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The reverse on my bike (06 502) had been working flawless until today. When backing out of the garage (level surface), at even half throttle, it hardly moved. Everything is tight, fluid full (2,500 mi on oil), reverse does not get abused at all.( Maybe that is the problem ) First and second shift/work perfect. Tranny was rebulit with the latest components and the extra capacity oil pan about 6k mi ago.
Any thoughts/ideas ??

This may be a real stupid response, but is the trannie going into the reverse gear? In other words, check the adjustment on the shifter arm and is the reverse handlebar button functioning properly. Sounds as if you may need to contact either Adrian or Tom Chadwell.
Buck

Buck,
I checked that the bolts and shifter arm assembly are tight and moving properly.
It "feels" like it is going in reverse, almost as if it is "dropping into gear", so I don't think it is the button. Yesterday, it would creep a little, today-dead. I'll call Tom or Adrian.
Thanks

Hi Bill,


I'm am fairly certain that on newer trannys like yours the band is not mechanically adjustable .
Here's how it works, and hopefully you'll find the problem yourself and it will be an easy repair.
When the engine is running, the pump in the tranny is being mechanically driven and developed pressure is sent to the valve body . Its dumped back into the sump when the shift drum is in the neutral position because the holes drilled thru the drum it allow that to happen . When you rotate the drum (shift to low)) the pressure gets redirected to the passage connecting to the first gear clutch ,and part of the planetary gears are held from moving , and the combination is in "low gear". Rotating the shift drum again(into high ) dumps the 1 st gear clutch pressure and at the time goes to the passage for the high gear clutch (behind the large right side aluminum cover). A different part of the planetary is held now and the combination of locked parts and not held parts
makes the output shaft rotate more that then the input shaft .
For reverse to work , first the drum has to be rotated to allow oil pressure to reach the 12v solenoid valve in the valve body by alignment of the holes again. When you press the Reverse button on the handlebar , you are closing a "momentary on" switch to send 12v to that solenoid. When that solenoid opens ,oil pressure will push against the back of the reverse piston. The piston pushes an "arm" which in turn clamps the band tight around the outside section of the planetary locking up a different gear combination. When that is locked, your output shaft will rotate in the opposite direction, aka reverse.
They have a "safety" valve in that reverse piston . Its just a ball against spring pressure. If you turn the throttle and the pump develops more than 50 psi or so, that ball lifts off the seat and all the pressure falls off preventing the piston from pushing so hard on the band that it won't break it at either end.
Check that you have 12v at the black wire at the tranny when you press and hold the reverse handlebar switch. If so, measure the resistance to ground of that black solenoid wire. I think its 80 ohms or so, be sure its has something, not open and not shorted to ground.. Check that fuse too.
I'd drive the bike up on blocks before putting a clean " throw away " turkey basting pan under it and dropping the pan. You'll have more room to look things over.
Check that the nut holding the soleniod coil is not loose. It also can not be too tight. Have a helper press the reverse button and feel that solenoid click on and off. Pull the reverse arm against the spring and remove the piston by turning it kind of sideways. it will come out easily. Look at the check ball and the seal . With that out , you can move the arm and see that the linkage is clamping the band around the drum tightly. Hopefully before you got this far , you have found the problem with a bad wire or electrical connection.! Jeff

Jeff,

thanks for the write up! That is a great clear and concise explanation about the inner workings of the trans. I can now visualize it. Have not worked on it yet but will look at the electrical aspect before removing the pan. I wll report back what I find.

Update: Even though the reverse piston seal looked ok I decided to replace it since I had it out. Also, the fluid was Polaris PS-4. Put in the recommended Racing 4T, (formally MX4T) and the first few times it was a little hesitant. After that, it has worked perfect. Fingers crossed

Glad to see it appears your trans problem is corrected, that has to be a relief. I've never seen Polaris fluid used in the BH trans, I always used MX4T in mine. Did I miss something being away for couple years?

Don

Don, When I bought the bike, Marv picked the bike up in Wisconson and trailered in down for me last year. While it was in his shop I had him change out the fluid. He recommended the ps-4. I had never heard of it either. Had always used the 4t with no issues.

Bill -

Thanks, that sure was a new one for me! Maybe I'll get a chance to see Marv for BW - I'd like to hear more?

Don