crank to rod slack – opinions ?

[jethro]

I got a 55 model Johnson rde-17 about 6 years ago as a perts engine. All there except ignition and flywheel and outer case parts.
I just looked at it again to refresh myself on what I found then ( i had forgotten-)
I had the evinrude clone sutting right beside it to compare it to . had the head off bothe engines for different reasons…….
On the parts engine- crank rotated fine and seemed free enough- but i noticed that I could wiggle the flywheel about 1/4 inch or so
WITHOUT the postons moving. On the good evinrude beside her- basicly no slack at all when wiggleing the same way—– (a good engine)

So there is slack in the system . so I took the thing appart some more and took the case appart and pulled the pistons.
Noticed that the wrist pin slack didnt seem to be anything unnatual looking – but I did notice i could wiggle the lower rod-crank connection
some— I could lever it sideways a little bit— so this appears to be the source of the slack- mostly-

Is there a general idea that the needles are the part that wears and gets smaller/worn as opposed to the crank pins or the lower rod diammeters ?
Would the needles alone be a likely enough thing to just try new needles and see if that takes the slack out ?

( i am new to outboards and 2 strokes- worked on airplanes and antique cars but new to outboards……. )

I sent Dan Gano a n e-mail about parts– but i have to try to determine what I need first !!!!! 🙂

The rest of the power head didnt look horrible- just the slack observed.

I think I want to clean the crank in case there has been water laying on the needles at some point- if the crank is trash I guess I need to know now…
( If i want to put the crank in the lathe to clean the crank pins and main areas- how fine a paper do I want to use – and what type ?
Can i use 2000 silicon carbide ? Selock manual mentions crokus cloth- but that may be hard to find these days……. )

I feel like I need a brain transplant from one of yall ……
thanks for any wisdom yall care to bless me with…..
Tim

[fleetwin]

Tim
Sometimes, sideways piston slop in the block can seem like slack in the rods/bearings. But, you seem experienced enough to tell the difference.
In any event, if there is a problem with the needles/retainers/crank/rod journal, it is usually visible to the naked eye. Water damage, pounding damage from detonation, should be visible once the pieces are cleaned up a bit. In any event, the 2000 grit stuff you mention should be fine for cleaning up the journals a bit. Finding it in a roll thin enough to fit inside the width of the crank journals will be the trick. I wouldn’t bother with the lathe, I would simply clamp the crank in a vise (please don’t let it fall out), and work the journals gently. Again, any damage should be pretty evident to the naked eye. You could always compare the measurements of the two journals. Generally speaking, these engines never get enough use to actually put much wear on journals/bearings. Damage usually is from water intrusion, or pounding damage from detonation issues. You could clean up the rod journals as well, and compare the inside dimensions of both rods. I am assuming you have noticed that the rod caps are unique to the original rod and can’t be swapped, plus they will only fit properly together when orienting correctly. Looking at the mating surfaces, you will note they are jagged edges, this is normal. The rod is manufactured in one piece, then actually split apart causing the unique jagged edge fit. Care must be taken when reassembling these rod caps, they must be manually aligned or the mating surfaces will be distorted and ruined when proper torque is applied. But again, you seem very machinery savvy and have probably already noticed this.
This just might be a case of defective needle retainers causing slop, hopefully a new set of needles/retainers will do the trick…
And sorry, I don’t have a manual for this engine so don’t know the actual journal dimensions, I’m sure someone else will chime in.

[A Hoskins]

2000 grit is too fine for finishing a crank journal. Crocus cloth is 320 grit and leaves the journal with a little bit of "tooth" which helps the needles roll, not slide. Rotating the crank while polishing is a good idea and a good way to get a nice even finish all the way around. Turn the crank slowly. In a lathe, maybe get someone else to hand-turn the lathe while you polish. My experience has been that a nice guy in an automotive oriented machine shop will probably give you a length of crocus cloth if you ask. Maybe trade him a 6-pack for it.

"Fox News" isn't.

