Britbike forum Forums Thread Like Summary - 650 transmission woes

I put the transmission back in and it feels like it is indexed right. I can change gears smoothly but then I will feel the quadrant slip. The gear shift lever will end up in the one o'clock or five o'clock position instead of the three o'clock position. The quadrant does not look worn at all. I replaced the plunger springs and the plungers don't look worn either. Anybody have any ideas what I am doing wrong?

Thanks,

Hi Anteojito, What year is motor? 4 or 5 speed?

I had similar problem on a ‘69 Bonnie. Problem was incorrect oring on gear shift shaft. ‘69 & older the shaft has a smaller groove for oring. So it needs the skinny oring.

Starting 1970 the groove & oring got larger. PROBLEM IS… many (most) parts sellers, sells late ring under early part #.

If you struggle getting gear shifter shaft into outer cover, you probably have incorrect ring. Shaft installed with correct ring it should rotate freely without binding.

As Madigen suggests check shaft is not slipping in quadrant when it’s out.

Also make sure the 2 curved springs are perfect condition. They tend to rust. I renew them unless perfect.

After installing the C shaped retainer plate. Leave plungers out. Move shifter lever many times. Verify the curved springs very reliably center the gear shifter lever.

Should you miss indexing it doesn’t effect centering of shifter. Missing indexing you can’t get 1st or top gear. Or less gears depending how far you miss.

Be aware plungers, gear shifter quadrant (the part the plungers go into are specific for 4 or 5 speed. Still that doesn’t prevent shifter from reliably centering.

On the ‘69 Bonnie I got wrong oring from 2 suppliers. Hardware store didn’t have suitable size. I found good size in my “spare” oring box from work. I don’t know what part #. Was from older Mercedes automatic trans or steering box.

Please let us know what you find.
Don

Thanks. I'll check those things too. I did have some issues getting the shift shaft in the outer cover. I'll take it all apart and take a look at the O-ring. I've replaced all the springs, I figured what the hell, why not. Funny how it can be a little thing that throws something out of whack. I'll let you know what I learned.

Kent

Being as you're pulling it back apart: be sure to grease/lubricate with gear oil all the moving parts in the outer GB cover. This cover is notorious for lack of lubrication and with wild temperature swings (Hot days cool/cold nights) can build up condensation and corrosion quickly.

Once or twice a year, I'll have a friend help me lean the bike way over on it's right (timing) side to coat the inside of the outer cover well with the gear oil from the gearbox.

Cheers,

Steve

Hi, I change trans oil every 2500 miles. About twice a year. I have oil suction equipment. I suck the oil out of outer cover every oil change. Has not really improved anything as far as rust goes. I still do it as why not do all I can to help things.

I gave a lot of thought to drilling hole(s). A few 3/32 holes I don’t think clutch cable end could pass through. I’ve had 2 cable ends break off as well. I was able to retrieve them through filler hole with skinny flex magnet.

Question. The earlier b’69 & older have trans vent in upper front of outer cover. The primary on these is vented into trans via clutch rod bore. A small venting through clutch cable & quadrant pivot shaft as well.

However starting 1970 650/750 the outer cover vent was not drilled. Trans now is vented into primary case via clutch rod bore. So now as bike cools trans sucks moist air from primary into trans. If I worked 30 years at dealer I’d know for sure, but I’ve noticed primary breather bikes trans seems to have about twice the rust. Plus rust you see on clutch parts.

Riding along on boring stretches of highway I ponder these things. I’m always looking to be better mechanic & make bike last longer. It’s a sickness!!
Don

I always found chain lube was a good thing to use on the trumpet's
gear change mech. Both the 500 and 650. Lasts really well.