Life throws things at you!

[jwonder]

In the middle of everything else I figured I would get some downtime and check/adjust the timing on my R51/3. I went to the garage, started it, adjusted the timing ever so slightly and shut it down. I was going to change plugs and found that one of the pushrod rubbers had split (see picture below).

They are not hard, and I was told (and have receipts from the previous owner) that the motor was rebuilt in the last 4 years. They look fairly new.

Now, I am sure I know the answer to this already but figured I would ask. (fingers crossed) Is there anything I can do with this without pulling the cylinder to replace them? There were no oil leaks but I only was running it on the stand.

Thanks for any guidance!

James

[schrader7032]

I hate when that happens! At least you see the issue whereas on the /5-on engines, they're under the cylinder. Since the pushrod tubes run uphill, they rely on splash inside the engine cavity to find its way into the opening and drain down to the valves. I'd be inclined to try some things just to keep what's left together. Maybe some heavy duty black zip ties...not sure of the temps at this point, but they'd probably hold up. Next would be some hose clamps...they're simple radiator clamps to other that are more sophisticated.

Ultimately there's a small, small chance that "stuff" can find its way into the cut. So, you'll need to replace them eventually. I suppose you could put the cylinder at TDC, loosen the four base bolts and pull out the top end enough without going past the piston rings. Replace the seal and reverse the process...do both of them. The cylinder base should really be cleaned and a thin layer of non-hardening sealant applied. You would need to be sure the pushrods found their proper home...probably best to loosen the rocker arms before start this.

[ahistand]

Unfortunately I think you’re going to have to pull the head and cylinder to replace it.
That kind of splitting can happen if the pushrod tube shoulders are too close to the engine case therefore squeezing the seals too much. But based on the looks of the one that’s not split they look about right, but it’s hard to tell for sure with a picture. It’s been my experience that most of the aftermarket rubber bits that are being made for these old bikes are really poor quality rubber. Nowhere even close to the quality of the original stuff. But sadly we don’t have much choice in who the supplier is. It’s a problem not only with rubber parts but other things too. The wiring harnesses currently coming from Germany are just horrendous quality now for instance.
If you do end up taking it apart, you might sort of carefully assess just how much the seal is being squeezed, and if you feel it’s too much you can tap the pushrod tubes into the cylinder a little deeper. Those seals will do their job just fine only being compressed a little bit.

[wa1nca]

In the middle of everything else I figured I would get some downtime and check/adjust the timing on my R51/3. I went to the garage, started it, adjusted the timing ever so slightly and shut it down. I was going to change plugs and found that one of the pushrod rubbers had split (see picture below).

They are not hard, and I was told (and have receipts from the previous owner) that the motor was rebuilt in the last 4 years. They look fairly new.

Now, I am sure I know the answer to this already but figured I would ask. (fingers crossed) Is there anything I can do with this without pulling the cylinder to replace them? There were no oil leaks but I only was running it on the stand.

Thanks for any guidance!

James

Looks like that push rod tube was never inserted all the way into the head and damaged the seal because it put to much pressure on the seal

The seal can be replaced by removing the 4 lower cylinder nuts
Then the cylinder can be move up enough to insert the new seal but will damage the new seal because the push rod tube is not inserted all the way into the head
So the cylinder needs to be removed and that push rod tube needs to be tapped in all the way so one edge of the tube is flush with the top of the head
Should also renew the cylinder base and head gasket at the same time
Good news is parts should be less than $20.00 and if you do the labor then just your time

Did you ever get your charging problem working

Tommy

[Micha]

I had the same issue with my R51/3.
I inserted the replicas that I purchased at Mark Huggett, Swiss.
They split in the same manner.
I was upset, pulling everything apart, again, and used the old one with a smear of heat resistant engine RTV.
Don’t know what to use or buy this winter, as I intend to overhaul the motor.

[Beemer100]

that sucks, James

but I'm afraid I would agree with Tommi ... the push rod tubes are not far enough in the cylinder head so that the shoulder of the tube applies too much pressure on the rubber seal. If you do the "KISS" method fix of the problem, you will end up with the same split seal.

IMHO - depending on your current weather - I would continue driving the bike and wait until it gets worse or you have another reason to pull the cylinder. The seal is more or less in the corner where the rubber gets squeezed into the opening of the engine case ... as long as this part is still intact ... you might be lucky.
In case you plan to cross the country I probably would fix it right now.

I am surprised about Micha's experience with Mark's rubber seals since I strongly believe his rubber parts are the best you can get in the market. Rabenbauer in Germany is also a very good source (my number one source for parts) but I think his rubber parts also come from Mark. So, I guess you won't find any better quality.

good luck
Klaus

[schrader7032]

Not sure if this is what people are seeing regarding the tube position in the head. Look at the head-side of the pushrod tube, especially the one that split. Notice the dark line that is about 2-3mm up the tube. Likely the line was the original position of the tube in the head.

Oak Okleshen provided a diagram that showed where the position of the tubes needed to be relative to the cylinder base. It was specifically for the /5-on bikes. So, not sure if it applies here. But this is what he recommended for positioning of the seals. This is my interpretation of what Oak provided.

[wa1nca]

Another possibility the tube is inserted correctly, but is not the correct length
The total length of the r51/3 tube is 94 mm
The total length of the r67/3 tube is 104 mm
The total length of the r68 tube is 100 mm

Tommy

[jimstravlin]

I am afraid you are going to have to pull the head and cylinder on that one. I can not believe this was not addressed correctly when the work was done. Actually if this was over looked I would want to see what is inside.I trusted a Harley machine shop to fit a pair of pistons on my R68 early on and after 6K miles i had to tear it apart only to find real problems culminating in a re-bore and a new pair of pistons...

[jwonder]

All,

I pulled the head and cylinder off today asI am all about making sure things are right and I am quite a perfectionist. Everything looked good as I was getting in there but as I was cleaning things up I noticed that the CYLINDER IS SLEEVED! Ugh.....

I have read that a sleeved cylinder does not transfer heat well, but this sleeve looks like it was put in very good and I have ridden the motorcycle and the motor ran great. The cylinder wall looks good as well. I would love to know your feelings on this! I would like any ideas on the sleeving of these cylinders for the R51/3. It looks like a good job IMHO.

Thanks for any help!!!