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2 Valve or 4 Valve ?


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2 hours ago, Daniel Smith said:

What used to be enjoyable about uprights & earlier laydowns was their unreliability. 

Every race was unpredictable in the sense that even if a rider was miles in front they could (and did) breakdown at any point.

Most breakdowns now are just dropped / snapped chains

Used to be quite often problems with the  mag ,some said that one's put on by Jawa  in the 70's were off cement mixers  .

Edited by FAST GATER
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3 hours ago, FAST GATER said:

Used to be quite often problems with the  mag ,some said that one's put on by Jawa  in the 70's were off cement mixers  .

The mags on Jawa and japs were quite temperamental, some worse than others, thing is back in the day they were used on pretty much every engine so you got many different makes and models used especially on japs, on the engines themselves having rebuilt a few japs now I’m surprised they lasted till the 60s, especially the early ones,,they were real flintstone technology,they didn’t have gaskets so oil literally came out of every join, obviously they weren’t back then because there was no such thing but the 2 chrome pushrod tubes on the front of the engine are now replaced with cut down shower curtain rails with a bit of bicycle inner tube in the bottom as a seal,when the 2 valve Jawa came along is was a massive step forward in quality and reliability 

Edited by THE DEAN MACHINE
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On 10/25/2024 at 6:36 PM, THE DEAN MACHINE said:

I use the head on one of GM uprights 

Can I ask if your original intention was to convert the whole engine to upright?

If so, could you advise me on what alterations would be required in order to mount it in an upright frame?

I ask because I have a Jawa 898 engine which had been converted from upright to laydown, I believe by Lew Coffin.

Now that its been redundant for a good few years, I want to mount it in a PJ upright framed chassis that I have.

I've got all the external components required, but am unsure what changes would be required to the engine itself.

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12 hours ago, AFCB Wildcat said:

Can I ask if your original intention was to convert the whole engine to upright?

If so, could you advise me on what alterations would be required in order to mount it in an upright frame?

I ask because I have a Jawa 898 engine which had been converted from upright to laydown, I believe by Lew Coffin.

Now that its been redundant for a good few years, I want to mount it in a PJ upright framed chassis that I have.

I've got all the external components required, but am unsure what changes would be required to the engine itself.

To convert, basically you have to move the sump/oil pick up so as it’s on the bottom when the engine is upright and the oil pipe (internal or external depending on engine)  is above the center of the main shaft also the flywheels have to be rebalanced, unfortunately quite a few that were converted to laydown had the sump chopped off and welded up and a new one was machined further round the cases so it’s not really possible to convert them back, the first laydown GMs had both upright and laydown sumps on so easy to convert either way 

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