What material to make thick motorcycle carb spacer / isolator.

[Rata222]

I have little experience with motorcycles. I purchased a little bike with a 125cc engine. The carburetor I bought needs to be spaced out to clear the cylinder fins. To do this, I purchased and used four cheap plastic carb spacers (or heat isolators.) They cracked after about a half hours time.

I want to machine a spacer/isolator about .800 thick, this goes between the carb and the manifold. I seen where one person had made an isolator from a hockey puck. I was thinking of doing that - or making one of aluminum. Does the hockey puck sound like a good idea? ( Better heat isolator, easy to machine and shape.} Or a more rigid aluminum one with a thin isolator?

Also, the current plastic ones have a O-Ring groove on the face and use an O-Ring to seal against the manifold. I don’t think this would be needed if a hockey puck were used. (Hockey Puck Durometer = 90). I can machine an O-Ring groove – but would a paper gasket not be just as good - even with aluminum? ? The phenolic isolators/spacers I looked at did not use an O-Ring. (I dont wish to machine phenolic. )

Does anyone have knowledge or advice on the best route to take? I machined a fixture today to help in milling - but undecided on material.
thanks
Jim

 

[Ulma Doctor]

maybe this will help....

Honda CT90 Carburetor Spacer from Scrap Aluminum

I'm doing a carb swap on a honda CT90, but the new carburetor interferes with the valve cover. i needed to make a spacer, i chose some scrap aluminum for the project i marked of the general size, and freed it from its entanglement... knocked the corners off with the 4x36 belt sander and...

www.hobby-machinist.com

 

[Aukai]

Phenolic plastic, heat spacer.

 

[Tozguy]

Does the hockey puck sound like a good idea

It does to me (as long as it is not the kind they use in Hawaii).

 

[Aukai]

 

[wrat]

A car can use a plastic spacer because the carb is attached to an intake manifold of some kind and is therefore far removed from the heat.
A bike, especially a small one, has the carb attached literally to the combustion chamber and, while not at first, will eventually get about as hot as the exhaust.
Plastic if you just want to experiment with some ideas.
Metal if you want it to work and not worry about it.

 

[Tozguy]

Heat insulation might not be the first concern here. A carb is constantly being cooled by the flow of intake air.
Vibration would be more of a concern if the carb mounted solidly to the cylinder.
Could we see a photo of what you have to work with please.

 

[Rata222]

Thank you for the imput guys. I have both aluminum material and Hockey pucks. For the fun of it -I went ahead and made one from the hockey puck this morning (sounded like fun) and mounted it - just to see .., It compresses somewhat but is very stout. The spacer shown in the other picture is what was used with the OEM carb. I tried stacking four of those spacers, but they cracked.

I am sure aluminum would work great, but I think you would want to add a plastic isolator.
I thought I would ask here, if anyone had experience with this, good or bad. Because its my go to forum for helpful and intelligent advice.
I dropped some of the rubber cuttings in a jar with gas - to see if there is any reaction. None yet.

 

[aliva]

Be sure it's NHL approved

 

[Rata222]

Follow up:
I am going to have to give a thumbs down on using the hockey puck for the carb spacer/isolator. I had put a piece of the puck in a jar of gasoline to see if it would hold up. After two days the gasoline discolored enough to make me nervous. I pulled the carb back off, after running the bike a good while, and the rubber on the ID edge was a little brittle. Others may have had success - but I wasn't happy with my results. I dont know if they make different compounds - mine said "practice" puck. I will look for an alternate material - better safe than sorry.
Thanks all for the input.