Engine leak testing

[Andreas Piepke]

I'll inspect the crank case with a magnifying glass tonight.
The Norton is a 1973 Commando 850 cm^3. I am owning it since 1987. It has about 20,000 miles and, to the best of my knowledge, the engine has never been opened since assembly at the Norton factory.

I appreciate your feedback, good news bad news: doesn't matter. The only thing that matters is to identify the real problems and solve them!

Andreas

[Andreas Piepke]

JP you really have a good eye! This weekend I took a photo of the right housing half:



Indeed, there is a crack starting from the cable recess. However, it does not extend into the crank case and is not the cause for the leakage. Maybe the little rubber grommet is too tight once the cables are in and caused this. I bought a new one and already opened up its interior so it fits into the case opening; but maybe not enough. I will try to fix the crack with JP weld as this doesn't seem structural.

Cheers

Andreas

[Andreas Piepke]

Hi Penton enthusiasts,

Lately I didn't do much work on my in-parts-again 1973 Penton Hare Scrambler. This post is not strictly Penton but for your enjoyment: I spent time making my 1973 Norton Commando operational again; here a short video of a test ride.

https://www.youtube.com/watch?v=3KopPQnFYts

I'll get back to my Penton now.

Cheers

Andreas

P.S.: Does this thing with not having the key in the ignition and the gloves on only happen to me?

[JP Morgen]

Good luck Andreas, maybe the center case gasket didn't lay flat, or it has shrunk and has moved off the case split area, been there, done that on a Sachs motor once.

[Andreas Piepke]

I had hoped for that too but, unfortunately, this doesn't seem to be the case. Have a look at an earlier post in this thread. When I split the cases I found the gasket in good order. I posted a photo, it looks ok to me. I am afraid the problem is with the left hand side crank seal, the one that is really hard to replace.

Cheers

Andreas

[Andreas Piepke]

Hi All,

Today I took my 250 ccm engine further apart to get the leakage problem resolved. I went from this:



To disassembled again. I still need to figure out what caused the engine to leak. Have a look at the two images below.

Configuration A:


This is how I had the left crank seal installed. Or does it need to go the other way around?

Configuration B:


This is my question for all KTM engine pros: which way around, A or B, does this seal need to be installed?
I further noted that the seal was sitting in there slightly crooked, perhaps the angular mismatch between sealing lip and crank pin caused the leak. I would greatly appreciate guidance in this matter as I don't want to take this engine apart yet another time!

Thanks in advance!

Andreas

[JP Morgen]

Seal should be installed as in your upper/first photo, open side in toward crankshaft. I would be wary of a seal with a metal outer sleeve, leaks can occur around the seal outer edge. Try to find a seal that has rubber around the outside diameter. Yes, a crooked installation could be problematic.

[JP Morgen]

Also check any areas of the case that have epoxy applied to them from the factory, could be porosity there, epoxy may have dried out and shrunk away from case. Clean, sand, reapply new epoxy if needed.

[KJDonovan]

Andreas,

When you initially rebuilt this, did you replace the O-ring under the aluminum spacer?

Thanks,

Kevin

[Andreas Piepke]

Kevin, yes I did. All seals, gaskets, and bearings have been replaced. The cylinder has been bored, a new piston installed, it has a new connecting rod too. There is nothing old in there.

Andreas

[Andreas Piepke]

Hi Penton Owners Group,

If you follow this post you might remember that a POGer with a sharp eye discovered a crack in the right crank housing half of my 1973 Hare Scrambler. Closer inspection actually showed this to be really the case:



This crack originates from the little cutout for the cables. I believe that the deeper problem is that the rubber grommet that fixes the cable is too tight (I noted this and despite opening up its interior it was still tight) and puts too much pressure on the thin walled housing. Small cause big effect.
In order to fix this problem I decided to mill out the crack so its top becomes a V-shaped groove that can be sealed with epoxy. The picture below shows part of that effort:



Further inspection showed that this crack had already propagated way beyond the feed through area:



My friends in the shop then used an end mill to produce a V-groove along the entire length of the crack:



The work area was freed from debris and paint residue using a steel brush and acetone:





After that we applied Miller-Stephenson two part epoxy 907 over a wide area to promote adhesion:



Let's hope that'll fix this problem. I will probably not install the little rubber grommet with the cable to keep any stress off this area in the future.

I've also pressed-in a new crank seal into the left housing, using the orientation identified here on this site:



I'll start re-assembling the engine today. Let's hope it'll work right this time!

Cheers

Andreas

[JP Morgen]

My choice would have been to have the case welded. I weld magnesium frequently, easy to do if very, very clean.

[Andreas Piepke]

Hi All,

I installed the left crank seal, have a look at the image:



I sits in there straight, shows no deformation, the lips are free of any imperfections. Hope it'll seal now! If not then I simply don't know how to do this.

The left crank housing oiled for insertion of the crank shaft and the transmission:



I oiled the piston (has two lubrication holes on the outlet side):





Transmission inserted. I've rarely done a more fidgety task than this. There seems to be always some part that falls off or is misaligned when doing this.







Next step: put the cases back together. Given how much tough luck I had the last time around with the leak tightness I will use an elastic sealant this time to help seal the housing. The paper gasket is awfully thin and this may help getting this tight!

Wish me luck!

Andreas

[Mickey Sergeant]

I'm with JP, I would have installed crank seals that are all rubber. I have never used one's with the metal outer. I would think you would have a better chance of sealing with the rubber one's

[Andreas Piepke]

It's in there now! I got the seals from Al Buehner, usually his stuff does work, I have to say. Let's see how it will come out.
I've put the crank housing together today, using elastic sealant (Yamaha brand Yamabond 4). As next step I'll put the cylinder and head in. After that I'll pressure test the engine on the bench. The left seal is still visible from the outside at this point as the left outer bearing isn't in yet. I hope that with a flash light I'll be able to spray both crank seals with soapy water and unambiguously find out whether or not the seals are tight.

Cheers

Andreas