Crankshaft bearing scored

[NJDan]

Hi. I've been trying to repair my Honda mower with a GCV190 engine since late winter, time permitting. (I ran it dry on oil and snapped the connecting rod last year.) The recommendation on this forum was to clean the crankshaft journal with acid and give it a try. I put all new parts inside the engine except I kept the same crankshaft and governor. I cleaned the journal with acid and emery cloth. The mower ran way too fast because I actually had a bad governor and didn't know it. OK so I replaced the governor and the engine ran great but it became impossible to restart. The crankshaft could only be turned with a socket wrench. It was really stiff. Was it because the bearing was torqued too tight on the crankshaft, was the shaft slightly bent, or what? That's the background.

Finally, I said what the hell and I bought a new crankshaft so that everything would be brand new and then I could eliminate some variables. I used plastigauge to check the clearance and I'm a bit tight at .001 so I torqued down a bit so now I'm at .0015, which I think should be OK and certainly can't be the cause of the frozen shaft. So everything is new and on spec yet the shaft won't turn by hand.

Long story ending: In running the new connecting rod bearing with the old crankshaft journal it looks like I scored the connecting rod lower bearing and the cap. See photo. I think the black marks are from the gasket material getting in the oil. If I run my fingernail across the bearing I can feel some tiny grooves once in awhile. Is this the probable reason the shaft won't turn? Can I smooth down the bearing with emery cloth and see if it then turns or will that screw up the clearances? I obviously don't have much experience but I've enjoyed learning a lot. I need to get this mower running ASAP so any feedback would be much appreciated.

 

[bertsmobile1]

Yes and yes and yes
Clean the cap with a scothbrite pad
Never touch any journal with any abrasive paper / cloth
The running clearances are measured in hundredths of a thou and you can rip that much metal off in a couple of strokes
So clean it up & pop it back in.
A bad governor can cause the oil to blow out the exhaust and a runaway engine will break the conrod .

 

[NJDan]

Yes and yes and yes
Clean the cap with a scothbrite pad
Never touch any journal with any abrasive paper / cloth
The running clearances are measured in hundredths of a thou and you can rip that much metal off in a couple of strokes
So clean it up & pop it back in.
A bad governor can cause the oil to blow out the exhaust and a runaway engine will break the conrod .

So you don't think the small scratches will be a problem? I think the black marks are from the gasket material mixing in with the oil for some reason. When I dumped the oil it was dark. I'm concerned that the same thing is going to happen when I put it back together -- that the gasket will somehow get into the oil. I'm using Permatex 82180.

 

[StarTech]

The trick is to let the RTV to cure overnight before adding oil as the oil prevents it from setting up properly. Using a surface prep/accelerator spray before applying the RTV also helps. Plus the screws should be only finger tight overnight and then torqued to spec.

A lot techs apply the RTV and immediately add oil to the system then they wonder why the have leaks soon after the engine is put into operation. The RTV never fully sets up because of the oil on it.

A better product to use is MotoSeal but you still need to let it cure properly.

 

[NJDan]

The trick is to let the RTV to cure overnight before adding oil as the oil prevents it from setting up properly. Using a surface prep/accelerator spray before applying the RTV also helps. Plus the screws should be only finger tight overnight and then torqued to spec.

A lot techs apply the RTV and immediately add oil to the system then they wonder why the have leaks soon after the engine is put into operation. The RTV never fully sets up because of the oil on it.

A better product to use is MotoSeal but you still need to let it cure properly.

Yeah, that's what I did pretty much. The instructions say to let it cure for an hour finger tight and then torque down. Let sit 24 hours. The first time I did it I let it sit for about a week and then added oil. It does say not for use in contact with gasoline. I did have a flooded engine due to a carb problem but I can't imagine that would dissolve the gasket material that easily. Maybe I can pick up some MotoSeal locally and give it a try. I can't keep taking this engine apart because the bolts snap left and right and I end up losing another week and $ for more parts..

 

[bertsmobile1]

I hope you only put it on the sump & not on the con rod cap .
You need to get a small 6" or 8" tension wrench so you get a feel for how tight the bolts should be done up if you are breaking them.

 

[NJDan]

I hope you only put it on the sump & not on the con rod cap .
You need to get a small 6" or 8" tension wrench so you get a feel for how tight the bolts should be done up if you are breaking them.

I'm using a torque wrench. The better quality bolts (the ones with numbers on the head) like for the crank bearing are not snapping. It is the cheaper ones that fail but I bought extras when I got the new crankshaft.

I did not use permatex on the cap. I'm inexperienced, not stupid!!

 

[StarTech]

Hopefully you are using class 8.8 or higher as those M7 rod screws (bolts) are torqued to 9 ft/lbs.

 

[NJDan]

Hopefully you are using class 8.8 or higher as those M7 rod screws (bolts) are torqued to 9 ft/lbs.

I think those bolts are 12. I have been tightening them repeatedly while checking clearance with plastigauge and they seem fine. The bolts for the sump cover are cheap.

 

[StarTech]