Britbike forum Forums Thread Like Summary - T140 clutch

Good day guys

I purchased a 1976 T140 a couple months ago and the previous owner started installing a new belt drive and clutch plates.
I finished off the job and tidied up the rest of the bike.
I having an issue with the clutch not disengaging with the shifter when riding. I've re adjusted it a few times now and have no l luck.
When i'm rolling along i can reach down and run through the gears with pulling on the shifter with my hand nice and smooth without using the clutch.
This ever happen to you? Any ideas what i'm missing here?

-i Steve, How much lift is the pressure plate getting? Does the clutch free ok before starting motor? Lift is very important. If possible, you want about .115-.120".

Spring binding is possible, but if you get the lift, springs are not yet bound.


Try adjusting the rod like this video. This is a very good way to do it. By the way the problem that causes the click in video is not having enough lever play during rod adjustment. That is the #1 place where owners go wrong.

The 5 speed gear dogs are steeply back cut. This makes it hard to shift without clutch or a dragging clutch. So you obviously have the knack of releasing pressure off the gears when shifting without clutch. Sounds like you know what you are doing.

Another thing that can get you is the nut coming loose on right end of main shaft. This allows the clutch assembly to move left/right as you pull lever. If you have small mirror you can look into filler hole & see the nut. A skinny finger like mine can reach & feel for looseness. Sometimes the lock tab inner tab doesn't hold in the spline or breaks off. Visually the nut/lock look ok, but has actually backed off. If get some extra slack in rod clearance, about 1 full turn. Then gently tap rod adjuster screw to right with screw driver forcing main shaft to right. Then pull clutch lever the rod moves main shaft to left, that is sure sign of loose nut.

Many T140 the adjuster screw is a bit too long & hits the plug on primary cover. Check for that. You'll see rub mark on inside of plug. Cutting slot end short & adding new slot with hacksaw is a good cure. This obviously reduces lift when it's hitting. With practice you can feel spring bind or something stopping free lifting of pressure plate, but with unfamiliar bike, not so obvious.


Unrelated to the clutch is the centering springs for shifter lever get rusty & weak. The cross over shaft made it harder to center lever. Later the centering springs were changed to thick heavy duty ones that center the lever much more positively. I always install the stronger springs. # 57-7051.
Don

Did you adjust the springs according to the manual?
Then cable and operating rod?
Measured the rod?

And what brand belt drive kit? The rod might need to me modified as a part of the installation setup?

Hi Steve, That's great news!! What is your rod lift now?

Regarding rear brake, what do you mean by full contact? Pads don't match disc diameter or not pressing hard? If pads are moving, but not pressing hard on rotor that's often air in line. Need bleeding. A task in it's own right. No short cuts.

However, a deteriorated rubber brake hose can do that. Actually deteriorated/aged brake hose can do the oddest things, even like act as a check valve making brakes stick on. Either of these can be intermittent. Service life of brake hose is considered 10 years. Some can last 20+ but don't count on it. DOT demanded month/year of manufacture to be marked on hose. Either in ink or molded in. Ink wasn't so durable...

Does pedal pump up & get firm, or does it drop after applying pressure to pads? Dropping is leaking cup seal.

Another however... The master cylinder/push rod relationship is unlike a car where push rod has a small clearance. Here the push rod is preloaded such the cup seal has specific clearance to the breather (vent) port. Really on an unknown bike with application issues like you have you may want to start from front & work rearwards.

The original master cyl is prone to rust. You can by seal kit, but any pitting from rust is no good. Stainless LF Harris cylinder is a good choice in my mind. Sold as cylinder with seals/piston, or as a complete set up with the "bracket & integrated push rod. The pedal stop & all the adjustments must be correct.

Caliper may be binding. If you push pads/pistons back & they pump back to disc, unlikely caliper is at fault.

Where to start? Look at hose age, change as needed. Bleed. Test. If no good look into master cyl adjustment. Or get new master, hose, fit/adjust master, bleed & see how caliper is. I've seen caliper piston seals go years. But if in question rebuild caliper. Then it will last many years.
Don

Hi, The threads are longer on this switch. However trial fitting switch without washers in the LF Harris stainless master I still had a few threads to spare before bottoming, even with the thin copper washers. Taking crush into consideration as well. I would have shortened threads as needed being mindful of metal chips.

The washers supplied with switch are thicker with a rubber membrane. Common in high pressure applications. I debated on those or copper. Decided to use supplied washers. No leaks.

