Float bowl drain screw FYI

Doing fuel wet level settings today on my '85 XJ700X and it bugged me that fuel would weep out the drain screw while I was checking the level in the site glass. I pulled one out and noticed there are no o-rings to prevent this....as there are on the VMax & Venture screws.

Pictured is a VMax screw on the right and XJ screw on the left. They are interchangeable.

 

Mikuni or Hitachi?

 

Mikuni

 

The float bowl drain screws used in the Mikuni BS28's (on the XJ550s) have the o-ring. see: http://xjbikes.com/Forums/viewtopic/t=31061.html

 

That they do. What seems a little strange is these screw holes are step drilled to accommodate the larger OD of the o-ring....like the VMax holes.

Must be the screws were switched at some point or were incorrect right from the get go.

There are a few other parts on the X that came from the VMax bin (or vice versa) the taillight lens and signal lights for example.

 

Yamaha is famous for "parts room engineering."

Some of the parts on our bikes are STILL USED on current products. Hey, if it ain't broke don't fix it.

As for the carbs, Yamaha bought them from Mikuni/Hitachi. Differences like that are squarely on the supplier. They probably weren't switched; why they got rid of the o-ring is a question for Mikuni's engineers. I'm betting it was because if the tolerances are tight enough, you don't need o-rings there; and they were eliminated to save on production cost.

 

Yeah, it's always about 'production costs'...can't really blame them I guess.

R & D dropped the ball in this case tho because they never changed the bore diameter, just removed the o-ring and o-ring groove from the screw which resulted, as you would imagine, in a fuel leak from the screw hole.

Very un-Mikuni like....very disapointing! 8O