Rebuilding top end with copper gaskets n stuff...

I wrote in another thread that my T140 sprang a leak from the exhaust rocker box gasket. The leak was due to the fact that the rocker box gaskets were super brittle, they just snapped. In the area of the leak, the gasket had basically crushed and powdered.

It was also burning oil, oil was making its way down the rocker box through studs and instead of being sealed by the head gasket, oil was making its way into the combustion chamber. Again, the composite head gasket material around this area was crushed and uneven and in no way in a condition that you‘d expect to seal.

Thought I’d share some progress with y’all...


The pistons and combustion chambers were very carboned up. You can see how black the two front through studs are due to the oil...



But, when things were cleaned up, the pistons, bores, valves, guides, etc were all like new (which they are of course having only done 1200 miles)...



Using gasket goo recommended by Matchless some time ago, I dispensed with the base gasket, this and the copper head gasket tightened the squish to 0.34”-0.36” which I’m very happy with. The inlet valves were SO tight in the guides, meaning I had to drift them out! I suspected bent valves, but they weren’t. I struggle to see how this could have allowed proper valve control at high rpm, which I am blaming for the followers being marked, valve tips bruised and valves not seating correctly. I can only assume the engine builder thought ‘they’ll bed in’. I relieved the guides, fitted new followers and ground in the valves. The rocker shafts were clearly old, the rockers excellent, so I put new rocker shafts in too...



I know its hardly a race motor, but I couldn’t resist removing some excess metal off of the club footed rockers! Allen head mushroom tappets went in too...


Gotta love Wellseal...



The head itself was in great condition, no real seat recession, nice smooth squish area, no sign of grenading, etc. I had assumed bad seat recession as I thought the valves were to ‘high’. Turned out the pushrods were odd lengths. So I put NOS ones in I had in stock. And more Wellseal! I also used Wellseal on the copper head gasket after I’d annealed it...



I annealed the copper rocker box base gaskets and, yup, used Wellseal! I put Dowty washers under the through stud nuts to stop the oil. I faced up the bruised valve ends, and fitted posh lash caps, just cos I had them in stock...

Pic 1. The centre 5/16" studs are fitted upside down but hopefully, you've fitted them the correct way up so the long unthreaded ends are bottomed in the barrel (as the upper ends have a short unthreaded section like the 3/8"studs)?


Red is the lower (internal) O-ring for the earlier pushrod tube. The upper and lower O-rings for the later 71-7191 pushrod tube are 71-1283 (Viton).



"• The round section “O” ring 70-7310 (Buna-n) and 71-1283 (High Temperature Viton aka Fluoroelastomer or FKM) are AS120. Nominal i.d is 1″ (0.987″) and a cross section of 0.103″ . When replacing the 70-7310 use a 71-1283"

Oil often leaks down the inner studs due to the original washers being insufficient diameter. The cure is to fit wider 82-2184 washers.

I need my head read!!!! 71 Bonny

Hi Folks, While peering into my intake manifold, as one does, I found something quite worrying. Seems as though one of the studs had broken through the head into the left intake port. Saw a little bit of light so got the old endoscope out to have a closer look - unfortunately, the stupid ...

www.britbike.com

Fast Eddie said:

I wrote in another thread that my T140 sprang a leak from the exhaust rocker box gasket. The leak was due to the fact that the rocker box gaskets were super brittle, they just snapped. In the area of the leak, the gasket had basically crushed and powdered.

It was also burning oil, oil was making its way down the rocker box through studs and instead of being sealed by the head gasket, oil was making its way into the combustion chamber. Again, the composite head gasket material around this area was crushed and uneven and in no way in a condition that you‘d expect to seal.

Thought I’d share some progress with y’all...


The pistons and combustion chambers were very carboned up. You can see how black the two front through studs are due to the oil...
View attachment 18168


But, when things were cleaned up, the pistons, bores, valves, guides, etc were all like new (which they are of course having only done 1200 miles)...
View attachment 18169


Using gasket goo recommended by Matchless some time ago, I dispensed with the base gasket, this and the copper head gasket tightened the squish to 0.34”-0.36” which I’m very happy with. The inlet valves were SO tight in the guides, meaning I had to drift them out! I suspected bent valves, but they weren’t. I struggle to see how this could have allowed proper valve control at high rpm, which I am blaming for the followers being marked, valve tips bruised and valves not seating correctly. I can only assume the engine builder thought ‘they’ll bed in’. I relieved the guides, fitted new followers and ground in the valves. The rocker shafts were clearly old, the rockers excellent, so I put new rocker shafts in too...
View attachment 18170


I know its hardly a race motor, but I couldn’t resist removing some excess metal off of the club footed rockers! Allen head mushroom tappets went in too...
View attachment 18171

Gotta love Wellseal...
View attachment 18172


The head itself was in great condition, no real seat recession, nice smooth squish area, no sign of grenading, etc. I had assumed bad seat recession as I thought the valves were to ‘high’. Turned out the pushrods were odd lengths. So I put NOS ones in I had in stock. And more Wellseal! I also used Wellseal on the copper head gasket after I’d annealed it...
View attachment 18173


I annealed the copper rocker box base gaskets and, yup, used Wellseal! I put Dowty washers under the through stud nuts to stop the oil. I faced up the bruised valve ends, which created space for posh lash caps...
View attachment 18174View attachment 18175

Click to expand...

