Manifold/Carb rubbers 912

[ZULU1]

My turn to ask for help ??

I have made new cast ally, horizontal short inlet manifolds for my HKS, very similar to the HKS horizontal manifolds but even shorter allowing the C of G of the motor to move forward. (project almost complete). I will be machining them this week.

I have bought the JBM Industries manifold rubbers from the USA, they are very much the same as the originals which are the similar units as a 912.

Rotax use the same supplier in Japan as HKS but HKS use a softer material.

On a 912 the rubber attaches to the manifold with a small "O' ring, there are several sizes according to engine type so it seems ?. The HKS never had this seal ?? Anyway, if anybody has a 912 manifold in pieces, I would like to know if possible:

Is the manifold itself machined to accept the O ring?. The size of O ring? and does the o ring go on the outside of the lip on the carb rubber. If possible picture would be grateful of the 912 manifold face ? this is what I will be copying..

I intend copying the Rotax and not the HKS design.

Hopefully somebody is about to change the rubbers this week...

Thanks Paul

[Morph]

Maybe this exploded view will help

[ZULU1]

Thanks Greg, that definitely shows a machined face on the inlet manifold as a location for the "O" ring. now all I need is the "O" ring size and then a matter of machining the ring.

Many Thanks Paul

[Z-MRP]

Hiya Zulu 1, I was browsing tech talk at the weekend and saw your post re made shorter inlet manifolds. Just a question on that. I have had many years in motorsport and spent long hours trying different engine set ups on the dyno tuner. What we found was that with changing inlet manifold lenghts and also exhaust primary lenghts, this can seriously effect where the motor will develop its best power curve at give rpm range. So the question is if you use the normal cruise rpm figure will the motor deliver the best torque figure at this setting. Just thought I would share this with you and you could maybe check it out if needs be.
Also sent you pm with postal details thanks