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CB250RS info please

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Oggers:
Dave

Many thanks for this - much appreciated. If the cam bearings are gone are we talking new head? As for rebore I don't really want to go there as it simply is not worth the cost. If things have worn between rings and bore would it be worth simply replacing the rings?

Renewing balance chain - Was this easy or a pig?

I assume renewing cam chain and tensioner is easy enough?

Cheers

Mark

Laverda Dave:
Hi Mark.
If the cam bearing surface is badly worn in the head and rocker cover both are effectively fit for the bin. There was a guy in Carshalton who was developing a bronze bearing insert repair, I actually saw it but he went out of business. As long as the oil has been changed on a regular basis and kept topped up you should be fine but obviously you won't know until you remove the rocker cover.
The balance chain was easy to replace although you have to do it with the engine split. The cam chain is a hy-vo or Morse type and spares are available. The cam chain tensioner is a sprung blade type, mine had no wear at all despite 15k on the engine.
You could try putting new rings in if the wear is within limits but my thinking would be why bother when the engine is apart anyway, if the wear was on or near its limits I would go for a rebore every time. The new piston will have new rings in the kit, an IMD piston and ring kit is about £50, rings alone will be £25-£30 and you'll have to run them in. The biggest issue you will have is removing the rocker shaft pins if the rockers require replacement, they really are a pia!
These are great bikes, a real hoot to ride and the engine is really easy to work on.
Keep us informed of what you decide to do.

AshimotoK0:
Think I  scanned these magazine articles on the CB250RS for Dave.
Useful reference

https://www.dropbox.com/s/318cabahyog0q9g/CB250RS_Strip_CMM_2011.pdf?dl=0

Laverda Dave:

--- Quote from: AshimotoK0 on February 25, 2022, 01:23:06 PM ---Think I  scanned these magazine articles on the CB250RS for Dave.
Useful reference

https://www.dropbox.com/s/318cabahyog0q9g/CB250RS_Strip_CMM_2011.pdf?dl=0

--- End quote ---

Yes you did Ash and they were a big help. I'm still looking for a FT500 engine if anyone has one lurking under a bench somewhere. I've just started back on restoring my Triton but the CB500RSA is something I hope to build next winter.

Oggers:
Dave

Once again many thanks. All advice is useful I feel. I haven't acquired the bike just yet, but if I do, for sure I'll check it out as you suggest. My problem with a rebore is cost and who does it. Up here in the wilds of Aberdeenshire you may appreciate that such delicate machining is something of a rarity amongst the tractor fraternity and the lump hammer appoach taken by the oil boys' machinists is not particularly encouraging- I should know as I am one of them....I'll give it some thought when I look down the bore for those tell tale wear marks!

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