Introduction and question

[Kitfox93eg]

Hi all my name is Ed Grasso finished a Kitfox 4 with a Rotax 912S and been flying about 13 years. I have a project that has been started by another and I will be finishing and redoing it to my standards. The engine was assembled when I got it but it had silicone coming out of the case halves so I'm doing a complete rebuild.

I have a question about the crank end play shims. The only way I can get the play in spec is with one shim installed. I have been told that you need three shims for other reasons. I'm thinking of cutting the flywheel hub (I have a lathe and machining back round so it's an easy fix) was wondering if any others have run into this and what was done to fix it?

Also as most know don't use silicone! Most of the oil returns were blocked and I'm sure some would have found it's way into the oil pump.

Thanks in advance and hope I have something to share with the group as I've been the automotive repair/machining field for 40 plus years.

Ed

[mike.smith]

Hi, Ed:

I've built my AeroVee 3 times (stories for another day). Using the recommended Permatex sealant on the case halves has yielded zero leaks for me. Silicone is definitely bad news and won't let the case halves mate properly. That means the required crank bearing "crush" will not be attained, which will wear out the bearings and the crank journals.

As for the end play I'd certainly talk to Sonex before you machine the crank. I've had two cranks and both required 3 or 4 shims. I've not heard of your situation in another AeroVee, but that doesn't mean it hasn't happened.

Hard lessons learned for me on the shims and rear seal:
- When you set the shims you will be doing it without the RTV to seal the end of the crank with the 8 pins. That RTV will add thickness and cause more end play than you figured when it was dry. So adjust your shims so you get the minimum play: around .003, rather than the high end of .006. it will take a lot of frustrating trial and error, but it's worth it. When you install the RTV and torque the gland nut, you'll likely find your .003 has turned into .004 or .005.
- Install the RTV EXACTLY per the instructions. Yes, there are instructions. Install the RTV and put on the flywheel and gland nut to finger-tight. Wait 1 hour, THEN tighten and torque. If you don't wait, most of the RTV will squeeze out and you'll have a leak almost right away. Wait at least 24 hours before running the engine or adding fluids.
- Install the rear seal just slightly below the surface of the back of the case, rather than flush or proud.
- Make sure you put a little white lithium grease on the rear seal before you put on the flywheel. If you don't then you risk tearing the seal as soon as the engine is turned over.

These are things I did not do in the past and regretted it. Learn from my mistakes!

[Kitfox93eg]

Mike, thanks for the advise I'll report what I find on the shim problem. I have talked to a few VW techs and all have told me that you need three shims for the thrust. I used Permatex on the case also and used to use it in the 70's when I worked on VW's.

Ed

[Kitfox93eg]

I cut .025 from the face of the flywheel and was able to use three shims. I now have the end play set to .003 and will check it after the silicone sealer and final torque. I had it mounted in the lathe and runout at the crankshaft boss less than .0005 before cutting.

Ed

[Bryan Cotton]

Ed,
I wish I had a lathe. Even better I wish I had skill with one! Great picture and solution.

[mike.smith]

Let us know how it all turns out!