CB750 F2 Primary chains

[archmill]

Hello, Have at last started re-building the CB750 F2 as a cafe racer and started building the engine this weekend. The last time it ran was 1982 and the guy who passed it on to me said it dumped all the oil on his boots so he stuck it in a shed. Have stripped the engine completely so I am starting from scratch.
Measured the primary chains and got a size from the oil pan face to the tensioner of 69mm so I recon they are done. Bike had only 25,000 miles on it.
Where is the best place to get new primary chains and tensioner.
Any advice greatly appreciated.

[Athame57]

I'd check out David Silver Spares for something like that. https://www.davidsilverspares.co.uk/

[Martin6]

Wear limit spec is 70mm. Does anyone know what this measurement is with a brand new chain?

[Athame57]

Wear limit spec is 70mm. Does anyone know what this measurement is with a brand new chain?

If you place a primary chain upright and the top row sags to contact with the bottom row the chain is finished. As to how close you'll let it come to that I guess is up to you.

[Nurse Julie]

Wear limit spec is 70mm. Does anyone know what this measurement is with a brand new chain?

If you place a primary chain upright and the top row sags to contact with the bottom row the chain is finished. As to how close you'll let it come to that I guess is up to you.

George, that only works on Hyvo primaries, like the 400/500/550's. 750 chains are different, they are not Hyvo, they are a lot thinner and there are 2 of them, side by side.

[archmill]

Seemingly new chains have a measurement of 65mm, at 70mm they are done.

[archmill]

Nurse Julie, how are you doing. You did the camshaft on this engine a few years back.

[Athame57]

George, that only works on Hyvo primaries, like the 400/500/550's. 750 chains are different, they are not Hyvo, they are a lot thinner and there are 2 of them, side by side.

Ding dong....getting ahead of myself Julie!

[AshimotoK0]

When you replace. "To stagger or not to stagger ...that is the question"

I chose to stagger mine.

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[Nurse Julie]

Always stagger Ash, I like a good stagger 😂😂😂

[Skoti]

Also there's reinforced heavy duty primary chains available that sag less than the standard original RK ones.

I think they are made by IWIS in Germany.

https://www.classiccyclecity.com/gallery/thumbnails.php?album=48

[Nurse Julie]

Nurse Julie, how are you doing. You did the camshaft on this engine a few years back.

Hi Archie. How are you, still fettling I see. Good on you.

[archmill]

" Wear limit spec is 70mm. Does anyone know what this measurement is with a brand new chain? "
And the answer is 63mm. Brand new chains and tensioner from CMSNL.