 150cc versions were marketed as "Jawa CZ" bikes since the motors were CZ & the frames were Jawa. The 150cc motor actually felt faster than the 250 version.

I'm sure an RD motor would make a great conversion. The only area I would worry about interference would be the frame backbone - I don't know if you could squeeze the RDs carbs back there.
 
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