Of course these days every last part must be inspected & etrial fitted.
Don

Aluminum crush washers work better than copper
On all my bikes with hydraulic brakes the bulky rubber hoses go in the trash can. I use AN3 PTFE lined braided stainless hose. I buy the fittings and custom fabricate all lines for a perfect fit. The AN hose is slim and looks nice on vintage bikes. Plus it gives a firmer brake feel...

Hi Steve, I use the Nelson brand hoses sold by most venders in USA. Canada I expect is same.

Sadly I've not been able to find the original style front stop light switch itself so separately. Too bad. I snap up any I find at swap meets.

My feeling is most the switches were accidently broken by owners taking the switch apart & lost control & broke the plastic. Once they understand how it attaches & the little fiddle it takes to wiggle it out they do fine. Of course by then it's too late. At least the flippers & buttons are sold separately. Even though flipper blades look similar the cam on back side is specific to application. So you can't willy nilly mix & match.

In their older years corrosion, shrinking of plastic causing loose rivets can make them go open circuit. A good plan to drill 3/32 hole in lowest part of switch casting as needed to let the water out. They take lots of water inside in the rain. I've had my lever/master off several times for various reasons. Including replacing master cyl. The switch is still working fine. If switch is not fractured too bad they can often be repaired. I still think it's too bad they don't make the switch & you could just solder it in.

The SPARX one is commonly sold. Genuine Lucas NOS is still available from a few venders or eBay. Good used switches come up on eBay on rare occasion. Bonneville Shop states the switch shown in their photo fits 73-78. Not true. '73 & 74 are different. On those years the kill switch is push button on left console, the flipper blade is high/low beam.

As Tridentman stated, Triumph added hydraulic switch in steel piping between trees. A better way in many respects. The top tree casting is different on these later bikes. You'll have to do some fabricating to add switch between trees, but a really good plan to do it that way.

If you have the banjo fitting on top brake hose, it's very easy to install a pressure switch banjo bolt brake light switch. The run wires from switch down to headlamp shell. Connect one side of switch to white wire (key on power), the other side to brown that goes into multi plug (power to brake bulb).
I installed one recently on '73 Bonnie that switch had broken & wires cut off. Came out nicely & doesn't look silly at all.

Click this link, scroll to post #28 for photo. This was from eBay. Not costly. It comes with connectors & wire jacket but was too short. I soldered longer wires on & slipped over some wire jacket. Wire jacket was melted to insulation. Carefully cut away. I staggered wire joints to fit into wire jacket smoothly. Be careful with sellers they don't give you metric. Correct thread is more costly. The correct thread is 3/8-24.


https://www.triumphrat.net/threads/oil-pressure-switch-woe.977950/page-2#post-2004146038


Here's the switch I used & place I got it from. Canada, shop around for good price.

https://www.ebay.com/itm/Brake-Ligh...3-8-24-/183568377385?hash=item2abd872629

If you PM me your email I have photos of most all this stuff.
Don

The only ones I've found in the proper thread are a bit long. One must double up the copper washers to make them work without leaking.

The original front brake switch was a real Mickey Mouse affair.
Even Triumph eventually recognized that by putting in a hydraulic switch --as per the previous post.
You can easily adapt the hydraulics to incorporate the 78 on switch and it then becomes reliable.
HTH

Fit a hydraulic switch and save the hassle of the original switch
The 79 type hides behind the yokes, or a switch/bolt that's more visible

The front brake light switch is part of the switch assembly.

https://www.thebonnevilleshop.com/p...and-switch-kill-switch-pn-99-1268-30708/



It would have had one but was probably cut off.

Hi Steve, Great you got the rear going. Front is really easy after doing the rear. You already know what you’re going to do on front. Get Harris stainless. Does front brake light switch still work? Be very gentle on removal. The switch is fragile. It’s wires are in switch console, but switch is inside the front perch casting. You have to remove a screw, then gently work it out. Extra pair of hands is handy.

I personally like the stock rubber hoses. Simple direct replacement. Use whatever you want. Be mindful of the support of lower hose as it must flex greatly. Keep in mind clearance to wire harness at steering head should you choose to eliminate the steel pipe between trees.
Don

Hi Steve, Lift .123 excellent! At least that victory is under your belt.

Pads not square to rotor? Like caliper is not lined up or axle is not square to bike? Or swing arm twisted? Caliper mounts bent? Correct parts for bike? That stuff comes to mind.

I've neve seen a caliper itself bent so pistons come out not facing each other. Not saying it couldn't be.

Looks like you have some investigating to do.
Don