Hi does anyone out there have the shaft/teeth ID & OD measurements of a 525-16371 inner clutch boss.

It appears to fit YAMAHA 1976 YZ100 / 1976 DT125 / 1976 - 1977 TY175 / 1976 - 1977 DT100 / 1972 DT1C. I'm lead to believe.

CMSNL has a typo and lists the USA 1976 DT175C parts list as 1972 DT1C parts.  DT1 clutch is not even close to the same part.

I have clutches and transmissions from most of the US 1969-81 125/175 Enduros, MX (USA "motocross model"), and YZ's that I used to build my six speed CT1.  As I said before, I'm pretty sure the 525 hub you are asking about is very likely the part you have in your 1G1 "outside the US" DT175 twin shock engine that you have already confirmed doesn't fit your YZ125X. 

Not sure if I have a 525 inner clutch hub that's not in an assembled engine, but if I can get up the energy I will take a look through the bins of parts for one.

Here are the CMSNL categories listed under "DT175".  I wonder if this is why we played games of "which one of these is different than the rest?" as children? 

Cheers Mark, Yeh that inclusion of DT1 was odd.
Anyway, don't bust a gut. Just trying to avoid re-splining the shaft if I cant find a IG8 16371 inner boss.

The 525 inner hub splines from a 1976 US DT175 measure 13mm by 16mm which I'm guessing is the same as your 1977 non-US 1G1 hub?

I checked my notes and I should have a complete 76 YZ125 clutch too...  ran out of steam looking but I'm down to the last couple of trans/clutch totes so should be able to find it in the morning.  

I will also look for a 1G8 inner hub if the 76 YZ clutch isn't found...  I'm positive I have a couple of those in my monoshock parts totes.

Ah ha, thanks for the measurements. Correct, mine is 13 & 16mm. Same as 525. So I can stop looking at those now.

Standing by re news on a whole clutch or IG8 boss. Fingers crossed. 

Thanks again.
 

I wrote a response hours ago...  guess I forgot to post it or something and can't find it now.  

I found the complete 1976 YZ125 clutch.  It is from a YZ125C, not X, so it has the 525 inner hub which is splined 13 by 16.   It was well over 100 degrees F in the shed by 10am... too hot...  so going to look for the 1G8 clutch inner hub and the correct outer clutch hub with the 74 tooth gear again in the morning.

I've just found a YZ100C 1J4-1637 (1976-1981) boss for sale at Sun Coast Cycle Sports. I gather, via my Yamaha parts manual is the same as the 1G8-1637. But not sure I can trust the manual. If the YZ125C one is different?
Did you manage to brave the oven shed again?
Tanx

Life got in the way...  supposed to be a lot cooler this weekend so I'm planning on looking in the morning.  

Interesting on the 1J4...  it might work with the 525 outer hub as the 100 probably had less plates...  but it also might slip under the increased power.

I did some checking and the 1J4 inner hub was used on a few years of the USA DT125 monoshock and I'm sure I have at least one.  It is shorter than the 1G8 but does have the larger spline...  

If I remember correctly, the outer basket on the DT125 is the same as the 525 but with a 71 tooth gear.  So the 1J4 inner might be what you need it you want to use your 525 outer basket from the 77 1G1.

Hopefully I'll be able to find all this stuff tomorrow and at least get you some measurements.