Lab is definitely right about those orange push rod seals
They are not heat resisting,they can not take the temperature of the head
They go inside the pushrod tube and the black ones to the top
I remember a shop doing this on my mate's t140d
We were heading from Highbury to shepton mallet
We got about halfway before the seals melted!
We took the head off outside the pub (no easy task as the shop had also crossthreaded the exhaust rose)
So we had to threadle the head out with one of the downpipes still attached!
I rode down to Bristol, went to "Charlie's " and bought a gasket set
I rebuilt the top end ,had a few more beers in the York house
Then went and pitched our tents on canons grave campsite
Just down the road from the bath n west
Cheers

Good feedback chaps... next time try and write it sooner please !!

Pushrod seals: it had red top and bottom when I stripped it and I have to say they looked good, they’d crushed into shape nicely. However the new ones I bought from AN were 4 black ones and they were a bit thicker and quite harder than I was happy with. I have a large tub of pushrod seals so I can select accordingly to get the best crush, and these red ones looked best. I can only hope they don’t do what your mates did Baz!

Stud washers: leaks on the inlet are understandable due to the suction, but mine leaked on the exhaust, they had large diameter washers, large enough to interfere with the gasket in fact. I considered doing the TSS mod, they had a chamfer in the head hole into which a small o ring was placed which then crushed down into the hole. But my stash of Dowty washers seemed to yield the ideal washer. Mine now has Dowty washers on those inner studs, so we’ll see how they hold up and I’ll keep the TSS idea in reserve for next time.

Studs: This is an interesting one. The pic shown at the beginning of this thread is how they were fitted by the previous builder, and is how I’ve re fitted them. The upper thread of the 3/8 studs is definitely the longer thread according to the manual. Which appears to show the 5/16 the other way around. I don’t think I’ve ever noticed this before, and I can’t think why it should be. I will have a look to see if I can remove them, but as they’re loctited in, they may be staying put this time !

Fast Eddie said:

Studs: This is an interesting one. The pic shown at the beginning of this thread is how they were fitted by the previous builder, and is how I’ve re fitted them. The upper thread of the 3/8 studs is definitely the longer thread according to the manual.

Click to expand...

Yes, as can be seen from the drawing and your photo, the threads at the lower end of the 3/8" studs stop at the barrel face and the upper thread is longer, however, the thread of the 5/16" stud does not stop at the barrel face, whichever way up it is fitted.

Original 3/8" and 5/16" barrel studs have the Unified marker at the upper end (which is a single turn of thread machined off) and Commando studs have this too where BS threaded studs were replaced with Unified during production (barrel base studs etc).
The change from Cycle to Unified barrel threads didn't happen until early T140 production.




The lower end of the 5/16" stud has a longer unthreaded section...

...which enables the stud to 'bottom' before the stud thread comes into contact with the section of unthreaded tap drilling at the base of the hole which could result in a high spot (or break) in the bore if the stud thread was forced into the unthreaded section as the 5/16 holes are very close to the bores.
If the 5/16" studs were loctited and turned in hand tight then they're probably ok.

Fast Eddie said:

Good feedback chaps... next time try and write it sooner please !!

Pushrod seals: it had red top and bottom when I stripped it and I have to say they looked good, they’d crushed into shape nicely. However the new ones I bought from AN were 4 black ones and they were a bit thicker and quite harder than I was happy with. I have a large tub of pushrod seals so I can select accordingly to get the best crush, and these red ones looked best. I can only hope they don’t do what your mates did Baz!

Stud washers: leaks on the inlet are understandable due to the suction, but mine leaked on the exhaust, they had large diameter washers, large enough to interfere with the gasket in fact. I considered doing the TSS mod, they had a chamfer in the head hole into which a small o ring was placed which then crushed down into the hole. But my stash of Dowty washers seemed to yield the ideal washer. Mine now has Dowty washers on those inner studs, so we’ll see how they hold up and I’ll keep the TSS idea in reserve for next time.

Studs: This is an interesting one. The pic shown at the beginning of this thread is how they were fitted by the previous builder, and is how I’ve re fitted them. The upper thread of the 3/8 studs is definitely the longer thread according to the manual. Which appears to show the 5/16 the other way around. I don’t think I’ve ever noticed this before, and I can’t think why it should be. I will have a look to see if I can remove them, but as they’re loctited in, they may be staying put this time !

