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57 lark rod bearing availability

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OzarkMike

Contributing Member
I recently picked up a 57 lark model 25532 to compliment 57 sportwin and my collection of various other motors of that vintage. when i got it home the first thing i did was try to check compression which was 135 top and bottom and for rod\wrist pin bearing slop by pushing down on the piston with a screw driver but was unable to feel any play. when i started it for the first time i could tell something was not right a pretty loud knock was comming from what appeared to be the powerhead so i assumed it would be a bad gear in the gear case but before i tore into the lower unit i decided to check the piston play again and i was dissapointed to feel about 1\16 slop in in the bottom cylinder. i proceeded to hop on my handy dandy computer and try to locate parts but have came to a halt when i was unable to locate big end bearings. this powerhead has too good of compression to really make me want to swap it out for another unknown unit but im not even sure if its the original power head cus the casting plug with the model number is missing i would think it would have some gray paint if it was a lark power head i know they used the electric motor wiring bake on paint for primer on these but the only gray is on the inspection\intake covers the exhaust housing cover head and reedvalve cover so its very possable that its a swapped on power head by the previous owners the guy i bought it from knows nothing about or so he says. so i thought id register with aomci and ask my question there but was unable to complete registration for some reason. my next move was to come here and ask here cus this is my other choice for finding info for my other various old motors i own if anyone has any input or a source for rod bearings id like to hear their opinions.
 
it appears that they are available by the set i was looking at the parts fiche and was using number 302529 which is a single roller when i should have been using 1-378152 which is a set lets see if i can find the rest of what i need now
 
I would check through intake side cover, see what it says. Might be piston pin slop too. I also check for degrees of crankshaft play while piston is not moving....measured on flywheel of course....view piston through opening. It's always nice to look at piston side, even if its only on intake.
 
well i did what you said i dont have a timing wheel but i doubt you could measure it its such a small amount of play i think im over reacting i was watching the piston in the inspection port while doing the test and the its really hard to see the piston move at all while pushing back and forth on it with a screwdriver and turning the crank it may just be im not used to roller motors all my other vintage omc motors have plain bearings and i cant tell any slop with those. im also able to feel a little slop in the top cylinder i didnt notice before but its also very little. if you look at the side of the piston it looks like there is lines in it probably where it was turned on a lathe and when you try to push on it after rotating the crank down you can barely see it move using the intake port edge as a reference. if i turn the flywheel back and forth the piston starts moving almost immediately but the rings being not the same exact size as the groove give a false sense of play without watching the piston you would think that it would feel like slop. i tried my best to measure the amount of play the piston has using a dial caliper and it wasnt working the best i could come up with is about 5 thou so i think its fine unless i got some flat needles that are coming around after so many turns that are causing me issues but i think i was just over thinking how much slop was in it the first time. im not sure why it felt like 1/16 before maybe i just aint very good at using a screwdriver as a measuring device. but it does sound like a clank on when pushed down im not sure why that is but the top cylinder isnt as noisy maybe just the way it echoes in the block i dont know
 
here is the sound its making i guess its time to tear into the gear box which i didnt wanna do cus it has been good at keeping water out so far
 
i removed the lower unit and its still knocking so its not the gear case im about to run it till something breaks at this point i dont want to tear the power head apart just to find out its not the issue last thing i know to look at is the recoil housing other than that im not sure what else to look at
 
does anyone know how much vertical play is allowed for the crank it has about .017 inches of play with very little to no runout
 
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