Pushrod tubes, seals and washers.

[Bleng]

Hi everyone - this is my 1st post, having read lots and found a great deal of info already. But I am still confused about what I need to refit the pushrod tubes on my '49 M18 correctly.

I have completely rebuilt (with more than a little help) the engine - the crankshaft was rebuilt with new (old stock) parts and the case reassembled. The cylinder barrel was re-bored and and oversize piston fitted. Everything else was cleaned, checked and refitted, using new gaskets and washers where necessary.
After a couple of test rides I have noticed 'wetting on the cooling fins around the cylinder head join and some smoke coming from the void 'behind' the spark plug.. which got me thinking about the pushrod tube tops.

Can someone tell me exactly what combination of washers and seals I should have on my engine -
a '49 500, with a compression plate and and iron head.

Why do I ask? Because the engine I dismantled had NO washers above the pushrod tubes at all - just 1 solid, brittle seal, which I replaced. So basically I have no washers above the pushrod tube, just the thick seal. Having read lots of posts I now know this is really not correct!
I have looked at the spare parts catalogue that shows 3 different washers and a rubber seal, but I cant seem to find details on what combination I need for my setup. (I did find some info for >48, 50>20 and 52> but nothing for '49 with a compression plate)

Any help is really appreciated.

[clive]

Well Sprids your example does not actually specify the combination for a 49 500. The 49 parts list suggests that with the compression plate fitted the 1/8 washer (A) alone should be fitted for the 500 and no lower dished washer (C) is specified at all. The 350 has no compression plate and it is suggested the top washer should be ony 3/64 thick. This implies the compression pate is 5/8 thick. I have seen two thicknesses! When I had a 49 500 I ran it without compression plate but with B above and C below. It was relatively OK for sealing but did tend to weep a bit after a few 1000 miles. I would be inclined to try two 3/64 washers above and the dished washer below with a compression plate but you are probably going to need to experiment especially if you are going to use o rings as advised by Sprids.

[SPRIDDLER]

Well Sprids your example does not actually specify the combination for a 49 500.

Indeed so, Clive. I deleted my post a couple of minutes after posting it as I intended to re-write it, having realised it wasn't sufficiently clear but got waylaid watching the cricket on Catch-up.

(Watching the women's football now so it's not the time to do it).

[clive]

Ah now you have deleted your post my reference to the B and C washers is a bit unclear............Happy viewing.

[SPRIDDLER]

Ah now you have deleted your post my reference to the B and C washers is a bit unclear............Happy viewing.

I think I must have deleted my post whilst you were typing your reply.
I got the impression from Ben's post that he had found all the info available. However, if not, here are the relevant bits from my deleted post.........

Pushrod tube washers and seals b.jpg

And the Viton 'O' rings for the tops of the tubes...........

Pushrod seals - Viton.JPG

and the two for the bottoms.......................

Pushrod tube bottom seals.JPG

[Bleng]

Thank you both - I am glad that I didn;t miss any obvious posts. I've tried measuring the compression plate in situ, but its a very imprecise game. For now I am going to hope that the plate is the standard one that is quoted as 1/8 thick. IF that is the case, then I am going with a plan to buy ALL the washers and glands and employ the dark art of 'trial and error' .
While I was looking into the forum prior to posting I did come across the diagram you reposted Spriddler - thanks again though as I as wondering about the the O rings versus the thick rubber gasket.. I can see one benefit is that I can experiment with adding and removing them to find the best option, but is there another reason for using the O rings over the gasket?

[clive]

Those who use o rings say they seal better and there is a specific size thickness and material they recommend. If you intend to use them I would still go for two top washers 3/64 each and the dished bottom washer in the first instance. As you say it's trial and error or do as I do and put up with a bit of weeping oil.

[SPRIDDLER]

I can see one benefit is that I can experiment with adding and removing them to find the best option, but is there another reason for using the O rings over the gasket?

Yes, the rubber sleeve seal will leak because they go rock hard (like Bakelite) over time. The Viton 'O' rings won't.
I have always greased them and put them in position and then inserted the p/rod tubes.

100_1411 (640x480) (2).jpg

...when I dismantled the engine it had NO washers above the pushrod tubes at all -

It's not always easy to see the upper steel washer(s)because they become carbonised and stuck hard in position, appearing to be part of the head casting. If you probe the hole with a screwdriver from the top (the side where the rockers would be) it will dislodge or catch on the washer.
I would definitely fit the dished steel washer, placed so that its profile is snug to (matches) that of the shoulder on the pushrod then fit whatever thickness of flat steel washers is necessary above the 'O' rings so that they squash firmly. However, when tightening down the head make sure that the pushrod tubes don't bottom out on the crankcase or they will split at the bottom.
You should be able to move them slightly when all is tightened down.

Pushrod tube to crankcase gap (640x480).jpg

Pushrods should move a tad (640x480).jpg

I guess you know how important it is to anneal the head gasket (even a new one) before fitting it,

[Bleng]

ok, so finally got round to getting the head off the bike, thinking i would see signs of a leak from the the tubes, but I think I have an oil leak at the head gasket... so do I leave the tubes as they are, re-anneal the head gasket and try again, or to I add the washers and o rings to the tubes and re-anneal the head gasket? Or is it something else I should look at? All thoughts, ideas, observations are very welcome
This photo is immediately after removing the head.

49_head.jpg

[Duncan]

You shouldn't really have any oil in the top of the piston looking to escape via the head gasket, does it look like oil is getting past the piston, was there oil in the valve pockets on the piston, did you have white smoke when running? If there is a lot of oil around the head gasket it can migrate in while you are removing the head making the gasket look wet.
As 1949 was a change over year I don't know what length the end spigot is on your pushrod tubes, often earlier iron head engines had a short spigot and are not suitable for stacking o-rings as the top one can pop out.
I would inspect your head bolts to ensure they do not look necked/stretched, replace if they are as they may continue to stretch in use and allow the gasket to blow.