Hi Merlo,

my problem is the top pushrod tube seals are actually in the head itself not at the top of the tube

Have you looked at the proper Triumph parts catalogue and workshop manual for your bike? If you look at the parts catalogue pages for the heads, you'll see all top prt seals sit on the ridge just below the top of the prt itself.

I'm not getting enough clampdown onto the head gasket
last time I used the thinnest cush rubber and the thinnest top pushrod tube o ring in the kit

Put new seals on the prt and the head gasket on the top of the cylinder block. The "E4752" seal shown at the bottom of each prt is a white or translucent square-section one about 1/8" thick. Put the cylinder head over the prt and fit some of the head bolts to steady it. You should be able to measure about a 20 thou. gap between the top of the head gasket and the underside of the cylinder head.

If the gap you measure is much greater, there should be two-similar-looking-but-thinner (about 1/10" thick) rings in your gasket set, replace the 1/8"-thick rings with the 1/10"-thick rings, repeat the above and measure again.

The "clampdown onto the head gasket" is imparted by tightening the head bolts. When you do this, the aforementioned 20 thou. gap is how much the prt seals will be squeezed. So you don't want too big a gap or you'll bend the head. However, if tightening the head bolts on to the head gasket closes up about that aforementioned 20 thou. gap, the prt seal will be squeezed a little and they will (should) then seal the prt. :thumb

Hth.

Regards,

 

As Stuart says,the 71 head does have a groove machined in it for the O ring seal.This can often be displaced when bringing the head down over the PRTubes so try it a few times and see if the rubber rings curl up.If you can achieve the temporary fitting a few times and the seals do not relocate,then it is time to bolt it down.A bit of oil on the seals will help to slide the tubes in.My own engine usually needs the thin lower seals but they may all be different depending on machining.If you fit too thick a lower seal.it is likely that it will also push out,and,force the steel band upwards before the seal pushes right out and leaks.Frustrating process to seal these tubes and time consuming to re-do the work.I do not always get it right first time and have to start again. Beginning to get it right after nearly 40 years though.My last dismantle to cure this leak failed,so i decided to spend more time and change the base gasket,tappet block seals and piston rings.It now stays leak free for about 3 years so far.I tend to get 10 years before i have to remove the head again due to other failures so its not a losing battle.
Just check you have got a 71 head fitted on the bike.

 

I had a leaky inlet valve guide so I pulled the head off to fit new guides, my problem is the top pushrod tube seals are actually in the head itself not at the top of the tube (the old seals were thrown due to their state so I'm not getting enough clampdown onto the head gasket ivé had four goes at it the last time I used the thinnest cush rubber and the thinnest top pushrod tube o ring in the kit everything was sweet after 38 miles I noticed a weep of oil on the top barrel fin now at 43 its starting to piss out I know the fix but I cant find the seals its about the size of a wedding ring and sits above the groove in the head where the tube sits. ps the heads fine it's as straight as an arrow.
any clues
thanks
merlo

It does seem an incorrect crush setting is your problem here.

The '71 push rod tube (PRT) has a ridge at the top that retains the O ring. Now, upon disassembly, the O ring may sometimes "stick" and be retained on its seat in the head. The oil seal is made between the machined face in the cylinder head and the ridge of the PRT separated by the viton O ring, with appropriate pressure applied.

The key to this is to achieve about .030" crush on this O ring. These old cylinder heads may well have been shaved to straighten, rather than re-bending them straight. Because you don't know whether or not any has been machined off the head (you can measure the head for thickness, an un-tampered head will measure 2.785"), you need to follow the method below to ascertain the exact thickness of the base washer (it's the white one with square edges, enclosed by the wedding ring)

Too much crush and you'll likely bow the head as you torque it down, too little and they leak.

To set the crush. Assemble the head onto the gasket, no seals on the PRTs. Measure the gap on the bottom of the PRT and then add .030” to .040”. Choose a white base washer (they can be obtained in several thicknesses) to make up this measured gap. PRT base washer thickness for new head and standard head gasket is .187” (.030”) to .197” (.040”). NB: The bottom PRT oil seal is actually another viton O ring placed into the groove on the inner of the PRT and not the white washer which acts only as a spacer to set the correct crush.!!

HTH. RR

 

Hi,

The '71 push rod tube (PRT) has a ridge at the top that retains the O ring. Now, upon disassembly, the O ring may sometimes "stick" and be retained on its seat in the head. The oil seal is made between the machined face in the cylinder head and the ridge of the PRT separated by the viton O ring, with appropriate pressure applied.

The key to this is to achieve about .030" crush on this O ring.
NB: The bottom PRT oil seal is actually another viton O ring placed into the groove on the inner of the PRT and not the white washer which acts only as a spacer to set the correct crush.

