Heat block

[Pecon]

Hi all

I'm running a 928 concentric on my '55 plunger and I am experiencing a problem recently. After a 50 mile run I noticed that the throttle appeared to be sticking slightly on idle. I stopped for a short time and when I tried to start the bike the throttle was stuck wide open. I managed to free it by loosening off the nuts holding the carb to the manifold. ( these were not over tightened, just barely pinched up ). This is the second time I have experienced this problem, the first time was about a year ago also after a long hot run. It appears that the body of the carb is distorting slightly with the heat so I wondered if a heat block between the carb and the iron head might help although unlike Triumphs and a Norton I have had none is listed or am I opening the way for some other problem?.

Cheers,

Peter

[Goldy]

Peter.
The heat block which was originally made of tufnol is used to prevent heat transfer from the head to the carburettor body, which will not work correctly if its hot, it is not for the reason that you post. I would think that the carburettor body is distorted.
All the best Goldy

[muskrat]

 Common problem with concentrics, overtightened nuts. I use at least a 1/8" tufnol piece and a good smear of silastic, tighten nuts till spring washers are just compressed. if it still sticks it would only be a 1/32 of a turn on a nut to release it.
Cheers

[Pecon]

Thanks guys, I was just a bit concerned that fitting one might upset the mixture as none was specified originally. I'll see if I can find one and will see how it works out. My original 276 is being overhauled at the moment so I will definitely go back to it when it is ready as the concentric seems to be more trouble than it's worth.

Peter

[chaterlea25]

Hi Peter,
The Tufnol spacer is well worth fitting to the 276 as well
Avoid those horrible thick gaskets 
Let me know if you need some tufnol to make one

Regards
John

[Housewiz]

Hey John,

I am about ready to jump into the 276 arena with two of them.  Tufnol - sounds like a tattoo on the forehead of a barroom brawler!!  I'm in the USA - where would I find this stuff?

Thanks,

Steve

[Pecon]

Steve

  I found a heat block on the TMS site. Very reasonably priced, however they do have a minium order which is slightly more than two of these. Go to Amal and look for heat insulators.

http://www.tms-motorcycles.co.uk/

Cheers,

Peter

[muskrat]

 I got a couple of sheets 1/8" thick from an electrical supplier down here. Make my own carb heat shields and Dynamo brush plates from it. There must be a supplier the same near you.
Cheers

[JulianM]

Here,
Mail order from the top!

http://www.amalcarb.co.uk/ProductSearchResults.aspx?SearchTerm=spacer


Regards,
Julian

[BSA_54A10]

Have a good look at your carb.
A lot of clowns cure flange distortion by rubbing it down on a sheet of glass, well and good.
What they don't do is deepen the "O " ring hole so when they refit it not only is there less meat on he flange but there is a taller fulcrum .
Add to that the total reluctance to replace the "O" ring when it gets too hard and you have the receipe for buggered carbs.

[bsa-bill]

What they don't do is deepen the "O " ring hole so when they refit it not only is there less meat on he flange but there is a taller fulcrum .

Yes I get the point of that but sometimes wonder about the rings supplied in carb gasket kits, there seems to be quite a bit of variety in the thickness of the rings in them, usual thing I suppose best stick to a good supplier.