Board index Flathead Power-Technical Questions, Answers, and Suggestions Big Twin Flatties top motor mount cracked

top motor mount cracked

Post Sat Jan 12, 2013 12:30 am

Posts: 109
even'n folks,
I've got 10k on my 39 UL, all newly built and up and running this past spring, have an annoying oil leak/weep at the upper valve covers, motor builder said bring her back and i'll fix it, requiring the top end to be pulled. he offered new rings and a valve job no charge for my troubles. so while i was stripping her to pull the motor i found the the top motor mount cracked and completely snapped off in line with the bottom of the backbone tube. this frame is an older reproduction frame. 1948 is the style with the long arm style top motor mount. also the Vtwin top motor mount has 2 fractures radiating out from the frame tab as well, but only about half way across the face of the mount. i used colony mount kit with varying thickness washers to shim mount properly, i took great care in setting motor up in frame square and true and gave the top mount proper shimming creating what i hoped would be a secure and trouble free install. being a 48 frame and a U motor i had a machinist made a front spacer that fit like a glove. so what do you folks think happened? poor quality frame, bad 48 style mount by design/ installer error? does this style frame lend itself to being weak by design or do the old oem pan frames never break there? i would like thank you all for your input and help, and any ideas as to how to repair the mount, i work with certified welders who can tig/mig/or stick weld for me, so gusseting/reinforcing ideas and type of welding input would be greatly appreciated ........mark andrews

Post Thu Feb 14, 2013 8:13 pm

Posts: 497
Location: Six miles East of Cheney, Wa.
Why no replies? Seems simple enough that the metal that cracked/split was an inferior piece of steel, and maybe too thin to boot. Sounds like you did everything to square up the engine on the mounts. You have probably fixed it by now, but just weld in a good piece of steel that is a bit thicker. Any gusseting you can do sure won't hurt.

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