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Bottom End Rebuild
- Thread starter Shipper
- Start date
Sounds like the shop you used did a fine job; you should feel the difference! Hope you had them tack weld the pins, the flywheels have a nasty tendency to walk, especially after the crank has been taken apart and rebuilt. Just out of curiosity, where did you find the .0015" spec? In the 78-83 factory manual, Mama Yama gave herself up to .002" of runout, and many if not most untouched cranks won't hit that easy mark.
Shipper
XS650 Addict
Obviously not a crank shaft expert therefore found me a great machine shop. If you're talking about the pins in the casing that hold the bearings in place then no, didn't tack weld those. If you're talking about pins somewhere in the crank associated with the flywheels well, that's above my pay grade and I aint having him go back in. Interested to know where these pins are. Thanks GOM.
PS, my manual (Clymer Crap) is saying .001 but this guy Im dealing with has a whole wall of manuals so I have asked him where he got the .0015 from and I'll let you know.
Talking about the rod big end pins that go through each flywheel pair.
Shipper
XS650 Addict
Gotcha. no welds. But I am Picking up my cam next week and ill take it with and see what he says. Thanks Grizld.
Shipper
XS650 Addict
Curious Grizld, did you tack both sides of the pins (inside and out)? or was one tack sufficient.
An article about crankshaft rebuilding and welding from Hugh’s Handbuilt,
https://www.hughshandbuilt.com/2011/03/15/failed-cranks-properly-build-weld-xs650-crank/
https://www.hughshandbuilt.com/2011/03/15/failed-cranks-properly-build-weld-xs650-crank/
Shipper
XS650 Addict
So, unfortunately $350.00 too late im guessing. Hate like hell to tear it down again ($700.00). Is it really that common a problem? Again unfortunate but the rebuild is for the original casing. I'm currently running a top notch second engine in the bike with lots of life but was really wanting to bring it back to total; stock.
Attachments
I just posted that for your information, I’m no expert, I’ve only built one motor and that was only a top end job. So I defer to the better mechanics on this site.
Shipper
XS650 Addict
Thanks Mailman. I will as well look forward to experienced comment. Or not?lol
Yes, it's a common problem, especially when the crank has been pressed apart. IMO it's enough to tack the pins on the outside of the flywheel. I didn't do the welding on my crank, that was done by Crank Works of Tempe, AZ.
Hugh has also gone to 3 smaller welds per pin in his crank builds.
Shipper
XS650 Addict
Really regret not posting prior to the crank rebuild. An expensive oversight now that it appears I’m going to need to have it pulled apart again to weld the pins and do it right.
My shop is also going to press the four bearings onto the cam shaft this week - anything I should know before I blow another chunk of change?
My shop is also going to press the four bearings onto the cam shaft this week - anything I should know before I blow another chunk of change?
Shouldn't need to. The bearings should go on and off by hand. In fact, some people leave the bearings off because it makes it a tad easier to get the chain around the cam. After the chains fastened, lift each end and slide the bearings in place.
No need to press. The bearings should be a slip fit.
Yes, OE camshaft bearings are a slip fit. But I bought a set of camshaft bearings from Yamaha a few years back that would have required a press, and no, a tap fit with a piece of pipe against the inside race would not have been sufficient. I stashed 'em and installed some good used OE bearings instead. Don't know what the deal is with those tight holes, the new stuff and the old stuff are both Koyo and have the same size code markings.
Shipper
XS650 Addict
Shipper
XS650 Addict
Thanks a lot for all of this gents. It’s really enlightening. One more question. If I slip the outer bearings off and tack three welds on outer flywheel and one on inner, is there any chance of distorting the metal around the shaft that holds the flywheel in place or the inner bearings? The guy who’s welding is a pro.
Bearings are pinned to the case to keep the outer races from spinning and wallowing out the seats. You have no slack at all for altering bearing position on the shaft. That's why pins get tack welds and shafts do not.
