18c inlet port size.

Penguin · Post by **Penguin** » Wed Sep 05, 2012 3:24 pm

Sorry folks, back again --

Looking at the data for the 1951 18C engine, gives me a 1-3/32" carb size,
Later engines went to 1-5/32"

So I order the "correct" size for my 51 serial numbered engine and now find I have a diameter of 1.229" (at the smallest point) inlet port.
Can I wearily assume this I have a later model head and thus I need to replace said carb, or is this the norm?

Existing carb is a very sloppy 932 concentric.

Thanks for the help.

cf160 · Post by **cf160** » Tue Sep 11, 2012 10:54 am

How does it run with the concentric?

Rob Harknett · Post by **Rob Harknett** » Tue Sep 11, 2012 11:53 am

https://www.jampot.com/article_read.asp?id=551
2 out of 4 topics current request carb info, plenty on this web site go to various places, forum, tech articals, look at sub sections etc just search carb. I have listed all matchless carbs with s few details. in the above file, just click on the link at the topEdited by - Rob Harknett on 11 Sep 2012 10:55:06 AM

Trefor · Post by **Trefor** » Wed Sep 12, 2012 1:00 am

Based on my experience with a 52 G80 running first with a 1 1/8 then with a new 1 5/32 concentric, your bike will probably run just fine.

cf160 · Post by **cf160** » Wed Sep 12, 2012 4:01 am

The 932 concentric is a very good carburettor . It is lucky you have such a good one on this bike.
If the needle and jet are correct , it will out perform the
older remote float Amals that were fitted in the old days. They even out perform the dreaded Mikuni!!!
David Potter
"Curse these fiends for trifling with us in a double sense!"Edited by - cf160 on 12 Sep 2012 03:02:49 AM