Model B motor mount

[dboeshaar]

I have a Rotax motor mount for my Model B build.

I just tried to test fit the mount and three bolts go in fine. The fourth bolt in the bottom of the mount is about 1/8" to narrow.

What is a safe way to widen the bottom two motor mount legs to get the last bolt to fit. I tried just pulling on it in place, but no way.

I don't want to crack the powder coat.

advTHANKSance

Dkb

[Murray Parr]

I have a Rotax motor mount for my Model B build.

I just tried to test fit the mount and three bolts go in fine. The fourth bolt in the bottom of the mount is about 1/8" to narrow.

What is a safe way to widen the bottom two motor mount legs to get the last bolt to fit. I tried just pulling on it in place, but no way.

I don't want to crack the powder coat.

advTHANKSance

Dkb

Another builder on this forum had that same issue, I think he resolved it by making an aluminium plug and pressing it into the misaligned hole in the bed mount and drilling a new hole in the correct location. He might chime in here.

Not sure how you are going to determine which hole needs moving but if it were me, I would favour anything that adds right thrust.

[Skippydiesel]

I have a Rotax motor mount for my Model B build.
Another builder on this forum had that same issue, I think he resolved it by making an aluminium plug and pressing it into the misaligned hole in the bed mount and drilling a new hole in the correct location. He might chime in here.

Not sure how you are going to determine which hole needs moving but if it were me, I would favour anything that adds right thrust.

I think you may be referring to me Murray.
Yes my Sonex Legacy (A)/Rotax engine bed adapter rail./bracket, holes did not match my Legacy engine frame/bed.
I contacted Sonex for assistance - Their (paraphrased )response:-

I shouldn't expect a welded component (Sonex supplied engine/undercarriage frame), to exactly match the adapter rails - I am still lost for words at such a quality control failure - do they not use a jig???
Ream out the (A) holes - Completely unacceptable. The Legacy engine frame uses thinner bolts than those now used in the (B) model - reaming would further weaken, an already suspect design.
I also asked why the adapter rails were not supplied without rail/frame holes. This would have allowed the builder to drill exactly where required - no answer.

My solution was to turn up some aluminium, interference fit "plugs". Plugs into freezer. Rails into hot water. Tap plugs into existing holes. Redrill connecting holes in corrcet position. Seems to have worked - now have about 57 hrs without issues, around this problem at least.
Hope this helps - good luck.