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Camshaft journal holder bolts

Posted: Mon Aug 16, 2021 1:35 pm
by Riderz13
Afternoon All,

can anyone help me with Bolts 5 and 6 numbered in the diagram?
reinstalling my cam journal holders and torquing them up to 12nm and 4 of them snapped. looking at the parts list they are different types (BOLT (6X39) and BOLT L:35) presuming they are both M6 but slightly different lengths? I couldn't see any difference? how many of the 5/6s are required and what is their correct placement?? the manual is not very helpful with this aspect. where is the best place to get replacements?

Thanks for your help in advance

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Re: Camshaft journal holder bolts

Posted: Mon Aug 16, 2021 3:19 pm
by MadMotoUK
Longer bolts fit on the exhaust side of the cam looking at the picture, ie; the front of the engine.

Re: Camshaft journal holder bolts

Posted: Mon Aug 16, 2021 4:33 pm
by Riderz13
yes that was my thinking.

But looking at an OEM parts seller page the requirements for quantities of each bolt are: 16 of the 6x39 but only 2 of the 6x35? so it doesnt seem logical that all inner journal bolts would be the same length?

Thinking about that the other logical move would be to have the other number 6 bolt on the inside of the corresponding journal holder, inlet side (I think its 'D' in the manual) as the other side bolts (number 4) need to incorporate the oil pipe? which would make sense if those bolt holes sit right near the highpoint of the combustion chamber, so you wouldn't want the holes 4mm deeper?

Probably just knackered old bolts that all need replacing 🤦‍♂️

Re: Camshaft journal holder bolts

Posted: Tue Aug 17, 2021 6:57 am
by MadMotoUK
Ah, only 2 shorter bolts. I would say that they are for the inner corners of the outer two journal clamps as you point out. The centre clamps are different. I would imagine it is to clear an oil gallery or suchlike. However, as I don't know the internals of this particular engine I can only use logic based on the diagram.

Re: Camshaft journal holder bolts

Posted: Fri Aug 20, 2021 4:07 pm
by moforockband
the shorter black coloured bolts are for the journals without the oil pipe. You use the longer silver ones for the ones for the oil journal pipe.
It's 10nm, not 12. Prob why they snapped. 12nm is for honda's. :)

Re: Camshaft journal holder bolts

Posted: Mon Aug 23, 2021 2:32 pm
by Riderz13
Ah thanks. So to your knowledge there’s no difference between bolts 5+6 on the parts diagram? It’s weird that you should say 10nm it defo says 12nm in the manual.

Re: Camshaft journal holder bolts

Posted: Thu Aug 26, 2021 7:16 pm
by moforockband
All the 73a engines i've worked on have only had 2 different length bolts to my knowledge. The torque is 8-12 nm, and I deffo wouldn't use the higher torque on 30 year old bolts and crankcase/head threads.

Re: Camshaft journal holder bolts

Posted: Sun Aug 29, 2021 3:25 pm
by Hubbskiboy
There's not a massive difference between 10Nm and 12Mn in my experience.
For example, I've torqued a bolt up to 10Nm and then adjusted the torque wrench to 12Nm and quite often it 'clicks' straight away.
Maybe a very small amount of movement.
Don't forget that all torque ratings in the manuals are for a 'dry' thread i.e. no grease or oil.
If you're using a bit of assembly grease on the threads, then best aim for the lower levels of torque quoted.
I think that's all correct, but Mofo always knows best. ;-)

Re: Camshaft journal holder bolts

Posted: Sat Sep 04, 2021 9:57 pm
by Riderz13
Thanks for the advice guys, will not be torquing up anything to the maximum spec now I can appreciate the age of the bike. just for the heads up I extracted the broken bolts today and there are definitely two shorter ones. they were two of the four that snapped so I obviously mixed those up with two of the others leading to four snapped.

now to find some replacements haha

As always thanks for the help! :)