PRIMARY CHAIN ADJUSTER

[terrylangley]

After a lovely 40ish mile ride in the sunshine last week I kept my Arrow running to empty the carb as usual but noticed an unhealthy rattle which I recognised as the primary chain needing adjustment. The chain had more than an inch of slack, not good!!! Turning the adjuster made no difference so either the rod or the nylon saddle nut, or both are stripped.I will be removing the chaincase in a couple of days to see. This prompted me to wonder why the saddle nut is made of nylon. The only answer I could think of is that being nylon it would be a nice tight fit on the road to aid assembly. Or could it be made in brass which is less likely to strip. Anyway has anybody tried making the saddle nut in another material, did it work and what is the thread?

Thanks for any ideas, Terry Langley.

[Ivor Collins]

Have you tried pulling the nylon adjuster out and turning the tang on the end of the rod?
If you have a 1/4 drive socket set, I think it’s the 4.5mm socket that fits a treat.
Ivor

[terrylangley]

Hi Ivor. Yes, in fact using a pair of self gripping very thin nose plyers I can pull the rod out up to the fixed nut so I am sure either the saddle nut or the rod is stripped. Should have the chaincase off by the weekend.
Thanks for your interest though. Any thoughts on why nylon for the saddle nut and what the thread is.
Terry

[Ivor Collins]

It sounds more likely that the nylon saddle nut has just been wound off the end of the adjusting rod. A special design feature was incorporated to permit this likelihood....
Either way you’ll have to remove the case to rectify.

In answer to your earlier question, I’m not aware of the saddle ever being made in anŷ other material, the nylon not normally a problem if used correctly and it rubs along the inside of the chaincase so needs to be a softer material to prevent fretting in that area. The threads used in that area are 9/16 unf in the end of the chaincase where the bung goes and No. 10 unf for the nylon nut on the adjusting rod
Good luck with it.
Ivor

[terrylangley]

The saddle nut was still on the rod and when the rod was turned clockwise as you do to tighten the chain it just stayed there. The rod just pulled off the saddle nut confirming a stripped thread. The rod thread was good but the saddle nut was stripped. I put a spare nut with a good thread on the rod and it was nice and tight. When I built this engine less than 500 miles ago the nut I used must have been worn but I did not notice it at the time. Lesson learnt, be sure to fit a nut and rod with good tight threads. This is a lot of work to just replace the saddle nut. At least the flywheel does not have to come off to fit a new nut. Unless anybody knows better than Ivor's suggestion I wonder if nylon was used to avoid any possible metal to metal rattles???
Still tempted to make one in brass!!! Just got to put it all back together now.Thanks for any thoughts, Terry.