connecting rod shims

[dalliance]

hi all
was givin a seagull that was frozen. thanks to this forum i got the piston out, but broke the connecting rod in the process. i purchased a new rod from the seagull parts man here in california.
when i talked to him he told me not to forget to use the old shims.
being a newbie at this engine rebuild i would have used the new shims. they look identical to the eye.
my question is that when i connect the rod to the crank shaft how loose or tight should it be ? easy to turn, a little resistance or hard to turn until it seats ?

thanks

greg

[Daryl]

Hi Greg I would be trying the old shims first, there does need to be some clearance in the bearing for the oil. If its too tight it will over heat the bearing & sieze. It should be free to turn. In the pic the conrod is brand new on an old crank & too tight it should drop down easily not stay where it is.

[Charles uk]

Seagull during the manufacture, assembled the big end with the 2 distance pieces keeping the phosphor bronze shell bearings in place, then the big end was bored to the correct size.

In theory all the distance pieces should be the same thickness, but as we're talking tolerances in the tenths of thousands of an inch I would be reluctant to swop them end for end let alone from a different rod.

With the right distance pieces in situ & the rod on the crank with the big end screws at full torque ( 7 ft. lbs) ( 1 Kg. M) & plenty of oil in the big end journal check to see if the con rod spins freely, if it doesn't like the one in the earlier picture try giving it a light tap with a small hammer on the parting line on either side, it could be that one of the distance pieces is tight against the big end journal giving a lateral displacement of the bid end making it appear too tight, the tapping will move the distance piece back to where they should be.

[dalliance]

thanks charlesuk
well today i had a chance to play with the seagull. i was looking at the crank shaft and didn't want to fight with it trying to see how the conrod would fit. i miked the crank and also the shaft to the drive shaft and they were the same size. so i tried the old shims but the conrod is still tight. it won't fall down, but its not far from it. so i decided to use the new shims. yes i tapped on the conrod and looked at the shims to make sure they were on straight and as far back as possible. the new conrods base where it connects to the crank is larger then the one it replaced, plus there is a hole in the bottom and also the bearing.
this is what i'm thinking. if i take some 600 grit wet/dry and wrap it around the shaft above the square portion for drive shaft, tighten down on the the con rod so its just snug and take a few turns with the conrod, then try it to see if its free on a trial and error bases.
putting the piston in the cyclinder is the last obstacle before reassembly.everything is clean or painted, have 140 weight oil,gaskets,new throttle cable,cork for gas valve. tested magneto have spark.
any suggestions or advise as to the conrod would be greatly appreciated
safe boating
dalliance

[Collector Inspector]

Fine valve grinding paste, tighten by hand until slight resistance to turning is felt and spin slowly by hand. Adjust the slight resistance every 10 turns. Do this twice.

After real good clean up, removing all paste, check that the rod falls under its own weight when torqued up.

Repeat if required with less turns until perfect.

Obviously you are close to that point now so take your time.

B

[Horsley-Anarak]

On my 102 AC the shims had little centre punch marks, this makes them very slighty thicker.

I would try this first before you start making the crank smaller.

H-A

[dalliance]

thanks

i will check and see if the marks are there

safe boating
dalliance