Crankcase pressure test fail :/

[shizznats]

So after rebuilding my LTD motor, I decided to be smart and do a crankcase pressure test this time around. I closed up the intake ports with expansion plugs and the exhaust ports with inner tube, hooked up a low pressure gas gauge to the fuel pulse nipple, sprayed the engine down with soapy water, and applied some pressure... which dropped almost immediately. The strange thing was that I could not see any bubbles coming from anywhere. I looked and looked until I finally decided to spray the bottom of the motor.. and lo and behold, I saw big bubbles forming right underneath the stator cover where there is a little hole. My best guess is that the RH crank seal is blown?? Any help is much appreciated!

[Trucker]

Better change the seals then

[jimvw57]

Maybe need a little sealant around the crank seals when you install them. Also keep the air pressure to under 4 or 5 PSI

Of course you realize the pressurizing the crankcase  won't show a vacuum leak which is what you should be more concerned about. And that will only show how it is sealing at that time. Once the motor warms up things may be sealing different.

[shizznats]

Thanks, yes that is true about it not showing a vacuum leak. This is concerning though as the manual says the crankcase should hold 10psi. If the air is coming from the bottom of the motor where the stator is, where there is a little hole in the bottom, am I right in thinking it is the crank seal?

Also, what kind of sealant can I put around a crank seal? ultra black RTV? Thanks!

[jimvw57]

I always use the same stuff I use on the crankcase, Yammabond, you want to use something that is gas immersion rated or there is a possibility that over time fuel could weaken it and cause a leak.

[gixxer6]

I never apply sealant to the crank seals.  Only grease the inside diameter. 

[shizznats]

Ok, thanks. One more thing... can I replace the RH crank seal without splitting the crankcase? Can I take off the stator cover, remove the flywheel (special tool needed?) and pop the crank seal out and put a new one in? Thanks.

[Joel]

You can damage your new seal if you don't split the case.

[shizznats]

With the ribbed seal like on the LH side I could see that happening, but I've popped in many regular smooth crank seals without issue and this one looks to be pretty standard. I'm more concerned about access... it looks in the manual like after taking off the stator cover, flywheel, and magneto, the crank seal is pretty far in and not easily accessed but it's hard to tell on the drawings in the manual alone.

[Joel]

It's much easier to work on that stinker with the motor out and the case split, so you can see where the placement is.

[gixxer6]

If you just replaced the seals with new, I wouldn't think its the seal itself leaking.  Maybe the crankcase seam is leaking?  What kind of sealant did you use? 

I suggest pulling the stator and repeat the soapy water pressure test to verify where exactly the leak is. 

[jimvw57]

Make sure the surface that the seal sits in is completely clean and smooth. i have seen corrosion buildup on the surface and it needs to be removed. The sealant on the outside of the seal is just an extra bit of insurance, much like greasing the inside of the seal.

Split the case and double check everything. Make sure the roll pin on the center seal is in the proper spot..

[shizznats]

So I took off the stator cover, flywheel (check out the homemade puller , and magneto and below is what the crank seal looked like. Horrible... completely hard, cracked, and rusted to hell. After prying it out however, I saw a bigger problem... the crankshaft has some serious rust and pitting on it. I'm not sure what to do at this point... whether to clean it with a wire brush bit for a dremel or some other way, but it is some heavy rust unfortunately. Any advice from what ya'll can see in the pictures (apart from a new crankshaft ? Thanks...

[Checkmarks]

Pull the motor and split the cases.  You can probably get away with sanding that surface smooth again.  Use a fan belt (cut in half) with some sanding paper 220ish grit.  Work on polishing only where the seal rides.  Finish up with 400 and then 600 paper/emery.  The fan belt should loop completely around the crank before working it back and forth.

Point is it could work.  End point, even if it does not and you smoke down the motor you still needed another motor.  You can buy a whole sled for the cost to make the repairs to this motor.  I would expect when you crack the cases the crank is toast.

If you have the 80 Ltd, save your pistons and cylinders.  Don't wreck them trying to save a few dollars 'testing' to see if your motor will survive a shade tree mechanic repair.

[jimvw57]

So I assume your 'rebuild' was just the top end and not the crank seals. As I have always said, crank seals crank seals crank seals....Any sled you get  you should put new seals in unless you can verify that it has been done in the last year or so. 

I have seen worse, if the bearings are good, clean it up and reuse it.