Repairing cylinder head bolts - G80S

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
Jdraper
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Joined: Mon Mar 07, 2011 9:41 am
Location: BUCKS UK

Re: Repairing cylinder head bolts - G80S

Post by Jdraper »

Helicoils are considered stronger than the original thread. The insets are quite meaty, so should take up the difference in diameter.. I guess time will tell on my unit.



Jeremy
56G80S
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Location: N YORKS UK

Re: Repairing cylinder head bolts - G80S

Post by 56G80S »

I used V coil inserts in the cylinder head. Maybe could've done a better job but they hold well and the rocker box was never so oil tight.

I have slightly relieved the thread entry into the head before fitting the inserts and made sure that I took the inserts into the head so the top coil is below the point of that relief.

Johnny B
Mick D
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Location: Aberdeenshire

Re: Repairing cylinder head bolts - G80S

Post by Mick D »

Hi

Helicoils and their generic equivalents are fine, I've fitted a fair few in my time BUT, in this case the thread in the head has been cut oversized and therefore a helicoil returning the thread to original is unlikely to be possible.

Also the rocker box bolt hole has been enlarged to accept the oversized bolt - I wouldn't want an original pattern bolt rattling around in an oversized hole, especially in a high vibration scenario such as the head steady.

If the thread in the head is good the best bet is to leave as is rather than risk damaging the head during an unnecessary repair.

Regards Mick
raffles
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Location: NORTHAMPTONSHIRE UK

Re: Repairing cylinder head bolts - G80S

Post by raffles »

What i would do is get your mate to make up a version of the correct bolt, using the oversize part to go into the
head then machine the correct size hexagon and threads on the top
Tony
markwhitelock
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Joined: Sat Sep 07, 2019 5:51 pm
Location: Hampshire UK

Re: Repairing cylinder head bolts - G80S

Post by markwhitelock »

Today has been a day of making swarf! Turned down some hex bar to make these custom oversized bolts to fit the threads in the cylinder head. They hold well, please with the outcome. Cheers for the advice :D

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raffles
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Joined: Mon Jan 01, 1990 12:00 am
Location: NORTHAMPTONSHIRE UK

Re: Repairing cylinder head bolts - G80S

Post by raffles »

Good job Mark to me the simplest and easiest way to go
Tony
bitza
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Location: SHROPSHIRE UK

Re: Repairing cylinder head bolts - G80S

Post by bitza »

Looks good, result, I like it when a plan comes together.
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ajscomboman
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Joined: Mon Jan 01, 1990 12:00 am
Location: HAMPSHIRE UK

Re: Repairing cylinder head bolts - G80S

Post by ajscomboman »

Very nice, don't forget washers though. Despite having a collar you don't want to be turning the bolt hex directly down on the ali rocker box.
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