Refitting 1978 F2 barrels

[dazm]

Hi there,

I have a 78 F2 and I'm just about to refit the barrels after fitting new rings, I have a gasket and large O rings for each cylinder and new small O rings but there also appears to be 4 other rubber slightly cone shaped rings on the middle four cylinder studs that I can't seem to find the part code for? Anyone have any info on these? Also any tips for getting the barrels safely over the pistons as I dont have ring compressors?. Any other tips for this stage of the rebuild greatly appreciated

Cheers daz

[Tomb]

I don't use ring compressors.

Where the chamfer on the bottom of the barrels meets the bore is a sharp corner, I always polish that off to a small smooth radius and polish the chamfer on the bottom of the barrels. That way the rings slip in easily with a bit of fresh oil.

[dazm]

Hi Tomb,

Thanks for the tip, makes sense to me, will give it a go. Is it a 1 man job or best with two to lower the barrels over the rings?. Was thinking of placing a block to catch the barrels so they can't drop too far as I get the pistons in place!. Also do I need to use any sealant on the gasket?, I've read differing opinions and don't wan't any excess getting in the oilways.

thanks daz

[Tomb]

I can only speak from my own none CB750 experiences.. As you're doing two pistons at a time I find it a doddle, the inside pistons 2 + 3 first with the outer 1 + 4 down out the way, normally the weight of the barrels is plenty to help slide the barrels down as you feed the rings in, once 2 + 3 are in the barrels you can rotate the crank so 1 + 4 come up whilst keeping 2 + 3 in their bores, (maybe a good idea to clamp the crank a little or slide some blocks under the pistons to stop the cank rotating back) now fit 1 + 4 pistons into the bores easing the rings in.

Lads on here will know the CB750s way better than me though.

[archmill]

Dazm, is it the ones indicated as "2" in the parts microfiche?

[Spitfire]

These might help, as to fitting the barrels I usually support the inner 2 pistons with big flat spanners and click each ring into the bore with my finger nails and a small screwdriver, the weight of the barrels does the rest.

Cheers

Den

[dazm]

Archmill,

It could well be the same part but the part I'm referring to is actually fitted around the 4 centerstuds on top of the crankcase so they mate with the underside of the barrels?.

Many thanks for the reply

daz

[dazm]

Den,

Thanks for taking the time to reply, from the images you have provided it looks like the parts I'm referring to are the stud gaskets? although on my engine there are no "knock pins" (dowels) on the center four studs, is this correct on the later F2 model?.

Cheers daz

[Spitfire]

This diagram is from the parts manual, the barrels have a total of 8 dowels,
2 on the front outside studs on the top of the barrels
2 on the front outside studs on the bottom of the barrels.
4 on the top of the barrels with seals (see diagram).
Note the cap nuts and copper washers on the head studs.
In the diagram above the position for the equivalent K model is also shown which is a bit confusing.



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Cheers

Den

[dazm]

Brilliant,

Many thanks all for your help.

Cheers daz