Cylinder Head t120

[andyw1260]

Hi All
         I am looking at getting a 67/68 T120 UK Cylinder Head I believe those two years are identical heads. But can the wise ones say what the difference is between a T120 head and a T120 TT head and is there any Difference with Between T120R and T120 heads.

[henry_norton]

I don't proclaim to be wise but.... yes, the 67 and 68 UK heads are the same (part no. E5348). TT heads were slightly different (part no. E5727) as they ran slightly bigger carbs - a whopping sixteenth of an inch bigger in fact - although I believe these heads were fitted to all US models from 1966 'til all bonnie heads were changed in 1969. H_N

[TBS]

Well all 63-70 T120 heads are the same shape , however from engine no DU 29738 (1966) the cylinder inlet ports were opened up from 1 1/8" to 1 3/16", so you could get an earlier head and have it ported to the larger size. Your machine would run 30mm concentric carbs. There is no difference between an T120 and a T120R head. The TT head had the inlet ports as 1 3/16" as standard in 1963.

[andyw1260]

Thanks for your explanation it,s great to have it explained by both of you.  thanks again  Andy

[andyw1260]

Hello All
             Sorry to trouble you again about this T120 head but I have been told by an Americian Moto Shop that all TT and T120 heads had 16 UNF threads in the states and never got 26 CEI threads. The UK heads changed in 69 to UNF from CEI.  
Can anybody confirm if this is true.  
Thanks Again     Andy

[TBS]

Ah well, I don't know where there are 16unf threads on a T120 head. The only threads are the rocker box outer bolt threads which there are 4, pre- 1967 26tpi x 1/4" post 1967 20tpi x 1/4" and the inlet stub threads which are coarse for 1970 onwards, but it really doesn't make any difference to the performance of the head. T120 and T120R threads are all the same, they made heads in thousands and wouldn't have changed threads for different markets, just think of the logistics, and why would they do that? No that information is incorrect and again the engines were built first and stamped when they were in the frame, so how would they differentiate , what engine for what bike, on a Friday afternoon!!!!!!!!!!!!!!!!

[andyw1260]

I see your point of view,  I was mainly thinking of the Exhaust Stub pipe adaptor thread and do you know what threads were used there on a 67 USA TT head?
  I have a lot to learn.  
Thanks for your prompt reply Mr TBS     Andy