View attachment 18183

Click to expand...

Well this happened to my mates t140d 38 years ago so maybe the composition of the red/orange seals has changed?
It was my understanding that you fitted the orange seals inside the tubes at the bottom and the black seals at the top
Later on it was recommended to fit the black seals top and bottom
It was definitely known about back then!
I can remember when his bike started pissing oil front and back saying I bet the shop fitted the orange seals to the top
If yours had orange seals top and bottom and was working ok then maybe they are different now?
Hopefully it'll be fine

baz said:

It was my understanding that you fitted the orange seals inside the tubes at the bottom and the black seals at the top
Later on it was recommended to fit the black seals top and bottom

Click to expand...

Fast Eddie's T140 I believe, has the later 71-7191 pushrod tubes with Viton O-ring at each end and not the red internal O-ring and square white seal at the base?

L.A.B. said:

Yes, as can be seen from the drawing and your photo, the threads at the lower end of the 3/8" studs stop at the barrel face and the upper thread is longer, however, the thread of the 5/16" stud does not stop at the barrel face, whichever way up it is fitted.

Original 3/8" and 5/16" barrel studs have the Unified marker at the upper end (which is a single turn of thread machined off) and Commando studs have this too where BS threaded studs were replaced with Unified during production (barrel base studs etc).
The change from Cycle to Unified barrel threads didn't happen until early T140 production.

The lower end of the 5/16" stud has a longer unthreaded section...

...which enables the stud to 'bottom' before the stud thread comes into contact with the section of unthreaded tap drilling at the base of the hole which could result in a high spot (or break) in the bore if the stud thread was forced into the unthreaded section as the 5/16 holes are very close to the bores.
If the 5/16" studs were loctited and turned in hand tight then they're probably ok.

Click to expand...

I have a Gilardoni alloy barrel kit on the shelf. That has UNC threads in the barrel, and uses UNF threads for the nuts, so they can only fit one way, no matter how hard you might try!

The centre 5/16“ studs fit exactly as you describe, there is circa 1/8” of thread still exposed when the stud is bottomed out.

The 3/8” studs have the short thread into the barrel and therefore tighten in all the way to the plain shank rather than bottoming out. This makes perfect sense to me as the stud shank provides accurate location for the gasket. I can’t really work out the logic for the 5/16” studs being different if I‘m honest.

Having looked closely, I can’t see any problem being caused by my 5/16” studs being ’upside down’ so I’m gonna leave ‘em be...!

My pushrod tubes do indeed look like the ones shown above by LAB, but they’re alloy, so I assume they’re aftermarket ones of some kind? They do look well made and fit well.

Baz, I’ll let you no if one of my red o rings gives up the fight... but until then I’ll give ‘em a go.

BTW, the only pushrod o ring I’ve had fail completely (it split) was a black one! Whatever type we use, we are probably at the mercy of whatever suppliers were used at any point in time...

Fast Eddie said:

I have a Gilardoni alloy barrel kit on the shelf. That has UNC threads in the barrel, and uses UNF threads for the nuts, so they can only fit one way, no matter how hard you might try!

Click to expand...

Agreed, although it doesn't apply to standard cast iron barrels.

Fast Eddie said:

The 3/8” studs have the short thread into the barrel and therefore tighten in all the way to the plain shank rather than bottoming out. This makes perfect sense to me as the stud shank provides accurate location for the gasket.

Click to expand...

Yes, and that was how they were fitted at the factory, however, John Healy has always maintained that it's not engineeringly correct and that the 3/8" studs should be inverted (as both ends are UNF) so have the longer threads at the bottom. The 3/8" studs will, then also bottom in the holes but the 3/8" stud requires a ball bearing or similar spacer to be inserted into each hole to prevent the stud thread running into the uncut section at the bottom of the hole as the single turn of relieved thread isn't long enough to prevent it.


I have always considered the inverting of the 3/8" studs to be unnecessary. Unfortunately, JH has stated that the factory 'fitted the studs upside down' which has led some Triumph owners to believe the end of the stud with the Unified marker should be the lower or inner end of any such stud.

I have the greatest respect for John Healey, especially when it comes to his knowledge and recommendations for mk11 carbs, he saved my sanity when setting up the carbs on this bike! But I don’t agree with his upside down stud theory in general, and more specifically doing it his way would lose the ‘register’ the stud shank provides and leave the head gasket far too much freedom to move around on assembly (possibly even creep in use) and could lead to piston to gasket fouling, especially on engines that have been rebored.

Anyhoo... I am pleased to announce that it’s now running again, but it’s too wet to road test it ...

