Britbike forum Forums British Motorcycle specific Brands Triumph bulletin board Bent Clutch Pushrod Question

Hi all -

My '82 T140ES clutch pushrod is slightly bent. Measured with a feeler gauge on a polished granite countertop, seems to have a bow/bend of about .006"-.008"

The reason I'm curious about this is is seems to be *just* enough out of round that the rod sticks/frees with slight difficulty in the mainshaft. I had to tap it from one end with a small screwdriver to push enough of the rod out to get a purchase on it to extract from the mainshaft.

Is this a common problem? If so, does it need to be fixed and how?

My first thought was to chuck up the rod in a drill and slightly sand/polish the unhardened middle portion...

Cheers,

Steve

I'd be curious as to why it bent in the first place.
Nice thing about this web site is I thought I had a lot of problems. My bikes are relatively trouble free when compared to some of the problems I read about here.

I've successfully straightened a bent clutch pushrod (not from a T140, from a BSA single) by marking the high spot (found by rolling on a flat surface, as you have done), and just bending it by hand, very carefully, until it was straight again. I can only think that clumsy handling by a previous owner / ;mechanic' caused the bend in the first place.

If I remember correctly (questionable) both ends of the mainshaft have bushes so the hole through the mainshaft is larger than the hole through the bushes. The rod should be straight and square ends. Otherwise the rod will bend under load, reducing the clutch lift.
Possibly someone tightened the pressure plate spring nuts enough so the springs coil bound and bent the pushrod.

desco - yes, that thought is there, just looking for guidance on a fix for the 'rod at the moment.

DMadigan - according to the parts manual, there is only one bronze bush on the gearbox end of the mainshaft.

Tigernuts - I'll see if I can give that a go.

Steve

The ID of the main shaft at the clutch end is only a little more than the OD of the rod, so no bush needed there.
The ID of the shaft at the timing side is much greater, so this is where the bush lives.

In the old pre-unit box it was easy to see how the rod could be bent, with the movement of the actuator, especially if there was an indentation in the end of the rod.

Not so easy to explain with the unit arrangement, which doesn’t put any lateral force on the end of the rod.

So why has the rod bent in the first place? In normal use it doesn’t have much work to do, and should be able to deal with the spring pressure at full lift easily.

Even if the rod is bent (for whatever reason) what real difference does it make?

A new one is cheap as chips.
About £10

HEY!!! Chips used to cost a quid!

Hi Steve, As you think any bending at all is no good. The pushrod is made of a sturdy metal like tool steel. Very similar to what's called "drill rod" in USA. It's a tool steel they make drill bits & other tools out of. I've made a few push rods from drill rod. Hardened each end. I've made adjuster screws from drill rod as well. Both proved very durable like factory ones.

If you cannot straighten clutch rod, it will need new one. The rod must be quite straight. Between the bushing & the clutch end of main shaft the rod is unsupported in the hollow part for about 6-5/8". So it must be straight. The rod must be very free fitting in the main shaft without even a hint of binding.

How the push rod gets bent I don't know. I've purposely coil bound springs during testing & I can feel lever stop when coils are bound. I've had T140 where adjuster screw hits plug. If you are paying attention, you can feel the lever all of a sudden stop like somethings binding or is wrong. But if you keep squeezing, it might bend rod. I never kept squeezing.

Back to your rod, from factory only the ends of rod are hardened. Maybe about 1/2" or so with the tips that are really hard. The rest is just stiff steel. So you can usually straighten rod. It will have spring back for about 24-48 hrs. So after you have it perfect. Come back a few days later, it's not perfect again. So it may take a few attempts & a tad of overbending. Some aftermarket (pattern) rods are fully hardened end to end. Those may be much harder to straighten. BSA nut on Ebay was selling them. I don't see any advantage to fully hardened.

I've checked many rods for straightness & all have been very, very close to perfect rolling them on flat surface. I've never personally seen a bent clutch rod yet...

