silly bollox

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I mentioned very early in the rebuild about extensive damage on flange next to main bearing I had repaired. emp in havant laser welded up like new and also fixed an rh4 head I have and exhaust valve guide crack in the rh10 in the pictures. can't recommend highly enough
 

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Fast Eddie said:
The “an 850 is better than a 920” concept is a bit subjective IMHO.

Firstly, for most peoples use in classic circles, I believe it’s totally true. The stock motor is a good performer by classic standards and more than enough for club runs, touring, etc.

Secondly, a poorly built 920 is, obviously, gonna be worse than a well built 850. And back in the day, I reckon quite a few 920s weren’t really up to scratch (using Swiss Cheese barrels, heavy car pistons, etc).

But... a well built 920, that has been built ‘as a package’ is a sweet thing. My Maney / JS 920 is incomparable to a stock 850 in terms of performance, it’s also a much lighter engine unit (by approx 17lbs), and whilst it shakes about at tickover, it’s unfeasibly smooth in use.
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If the piston weight is greater, the motor usually won't spin up so quickly. The trade-off is between piston weight and extra capacity. A 2mm oversize 850 is probably almost 900 anyhow. For touring, I would not bother. For racing, methanol fuel is a much better way to go, if there are no fuel checks or it is permitted.
 
For a touring bike - if you go 920, how many oversizes do you have remaining for rebores ? Might be a short term strategy for long term usage ?
 
acotrel said:
If the piston weight is greater, the motor usually won't spin up so quickly. The trade-off is between piston weight and extra capacity. A 2mm oversize 850 is probably almost 900 anyhow. For touring, I would not bother. For racing, methanol fuel is a much better way to go, if there are no fuel checks or it is permitted.
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Exactly, and some kits used to use bloody heavy pistons!

JS 920 pistons are actually slightly lighter than stock 750 pistons...
 
Great looking bike and wonderful build pictures. Now I want an audio to listen to. She must sound terrific.
 
Scout63 said:
Great looking bike and wonderful build pictures. Now I want an audio to listen to. She must sound terrific.
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went out early this morning to beat the traffic. went under the same railway bridge twice in quick succession! ;)
 
Fast Eddie said:
Exactly, and some kits used to use bloody heavy pistons!

JS 920 pistons are actually slightly lighter than stock 750 pistons...
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nigel.noticed all these posts since I started on here. all the same thread. acotrel… wedding night. I really think you coulda tried harder darling. never happy with a single post!
 
freddie1105 said:
nigel.noticed all these posts since I started on here. all the same thread. acotrel… wedding night. I really think you coulda tried harder darling. never happy with a single post!
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everyone is entitled to an opinion. he just takes the piss
 
as an aside. what does it matter how many rebores you can have? you have the barrel off anyway. new liners are 70 quid and you keep the pistons. you have to take the barrel off either way!!!!
 
freddie1105 said:
as an aside. what does it matter how many rebores you can have? you have the barrel off anyway. new liners are 70 quid and you keep the pistons. you have to take the barrel off either way!!!!
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i'd like to say a big thankyou to. js engineering and matt at cnw. these guys are why so many of us can keep improving our commandos. mr comstock ain't too shabby either;)
 
Clean and crisp.... Yes blue is very fast, ..... and leaks less too from what I hear. Beautiful machine all joking aside.
 
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