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Messed up motor mount threads

JwWright57

Well Known Member
Man, sometimes i just hate this plane. There have been SO many little things and some big things too. Long shipping times, hanger rash, changes mid construction. It just seems to go on and on.

Now I finally received my 912IS (after waiting almost 6 months) and right off the bat there is an issue. The threads in the case for the upper left motor mount seem bad. First I thought it was the mount. And then I thought it was the bolt itself. So after trying another bolt I finally tried to screw the bare bolt into the case and it only goes in for a few turns then stops. WTF!

I’m kinda at a loss right now. Looking at the Rotax web site they direct you to a “dealer”. And of course there are none anywhere near me. At this point I feel like taking a sledge to the whole dam project.

Any suggestions would be most appreciated.
 

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Have you checked the bolt hole depth and visual appearance of the threads? Is it just the one mounting hole? Have you tried a bolt that works in another mounting hole? If the threads are there you could chase them with a tap.
 
Have you checked the bolt hole depth and visual appearance of the threads? Is it just the one mounting hole? Have you tried a bolt that works in another mounting hole? If the threads are there you could chase them with a tap.

Yes i tried another bolt that went in the other hole fine. I’m really hesitant to even try and retap a brand new 30k motor. To get to the hole you’d need to take off a bunch of **** to be able to get a tap in there.
 
Thread Gauge

Something like this can be useful in insuring you are using the right bolt or tap to chase the threads.

https://www.amazon.com/gp/product/B07J9V9JTK/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

Also, if you can get a bolt in, you should be able to get a bottoming tap in.
I bought a tight quarters tap handle like this that can be used with a socket and ratchet.

https://www.mscdirect.com/browse/tnpla/55233027?cid=ppc-google-New+-+Threading+-+PLA_s7WWE3Qsy___164110844049_c_S&mkwid=s7WWE3Qsy%7cdc&pcrid=164110844049&rd=k&product_id=55233027&pgrid=37806547660&ptaid=pla-79862503504&gclid=CjwKCAiA_9r_BRBZEiwAHZ_v15KQeT0dq54lI-mG6DqNBwlvBhHkM9xKmwdN37uXUNkFsr0dhJNduBoCZXMQAvD_BwE
 
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Unfortunately these things happen. Its best to take a deep breath and walk away from it for a little while. I've had to do that a few times. I know I'm just going to make the situation worse so I walk away. Then I come back a day or so later when I can have a fresh perspective. I've found this works pretty well. It doesn't make the problem go away but it does help get it resolved.

I recently ordered some new klixon breakers. I opened one to just take a look and would you believe one of the screws isn't threaded at all. Not a single thread. Unbelievable. Anyway I realize its not on the scale of your issue but things happen.
 
I opened a ticket with Lockheead aviation and Rotax looks like they might have to re-thread the hole or redo it with a helicoil. Amazing on a brand new fing engine
 
It's a good thing you caught it, but annoying. At least they are going to fix it and it is better that the dealer does it rather than try to DIY in case it gets worse and then it becomes your problem.
Somebody on the production line must have been having a bad day when that engine rolled off!
 
Yeah even though you might be able to fix it I don't think I would try. It's really their problem to resolve not yours.
 
Yeah even though you might be able to fix it I don't think I would try. It's really their problem to resolve not yours.

Lockwoord aero is on the case! This is the latest update;

I've been told there is a special tool that is used to correct thread problems of this type. I've also been promised some information soon on the source for said tool.
Apparently it's a tool that corrects threads going from the inside out.
 
"Now I finally received my 912IS (after waiting almost 6 months)"

Im getting ready to place my 912is engine order through Vans. Was the 6 month delivery time what you were expecting? Where you given a delivery estimate when you first placed your order? Was your engine delayed after you placed the order?

I have the money now and id rather order the engine early anticipating delays versus wait to order and have a months long break in my build process. Thanks
 
Most likely a Back Tap Thread Repair Tool. Sort of a threaded expanding collet that engages the threaded portion below the "screw-up". Fairly long tool not good for confined space.

Looks like this...
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I know the feeling!

This type of incident is not uncommon when dealing with building an RV and especially when not close to help.

I am not sure how many times in the last ten years I have approached my RV 7 project with a very large hammer and an attitude towards ending the project in one last blaze of glory..... BUT .... you march on! I am very close now to that RV grin day and it does get easier as you find fellow builders and some help.

So keep on keeping on and one day you will be on the numbers and pushing that throttle forward for first flight.

Sorry I dont have any ideas on motor mount but going to the Original Manufacturer and or sales agent would be my first step. The mount Should have come ready to go.

Good luck
Dave
 
Lockwoord aero is on the case! This is the latest update;

I've been told there is a special tool that is used to correct thread problems of this type. I've also been promised some information soon on the source for said tool.
Apparently it's a tool that corrects threads going from the inside out.

"Now I finally received my 912IS (after waiting almost 6 months)"

Im getting ready to place my 912is engine order through Vans. Was the 6 month delivery time what you were expecting? Where you given a delivery estimate when you first placed your order? Was your engine delayed after you placed the order?

I have the money now and id rather order the engine early anticipating delays versus wait to order and have a months long break in my build process. Thanks

It was just the normal wait time when I ordered. The engine mount seemed to be the holdup. Even after there are still a few items back ordered.
 
Most likely a Back Tap Thread Repair Tool. Sort of a threaded expanding collet that engages the threaded portion below the "screw-up". Fairly long tool not good for confined space.

Looks like this...
-

Thx Jim. That looks like what i was envisioning. The big problem is there is little access to these threads. A cylinder may need to be removed to use a tool like that
 
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