Shop manual states rod is 7/32" (.2187"). I've measured several. They tend to be smaller diameter by about .002-.003" from factory. The length of rod is stated in manual to be 11.812-11.822" About 11-13/16 in length. In my observation this is pretty much the case on original 650 rods.
However I've measured length of original T140 750 type rods & they have all been shorter by about .030" at 11.750" (11-3/4"). Yet... part # is the same.

I had a few bikes where rod or screw was problematic. A 1970 Tiger where rod wore a step in it about 4-7/16 from clutch end. Rod was replaced. New rod wore the same. Owner just lived with it.

My '73 Tiger did exact same thing!! Turns out this is caused by a burr in the bore of the main shaft where it necks down to the narrow on clutch end. The main shaft is hardened. I attempted to drill off burr, couldn't do it, shaft was too hard. I tried to crack it off driving hardened rod down bore. It was too strong to crack off. The burr could be plainly felt sticking a probe into the hole in main shaft & seen by shinning light into bore with shaft on bench. Indeed it was a burr. The burr narrowed rod by .016". The ID of the burr was a whisker larger than .218".

I observed this step & recorded wear. It was not wearing any further than it had in 11000 miles from new. I turned rod around. It started wearing decided new step in less than 100 miles. So I turned it back around while deciding on what is best way to proceed.

So I ended up making a custom rod that necked down at the burr such the step in rod always cleared burr. The ID of my main shaft at the left end was looser than normal. So I was able to use oversized rod 15/64" & neck it down at burr. Tapered the neck down transition smoothly to reduce the stress riser from the narrowed area. Turned the right end of rod down to .218" where it goes into bronze bushing. The left end of rod was 15/64 diam. for 3-3/4". Inspection of bronze bushing showed it was in perfect condition, even after 36000 miles. So that was not part of problems. This custom rod has worked very well & doesn't wear a step in it anymore. Been in bike a good 20000 miles now & still is.

As you may have guessed the factory rod on my bike was quite loose in clutch end of main shaft. 1/64+" wobble. Loose as a goose!! Yet... the custom rod which is a perfect fit gives no improvement in any way I can tell. I swapped old & custom rod a few times & extensively road tested. The wobble just didn't matter in real life. Truthfully, I could have just left the old rod in with the groove worn in it.

I've measured the bore in a handful of main shafts. It's all over the place, & can vary by .017".

The overall length of main shaft is about 11-1/8' long. The counter bore where bronze bushing goes is drilled about 6-7/8" deep, which means the narrower rod bore at clutch end is about 4-1/4 deep. The pressed in bronze bushing is about 3/8" long. Bore of bushing is supposedly clearance for rod. The bore of some of the new reproduction bushings I've been involved with is drilled too large. Even after pressing in new bushing bore feels worn out. Unless your bushing is really worn, new one might be worse...???

The factory rod adjustment screw is much longer than it needs to be. Pretty much all of the right foot T140 I've been involved with including my own, the screw hit the plug. A few actually wore hole though the plug & oil leaked out of slot. Owners said theirs is not hitting. But... removing plug it was. I've cut the screw shorter on slotted end & reslotted with hack saw.

To cut screw, take a donor 3/8-24 nut. Cut nut through to bore starting at a point of the hex. Deburr threads. Now screw adjuster screw into nut leaving the amount you want cut off exposed. Put nut in vise tightly such you can hacksaw screw tip off without screw spinning in nut. Deburr cut surface of screw. Put screw in nut with cut end sticking up the amount of depth of screwdriver slot you want. Again put nut tight in vise. This will allow easy cutting of slot without screw turning & there will be zero thread damage to screw threads. I have made these screw holder nuts for almost every size bolt/screw on bike. A safe & easy way to cut bolts & screws.

I've not seen many complaining of the plug wearing through on left foot shift bikes. Maybe factory modified casting of primary cover depth?

