gear selector box.

[machten]

Bob,

Here's a list of things I looked at to properly fix my 750 Sport selector box. I didn't have to deal with all of them, but I did check them all. In my opionion this is one of the most complex mechanical components on our bevels because of the number of contibuting clearance factors to making it work correctly. I'm sure others could add to it, but here's my list...

Internal case Spindle bushes
External case spindle bush
Return spring
Detent Spring
Fork Spring
Gear lever on spindle
Gear lever on push rods for rearsets.
Selector cam adjuster setup
Fork spindle wear
Fork contact surfaces

Now imagine an old well used selector box and add up all the wear clearances that could be in there. I'm no expert, but tidying up some of those made a huge difference for my Sport, which is pretty much the same mechanicals as a single. No guarantee any of this is your problem, of course...just sharing...

btw, a regular contributer has all the bits to correct most of these...

Kev

[Bevel bob]

Hi Octane, I have had a few sessions playing with the external adjustment, on the last occasion I was about 30 miles from home when it seemed a good idea to experiment. Living on one of the most crowded places on the planet ,on the outskirts of the capital ,you can imagine the joy of negotiating the traffic with only two high gears working.

[Dave450]

Bob - to check your selector box, I find it easier to remove it and clamp it in a vice with soft jaws and a rag. Click it up and down the box without using any hand pressure as the gear lever returns. When the spring returns the mechanism to the central position, there should be a definite and immediate 'clunk' as the selector fork slides over the pins on the selector shaft and the detent ball clicks home. Any delay means that the return spring is not centred and needs to be adjusted using the eccentric. It often selects crisply one way through the box but not the other. Adjust the eccentric until you get crisp returns in each gear position up and down the box with no delay and without needing a slight nudge to get into the next gear position.

New bushes in the box and cover are worth doing if there is any appreciable 'slop'. If you decide to replace the bushes, then replace the return spring as well. They tend to break after many years of use (ask me how I know). The eccentric adjuster should be a snug fit in the groove in the return spring holder, and the coil spring - between the selector fork and the cover - should have enough force to push the selector fork down onto the selector shaft between the pins. Replace that it it looks tired, but usually they are fine. Check the splined gear shift shaft for wear where it bears in the bush in the outer part of the box. One or two thou out of round shouldn't matter in practice, but if there is a noticeable wear lip, then a new bush won't solve the problem. The fork, selector shaft (with the pins) and return spring holder are very hard and usually show little if any wear, but are worth checking while you're in there.

Once you have the selector box working as it should, you can then discover if the selection problem is inside the gearbox or not (hopefully not).

Dave