main journal scratched; please advise
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Teching In
Joined: Oct 2010
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From: Anthem, AZ
main journal scratched; please advise After measuring with a micrometer, there are a few extremely fine scratches on the main journals of my crank. They are so fine that I can not feel them with my fingernail. There are no raised edges. At least not in a practical sense. I'm sure an uneven surface would be seen with a scanning electron microscope. You can even see scratches that result from the polishing. After all, that's what polishing is. Inducing finer and finer scratches into a surface. There is no perfectly flat surface.
They are hard to see under normal light. This picture looks terrible and much worse than if you were to see them in person. Should I have them polished? I need some frank advice. But, I also want to know at what point would I be giving in to internet hysteria if I take the crank back to the machinist and have him polish the journals. I really want to assemble the bottom end now and not have to get back in line at the machine shop. BUT, I don't want to do anything careless either.
Ugh! I don't have enough experience to make this judgement call. Please advise. I really want to ignore them and put this engine together. Unless they are certain to cause problems.
Thanks for any advice!!
They are hard to see under normal light. This picture looks terrible and much worse than if you were to see them in person. Should I have them polished? I need some frank advice. But, I also want to know at what point would I be giving in to internet hysteria if I take the crank back to the machinist and have him polish the journals. I really want to assemble the bottom end now and not have to get back in line at the machine shop. BUT, I don't want to do anything careless either.
Ugh! I don't have enough experience to make this judgement call. Please advise. I really want to ignore them and put this engine together. Unless they are certain to cause problems.
Thanks for any advice!!
TECH Addict
Joined: Dec 2017
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have them polished
But yes, polishing should fix that right up. Bolt the crank by the flywheel flange to something REAL secure, like a wall, at about waist level, sticking straight out; wrap a strip of sandpaper around the journal, such that it goes all the way around it, with some transmission fluid or 2-stroke oil under it; wrap about a 4' piece of an old V-belt 1½ turns around that; then do what seems obvious next. I'd suggest starting out with 400, then 1200, then crocus cloth. I think when you see the results you'll do it to all 9 journals and the seal surface as well.
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Joined: Apr 2014
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Not sure about this "have" thing; sounds like that would involve another human. IMO that's to be avoided whenever possible. The less humans with their p****pullers in a project, the better.
But yes, polishing should fix that right up. Bolt the crank by the flywheel flange to something REAL secure, like a wall, at about waist level, sticking straight out; wrap a strip of sandpaper around the journal, such that it goes all the way around it, with some transmission fluid or 2-stroke oil under it; wrap about a 4' piece of an old V-belt 1½ turns around that; then do what seems obvious next. I'd suggest starting out with 400, then 1200, then crocus cloth. I think when you see the results you'll do it to all 9 journals and the seal surface as well.
But yes, polishing should fix that right up. Bolt the crank by the flywheel flange to something REAL secure, like a wall, at about waist level, sticking straight out; wrap a strip of sandpaper around the journal, such that it goes all the way around it, with some transmission fluid or 2-stroke oil under it; wrap about a 4' piece of an old V-belt 1½ turns around that; then do what seems obvious next. I'd suggest starting out with 400, then 1200, then crocus cloth. I think when you see the results you'll do it to all 9 journals and the seal surface as well.
So hold this crank up to the wall and just put the bolts in huh, I guess the smart thing to do would be have someone help
hold this crank up while you put the bolts in, about waist high so I guess its easy to manipulate the abrasives. I enjoy Learning stuff.
I will definitely remember this and share this knowledge with some of my friends. Thank you.
TECH Addict
Joined: Dec 2017
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Yes I have bolted a crank to a wall (literally): I used 2 lag bolts and ran them through the flywheel bolt holes into a stud.
I've also bolted them to blocks, engine stands, and maybe other things, in the same manner. Just, find something solid and substantial, that you can put lots of force on and not move it, but at the same time you don't hurt the crank in any way. A REALLY BIG vise might work. Acoupla big clamps on top of a real solid workbench might work. Just kinda use your imagination.
I've also bolted them to blocks, engine stands, and maybe other things, in the same manner. Just, find something solid and substantial, that you can put lots of force on and not move it, but at the same time you don't hurt the crank in any way. A REALLY BIG vise might work. Acoupla big clamps on top of a real solid workbench might work. Just kinda use your imagination.
I’ve done the abrasive roll myself by hand, but only laying on the bench. It’s heavy enough to where it won’t move. No need to bolt the crank to anything. It doesn’t require much pressure to polish light scratches out of a crank. You certainly don’t want to apply enough pressure to remove anything. Easy does it here.
Now, if it’s deep enough to hang a nail on, or feel, then that’s different. I’d take it to a shop at that point.
Now, if it’s deep enough to hang a nail on, or feel, then that’s different. I’d take it to a shop at that point.
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I wouldn't touch any crank with 400 grit, not event 1000. Amazon sells sand paper as fine as 12,000 grit. I personally have as high as 7000 and that's the most I'd use on something like this. They're just witness marks and likely have little to no effect on anything.
Try running a safety pin over those very lightly as see if they hang up.
If you do the sanding method, please go with a very high grit and a lubricant. Good luck.
Try running a safety pin over those very lightly as see if they hang up.
If you do the sanding method, please go with a very high grit and a lubricant. Good luck.
If you made those marks just by touching the journal with a micrometer and you cant feel them then they are likely just surface marks and require no touch up and you should just run it.
You could lightly touch those spots with a wet scotchbrite pad and see if they go away.
If not lightly rub with wet 2000 grit sand paper. Higher grit if you can find it like mentioned above.
I don't see this taking any real work or any actual pressure being applied to sand paper to remove.
You could do it how the did the crowmod and hold scotcbrite agains the crank while someone cranks the motor lol.
You could lightly touch those spots with a wet scotchbrite pad and see if they go away.
If not lightly rub with wet 2000 grit sand paper. Higher grit if you can find it like mentioned above.
I don't see this taking any real work or any actual pressure being applied to sand paper to remove.
You could do it how the did the crowmod and hold scotcbrite agains the crank while someone cranks the motor lol.