Britbike forum Forums British motorcycles in general British motorcycles in general TR6R gear selection issues

Hi,

I’ve recently bought a 1970 TR6R that had an engine rebuild ten years ago. Everything runs fine, except selecting gears.

Sometimes I can kick the lever up or down and nothing changes. It feels like it has clicked but I stay in the same gear. Other times it finds neutral between other gears and again is difficult to get out of. Getting into 1st from neutral can be tricky too.

I’ve done some searching and I have found a lot of posts regarding the correct methods of indexing the gears, so I am assuming maybe this could be a problem. Alternatively I wonder if the issue lies in the mechanism, like the plungers meshing with inner quadrant?

I haven’t put many hours on it, as it is a recent acquisition, but it feels that smaller movements on the lever with the revs low makes for more consistent changes, but I really need more time riding it to figure out if any improvements can be made by differences in technique.

I’ve had quite a few motorcycles over the years, including other Triumphs, but have not had this much difficulty in making gear changes so don’t feel it’s me doing something wrong.

Anyway, any advice regarding either potential causes or tips to try out when next out riding so as to asses the issue further would be greatly appreciated.

Thanks,
Scott.

if the gears shifted correctly one time, then tbey are indexed correctly forever.

sounds like the quadrant return plungers are sticking. this could be rust in the plunger bore in the quadrant or old quadrant selector springs.

you can take off the outer cover and look without disturbing anything inside.

if its rusty and the plungers dont pop out onto the floor when you move the shift lever, then thats the problem.

Hi Kevin,

Thanks for the reply. Yes, the gears are in the right position, as in 1st all the way down, neutral, and then three up with 4th at the top. And it is possible to go through the gears without finding random neutrals or getting stuck in the same gear, but only with a lot of luck it would seem.

I’m happy to open up the cover and have peek. Hopefully it will be what you suggest! Thanks.

+1 with Kevins diagnosis.
If you find these to be the cause of the problem then fit new curved springs and lightly grease everything before replacing the cover.
HTH

Thanks Tridentman. I’ve ordered some new springs and plungers, as well as a pair of return springs for the quadrant.

The PO has said that he wasn’t aware of any issues, having ridden it a couple of weeks ago, and that it doesn’t like it unless you’re wearing sturdy boots and you give it some.

Not sure my riding boots or technique are the issue, as i have plenty of bikes and don’t seem to have this issue, including a a ‘73 T140. I know that has springs and not plungers, but I can change the gears fine on that.

Just in case, can anyone vouch for a 650 unit needing a different technique in its gear changes that I may have missed on other bikes?

Thanks.

No different technique needed IME.
HTH

Of course not. Had to check though. Thanks.

no no dont be stomping

as kevin cameron once said

take that, and that! the rider will get even.

the geabox does not care.

you shoulf be able to shift easily by hand. if the camplate doesnt go where its supposed to, then all the symptoms you describe are consistent. there may be something else, but for sure look at the sptings snd plungers

Following on from Kevin's reply- With the bike in the centre stand if you can click up and down through the gears with just your hand on the lever, with some rocking of the rear wheel back and forth (engine off), the gears are ok. If out on the road you still can't select gears properly then it is the clutch that is at fault I would have thought.

Getting into first from neutral with the engine running requires a pause after pulling the clutch lever and then allowing the revs to drop to idle for a silent click in. When my clutch was dragging it was really difficult to get it to go into first at all.

Out on the road you have to be a bit careful with gear changes. Mine is usually ok but if I do it in too much of a rush I can get a false neutral

Dave

I roadrace a 4 speed. If I don't take my time to deliberately clutch and shift, it WILL wind up where it shouldn't be. A 4 speed is a tough gearbox but it is not a modern design and you cannot expect it to shift like a Honda.
And Kevin's advice is sound.

Thanks for all the replies.

I have just got off the phone to chap I know who has years of experience in building 650 twins, and he said to check the clutch first, specifically that the pressure plate is true when it lifts with equal pressure on the three springs. He was adamant that I need to confirm this first as most gear change issues of this nature would be due to the clutch not disengaging properly.

I’ll check that first and see what condition the plates are in also.

my LSR four speed also doesnt like quick shifts. it will bounce right back out, even with the plunger spring shimmed. i pull the clutch, count one, two, shift, and then1 open it up

Thanks for the advice. I was taking time to between changes to let the revs drop before changing, it definitely worked better when the revs we’re as low as possible.

So.... I have spent the evening yesterday going through a few jobs. First I took off the primary cover and checked that the tension on the clutch pressure plate was even and that it spun true when kicked with the clutch in. It was spot on, no wobble... all nice and even.

