xs400 38mm or 39mm

[a40nabowl]

So I just got my xs and I was told that the forks are 38mm and since I was missing 1 fork cap, I have been looking all over for a fork cap or set. I finally found a place where they have a set and before I ordered I decided to take my micrometer out and measure it. I have a set of 35mm of my shovel head and it measured 35mm so it is accurate, then on my xs it said 39mm. What gives? What comes on a 1977 xs400? They guy who sold me the bike said 38mm

This is what I have

and this is what I was about to buy for a 38mm

 

[a40nabowl]

UPDATE!!!!!!!!
It measured 39 in the middle and 38 at the top.

 

[xschris]

They look like a fork cap from a later xs650 not a xs400 The 77-82 xs400 don't use a screw on cap.

 

[drewpy]

I think the standard diameter was 34 -35mm

 

[a40nabowl]

I looked at the fork caps for xs650's and they do not look anything like this. the gap between the threads and the is like .5" and the ones I have is just enough for a rubber washer. I had my suspicions that these forks may not belong on this bike since the wheels and the larger rotor would need relocation of the front calipers.

 

[drewpy]

look like fz or fzr forks without the antidive.

http://www.cmsnl.com/yamaha-fzr400a-1990_model9585/partslist/

 

[a40nabowl]

look like fz or fzr forks without the antidive.

http://www.cmsnl.com/yamaha-fzr400a-1990_model9585/partslist/

Dude, you called it!!!!!! even the wheels. I was thinking I had GS500 wheels, but I can see it is fzr wheels. Thanks

 

[drewpy]

your welcome, only coz I just got an FZ600 and did a bit of research on the model range

 

[a40nabowl]

your welcome, only coz I just got an FZ600 and did a bit of research on the model range

Nice! just do not loose the fork caps, it is impossible to find a set of fork caps for 38mm forks. I was minutes from ordering a complete set of forks just because I could not find a set. I found some on a ducati website that look just like the ones i got as you can see in the photo above.


Once I get the bike on the road, I think I will see if I can find anyone trust worthy to convert my rear to fit the fzr swing arm.

 

[drewpy]

they're air caps on mine