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Interesting Pushrod Tube Seal Horror.Tapered head? #600338
05/20/15 1:06 am
05/20/15 1:06 am
Joined: Feb 2015
Posts: 268
Melbourne Oz
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Steven A Offline OP
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Steven A  Offline OP
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Melbourne Oz
Hi All,

My pushrod tube seals so flummoxed me that I put my T140D in the shed 20 years ago. With the internet and the Vintage Bike article at hand I am going to fix it. Here are some pics.





Notice that this is with two head gaskets.



Inlet side looks ok.



The tubes.



So a bit to sort out. One tube is 4.5" and the other 4.476"+0.030". They are not exactly the same in construction. Block to lower seal is 0.19". Head gaskets are .04". Clearly needed the red 'O'ring up top. I will let you know what the head measurements are. It looks like it's not level.

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Re: Interesting Pushrod Tube Seal Horror.Tapered head? [Re: Steven A] #600341
05/20/15 1:13 am
05/20/15 1:13 am
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Posts: 268
Melbourne Oz
S
Steven A Offline OP
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Steven A  Offline OP
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Melbourne Oz
Tube top detail.


Re: Interesting Pushrod Tube Seal Horror.Tapered head? [Re: Steven A] #600351
05/20/15 3:55 am
05/20/15 3:55 am
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Posts: 9,688
Scotland
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Stuart Offline
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Hi Steven,

You don't say what model or year your bike is but some general advice I've accumulated from experience and places like this Forum:-

. Check what the bike has now all left Meriden together. Triumph had several goes at trying to make a reliable and simple pushrod tube seal and later bits aren't always backwards-compatible. Otoh, p.o. didn't always realise, or care, and any Triumph still around today went through periods when spares supply was dire.

. Don't mix-'n'-match parts from different years unless you know they work or you're experimenting; if the latter, don't be annoyed if it doesn't work.

. Trial-fit parts together so you can see they fit together - e.g. don't just drop the head/rockerboxes on the assembled barrels and pushrod tubes and assume the top of the prt fits in the head or rockerbox. For every Triumph worker that still rambles fondly about his/her time there, there was at least another that didn't gas except about the money at the end of the week.

Hth.

Regards,

Re: Interesting Pushrod Tube Seal Horror.Tapered head? [Re: Steven A] #600354
05/20/15 4:51 am
05/20/15 4:51 am
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Posts: 268
Melbourne Oz
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Steven A Offline OP
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Steven A  Offline OP
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Melbourne Oz
The bike is a 1979 T140 D. I have owned it from 1984. It has had one rebuild done by a shop in Stratford in London. That was in 85. I rode it until 95.

Re: Interesting Pushrod Tube Seal Horror.Tapered head? [Re: Steven A] #600355
05/20/15 5:00 am
05/20/15 5:00 am
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Posts: 1,561
UK Berks
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easier for us here in the uk but I would just buy two new push rod tubes for a 79E/D plus a couple of extra sets of seals while I was at it. plus the "wedding bands"

I'd also check that the tappet guide blocks are square, just incase.
https://bigdcycle.com/tempbooks/tri/750/1979.pdf

as stuart says, a couple of trial runs is good.
I lightly rub the PRT seals with a bit of silicone and use them when it is a bit tacky.

Re: Interesting Pushrod Tube Seal Horror.Tapered head? [Re: Steven A] #602133
05/31/15 8:33 am
05/31/15 8:33 am
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Posts: 268
Melbourne Oz
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Steven A Offline OP
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Here is my trial assembly.



Using a hole gauge we get the gap without head gasket.



MASSIVE!!

Measure the various bits.











The head at four corners.

















Pushrod Tubes.


[img]http://i850.photobucket.com/albums/...44803.jpg[/img]

[img]http://i850.photobucket.com/albums/...44550.jpg[/img]

They fit in the head.

[img]http://i850.photobucket.com/albums/...25610.jpg[/img]

Seem to have maxed out on images.

Last edited by Steven A; 05/31/15 8:36 am.
Re: Interesting Pushrod Tube Seal Horror.Tapered head? [Re: Steven A] #602134
05/31/15 8:38 am
05/31/15 8:38 am
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Melbourne Oz
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Steven A Offline OP
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Steven A  Offline OP
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Melbourne Oz
Pushrod tubes





That fit in the head.



I think this has the wrong pushrod tubes but I'm open to sugestions.

Re: Interesting Pushrod Tube Seal Horror.Tapered head? [Re: Steven A] #602137
05/31/15 8:58 am
05/31/15 8:58 am
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Posts: 473
Death row next in line norfolk
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I think you should have a thin o ring that fits inside the pushrod tube at the bottom then another thin o ring over the tappet block then push the metal sleeve (wedding bands) down over tappet block and one more o ring at the top. The white square section seals are obviously to thick.I know Triumph changed the seals to o ring type I have them on my own bike that has a complete 71 top end with same style pushrod tubes.I use Wellseal compound and never had a leaking tube.Dave


1941 BSA WM20
1958 TRI-BSA 750 PRE UNIT
1957 THUNDERBIRD
1932 R E MODEL GS SPECIAL
1947 BSA YM21
Re: Interesting Pushrod Tube Seal Horror.Tapered head? [Re: Steven A] #602139
05/31/15 9:24 am
05/31/15 9:24 am
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Posts: 7,330
Back on the mainland!
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Back on the mainland!
So if you subtract out the two headgaskets (.04" X 2), you get an initial crush figure of .0695", you're getting closer!

Are the head bolts finger tight? I would push down *gently* on the head to be sure all the PRT seals are properly seated. I would also measure crush with the head gasket you're going to use installed.

There are PRT seals (the white ones that are square in cross-section) available in a couple of different thicknesses. Try some slightly thinner ones.

