Yz125 crank not turning

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12/20/2018 3:01 AM

Hi all , have my 03 yz engine stripped and put it together this morning and the crank is not turning easily at all. It’s not in gear or anything but it’s extremely stiff, it was all good before I opened it. Have no idea what’s the issue, all help appreciated as I want to put the engine on soon. Thanks

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12/20/2018 3:36 AM

What exactly do you mean by "engine stripped"? Did you do a complete tear down of the engine ie..split the cases and all? What did you change on the motor? just a few questions to help figure out what could be causing your issue. Also, does the crank not turn, or is it just tough to turn?

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12/20/2018 4:01 AM

pkiczuk wrote:

What exactly do you mean by "engine stripped"? Did you do a complete tear down of the engine ie..split the cases and all? What ...more

split the cases and replaced one bearing, it will turn but it takes excessive force it’s very hard. Just reopened them and it’s perfectly free, except every few turns it seems to catch something, but then it’s okay again. Any ideas? Thanks

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12/20/2018 4:21 AM
Edited Date/Time: 12/20/2018 4:26 AM

with the case split, when you look at the crank, do you see any marks that could indicate something rubbing up against it? its odd that every couple of turns it's catching something, I would try to find whatever its catching. Its also possible when you have it together, whatever its catching on is multiplied by the fact that you have bolts torqued down. Make sure all of your bearings are greased if you haven't already. Then what I would do, it may be tedious but, start putting it back together and after each step check the crank and see at what point you get to what you were describing. Then you should have a place to look for whats causing the issue.

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12/20/2018 4:35 AM

pkiczuk wrote:

with the case split, when you look at the crank, do you see any marks that could indicate something rubbing up against it? its ...more

Yes all looks good, I treble checked everything and it was fine until I tightened the case bolts, and back to the start again ????

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12/20/2018 5:10 AM

Replace both crank bearings and seals.

Paw Paw

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12/20/2018 10:00 AM

Make sure your not over tighten the case bolts.. 2 if the crank isn’t true or the rod side clearance is to big that will make the crank wider.. but for sure use a inch pounds torque wrench on the case bolts..

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12/20/2018 10:07 AM

Might be an added wrong piece, or a piece missing for case halves to 'bind' on torque. Something is 'amiss'.

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12/20/2018 10:11 AM

Might be an added wrong piece, or a piece missing for case halves to 'bind' on torque. Something is 'amiss'. Also, if something isn't completely 'seating' in all the way, also causes binding.

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12/20/2018 10:15 AM

Look at the crank from the top and check if the crank is offset to one side or the other. Sometimes when the cases are assembled, the crank gets pushed off from centre and binds. You might have to give it a wack with a hammer (and piece of wood, of course) to get it centred. You might hear a pop when the crank gets centered, but then it should spin freely.

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12/20/2018 10:17 AM
Edited Date/Time: 12/20/2018 10:20 AM

If you think everthing is installed properly and together correctly you can put a block of wood against rhe end of the crank (to protect the end of the crank) and give it a good wack endwise with a hammer. It may just need that to seat all the bearings in place after having the cases split.

Edit: looks like OldnBroken beat me to it. As they say; great minds think alike smile.

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12/20/2018 10:21 AM

OldnBroken: Exactly. The crank is being pinched between the case halves and preloading the main bearings causing the drag (I trust the clutch basket isn't on yet). Ideally, you want to use a crank install tool on the left side to pull the crank into the left side case to prevent this. Whacking the crank will work, but might possible create more runout in the crank. In a pinch it will work. I used to get a section of pipe to use as a spacer over the left crank axle and use the flywheel nut and washers to "suck" the cases togetherso the crank remained true.

