1961 G12 CSR - Top End Rebuild

[AFPU]

Hi All

I relative Newbie here, not only to the Club but also to the marque and to some extent rebuilding Brit bikes.....my last one was a BSA B25 about 40 years ago!

I am beginning a top end rebuild on my 1961 G12 CSR and am having a problem removing the inlet manifold. Having undone all four nuts the manifold is reluctant to come away even after a few whacks with a rubber mallet (gently of course). Any suggestions as I am concerned about damaging the mating surfaces?

[clive]

The done way to assemble the top end is to put the manifold in place before bolting down the heads or it may not be possible to fit it. Logic would suggest undo the cylinder head bolts before trying to remove the manifold.

[AFPU]

Hi Clive, many thanks and I'll try that, I was planning on only working on one cylinder at a time but can unbolt both heads.

[AFPU]

Hi Everyone and here's wising you all the best for 2022.

With regard to my top end rebuild, which is going slowly as I have been focused recently on acquiring the necessary parts that I will need; I now have both cylinder heads and inlet manifold off and cleaned up. The piston tops have been cleaned of carbon build up and turned out to be Hepolite +.040 (Part number 16023); and new rings acquired from Cox & Turner. The bores seem OK so all I need to do now is get the barrels off, clean and paint these, fit the new rings and then re-assemble.

However, the barrels seem to be stuck fast. They had beads of what looks like Blue Hylomar around the base, which I have cleaned off, and after applying some gentle heat to soften any remaining external sealant and whacking the barrels with a rubber mallet, there is no movement at all.

So does anyone have any tricks to suggest to get them to budge without risking damage?

[g80csp11]

often the trick is to remove the studs ( 2 nuts locked together ) then you can twist the barrel to break the gasket seal . in addition they may be a tight fit in the crankcase so some gentle heat with a hot air gun may help
resist levering the fins or you will surely break one - see how many old barrels have broken bottom fins

[AFPU]

Many thanks, I'll have a go at removing the studs and see how it goes.

[AFPU]

So I have removed the studs from the left-hand cylinder but still not able to budge it. I'll have to try and make something up to locate into the studs holes and try and twist the cylinder a little to break the seal.

As far as the right-hand cylinder is concerned the two outer studs will not budge and I am worried about breaking these, so am trying to soak the tops of them at present.

Good job I was not planning on getting the bike on the road until April, so no rush but it would be nice to get the thing apart so I can then begin the rebuild.

[ajscomboman]

Personally I'd not be too quick to remove any studs that won't budge. I have some Maple hardwood wedges which I place carefully under the barrel fins and also between the gap above. I tap the lower ones in gently whilst heating the cases with a hot air gun. if they don't budge straight away I tend to tap a little more then walk away leaving over night to see if the seal begins to break.

[AFPU]

Thanks ajscomboman I'll give that a go as like you say I am loathe to try and remove any studs that won't budge.

[AFPU]

Today after what has been weeks of trying, I have finally managed to get the RH barrel to budge and been able to lift it off. It was a combination of applying heat, long thin craft knife blades to scrape out any crud and and using the ends of ring spanners to lever the barrel up. I am not sure what was holding it so fast, but it sure took a lot of effort to get it off. The LH one was so much easier to remove.

My challenge now is how to clean off the crankcase mating surfaces and mouth without getting any bits of crud into the crankcases. My guess is some will find their way in so I am thinking that once cleaned up and the barrels are off I could drain the oil and flush the cases through with the sump plug off to get rid of anything. Does that sound OK?

Also the crankcase mating surface for the LH cylinder barrel shows signs of the barrel having been levered off by some previous owner, so in order to deal with any imperfections I was considering using Loctite 518. So does anyone have any experience of using this gasket sealant?