Primary chain tension - '58 Huntmaster

[Nickfrank]

I have a few questions concerning this procedure as the primary chain seems to be slapping against the bottom of the engine casing at idle. While I have a workshop manual of sorts, there are no diagrams by which I can be guided. Instructions say the chain tension is adjusted by pivoting the gearbox as follows:
-slack off the pivot bolt which is below the gearbox and which passes through the two lugs on the cradle tubes.
- is this bolt just to the right of the centre kickstand nut in the 1 o'clock position?
-similarly slack off the the clamp bolt passing through the engine plates above the gearbox.
- is this bolt on a bracket with a U shaped cutout underneath the air filter box?
-at the top rear extremity off the offside engine plate will be found the draw bolt adjuster; rotating nut on the draw bolt swings the gearbox about the pivot bolt.
- I removed the circular chrome plate thinking I could get to the chain but I think all I'm looking at is the clutch?? Does the entire left side engine cover have to be removed? If yes I'm assuming I will need a replacement gasket before I do this??

Any advice is, as always, appreciated. Thanks.
Nick

[nevhunter]

There's a few Tricks in this procedure You need to finally adjust the thing by moving it forwards so the adjuster holds it against the pull of the rear chain. That means get it slightly too tight and ease it forward till it's right. Don't fully slack off the top and bottom studs. Leave some tightness on them but not enough to overload the adjustment. Tighten both firmly and recheck. It also pays to check what effect tightening the rear chain has on the front one. If there's play in the gearbox bearings near the sprocket it will tighten the front chain when you take off and load the rear one. Squeeze the chain together to simulate tightening it and observe the effect on the front one and allow for it. Also check any chain in a few positions as there may be tight spots. Nev

[Nickfrank]

Nev, thanks. That's good info for when I've actually exposed the primary chain to adjust it but I'm several steps short of that per the questions I was asking. i.e. which bolts to loosen to pivot the gearbox and what do I take off to get at the primary chain itself?

[chris.shearwood]

Nick,
Where are you located? There might be someone living nearby who could show you how to adjust the chain.
Regards, Chris

[Simon.Gardiner]

Nick
You don't have to remove any covers to do the primary chain adjustment. Just unscrew the big flat (slotted) filler plug about halfway along, towards the top of the chaincase.
The adjuster nut (or drawbolt ) is the one on the bracket with the U-shaped cutout.
The bottom pivot is the big extended hex head right underneath the gearbox kick-start cover (ie on the off-side) . It's probably the only hex in that area that isn't a nut on a stud (most every other fixing in that area on the off-side is a nut on a stud). Be aware that this a special bolt that extends right across and carries the 5/16 nut (on its reduced diameter, extended tip) that secures the bottom of the primary chaincase, underneath the clutch cover. You need to slacken that nut before slackening the lower pivot bolt (and then re-tighten it as a last thing when you've finished).
The top clamp should be a long stud, going through just the engine plates and the upper gearbox mounting. It's not the one that goes through the frame lug. The nut to loosen is below the oil tank - the stud is held captive in the engine plates so you don't need to anything with the nut on the other end, behind the primary chaincase. As I remember it doesn't really matter if you undo both these nuts - as long as you do them both up afterwards.
Two things to bear in mind:
- as other have said, moving the gearbox to adjust the primary chain also changes the tension of the secondary chain, tightening the primary chain slackens the secondary. (Loosening tightens the secondary and to deal with that you need to slacken the secondary off first - obvious, sorry.)
- final tightening of the gearbox clamp and/or pivot bolts can (in my experience it invariably does) alter the chain tension, you need to check carefully that after the clamp and pivot bolts are tightened up the chain tension is still correct (this bit can be quite exasperating - it's why Nev says not to slacken the clamp and pivot bolts off too much but if you're not used to this it may not be easy to work out how much is too much and anyway final tightening up can still mess up your settings.
Chain tension is 3/8" total slack, through the filler-hole in the chaincase. That's measured without putting any great force on the chain to really push it to its extremes.
( 3/8" is at the loosest spot - again, obviously! I usually find that by sticking a finger under the chain and slowly turning the engine over with the kick start, with the spark plugs out on a twin, to get a feel for where the chain is floppiest.)

Hope that ain't too many words.

SG

[Mick D]

Hi

Location of the gearbox pivot and clamping bolts:

GB Pivot and Clamp.png (364.31 KiB) Viewed 2438 times

Regards Mick

[Nickfrank]

Chris, thanks for the offer but I'm located in Canada (Ontario) and Ariels are as scarce as hens teeth over here so no local assistance is available.
Simon, thanks for the detailed description. Clear as mud haha! but a hell of a lot better than the description in the manual. Mick, thanks for the pic - worth 1000 words as I had the wrong clamp nut. I was undoing a nut to the rear of that that had a threaded end and travelled up and down a bracket as you loosened or tightened it. No idea what that is.

So thanks everyone for the help. I will dive in and see how it goes! It has to be easier than changing a head gasket lol. Nick.

[Mick D]

Hi

I think you are referring to this one, which is the facility to adjust the gearbox position once the pivot / clamping nuts and possibly the secondary chain have been loosened:

GB Adjuster.png (361.49 KiB) Viewed 2400 times

If you've changed a head gasket on a Huntmaster adjusting the primary drive is a doddle.

Regards Mick

[chris.shearwood]

Chris, thanks for the offer but I'm located in Canada (Ontario) and Ariels are as scarce as hens teeth over here so no local assistance is available.

Nick,
Where in Ontario are you located? There are lots of Arielists living in that province.
Regards, Chris

[Nickfrank]

Mick, yes got it now re the draw bolt being the adjuster! Chris, I live in Peterborough and belong to the Canadian Vintage Motorcycle Club but I'm not aware of anyone in the Club with a Huntmaster.