Aluminum brazing – Am I getting better?

[PM T2]

Relative to Joe’s answer about crankshaft bushings;

In the small Evinrude and Elto motors of the late 1930’s and early 40’s, crankcase bushings are difficult to repair because of the way the crankcases were being made at the time. The bronze bushing was inserted into the die cast tooling and the aluminum was cast around it, then the bushing machined to final dimension later. You could theoretically bore the bushing out to accept a pressed-in insert but the wall would be dangerously thin.  if you bore the bushing material completely out, you will find yourself with a bore that is quite rough as well as quite un-round. These crankcase castings were designed to be replaced if the bushing got worn out, making them rebuildable was not part of the engineering plan at the time.

In expanding on another point of discussion, excessive piston ring side clearance is many times the biggest culprit on compression loss. If your ring gap measures OK and you still loose compression, try loading the ring grooves with grease before you install the rings. Squeeze that mess into your cylinder and retest compression. Chances are it will be quite good. Now start and run the motor to burn all the grease out of there, and when the heavy smoke finally clears and you can see your hand in front of your face again, check compression to see how much it varies from when it was loaded with grease. If you find much of a difference, you should have your answer.

Hope this helps.

Best,
PM T2

He's livin' in his own private Idaho..... I hope to go out quietly in my sleep, like my grand-dad did..... and not screaming, like the passengers in his car...

1 user thanked author for this post.

bob-d

[jeff-register]

Tubs,
Great work & finishing. Back a few centurys when I was 20, I knew another dirt bike rider who could fix a broken aluminum case using a peice of aluminum case to weld a cracked case with a cutting torch. Talk about a “boathouse” repair. Tom was not all there from a motorcycle accident that almost took his life.

[Author]

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