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Cylinder spigot cracks 1968 750

Submitted by dean_miller on Sat, 05/04/2014
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Commando

Hi Gents

i am in the process of restoring a 1968 fastback commando. When I lifted off the cylinder I have found the spigots at the bottom of the bores are both cracked at the back side from the radius of the Conrod cut out. The cracks run up till they reach the base flange then turn and run along the flange. See pics. I have had a look at previous thread and found the same thing on a domi but nothing for commando's.

My question is... As I am going to get the cylinder bored due to corrosion in the bore. Would it be better to get the cylinder re-lined and go back to STD or get a good second hand one. Any other suggestions welcome.

Also when the bore is re-lined, is the spigot completely removed or is ipart of the old one left behind? I have never had a liner fitted before.

Also wondering if anyone can recommend a good company to carry out this repair. Was thinking about SRM as they seem to have a pretty good rep' or may try and find a repairer locally. (Am in Abu Dhabi UAE)

The bore is STD now and has done about 17500 miles.

thanks all,

Dean

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Submitted by pwhite105 on Sat, 05/04/2014

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Hi Dean

My Commando suffered similar problems and I went to BLR Engineering in Surrey who did a good job? They're in the Services and Suppliers Database. I've not had any experience of SRM but similarly have heard they're very good. Here's a pic of my catastrophe to make you feel better?

Commando 750 Spigot

Submitted by anthony_curzon on Sat, 05/04/2014

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I had a set of Atlas barrels that I bought in Americathat werevery badly damaged at the base, as per Peter's picture.The rest of the barrel was in really good condition, and it would have been a waste to have scrapped it. I took it to Tony Hartlen at The Rebore Shop in Surreyand he recovered the barrel for me byrelining the bores. I have had a lot of my barrels relined by him.

Submitted by dean_miller on Sat, 05/04/2014

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Hi Peter & Anthony,

Thanks for the info,

Just wondering if when you got the barrel the new liner completely replaces the whole thickness of the spigot?

Thanks for the picture Peter, I don't feel so bad now....

Seems strange that Norton would machine the barrel like this and not blend the sharp edge. This is just inviting cracking...

Also can you let me know aproximate cost for a re-sleeve. I will have to factor in postage aswell.

cheers D

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Submitted by pwhite105 on Sat, 05/04/2014

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Hi Dean, I recollect that BLR rebored the cylinders and inserted the liner taking it back from +40 thou' oversize to "Standard" - they just left the remains of the old spigot area as it was. As for the price - this happened a few years ago and I'd suggest you need to get some current quotes from the engineering company you choose. Don't expect it to be too alarming - probably less than your shipping costs!

Peter

 


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