Author Topic: Alloy cylinder head :bronze inserts  (Read 1059 times)

Offline 1660bob

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Alloy cylinder head :bronze inserts
« on: 16.06. 2010 08:12 »
Hi all, I am considering having work done to restore a S/R head .It needs seats/guides/valves/skimming/welding the whole lot really so is going to cost plenty.Looking at the head before i decide, I see that the five bronze threaded inserts used to fasten the rockerbox down are all standing proud of the upper joint face by  varying amounts, perhaps up to 10thou or so.It seems as if they have been stretched or pulled up slightly due to overtightening.
Has anybody come across this problem? The rockerbox sits well off the joint face as a result. I can flat them down no problem, but do they come loose/pull out?. Incidentally, only one insert has split the alloy in the usual fashion seen on alloy heads- the other four are OK, Cheers, Bob.

Online BSA_54A10

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Re: Alloy cylinder head :bronze inserts
« Reply #1 on: 16.06. 2010 09:58 »
AFAIK there are no inserts factory fitted.
These would have been done by a PO.
You really need to take it to a specialist thread restorer as it is some thing that can not be diagnosed over the web.
There are 1/2 dozen or so different types of inserts and either yours were not fitted down far enough or were not locked in properly.
In any case you must now use an anti-sieze compound when you reassemble to prevent them undoing when you dissasemble the rocker box in future.
Bike Beesa

Offline MikeN

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Re: Alloy cylinder head :bronze inserts
« Reply #2 on: 16.06. 2010 10:51 »
AFAIK there are no inserts factory fitted.

I hate to disagree,but every alloy head that i have seen (ive had 6) has 5 bronze inserts to hold down the rockerbox.Including the one im selling on ebay at the moment. Im certain that they are factory fitted.

Offline muskrat

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Re: Alloy cylinder head :bronze inserts
« Reply #3 on: 16.06. 2010 15:00 »
Yep, their original. I've had s few do that. Helicoils fixed it.
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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