[fleetwin]

quote gbm:

2000 grit is too fine for finishing a crank journal. Crocus cloth is 320 grit and leaves the journal with a little bit of “tooth” which helps the needles roll, not slide. Rotating the crank while polishing is a good idea and a good way to get a nice even finish all the way around. Turn the crank slowly. In a lathe, maybe get someone else to hand-turn the lathe while you polish. My experience has been that a nice guy in an automotive oriented machine shop will probably give you a length of crocus cloth if you ask. Maybe trade him a 6-pack for it.

Good point, you really don’t want those journals to be super smooth…

[frankr]

fleetwin pretty much said it all. Any wear at the big ends of the rods will be easy to see with the naked eye. If the surfaces are smooth and the rollers are not flat-spotted, it is OK. They just don’t wear out unless it has been ingesting water or something–and you would see the water marks or pitting. 1/4" slop is just too much for roller bearings without obvious visual defect.

Having said all that, take a better look at the wrist pins. Those were prone to wear on the 25hp motors. Both the bushing in the rod, and the pin fit in the pistons.

[jethro]

Thanks for the helps there…..
i have to get a clean debticated table up and lay all the cleaned parts out and carefully inspect everything with a 10X magnifier. I think I kind of
suspected that the needles in the rods had rusted from errant water in them many years ago…..
Now when i look at the lower rod races I can kind of see very faint slightly darker stripes which looks like old rust stains from the needles— they
appear to coencide to where the needles lay inside the race…… When I look at the rollers I dont see any pitting -but I havnt cleaned then and
looked at them under mannification yet (but I will in the next dat or two)
The top rod bearings- I can slide then on the pin easily- but I can not TIP them. Before i removed the rods from the crank- i COULD TIP them
a little bit- which makes me thing that the slack was comming from there……. I wouldnt think you should be able to tip them if they were
in a normal condition….. ( I could grab the piston and tip the lower rod bearing- moving the piston about 3/16 to 1/4 inch pivoting at the
needle bearing in the bottom of the rod. )

I am thinking a new pair of rods and new needles for the rods and crankshaft might be a safe ,first try —— Does that sound like a good way to go-
or should I try to obtain a good used power head ??? or both even ?

FYI- thanks for the correction on grit size for cleaning crank—–ill try NAPA for crokus……
I did remember about the rod caps being cast and then broken in half when made -leaving a jagged, unique junction…. thanks though…
You never know what you dont know till someone tells you……. (hopefully before parts get broken 🙂 )

I have taken appart and overhauled several antique car engines, and a couple aircraft engines to different stages- but I am just getting
into 2 cycle marine engines. Lost of strange and new features on them.

I have a 10 to 70 X sterio microscope- I may look at the needles under that to look for rust evidence. (after soaking with acetone in a jar)

Will report further once I have carefully cleaned, inspected under magnification and noted any flaws……

Thanks
Tim

[fleetwin]

Well, these engines fit together fairly loose when compared to automotive or aircraft stuff….So, it is hard for me to comment on tipping the assembled rods up and down on the crank. Did you check the wrist pins and corresponding piston bores like Frank suggested, I completely overlooked that important point. I would clean up and check the crank before deciding how to proceed. Maybe you can find a damaged powerhead (cylinders scuffed/aluminum corroded) than will provide a decent crank/rods. I would definitely just replace the needles and cages though, with new OEM stuff.
Before getting in too deep, you will want to evaluate the rest of the engine. Start by draining the gear lube (remove the top and bottom fill/vent screws but do not remove that phillips screw!). If the gear lube is milky/pure water, then you will have to disassemble that gearcase as well.

[jethro]

I did give the piston and cyl. bore a quick and dirty check with the digital calipers— same to within half a thousanth— not th eproper measuring
tool for that– but it didnt appear off much.
I get the impression that the needles in the lower rod bearings have some degradation from rust. I would think that would create slack—-
once I get the crank and the rod surfaces cleaned and looked at- i will have more spicifics to report.
This was a parts engine — so I had planned to do a dis-assyembly of everything- assuming nothing good…..till I see otherwise.
If parts look good- I plan to sandblast (where appropriate) parime and paint and re-gasket as i go……
Have to put my core parts to soak tomorrow to prep for cleaning and inspection.
Thanks for the guidance— will keep you posted on how the rod/crank surfaces look ……
Tim

[Author]

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