I wonder if the factory shortened clutch rod .030" in an attempt to gain more clearance? It wasn't enough. The 650 originally had thick seal on plug. They went to oring. The oring seemed fine on later 650. The 3 row chain crank case is a different casting. It's slightly wider than 650, but not quite wide enough??
Don

Hey Steve, if you need a replacement pushrod, mainshaft bush, or adjuster pin, we can help. We offer an adjuster pin with a ball bearing in the end as well.
-Dave
https://www.thebonnevilleshop.com/p...e-tiger-clutch-pushrod-pn-57-1736-t1736/
https://www.thebonnevilleshop.com/p...x-mainshaft-brass-bush-pn-57-3988-pt108/
https://www.thebonnevilleshop.com/p...tch-adjuster-pin-nut-pn-57-2159-14-0403/
https://www.thebonnevilleshop.com/p...clutch-adjuster-nut-pn-57-2159b-14-0403/

Just looked at your link for the ball-end adjuster pin. It's made in UK - how is it that these things are sold in the US but not (apparently, because I've never come across them) here? Looks like I'll have to pay for postage from USA, plus UK postal & import charges. Can you say who makes these?

7/32 silver steel. Cut and harden ends.
Use 2 bits with a ball bearing in the centre.
Job done.

I'm not so sure that the ball should be in the middle Nick, if indeed there needs to be a ball at all.

The bore for about two thirds of the length from the timing side is big. I wouldn't want the ends of the rods with a ball floppping around in there.

I would put that in the few inches beyond the smaller ID in the shaft, if you're going to do it at all.

But why do it anyway? Just think about it, when is the rod under stress?

Hi, Thinking about putting ball in rod... As Koan most importantly pointed out the "7/32" bore is only about 4-1/4" long from clutch end. You drop the ball in the hollow, you'd better have a skinny magnet for fishing it out.

Koan said why do it anyway? Good point!

This adding the ball is an old idea that's been used for some years. Even going so far as to put radial needle bearing in the mix, under the pressure plate.

Bonneville shop sells an adjuster with ball in end. What is the true advantage in that in real life operation?

I have enough experience to see the wear patterns of the rod, adjuster pin & thrust pad in the 3 ball lever. I'll give my observation & thoughts, take it for that.

Every smoked (heat damaged) bushing & rod end, screw end, thrust pad I've seen was caused by one thing alone... Not having proper clearance of clutch rod. If owner maintains proper rod clearance these parts have a very, very long service life. 40k miles barely any wear.

However... you let the rod go to zero clearance it will overheat very quickly as it is forced to rotate against its end. This damages the bushing fairly quickly.

As was suggested, the rod when properly adjusted is simply along for the ride while riding down the road. No force on either end or even in center. The oil mist in primary & trans are enough lube with no load to give zero wear. The rod will eventually rotate about same speed of main shaft & it has mist oiling as well. We simply don't see wear on sides of rod (mine did but that was from a burr which factory should have removed). The rest of my rod had zero wear.

The rod is hardened to a good degree so the end in the bushing doesn't wear.

The return spring keeps thrust pad in 3 ball lever from turning. The rod adjuster pin is rotating at main shaft speed so it's not taking wear.

When pulling in clutch shifting there is force & differing rotation speeds of all these parts. However during shifting it's only for a brief moment.

At a stand still with trans in gear like at a red light, there is zero rotation. The main shaft is not turning at all. So zero wear.

The main force is while you are pulling in & letting out clutch lever. We ride the canyons & city all the time. Shifting continually. Just to the coffee stop I gave up counting after about 300 shifts. I work with friends on their bikes & track this stuff. We keep the rod adjusted. Check adjust at every oil change at least.

6 bikes, basically zero wear of the rod & related parts.

Feeling a couple of clutches with ball added to "cut" rod, I sure couldn't feel a trace of difference in any way. It just felt like the clutches with the factory arraignment. Does the added ball make things last longer? I don't have long term data, but wear is simply not an issue.
& ramps wear on the 3 ball lever assembly. The pivot hole can wear on very high milage, rust probably kills most of these assemblies. On fairly rare occasion the hardened tip of the adjuster screw breaks off even if its never been overheated or out of adjustment. I've heard of only 3 tips breaking off in 9 years. Mine & 2 online.

