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Old Feb 21, 2012, 05:56 PM
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Marietta GA.
Joined Jan 2011
338 Posts
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best way to modify engine mount help?

Guys, I`m trying to fit a Saito 100 in my Katana 50 where I had a .82...Here is the problem the 100 has a pretty good bit wider crankcase and won`t fit in between the factory beam mounts.I tried to drill the holes(on the mounts) out to give it some slop, but its not enough..I recognize the best way would be to redrill it and insert new blind nuts but they would right on time of what I have in there for the .82..Whats the best way to get this corrected?? here is a pic...
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Old Feb 21, 2012, 06:01 PM
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earlwb's Avatar
USA, TX, Grapevine
Joined Dec 2008
13,363 Posts
Remove the motor mount, then pop the blind nuts out. Fill in the holes with epoxy and a filler such as sawdust or micro balloons. Then after the epoxy cures, mount the engine and mount up to the firewall, mark the new hole locations and drill them. Insert the blind nuts, etc and you are in business again.

I like to save some of the sawdust I collect from sanding balsa and plywood when building a kit up. Then I take some sawdust and mix with the epoxy to make a filler paste to use for things like this. Of course you can get some microballoons to use for the same purpose too.
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Old Feb 21, 2012, 06:36 PM
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Marietta GA.
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thanks! thats why I asked...Jason
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Old Feb 22, 2012, 08:54 AM
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USA, TX, Grapevine
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You are welcome. Another source is to get yourself a container, and watch around your area for someone doing some repair or construction work with a tablesaw. They'll usually let you get some of the sawdust left over after they've sawn some boards. Of course they might think you are a bit touched though.
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Old Feb 22, 2012, 07:52 PM
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United States, LA, New Orleans
Joined Sep 2011
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the sawdust method works, but what i do is make sure i have an assortment of small dowels handy. sizes between 3/16 and 1/4 are usually sufficient. when i need to redrill a firewall i just pop the T-nuts out (a soldering iron inside the threaded portion of the nut helps soften the glue) then drill out the hole to fit my dowel. put some epoxy or thick CA on the dowel and the hole, and push it in. when the glue dries, cut it off flush and sand it flat. you can fuel proof it if you need to after that.

the dowel makes the firewall redrillable and it wont cause your bit to creep if you have to drill through one part of your dowelled hole. an added benefit is that one 24" dowel is enough to last you virtually until the end of the universe since youre only using 1/4" at a time.
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Old Feb 22, 2012, 11:23 PM
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United States, MI, Macomb
Joined Apr 2009
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You might try one of the Dave Brown round mounts if you have the room. You could transfer the firewall blind nut pattern to the new mount and drill it out to match. The one below is a 90 size, but they also have a 120 size.

http://www3.towerhobbies.com/cgi-bin...?&I=LXB880&P=7
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Old Feb 23, 2012, 10:41 AM
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United States, TX, Weatherford
Joined Dec 2006
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I just go down to Home Depot or Loews and buy a dowel the same size as the holes, cut off small pieces and glue them in the old holes. The dowel will last forever and provide many opportunities to be used in the future.

I also go to Harbor Freight or Northern Tool and buy a set of extra long drills. They usually have five in the set and range up to a 1/4 inch in diameter. Makes it nice and easy to redrill holes for throttle rods/cables. Allows one to drill through formers located further back in the fuselage for routing the tubing that carries the throttle rod/cable. And I use the same dowel to glue up that old hole too.
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