Triumphrat

Eggman

I tried the classic forum, but I haven't gotten any replies...........Is it a straightforward conversion to put a 750 kit w/ an alloy (9 bolt) head on a pre-unit bottom end? I have seen a post (somewhere) that recommends a 9 bolt set-up to mitigate head gasket issues. Maybe a simpler question is...........will a unit type top end fit a pre-unit bottom end? I heard mention of tappet blocks being different, but it wouldn't bother me to update those either.
Thanks in advance,
The Eggman

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freebeer

Shouldn't be a problem. I have a generator style pre-unit bottom with a 9-bolt alloy head and an 800cc top end. Most internals, I've found are relatively interchangeable within the same size/class bikes.

Another thread I started had a reply from DAGAD that seems to indicate that prior to 1954, there may be some issues, but that post referred to the crankshaft.

Tappet blocks should come with the cylinders, no? Just remember to use the 'R' tappets.

Eggman

Concerning the tappet blocks...................different people have different ideas on what comes w/ what when buying used parts. It would be nice, however. What makes an "R" tappet an "R" tappet?

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kludge

'R' tappets have a larger radius than the standard ones. IIRC it's 1.50" vs. 1.25", or is it 1.25" vs. 1.00"?
The larger radius reduces wear on the cam flanks if you are running something like the E3134 cams.

If you buy a new cylinder it will not come with tappet blocks. If you buy a used one it will, since they are a chore to remove. Most people won't bother.

As to your original question, you can fit a unit 650 cylinder to pre-unit cases. Morgo made a 750 kit for the unit engine and 9-bolt head.

[ This message was edited by: kludge on 2007-06-21 02:46 ]

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My other ride is 28m2 of nylon

Eggman

Thanks Guys! I appreciate the help!

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