Crankshaft Sticking

[emmo1210]

Hi Guys,

Rebuilding Evinrude 90 v4 engine which i recently bought.

Installed crankshaft today and con rod bearings and caps.

Problem when torque up one of the rod caps, when I try to turn the crankshaft its sticking in about 4 places on a full turn. Seemed to rotate alright before dismantling.

Loosening cap screws turns fine again

Tried reinstalling cap and bearing good few times with no luck.

Bearing looks alright, is it likely to be damaged or what is likely problem?

Rgds
Emmett

 

[bktheking]

Re: Crankshaft Sticking

Are you making sure the caps are the right way around?

 

[trendsetter240]

Re: Crankshaft Sticking

I agree with bktheking..those caps need to be on not only the right way round but perfectly matched into the existing groves. You can't mix and match those caps either, they must go back onto the rods they came off of.

When installing the caps use a pencil or fingernail to check that the cap is perfectly mated onto the rod. If a ridge can be felt it is not on properly.

 

[emmo1210]

Re: Crankshaft Sticking

cap definitely on the right rod and the right way around. Shall try it again but have tried a few times already.

 

[bktheking]

Re: Crankshaft Sticking

What are you torquing them to, measurement?

 

[emmo1210]

Re: Crankshaft Sticking

40 N m as per manual. The other screws are torqued to this with no problems

 

[emdsapmgr]

Re: Crankshaft Sticking

A couple of things to check. The later rod and cap have alignment dots, both of which must be mounted up (toward the flywheel.) If you get the dots right, you will have the rod cap on right. This is not so much a binding issue, but an oiling issue. The factory manual says you must align the rod caps with special tool 396749 prior to torquing so that the cap goes on properly/squarely and does not bind. I always hand fit my caps on my personal engines-but some use this tool.

 

[emmo1210]

Re: Crankshaft Sticking

emdsapmgr,

I checked the dots and all are correct, facing flywheel etc.

I took a closer look to see that that there is an ever so slight dimple up on one side of the con rod bearing surface just over the mating line, ie a half a dimple on the rod surface and the cap surface.

With the cap off, and the bearing around the crankshaft and rod in place the bearing itself will not turn around by hand, it turns a little then sticks.

Is this dimple likely to be the problem then?

If so can it be files off or what is the normal procedure?

Thanks
Emmett

 

[trendsetter240]

Re: Crankshaft Sticking

emdsapmgr,

I checked the dots and all are correct, facing flywheel etc.

I took a closer look to see that that there is an ever so slight dimple up on one side of the con rod bearing surface just over the mating line, ie a half a dimple on the rod surface and the cap surface.

With the cap off, and the bearing around the crankshaft and rod in place the bearing itself will not turn around by hand, it turns a little then sticks.

Is this dimple likely to be the problem then?

If so can it be files off or what is the normal procedure?

Thanks
Emmett

Any binding or sticking and that bearing will be destroyed when running. Remember that crank is going to be spinning up to 6000RPM.

Personally I would replace the connecting rod. You might be able to file it out but would you want to risk having that bearing fail after all the time and money you've invested?

 

[14ftgrumman]

Re: Crankshaft Sticking

Can't understand why you have the problem now and didn't before?

What prompted the rebuild? Is that crank throw discolored?

 

[emdsapmgr]

Re: Crankshaft Sticking

I would not file anything. I'd probably replace the rod in question, as Trendsetter suggests.

 

[Tim Frank]

Re: Crankshaft Sticking

Is the crank shaft throw damaged in a matching pattern?

 

[emmo1210]

Re: Crankshaft Sticking

Well i bought the engine with damaged cylinders so never had it running.

Had the maintenance work completed.

Perhaps, although i dont think so, the bearing surface damage happened when i removed the piston from the block.

I guess your right, i will try to source one around, not that easy in Ireland though.

Thanks
Rgds
Emmett

 

[emmo1210]

Re: Crankshaft Sticking

The crank journal itself has a pattern all the way around, horizontal linesevery 4-5mm. Feels smooth on finger though.

 

[Tim Frank]

Re: Crankshaft Sticking

Sounds like a small piece of "shrapnel" got loose inside.

 

[emmo1210]

Re: Crankshaft Sticking

I see. it looks to be a pattern of the roller bearings, do you think the crankshaft would be ok?

 

[Tim Frank]

Re: Crankshaft Sticking

If the crank is straight, and the journals are round and smooth within limits, as far as I know the crank should be fine.
But get some more opinions.

My comment about "shrapnel" was in relation to what you described as a "dimple", which I took to mean a bump...extra material, rather than a depression. So it must have come from somewhere.

 

[emdsapmgr]

Re: Crankshaft Sticking

It is not ususual for the cranks to have a lined "shadow" apperance on the crank journals. It is usually where the oily roller bearings were sitting for a long period of time, perhaps over the winter. It is more of a visual thing, and does not usually affect the actual running surface.

 

[emmo1210]

Re: Crankshaft Sticking

Think i will look for a replacement rod then.

Thanks for all your help guys, very much appreciated

Rgds
Emmett