Steve





Originally Posted By Steven A
Here is my trial assembly.



Using a hole gauge we get the gap without head gasket.



MASSIVE!!


'77 T140J
"Vintage Bike". What's in your garage?

"The paying customer is always right."

Fitting round pegs into square holes since 1961...
Re: Interesting Pushrod Tube Seal Horror.Tapered head? [Re: Steven A] #602162
05/31/15 12:09 pm
05/31/15 12:09 pm
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ohio
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Steve, at one time I measured 3 different thicknesses from my box of spares, which is odd because they all came with 76 T140 gasket sets or were ordered by the part number from the 76 T140 parts book.


When given the choice between two evils I picked the one I haven't tried before
Re: Interesting Pushrod Tube Seal Horror.Tapered head? [Re: Steven A] #602182
05/31/15 2:04 pm
05/31/15 2:04 pm
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Posts: 9,688
Scotland
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Stuart Offline
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Hi Steven,

Originally Posted By Steven A
I think this has the wrong pushrod tubes but I'm open to sugestions.

Agree that you should measure with the head gasket in place.

The '79 and '80 750 twin parts books show two different prt and two different bottom sealing arrangements. frown However, '80 uses the 71-1283 'O'-ring top and bottom that the '79 uses just at the top, so it should be relatively cheap to experiment? bigt

Alternatively, there's at least two, and possibly three, thicknesses of the white seal you've fitted at the bottom of the your bike's prt:-

. 70-4752 should be approximately 1/8" thick; i.e. it should be square-section, because the seal is 1/8" wide;

. 70-3547 is also 1/8" (approximately) wide, but only 1/10" (approximately) thick;

. Not sure about 70-1496 as I don't have any to measure.

Hth.

Regards,

Re: Interesting Pushrod Tube Seal Horror.Tapered head? [Re: Stuart] #602456
06/01/15 6:43 pm
06/01/15 6:43 pm
Joined: Feb 2015
Posts: 268
Melbourne Oz
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Steven A Offline OP
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Steven A  Offline OP
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Originally Posted By Stuart
Hi Steven,

[quote=Steven A]

The '79 and '80 750 twin parts books show two different prt and two different bottom sealing arrangements. frown However, '80 uses the 71-1283 'O'-ring top and bottom that the '79 uses just at the top, so it should be relatively cheap to experiment? bigt



This is the key to it. Now that I think back it did have an O ring at the bottom. When I tried to make it like the 79 parts book the trouble began.

Can anybody point me to the 1980 parts book on the web or alternatively post a scan of the relevant pages.

Thanks Everybody.

Re: Interesting Pushrod Tube Seal Horror.Tapered head? [Re: Steven A] #602459
06/01/15 7:06 pm
06/01/15 7:06 pm
Joined: Mar 2006
Posts: 3,562
Norfolk, UK
L.A.B. Online content
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Originally Posted By Steven A
Can anybody point me to the 1980 parts book on the web or alternatively post a scan of the relevant pages.


http://bigdcycle.com/triumph-parts-books/

http://raskcycle.com/parts/pushrod.html

Re: Interesting Pushrod Tube Seal Horror.Tapered head? [Re: Steven A] #602602
06/02/15 1:47 pm
06/02/15 1:47 pm
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I think august 1979 was changeover year for o ring at the bottom.Dave


1941 BSA WM20
1958 TRI-BSA 750 PRE UNIT
1957 THUNDERBIRD
1932 R E MODEL GS SPECIAL
1947 BSA YM21
Re: Interesting Pushrod Tube Seal Horror.Tapered head? [Re: Steven A] #602865
06/03/15 5:10 pm
06/03/15 5:10 pm
Joined: Feb 2015
Posts: 268
Melbourne Oz
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Steven A Offline OP
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Now the issue is, what is the seal crush for O rings top and bottom?

Re: Interesting Pushrod Tube Seal Horror.Tapered head? [Re: Steven A] #602885
06/03/15 6:49 pm
06/03/15 6:49 pm
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Posts: 1,593
Shingle Springs, California
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Total crush with all seals in and stock head gasket is about .040.


Bob


73 Triumph T140 Main Ride
70 Bonnie
67 BSA West Coast Hornet

56 Chevy

Who are the brain police?



Re: Interesting Pushrod Tube Seal Horror.Tapered head? [Re: Steven A] #603074
06/05/15 5:10 am
06/05/15 5:10 am
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Posts: 268
Melbourne Oz
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Steven A Offline OP
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Melbourne Oz
John Healy's tech notes in Vintage Bike 2010-4 state the barrell thickness under the tappet block as 0.78 - 0.8 inch.

I used a little hex nut to drop in the groove and enable the measurement of this dimension. The result is 0.958 - 0.126 = 0.832 inch. So that's 32 thou to much.

http://i850.photobucket.com/albums/ab69/...0531_151155.jpg

http://i850.photobucket.com/albums/ab69/...0531_151032.jpg

Does any one have an opinion on this.

Re: Interesting Pushrod Tube Seal Horror.Tapered head? [Re: Steven A] #603520
06/08/15 5:18 am
06/08/15 5:18 am
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Posts: 268
Melbourne Oz
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Steven A Offline OP
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I have properly measured my head with a depth micrometer.



The head is 2.772 inches on the exhaust side. It is 2.79 on the inlet side. The meat was taken off the lower face as there is a discrepancy between the distance from the push rod tube recesses and the lower face of the head, 1.692" and 1.679".

This explains why the exhaust side seal was always worse off than the inlet.

So it has been butchered. However my machinist can level this up. It is clear that the 2.775 specified in John Healy's article must be for the 650s. So what is the correct head thickness for a 750? If I know this I can start to sort things out.


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