There is nothing wrong with adding a ball in the rod, or ball on adjuster screw, fixing a problem that doesn't exist. Kind of like lacey underwear, you can't see it. It doesn't work any better than plain underwear. But it looks pretty & makes you happy. So you spend your $$ on what you like & want.

If you just want to ride your bike. The normal parts work well & last a really long time. Most riders can easily go 1500 miles between rod adjustments. So check rod adjustment at the 1500 oil change.

Since we're on subject of clutch parts, most alloy pressure plates are lacy underwear also. The MAP cycle is the only one I know of in current production that actually gives better pressure. Even then mostly for 7 plate kits. I'm not a fan of the MAP cycle rod with ball. They sell the plate sans rod/ball for less & it's the better value in my mind.
Don

My guess that the ball in the adjuster is harder than the screw and saves hardening the end.
The lifter is outboard of the mainshaft bearing housing where is no oil flinging about. I am not sure how much mist is on there but if you want to make sure the lifter and shift parts are lubricated the bike should occasionally tilted over to let the gearbox oil flood the parts.
At a stand still with trans in gear the mainshaft is not turning but the clutch with pressure plate is and the pushrod is loaded so one face of the pushrod is rotating.
You can get rid of the adjustment problem with a self adjusting hydraulic setup.

Jeez, you all ride like old ladies and stuff wears out that I never pay any attention too..lol. When you start a fresh Triumph, the parts wear to 50% in the first few minutes...But the next 50% can take a long time or just another few minutes...

At a standstill with engine running, in gear with the clutch free, the mainshaft is not turning, the clutch centre fixed to the mainshaft is not turning and the pressure plate, held in place by nuts springs and cups on studs held in the clutch centre, is not turning.

The clutch basket and the driving plates are turning. The movement bears on the clutch rollers.

Hi; I am with an opinion similar to Hillbilly bike. 0.006 is nothing. You will never have a problem with that; only as TR7RVMan; is saying, put the right clearance between the parts; and just that.
Ho many km do you put on the black top? when you are at a traffic light or car jam do you pull the clutch all the time or use N?

TT - You are right,the basket is turning, not the hub and pressure plate. Brain fade.

I didn’t think of it until reading the TR7 man posts above. I also was under a vague impression that the rod end was wearing away while I was waiting at lights with the clutch pulled in.

Just something i've always done, i suppose because because i always added extra plates, and
when racing was using a manx box + clutch.

Very interesting discussion.
For some reason BSA seemed to think that the rod needed a ball bearing at the end of the rod under the lever assembly. But they also use a separate short rod at that end, the clutch rod does not touch the lever.
I'm also interested in your comment about the length of the rods sold for T140. It seems that once properly adjusted on my late T120V my adjuster bolt is screwed in to the point where there are barely enough threads showing to put on the lock nut. I've never measured the rod, maybe it's the shorter one for T140? Would be tough to order the correct one when they are the same part number.

Hi David, Easy to remove screw & pull rod with skinny magnet & measure.

But we’re talking a lot of threads here….

The tip of your screw isn’t broken off is it?

What pressure plate are you using? Triumph steel or alloy?

Exactly what plates are you using?

I ran into this once with Emgo 6 plate.
The stack didn’t look tight. Top steel was too far out. Trial fitting pressure plate there were few threads remaining on screw.

Turns out Emgo plates are their own deal…. Emgo frictions are thicker than normal. Emgo steel plates are thinner than normal to compensate. So if using Emgo you need all Emgo.

Problem is shops sell Emgo & they don’t bother telling buyers this. I expect some shops don’t even know this??

Another thing that causes this is loose main shaft nut. With a tiny mirror & stick light you can see nut through filler hole. You can stick finger in hole & feel nut if your fingers are thin enough.
Don

Yeah those nuts need Loctite.

What nut do you refer? I mean, I am trying to visualize how to fit a mirror there to see but do not see how you can see it (the gbox nut) because the clutch nut is behind the pressure plate so...