Fast Eddie said:

I have the greatest respect for John Healey, especially when it comes to his knowledge and recommendations for mk11 carbs, he saved my sanity when setting up the carbs on this bike! But I don’t agree with his upside down stud theory in general, and more specifically doing it his way would lose the ‘register’ the stud shank provides and leave the head gasket far too much freedom to move around on assembly (possibly even creep in use) and could lead to piston to gasket fouling, especially on engines that have been rebored.

Click to expand...

I agree that for a normal road bike it's unnecessary, however, there does appear to be an engineering argument for bottoming the head studs with a 'dog point' (that the 5/16" studs have).

Yes, there does appear to be an argument... put forward by those selling a solution

Seriously it’s an interesting point, I’ve heard the argument before. But I still struggle with it, I don’t see why the load on the threads is uneven? If the threads are well formed, and uniformly engaged, then I’d have thought the load was evenly spread, irrespective of the ‘start point’ of the load?

I though dog point fasteners were to help stop cross threading.

Well sodding hell... never sodding mind sodding stud sodding threads for now... I’ve had rather more pressing matters arise...

So, half way through my test ride I detect bad noises, make it slowly back to base for a proper listen and OMG... yee-yar, yee-yar, clack, clack, clack, yee-yar, yee- yar... etc...

I’ve never heard anything like it! It sounded utterly catastrophic.

I’ll cut to the chase for y’all:

Lash caps: I only fitted them cos I’d got them left over from the Norton build... I didn’t use them cos I just thought they were another potential failure mode... well I was right, one of them popped off! Clearances were fine, everything looked bang on, but off it popped off leaving an 0.80” tappet clearance = clack, clack, clack...

Copper rocker base gaskets: The exhaust ones rubbed on the pushrods and created this horrid and perplexing yee-yar, yee-yar sound. It didn’t do this when cold, only when up to temp.

Back in the workshop......copper gaskets in the bin (after annealing they’re way to soft to file or drill) replaced by OEM style paper ones. Lash caps thrown as far as I could in 4 separate directions. All sounds good now, hopefully it‘ll be dry enough for a road test tomorrow.

What a f***ing carry on !!

Sorry about all the problems; but do appreciate sharing of the "horror" story. Maybe others of us --- (me) --- will take the proper rebuild actions ... to avoid what you've been plagued with. With all the issues, fettling, grinding, making fit, adjusting --- and adjusting again, sloppy machine tolerances etc. etc with my Brit bikes over the years; sure does make me appreciate my 1978 and 1980 KZ1000s. (where everything fits, and works ... no problems.)

nortriubuell said:

do appreciate sharing of the "horror" story. Maybe others of us --- (me) --- will take the proper rebuild actions ... to avoid what you've been plagued with.

Click to expand...

That’s why I posted it.

I don’t know why the lash cap came off. It has a .100” recess that the valve tip sits in. I had set the tappets slightly slack to allow some regular ‘nipping up’ of the head fasteners. They were set at .008” and .010” instead of .006” and .008”.

I was so eager to see what may have gone wrong that I levered the spring down and re fitted the lash cap. And when I did, I had bang on .008” thus ruling out my hypothesis that it could have been down to the push rod not being located properly on assembly, then seating itself and creating a large clearance.

Re fitting it was difficult, how on Earth it popped off by itself, not even at high revs I might add, I really do not know. I can only guess that the rocker angle causes a sweeping / arcing motion that may have tipped / levered the cap in some way? Whatever the reason, no more lash caps on my Triumphs !

The copper gasket issue is also difficult to resolve, fitting the rocker boxes and getting the pushrods lined up can be a real PITA. But it’s made easy by the rocker box base gaskets having pushrod location holes in THE RIGHT PLACE. Without a known good template it’s not really possible to check the holes are correct as there’s not a lot of margin. I know that some paper gaskets touch as I’ve seen plenty of pushrods with polish marks on them, but I assume that with paper it doesn’t matter... with copper it does. I think the best way to use copper gaskets would be to cut the holes out completely and use a ‘jig’ or ‘comb’ to hold the pushrods in the correct place during assembly. I used to do this on race bikes where we used wild cams and offset rocker buttons, the pushrods then moved differently so the gaskets needed the holes removing. But it was a bit of a faff.

Was it an inlet that popped off? just thinking about the tight valves pre fettle, could they have gone tight again with heat and be hanging slightly.

Are the lash caps a baggy fit?

Like the description of the noise it made, didn't Chitty Chitty bang bang sound similar?

storm42 said:

Was it an inlet that popped off? just thinking about the tight valves pre fettle, could they have gone tight again with heat and be hanging slightly.

Are the lash caps a baggy fit?

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That wudda made sense wouldn’t it. The T140 inlet cam is the full race Spitfire profile, which wudda made more sense too.

Sadly, ‘twas the exhaust.

The lash caps were a tight-ish push fit.