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Airhead Heads
Posted: Mon Jan 09, 2012 8:09 am
by Bob Distelcamp
I have a general question, I was looking at a pair of R100 heads, The casting # is( 1 263 948 ) The owner
states that the heads are from a R100cs with 40mm Ext. ports. I have no way to measure the ports, can you
tell me from the cast number???
THANKS BOB D
Re: Airhead Heads
Posted: Tue Jan 10, 2012 4:00 pm
by mattcfish
A 100CS would have 40mm exhaust valves and 44mm intake if the heads are original.
Not sure if you can tell anything from the casting #'s.
The part numbers are...
11121337073
CYLINDER HEAD LEFT (from 11/78)
11121337074
CYLINDER HEAD RIGHT (from 11/78)
...but.... I don't think those are actually stamped on the heads.
Re: Airhead Heads
Posted: Tue Jan 10, 2012 11:06 pm
by vanzen
I am guessing, but I will say that the casting #s may not provide positive identification.
However, for @ $10.00, the price of a (cheap /Harbor Freight) set of vernier calipers –
the original issue, "I have no way to measure the ports"
would easily be resolved.
Re: Airhead Heads
Posted: Wed Jan 11, 2012 9:30 am
by chasbmw
Mind you it's always possible to bore out 38mm exhausts so they will take 40mm pipes!
Charles
Re: Airhead Heads
Posted: Wed Jan 11, 2012 9:55 am
by vanzen
40 mm = 1.5748 "
38 mm = 1.4960 "
Even a 12" ruler would provide an answer.
Re: Airhead Heads
Posted: Wed Jan 11, 2012 1:30 pm
by Major Softie
vanzen@rockerboxer.com wrote:40 mm = 1.5748 "
38 mm = 1.4960 "
Even a 12" ruler would provide an answer.
1 - 9/16" = 1.5625"
1 - 1/2" = 1.5000"
Yep, a ruler that only goes down to sixteenths is all you need. 38mm is just a hair under 1 - 1/2", and 40mm is an almost imperceptible amount more than 1 - 9/16".