Next i removed the gearbox outer cover and checked the plungers and springs. All seemed fine although the top one had a couple of knicks in them, all looked fine. I replaced the plungers, springs and lever return springs with the new LF Harris. The new plungers had a smaller step than the ones I pulled out, but don't see if that would make any difference?

I put it all back together again, and then ran through the gears by hand, whilst using my other hand to rock the rear wheel.

Each change has two stages, one where the lever moves to allow the plunger to engage the teeth on the quadrant, and then the second where the quadrant, cam and followers move and engages the gear. I change up to 1st, 2nd and 3rd without any problems.... but at 4th gear it quite often feels like the first stage is happening but it won't go any further and move the quadrant. If I push down slightly on the lever and then back up I can sometimes get it all the way into 4th. Sometimes it's fine, othertimes it just won't do it.

It also finds a neutral between 3rd and 4th.

I can go down all the gears better than up.

I haven't ridden it yet, so not sure how it will be affecting by a running engine, but will try to get out for a little blast later today.

What I didn't check was the tapered edges of the plate that hold the plungers in, and if there was any damage. I'm also wondering if there may be any issues with the cam plate? I'm at a loss to be fair so any help as to where to look next would be much appreciated. Many thanks.

Hi Scotto,
This thread really belongs in the Triumph section, as it's Triumph specific, but let that be.

Firstly; the new plungers had a smaller step you say. That could possibly indicate that your previous plungers were 5 speed ones. They would cause under-shifting in a 4 speed box, and could well be the reason for your gear selection issues. The tapered plate may possibly be worn but IME they rarely cause much trouble.
Faulty indexing is of course another possible cause, but as your box now seems to be shifting fine, I think we can disregard that, for now at least.

Secondly, while rocking the wheel is what we do when checking gear selection in the garage, there's no substitute for running it on the road. I think you may actually have solved your shifting issues, from what you say. If you try you can find neutral between any gears. Earlier camplates actually had plunger indents between gears to facilitate finding neutral. Why is another question.

SR

Hi SR, thanks for the reply. I really hope you’re right. The weather was wet and windy today so, unfortunately, I didn’t manage to get out for a ride and test the gears for any signs of improvement. Tomorrow is sunny and dry so I should be okay to put a few miles and, hopefully, you’re assessment of the plungers may be true. Fingers crossed. Thanks

Well, it’s lovely and sunny (but cold!) and I’ve just taken the TR6R out for its first ride since doing the work and I can confirm the problem has been sorted!

It changes perfectly through the gears, or as good as expected for an old Triumph. Still the odd neutral and clunky 1st, but I’m well chuffed. Actually had enjoyable ride without getting stuck in 2nd the whole way.

I’m assuming the change in plungers was the root of the problem. Job done….

Well done! Once you get the hang of it, the 4 speeder isn't a bad gearbox. It dislikes speedshifts between 2nd and 3rd, whether up or down, and the crunch into first comes with a Triumph part number according to some. I've managed to set up some clutches so well that they don't, though perhaps more by luck than skill. Blipping the throttle on downshifts soon becomes second nature, so much so that I still do it on my modern bikes!
But relax and learn to know your 4-speeder and once you master it you may well come to enjoy it.

SR

I have found that a too-thick gasket on the inner cover can contribute to false neutrals. Not sure what it does or doesn't do, but that's my experience.

excellent.

do your old plungers have a groove machined around them near the top? im curious too as to whetuer you had five speed plungers. aftermarket 5 speed plungers might not have them tho

Hi Kevin, sorry for replying so late to your post. Nope, the plungers I pulled out do not have the machined groove around the top.



These ones were a bit worn and had tapered.

I found this article which has a good picture of the step on the plungers side-by-side. It shows that the 5-speed has a bigger step than 4-speed.

http://vintagebikemagazine.com/tech...-of-a-4-speed-to-a-5-speed-transmission/

if it works correctly you seem to have the correct combination. triumph had a habit of changing things around without a lot of documentation, and even when they did issue service bulletins and so forth stuff didnt always get preserved where you could find it. and like with the plungers, the parts just look the same until you have both in your hand to compare

im always learning stuff i didnt know from people here.

Yeah, from my searching of other posts here and elsewhere it looks like, at the risk of coming off a bit nerdy, the 4-speed plunger part number 57-0406 seems to be referenced in lots of manuals wrongly for later 70's 5-speed models.

For all of the misinformation that the internet throws up, I couldn't imagine going back to pre-internet days again. There's no way I'd be able to do what I do on my own with only a Haynes to reference

I started in this hobby with a Haynes manual and the MAP catalog. Every order was COD and took at least a month to arrive. We don't know how good we got it!