2017 HH GST 150 Platinum - Leaking trans fluid conundrum
 

My 180CC big bore install / rebuild is done and the engine runs really well. I still have a bit of tuning to do on the Mikuni VM26-606. I'm at a 180 jet now, worked my way up from 160.

I am having a frustrating problem with the FNR transmission. I've had the case apart several times verifying as best I can that everything is assembled correctly but I don't see any issues. Gearboxes have never been my favorite thing to work on.

On the bottom of the trans case the locating bolt, washer, shaft, spring and ball bearing are installed. However, if I tighten the bolt so that there is not even slight tranny fluid seepage past this bolt, I can't change gears at all using the shift lever. However, if I back off this bolt enough so I can shift into F and R, I get a slight leak at the bolt when the buggy is in use. I'm thinking maybe the washer needs to be replaced or, and more likely, I have something slightly off in the gearbox.

The picture shows the bolt I'm talking about.

Anyone have any ideas?

I ended up getting a slightly thicker M14 copper washer plus a 1.5mm thick synthetic M14 washer. Using both of these stopped the leak while letting me retain the correct pressure on the gear cylinder.