Ahhh ... no.

As Merlo knows already from his Trident, the "white washer" is flexible and it can be squeezed between thumb and forefinger; otoh, the same cannot be done to either 'O'-ring. There is absolutely no possibility whatsoever the "white washer" won't deform and all '.030" crush' will be on the top 'O'-ring. Not only does that need suspension of certain physical laws, it also wouldn't need the 71-1707 "wedding bands" to stop the "white washers" deforming enough to be squeezed from under the prt when the head is tightened down (which, for something that isn't an oil seal, will allow a remarkable amount of oil to leak out).

Measure the gap on the bottom of the PRT and then add .030” to .040”.

This range is debatable. It comes from a 47-year-old Triumph Service Bulletin that contains a number of errors. Today, many work with lower 'crush' figures and achieve oil-tight sealing.

Hth.

Regards,

 

Gday, thanks for your imput fella's, I fully understand what your saying that's the same process for my trident my problem is here I can find O-rings thin enough for my setup thus I need the seal that fits in the top of the head which I know nothing about.PS this is not my head.
thanks
merlo

 

Hi Merlo,

I fully understand what your saying that's the same process for my trident

Just to be clear, Trident prt protrude through the head and seal in the rocker-boxes, and use the same square-section "E4752" seal top and bottom of each prt. Otoh, twins' prt seat in the head.

my problem is here I can find O-rings thin enough for my setup thus I need the seal that fits in the top of the head which I know nothing about.PS this is not my head.

Our problem is you aren't being clear enough. '71 650 twins seal the prt how it's shown in the parts book:-

. Where you've put a purple line on the picture of a prt is where 'O'-ring 71-1283 (E11283) fits.

. There aren't any thinner 'O'-rings - 70-7310 (E7310) and 71-1283 (E11283) are both the same size - diameter and thickness. Thanks to @johntioc, we know the reason for the different part numbers is 70-7310 was Buna-N and 71-1283 was Viton; as the top 'O'-ring must be Viton, it's likely any you buy today are all Viton.

. The only possible variation is the thickness of the white or translucent 'O'-ring shown as "E4752" at the bottom of each prt; the two options have been posted already.

. There aren't any other seals on the prt; if you need a "seal that fits in the top of the head which [you] know nothing about" and it isn't one of the three in the parts book, 'fraid someone's been buggering around with the particular head you're looking at; why would anyone else except said someone know anything about it?

Hth.

Regards,

 

i may not be clear on your problem - but the only "seal" that goes in the area indicated is an O ring - put it on the PRT and offer it into the head

 

Why is this conversation going on in 2 separate threads?
If your gaskets are too thick you can use a razor and thin them to fit. I had to do this with my Frankenstein 66 T120 Bonny head on the 70 TR6R.

 

Gday, thanks for your imput mate , I fully understand what your saying that's the same process for my trident my problem is here I can find O-rings thin enough for my setup thus I need the seal that fits in the top of the head which I know nothing about.PS this is not my head.
thanks
merlo

You may need to consider the .080" copper gasket to give you more clearance. RR

 

Anybody ever notice that the pushrodtubes are not even perpendicular?

 

Now,i take on board some of these recommendations,so i went into the garage to check out some assemblies.Now i took my head with me but still cant find the arse part to fit it on.Do i use a sealant,or a lubricant to insert the head into the arse.?
Still laughing at the antics today.Makes some good light reading on a cold day with nothing much to do.
Yes,the pushrod tubes do lean in which can also contribute to why the seals often leak.What a design.You may also note that the engine on an OIF bike is not central to the frame and the footrests,if you look down,look well out of alignment but are correct.We were really chucking bikes together in the 70s and a few inches of play here and there might not be noticed.

 

We plumbers call that stuff nightmares ? there would have been no need for crush at all if the mating flanges were flat!
I actually modified the prt flanges slightly to accomodate this, but i really think you need the same shape and material on the upper and lower seals. (Which actually are seals, no matter what people think) in order to compress equally.

 

The push rod tubes on my old AJS 500 are sealed in a similar manner. There are large 'o'-rings that sits over the the cam follower bushes in the top of the crankcase. The lower end of the push rod tubes are flared to sit over those 'o'-rings. At the top, the push rod tubes are reduced in diameter and there is a rubber 'sleeve' about 1/2" long that fits over the reduced diameter with a steel washer either side of it. That fits into a recess in the cylinder head. When the head is assembled onto the cylinder and tightened down, the top rubber sleeve is compressed between the two washers and seals in the head and the bottom 'o'-ring is compressed under the tube to seal the bottom.
It's one of the few places this engine doesn't leak oil from!!

 

At least they are straight.. ?

 

Also a very real possibility for the utterly shameless ?
(Only did this as a means to positively locate the leak..)