Cylinder dowel o-ring placement?

jbeebe

Been Around the Block
2nd new thread of the day, at least i'm staying busy!

Take a look at the parts diagram for a '75 Honda XL100:

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That o-ring...Is there only 1 on that dowel, or are there 3 (one for each dowel)? Do I put the dowel in the cylinder, then the o-ring around the dowel, then put the cyl. head on? I just don't see how the o-ring can fit inside the "groove" around the dowel without causing a leak. Also, can I just use a properly sized viton o-ring from my assortment?

Thanks!
 
Only one of the dowels has an o-ring. I put it on the dowel, then insert the dowel into the cylinder. I can't comment further since I've always used the o-rings supplied with my gasket kits.
 
Only one of the dowels has an o-ring. I put it on the dowel, then insert the dowel into the cylinder. I can't comment further since I've always used the o-rings supplied with my gasket kits.

Thanks for the info! the o-ring doesn't fit snugly around the dowel, that's why I asked. I'll mess around with it and see what I can do.

Thanks again.
 
It's a loose fit around the dowel and is held in place by the head gasket. That's all it needs.

BTW on your piston, you are close to 1mm over so you may have to look at 52mm and larger pistons. Maybe a 125 top end if it fits or aftermarket piston from somewhere like https://tboltusa.com/store/tb-parts-c-68.html
 
I'm 90% sure the stud spacing changed bur don't remember which year. The eartlier one piece head model was same as 125 but I think later ones were bigger than XR75 and smaller than 125. Measure diagonal between studs. Oh, you also need to havce cases bored for a 125 cylinder spigot
 
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