Checking cylinder head bolts

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MalcW
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Checking cylinder head bolts

Post by MalcW »

Hi all. Now I've done around 450 miles on my Model 31 since getting it running I thought it would be a good idea to check the tightness of the cylinder head bolts, especially as there's a bit of an oil leak from the LH cylinder base when pushing on a bit. I've never had the heads off. Would it be best to slacken them off and then ensure they're all torqued down evenly, or leave them alone and just check that each one is at least the required 16 ft lbs.

Thanks,

Malc
Mick D
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Re: Checking cylinder head bolts

Post by Mick D »

Hi

As you've no idea what torque is applied to the bolts I'd back them all off a quarter of a turn and re-torque all to the same value.

Regards Mick
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dave16mct
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Re: Checking cylinder head bolts

Post by dave16mct »

22 ft lbs for the headnuts on the twins.
Dave.
MalcW
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Re: Checking cylinder head bolts

Post by MalcW »

Hi Dave

According to the '57 to '64 Matchless All Models Workshop Manual in the archives, it was 16 ft lbs originally, and 25 ft lbs for models with the 3/8" studs (see page 78). On page 101 it says that these larger studs were introduced for the 63/64 models. My bike is 1960, so I was going to work on the lower value? Are you suggesting that 22 ft lbs should be used across the board?

Cheers,

Malcolm
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Rob Harknett
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Re: Checking cylinder head bolts

Post by Rob Harknett »

Check the hand book. It should tell you after 500 miles of removing the head, it should just be tightened. Order of which bolts should be tightened is very important, to ensure it is tightened evenly.
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dave16mct
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Re: Checking cylinder head bolts

Post by dave16mct »

There are mistakes in some workshop manuals. On page 25 of the same manual you refer to it says 22 lbs ft. Also on the last pge of the 49-55 Neill twins book it says 18 lbs ft! The accepted figure is 22 lbs ft. for the 5/16" studs.
Dave.
MalcW
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Re: Checking cylinder head bolts

Post by MalcW »

Hi

22 ft lbs it is then, tightened in the correct sequence.

Many thanks,

Malc
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griffin
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Re: Checking cylinder head bolts

Post by griffin »

I always tighten them down to just before they shear...….. ;)
bitza
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Re: Checking cylinder head bolts

Post by bitza »

And always listen for sharp crack, then you know you have overtightend the little b.....s .
MalcW
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Re: Checking cylinder head bolts

Post by MalcW »

Slight snag with my original idea to check the head studs for tightness - my torque spanner is 1/2" drive, and I have no 1/2" sockets that will fit down the holes. Anyone know the nut size? I could perhaps get a box spanner that fits, and then torque that?

Malc
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