Guess I'll run the "tight and binding crank" motor now....

[WATERWINGS]

I don't know if ya'll remember the tough time I had with a motor I put together a couple of years ago....

When the two 1/2's of the block were torqued down, the crank had some light "catches" in it...

If I turned the flywheel by hand, at a faster speed, you couln't feel it.....but if I turned it VERY SLOWLY you could feel the catches.....


(If someone can tell me how to post the link to that thread, I'll link it)


What I found out was, that someone had taken a scotch bright pad, (or lite sanding disk) to the block split surface to clean it up.....well...they took meat off the block surface, and the crank bearing journals were a little tight.....(EDIT) and egg shaped......


I have a new sound/vibration in the motor I'm running now, and need a spare to run while I tear my present motor down....so, I figured this would be a good time to see how long the "tight and binding crankshaft" motor will last....

The motor is all together, with new rings, and exhaust chest cut, just needs to have heads, intake, and electronics installed.....

What is the worse that can happen?...the motor is possibly junk already....I have already put LOTS of time into it, with tearing it down time after time, to find the problem....

It may last 5 minutes....it may last 100 hours or more.....I guess we will see....

[transomstand]

http://www.screamandfly.com/showthread.php?32069-Tight-and-binding-crank-problem-solved&highlight=crank

http://www.screamandfly.com/showthread.php?32597-Latest-on-tight-and-binding-crank&highlight=crank

[daveswaves]

John, it is possible that the needle bearings were skidding due to no load when you were hand turning it. After all the things you tried first time around all you can do is run it.

[flabum1017]

Do a racer's break-in.... either it will wear in or seize...

[Tom Foley]

Probably trash in the upper or lower main bearing , run it till it dies . Check back in 10 hours !!

[Ace]

Had one of those, paid $200 for the block,it was a 200-2.4. Had some extra parts so I made a powerhead. The crank would lock up everytime I put the bottom cap on. Tried changing the bottom bearing but the same issue. Shaved down the bottom cap and it turned freely. Motor ran perfect for years, still have it.

[WATERWINGS]

If I remember correctly, the 7 petal front half, (from another motor) had the east amount of "catch" to it....I assume that is cause it may be worn more?.....

The "catchy" five petal front half is the matching mate to that block....I may go with the 7 petal cause it seems looser....

[Forkin' Crazy]

Do a racer's break-in.... either it will wear in or seize...

LOL, kind of like letting it clearance itself. ;)

[WATERWINGS]

I think that most builders wouldn't even have noticed the "catch" cause if you spin it at a normal hand turning speed, you can't feel it....only when you turn it VERY slowly can you feel it....

What is a "Racer's Break-in" ?.....Damn the torpedoes....FULL SPEED AHEAD?

[Capt.Insane-o]

Meh, my underneath the work bench put together from 8 different motors 260 was like that, runs fine. I let it idle in gear for an hour at the ramp. That was the only special attention it has gotten. Run it.

[WATERWINGS]

Wow....I thought the "catchy' motor was mostly assembled.....I pulled it out of the barn last night, and found that It only has a crank in it right now.....(and a BAD crank too).....

I guess I tried another crank just to see if that made a difference.....(its been a few years since I messed with it)

My fastest job might be to tear down the motor that I am running now to see where the vibration is coming from....and replace the (bearing) or whatever the problem may be.....

I have FIVE rotating assemblys right now in my garage....the ALL of them need something.....well, ONE of them is junk, (the one that I got ripped off on from this site)....hopefully the crank is good in that one.....

[mirage243]

What is a "Racer's Break-in" ?

A couple of years ago I was at the Litchfield race and lost a motor on Sunday morning during first round and was fortunate enough to win(motor let go as I was going through the traps) I hadn't had a chance to break in my spare powerhead yet, but we strapped her on and went to second round. The first time that motor started it was able to run for about 15 seconds and then we turned her 10k, ran that motor for the rest of the year with no problems. that's a racers breakin'.

[specboatops]

John,
You just need to quit messin with all them women we see on your boat in the summer and get er done ....... other wise they'll be on someone else's boat this summer;)

[jphii]

A couple of years ago I was at the Litchfield race and lost a motor on Sunday morning during first round and was fortunate enough to win(motor let go as I was going through the traps) I hadn't had a chance to break in my spare powerhead yet, but we strapped her on and went to second round. The first time that motor started it was able to run for about 15 seconds and then we turned her 10k, ran that motor for the rest of the year with no problems. that's a racers breakin'.

That's the only way to break in a motor. :iagree:

[terry taylor]

Put lots of oil in the mix thanks.

[Eagle One]

I haven't read all the replies here but I've found several instances of the lower main cap pushing the lower mainbearing up and binding the crank. This can be fixed by removing a slight amount of material off the bearing side of the cap itself.

[ChrisCarsonMarine]

When tightening the lower main cap binds the crank it's almost always gonna be for one of two reasons...
1. The seal rings have worn into the block,and your new crank or crankcase cover dose'nt line up with the grooves in the block...fix the grooves so the crank can be pushed up where it belongs.
2.The crank has flanged center mains,and has been fitted with captive style center main bearings,instead of open race bearings.
The bottom main,main cap,and the machined pocket above the bottom main create a clamp that sets the height of the crank,and maintains the rod angle at 90 degrees.I don't think either problem would create only a minor catch,but more likely a constant drag,Chris