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What plugs do you use?

OLD_Gav P

New member
OK so what type of spark plug do you lot have fitted in your 912s?

The reason I ask is that, since I've had NGK B6HS plugs fitted when my new carbs were installed, the engine has been overheating when driven for some time at high revs (ie on the motorway at 80mph+). I think the "officially" recommended plugs are what I used to have, which were Bosch W6BC (i think thats the code anyway)... and I never had any problems with the engine running hot with those.

Of course it could be to do with the carbs, but in all other ways the engine is running much better than before, eg no flatspots or stalling. Theres also nothing wrong with the cooling system - ie no missing tinware or blocked up ducting, so I'm thinking perhaps my engine just doesnt like these new plugs!
 
I doubt it is the plugs causing overheating, seehttp://home.clara.net/dave.moore/plugs.htmlThis explains bettter than I could how 'hot' or 'cold' plugs do not determine cylinder temperatures but are designed to be optimised to those temperatures. Your problem is more likeley incorrect mixture setting for higher engine r.p.m. as you say you have changed the carbs and all was well previously.
Hope this helps,
Jon
 
I use B6HS and I have to say there are great, I would look towards the carbs. Have you put it on a rolling road, as they should be able to check the jetting etc?
 
Wow, theres plenty of info on the link there Jon (C).. pretty interesting stuff - cheers.

The reason I was thinking about the plugs is that apparently, the main jets in the recon carbs are already larger than the ones I had in the old carbs. So in theory it should already be running richer than before. I understand that the only adjustment to the fast-running mixture is to change the size of the main jets?

However, I am definitely thinking of trying larger jets anyway. Sounds like the plugs would be unlikely to cause overheating then...
 

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