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K&B 3.5 Gold head con-rod

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K&B 3.5 Gold head con-rod

Old 12-13-2015, 05:51 AM
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billf1973
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Default K&B 3.5 Gold head con-rod

Okay I have a issue with replacing the con-rod in my 3.5 K&B outboard. I have tried the original bone style and the new style. There is some slop in the bushings on both ends. Any suggestions? Or is there supposed to be some movement and not snug?


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Old 12-13-2015, 03:24 PM
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ob nut
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What crank do you have? 12mm or 13mm? Believe the 12mm has a "L" stamped at the end while the 13mm has "13" stamped. Old eyes, can't quite tell on the pics what is stamped.
Old 12-13-2015, 08:12 PM
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Ron Olson
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Mark, it looks like a 13 on the counterweight. The pix are fuzzy but I could make that out.
Old 12-13-2015, 10:45 PM
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Thanks Ron, that is what I thought. Just couldn't quite make it out on the small pic. There should be slight movement of "side to side" on both the crank and piston. But if there's a lot of "up / down" play, then there's issues. Have you tried another crank or wrist pin?
Old 12-14-2015, 08:41 AM
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That ain't sloppy. I bought a new SS and the thing didn't have any bushings on the con-rod! It was no wonder that I could never get the thing to run right.
Old 12-14-2015, 05:36 PM
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ob nut
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But when you opened it up to investigate, it voided the warranty!
Old 12-16-2015, 06:00 PM
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Thanks for the info guys. I didn't try another crank or pin. Don't have any. I will see about the movement direction.
Old 12-22-2015, 03:47 PM
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ob nut
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If you need another crank / pin, let me know. Think I have a few extra pins and possible a crank. I'm in the process of selling off my K&B 3.5 motors / parts.
Old 12-22-2015, 03:56 PM
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billf1973
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ob nuts, thanks. I am still trying to figure it out. Not much time to look at it lately.
Old 01-31-2016, 03:11 AM
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Okay guys, here is what I found out. It was a 13mm crank. After trying to reassemble the engine,the piston would not go into the sleeve again. I think the sleeve and piston need replaced. When using force to put back together they were both compromised.
Old 02-02-2016, 05:50 PM
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ob nut
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Yea, force is not a good thing for these little motors. I'd have to check what is in my parts supply, but I may have a used or even a new p/s if you are interested. I'm slowly working away from K&B 3.5 motors.
Old 02-03-2016, 07:13 AM
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How did you attempt to install the piston? I have never heard of a piston not going back a cylinder it came out of.......The cylinder is tapered, tighter at the top, piston goes in from the bottom.
Old 02-03-2016, 12:45 PM
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Originally Posted by moparbarn View Post
How did you attempt to install the piston? I have never heard of a piston not going back a cylinder it came out of.......The cylinder is tapered, tighter at the top, piston goes in from the bottom.
That's what I was wondering also. Put the piston in then slide the sleeve in, it's usually that easy. Trying to put the piston in with the sleeve installed presents a problem. You can't do that.
Old 02-03-2016, 04:11 PM
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Originally Posted by Ron Olson View Post
Trying to put the piston in with the sleeve installed presents a problem. You can't do that.
That's how I have to install new P/S in my MAC's, CMB's, OS's..The same goes for the 11's, 13's and 7.5 redhead I have. Since K&B 3.5 has the front end removable, it's easy compared to the other motors. Just gotta be careful about how it's done.

Last edited by ob nut; 02-03-2016 at 04:15 PM.

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