Fieldmaster and huntmaster primary case

[Ronbaxter]

I posted a request for a 1953 KH 500 twin inner primary case in the spares forum, but I am wondering if the later inner case will work for the kh 500. I see a number of later primary cases available and they look quite similar. Does anyone know if a later inner primary case will work for the earlier 500? I. Am putting a 1953 KH 500 twin together and I realize it came with a primary case for a single. So I was wondering a couple of things, will a later inner case work (it looks like it will) and is the outer case different or will the single outer case bolt to the twin inner case? I hope I have described the question well enough. I have a number of British bikes but this is my first Ariel twin.

[will_curry]

There are at least two sorts of KH primary chaincase. The first fits rigid and plunger
frames and the second fits the swinging arm frame. The first sort is longer than the
second and has a hole through the middle for the footrest which the swinging arm
one doesn't have.

[Ronbaxter]

Good to know. Mine is a plunger with the hole for the footrest. I wonder the rigid and plunger primary cases are all basically the same. It looks like the later ones have an extra piece at the top rear with 2 threaded holes and what looks like an extra hole close to the clutch hole.

[Ronbaxter]

Will, thanks for that info! It is clear that the newer cases I was looking at will not work. They are missing the hole for the foot rest. I can’t believe I missed that! Well its back to searching the world for the seemly rare kh plunger inner primary cover.

[JohnnyBeckett]

hi they come up a lot on EBAY and have you tried the club spares , and look on drags website and find the part number of the case you need so you can get the right one, i have got a case but it is for a swinging arm frame

[Vincent.vanGinneke]

Good luck Ron...these long KH/KG inners are the hen's teeth in Ariel fourstroke twin cilinder land.
The short ones you can find relatively easy but are of no use at all for you.
Maybe ask Jorgen from Denmark and empty your piggy bank

[Ronbaxter]

Thanks for the suggestions, I will try those sources. Johnny, can you measure the step down distance for me? I am now looking at modifying the inner case I have. Cut the area that is stepped down, mill the surfaces so they give the proper step down distance and reeled them. Even if I can’t clean it up completely at least I will have the bike on the road.

[JohnnyBeckett]

hi Ron sorry i can not get to it for a few months i have just had a big life changing op so i can not drive or do anything otherwise i would go to the workshop and measure it for you

[Ronbaxter]

Johnny, No worries I am sure someone can get me that measurement. I hope you have a good recovery.

[paul.jameson]

If you are an AOMCC member (which from the colour of your name on your posts it appears you are not) contact Membership Secretary Roger Gwynn and ask for a copy of the drawing.

But be warned that the KH used a larger dome to cover the cush drive than the single cylinder models. This is not obvious until you reach the assembly stage and the two are very difficult to tell apart if you see one at an autojumble. Webmaster John Nash is the expert on this problem.