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Post subject: Crank precision in millimeters? And some other questions.
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Billy  One-handed Stoppie! Joined: 12 Oct 2007 Total posts: 2216 Location: Sweden arise! |
Oi!
Thinking about rebuilding the crank but need to know some stuff.
What are the torelances in mm's?
And is there anything strange you need to think about when doing the job except being careful and all that crap? I know how i shall do the whole process and i know how you make the crank parts paper weights. I know about cracked webs etc. But i would like to know if there's anything i might have missed in my plans.
Heat the webs up a bit when pressing? Is that even recommended? I want to know everything. I want to know what NOT to do!
Oh, and how much pressure are normal for a stock crank that has never been apart? 20 tons? 
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Posted: Sat May 17, 2008 10:09 pm
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ief Powerband Master Joined: 27 Jan 2004 Total posts: 777 Location: netherlands |
only thing i know is that it is way less than 20 tons, 4 or something?
and it's not as simple as it seems.
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Posted: Sat May 17, 2008 11:29 pm
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Post subject: Re: Crank precision in millimeters? And some other questions
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dwayne Sunday Rider Joined: 27 Apr 2008 Total posts: 31 Location: Mankychester, oop north |
| Billy wrote: |
Oi!
Thinking about rebuilding the crank but need to know some stuff.
What are the torelances in mm's?
And is there anything strange you need to think about when doing the job except being careful and all that crap? I know how i shall do the whole process and i know how you make the crank parts paper weights. I know about cracked webs etc. But i would like to know if there's anything i might have missed in my plans.
Heat the webs up a bit when pressing? Is that even recommended? I want to know everything. I want to know what NOT to do!
Oh, and how much pressure are normal for a stock crank that has never been apart? 20 tons? |
Let a professional crank builder do it or it will end in tears.
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Posted: Sun May 18, 2008 12:08 am
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BillyOne-handed Stoppie! Joined: 12 Oct 2007 Total posts: 2216 Location: Sweden arise! |
| ief wrote: |
only thing i know is that it is way less than 20 tons, 4 or something?
and it's not as simple as it seems. |
That little?  It was 6 tons on a moped crank with a 14mm pin i took apart once.
I know it's not easy and i expect it to take time, but i think i can do it.
I have some experience with it (not much if you compare with crank rebuilders but enough i hope) and know how you true it.
It will be a challenge but i'd rather try it and fook it up then paying silly money for a pro to do it. Cheap bastard me.  It doesn't make any sense when i think about it but what the hell..
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Posted: Sun May 18, 2008 12:23 am
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Bare All-gear Wheelie! Joined: 28 Jan 2006 Total posts: 1916 Location: Vancouver Canada |
Out of coincidence someone posted this instruction page.
http://www.rrracing.co.nz/crank/index.html
Although in fairness.. given that Proven Competent/Experienced Crank rebuilders only charge $100 labour for a rebuild . One would REALY have to have a DIY compulsion to bother.
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Posted: Sun May 18, 2008 1:03 am
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BillyOne-handed Stoppie! Joined: 12 Oct 2007 Total posts: 2216 Location: Sweden arise! |
That's actually where i found out how to split the crank, but thanks for the link anyway!
| Quote: |
| Although in fairness.. given that Proven Competent/Experienced Crank rebuilders only charge $100 labour for a rebuild . One would REALY have to have a DIY compulsion to bother. |
Yeah, but i want to do it. I know it might be the mistake of my life but i'm more of a gambling person.
But i don't think it's as hard as they make it sound, probably a bit tricky and time consuming but the only thing you need to be 100% careful with is to press it straight. Don't think that's gonna be a problem actually. And if it all goes like crap i'll just lay myself in the shower and cry like little girl.
Edit: I see the dude has updated the crank rebuilding site, there was only 2 pages yesterday i think. Now there's the tolerances and everything! 
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Posted: Sun May 18, 2008 1:58 am
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strokersquidPowerband Master Joined: 03 Nov 2004 Total posts: 501 Location: Bay Area Northern California |
putting it back together is the dickens...
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Posted: Sun May 18, 2008 6:55 am
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| xen-uno Joined: 27 Jul 2005 Total posts: 845 |
Some crank specs here ...
http://www.angelfire.com/hi3/smokeonthewater/rzeng1.jpg
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Posted: Sun May 18, 2008 2:26 pm
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jante350 RD/RZ Jedi Master Joined: 05 Aug 2003 Total posts: 5229 Location: Bergen, Norway |
Ive done it myself once, trued it with a micrometer on a lathe by twisting it with a big vicegrip thingy.. scored the webs a bit, but it did come out somewhat ok in the end.
It lasted a good 10.000 miles or so before it started to go off, but this was on an underpowered aircooled 350, wich didnt run very well because of a shitty top-end that was actually HONED up one size instead of a rebore.. mind you this was on a student budget a good 10-14 years ago... I would never ever do that again, it took so much time, and the result was actually really crappy... I bought a second hand crank, and let a pro do the job with all new OEM stuff, and the engine was a breeze afterwards compared to my redneck-hammer crank..., especially with a lightly tuned top-end aswell...
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Posted: Sun May 18, 2008 4:39 pm
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BillyOne-handed Stoppie! Joined: 12 Oct 2007 Total posts: 2216 Location: Sweden arise! |
Nice, but it's for the RZ, the 4l0 crank ara a bit different but i guess the side play at the connecting rods are the same? I have the measures on the webs width etc so i think i have it all now.
| jante350 wrote: |
Ive done it myself once, trued it with a micrometer on a lathe by twisting it with a big vicegrip thingy.. scored the webs a bit, but it did come out somewhat ok in the end.
It lasted a good 10.000 miles or so before it started to go off, but this was on an underpowered aircooled 350, wich didnt run very well because of a shitty top-end that was actually HONED up one size instead of a rebore.. mind you this was on a student budget a good 10-14 years ago... I would never ever do that again, it took so much time, and the result was actually really crappy... I bought a second hand crank, and let a pro do the job with all new OEM stuff, and the engine was a breeze afterwards compared to my redneck-hammer crank..., especially with a lightly tuned top-end aswell... |
Maybe the problem was that you pressed it wrong/un-straight. (the holes in the webs takes alot of damage from it) Maybe that and a crank that had been apart earlier so it wasn't tight anymore?
Maybe you were just a retard? Just kidding, otherwise i dunno what went wrong, hope it doesn't happen to me. 
FYI btw, when you true the crank you usually use a brass hammer and smack on the webs to make them turn on the crank pins, but keep all the bearings covered because those hammers lose small bits of material when you use them on steel. 
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Posted: Sun May 18, 2008 5:34 pm
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| xen-uno Joined: 27 Jul 2005 Total posts: 845 |
Aye Billy ... dim's A & F may be different, but the tolerances shown should be correct for LC cranks as well.
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Posted: Sun May 18, 2008 5:50 pm
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BillyOne-handed Stoppie! Joined: 12 Oct 2007 Total posts: 2216 Location: Sweden arise! |
| xen-uno wrote: |
| Aye Billy ... dim's A & F may be different, but the tolerances shown should be correct for LC cranks as well. |
Okey.
Btw, any ideas of how much press is required?
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Posted: Sun May 18, 2008 6:18 pm
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