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Motor Mount, how-to

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Motor Mount, how-to


Post by 64duo » Thu Jan 31, 2008 10:33 pm

What exactly is the procedure for mounting the engine to the frame of the bike. I constantly see pan cases with repairs to the front (usually) or rear mounts. I have heard or read that some shimming is or may be required, but how do you judge what is needed, front mount first, rear mount first, top mount?? When the engine is just naturally sitting in the frame, where do you start, and if this is so common a procedure why are so many engines running around with damaged cases? Can someone relate a step by step guide to doing this critical procedure correctly?

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Post by VintageTwin » Thu Jan 31, 2008 10:41 pm

Tighten the (complete motor, not just short-block) rear mount bolts. Use a feeler gauge to determine if one side of the other front tabs have a gap. Either cut off the feeler blade and trim it as it sits, or order a small range of shim stock from http://mcmastercarr.com/
Note: the top motor mount on a Panhead (only) has a bit of free-space between the top mount-to-cylinder head fingers. This will allow the top motor mount (which may still need extra shim stock) to fit parallel to the top frame mount tab.
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Last edited by Anonymous on Sat Feb 02, 2008 4:03 am, edited 3 times in total.

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Post by fourthgear » Thu Jan 31, 2008 11:49 pm

Don't forget to shim the top motor mount also, between frame and upper motor mount, most need some .You can get the top mount shims from JP'S, and the like.

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Post by VPH-D » Fri Feb 01, 2008 6:26 pm

Some of the shim washers for the top motor mount bolt are still available from H-D. Make sure the top motor mount is parallel to the frame motor mount, and not bent inward by improper installation. Use the shims to fill the gap between the mount and the frame. The top motor mount is installed after the 4 bottom bolts.

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Post by Ripley/Fla » Sat Feb 02, 2008 3:03 am

All this goes for the transmission too. That's why the studs get loose. Scrape all the paint off all mounts. Start with your trans plate. Level the rear engine mounting pad by propping up the bike as necessary. Any decent level will do as the chunks are connected by chain and will stand some error. Put the trans plate in place and see if you have any diagonal rock. If you do, put shim stock underneath the rear corner that will take out the rock and bring the trans plate to the approximate same level as the rear motor mounting pad. It probably wont be perfect. (As stated, McMaster Carr has a nice brass shim stock assortment set). Then plop your trans in place to the approximate center of the slots. Carefully rock the trans diagonally and try to feel any up and back shake. ( you can also do this with the trans out of the bike, upside down, and rock the trans plate up and down) Again, shim the corner to bring the trans level to the motor, if necessary. What you want to do is get all 4 corners sitting on solid ground so one stud will not be stretched out of the 50 old year case. When all this is done go to your right side trans bolt and shim if necessary so you are not pulling down the case to the right. I would not be afraid to shim the entire trans plate up to get a nice fit to the slotted frame bracket, if it is too high. On my current bike I needed a .016 shim under the trans plate left rear corner and a .003 shim under the left rear corner of the trans. It also needed a .005 under the right side frame bracket. Sounds anal, but these are old machines and need to be handled carefully. Oh, by the way, PANS RULE!

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Re: Motor Mount, how-to


Post by 58flh » Sun Mar 18, 2012 12:09 pm

ALL the posts that I read threw are correct!--(The Tranny is very important to get it right!)--I like to add 1 more thing to shimming the motor!----After the rear mounts are tight/& hopefully you put the correct bolts in thier perspective holes :lol: ./Had to say that --you dont know how many backyard (do it yourselfers ---- that up!). & by now you figured whats needed for front shimstock!/Tighten the top mount (properly) of coarse ---NOW look & see how much clearence you have between head & seat-tube!(I shoot for a min of 3/16--they call for a 1/4---then again all are DIFFERENT)--meaning pan-tops!--I had 1 pan that was a barstomper, &it had extra rings for spring clearence & real fat D-Rings!----The head had 3/16 of clearence/once I took off all the garbage bolted to the head!, So that was good to go,I bolted her up & had to (DREMMEL the D-RINGSSS,yes more then 2 were added for spring hight!---Let me reword that it was 1-D-Ring, all the other 2 were gaskets to provide lift for spring clearence!.----I dremmeled enuff to give 1/8 clearence(cold), apparently I was worried about the motor reaching operating temps. & Expansion of cyl, heads d-ring.----But it worked out fine!!!(I guessed that 1/8 of clearence on the ring, also I cut it in a way that would travel as the head & cyl. expanded,& gave it an upward-towards the pancover top cut!-about a 1/4 in Dia. & a1/4 in hight!. ALLS WELL!---I just added this piece of info because you never know what will roll threw your door to FIX.(FIX--simple word but try getting there sometimes!)--Enuff talk--GOOD-LUCK to everyone-----RICHIE 8)

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