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12/20/2018 10:23 AM

Make sure you installed the bearing straight. If its crooked or your crank isnt centered its not going to work

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12/20/2018 10:50 AM

OIdYZRider1 & DynoDan22, we are all in agreement then, and this problem is solved! laughing I agree though, if a more sophisticated tool than a hammer is available that would be ideal laughing

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12/20/2018 1:29 PM
Edited Date/Time: 12/20/2018 1:52 PM

NEVER hit the crank end with a hammer with or without wood it can knock it out of true You may have some crank bind but you can release that by tapping the outer cases with a plastic hammer at the front motor mount hole. This tool will keep everything true and straight when installing and its from K&L supply but you can order it trough walmart and save about $50. There are also crank install tools for setting the crank into the cases. https://www.walmart.com/ip/K-L-Supply-35-9804-Crankshaft-Installing-Jig-Tool/145441950?wmlspartner=wlpa&selectedSellerId=11775&adid=22222222227147952379&wl0=&wl1=g&wl2=c&wl3=256534637198&wl4=pla-422162512051&wl5=9028715&wl6=&wl7=&wl8=&wl9=pla&wl10=125214892&wl11=online&wl12=145441950&wl13=&veh=sem
Photo

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Ed Johnson

12/20/2018 2:48 PM

Thanks for all the reply’s, problem solved... I opened the clutch side casing and gave the crank a couple of whacks, it’s turning perfect??

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12/20/2018 2:51 PM

Also, I found a spacer(washer) in the clutch side casing loose and I have no idea where it goes? Does anyone know.. I’ll send a picture shortly

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12/20/2018 5:40 PM
Edited Date/Time: 12/20/2018 5:44 PM

yz8103 wrote:

Thanks for all the reply’s, problem solved... I opened the clutch side casing and gave the crank a couple of whacks, it’s ...more

Now you have a out of true crank. Oh well it's a 2003 so who cares blush go to Yamaha parts online and pull up a parts microfiche that will list all the parts and drawing for your model then look and see where you are missing a washer

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Ed Johnson

12/20/2018 6:39 PM

Just tap it in. Give it a little tappy.

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12/20/2018 8:21 PM

Caseclosed713 wrote:

Just tap it in. Give it a little tappy.

364 more days until next year's hockey try-outs... I gotta toughen up!

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12/20/2018 8:47 PM

yz8103 wrote:

Thanks for all the reply’s, problem solved... I opened the clutch side casing and gave the crank a couple of whacks, it’s ...more

lostboy819 wrote:

Now you have a out of true crank. Oh well it's a 2003 so who cares blush go to Yamaha parts online and pull up a parts microfiche ...more

Nah man, they aren’t that fragile. They are hard enough to true with a hammer whe thy are out of the cases and you are hitting it perpendicular to the crank pin, let alone when it is installed in th cases, supported by the bearings and you give a little tap on the end. I’ve never had a problem, going on 20 years of doing it this way. I’m not saying it can’t be done, but I think it would take some pretty wreckless and excessive hammering.

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12/21/2018 1:55 AM

why use a hammer at all when a warmed up bearing will let the crank sink in under its own weight.

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12/21/2018 1:33 PM

Caseclosed713 wrote:

Just tap it in. Give it a little tappy.

slipdog wrote:

364 more days until next year's hockey try-outs... I gotta toughen up!

Get in your home crank! Don't you wanna go home?!

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12/21/2018 1:42 PM

Caseclosed713 wrote:

Just tap it in. Give it a little tappy.

slipdog wrote:

364 more days until next year's hockey try-outs... I gotta toughen up!

psg119 wrote:

Get in your home crank! Don't you wanna go home?!

Just a little tap tap taparoo

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2017 RMZ450
2005 YZ250-sold :,(
1998 YZ250
2005 KX250F

80% of the time it works every time
IG @2HRacing
Thanks to : Factory Effex, N2Dirt, Acerbis, DT1, Fasthouse, Matix, FMF, ASV, 100% & Mika Metals

12/21/2018 3:42 PM

yz8103 wrote:

Thanks for all the reply’s, problem solved... I opened the clutch side casing and gave the crank a couple of whacks, it’s ...more

lostboy819 wrote:

Now you have a out of true crank. Oh well it's a 2003 so who cares blush go to Yamaha parts online and pull up a parts microfiche ...more

Thanks man!

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12/23/2018 10:52 AM

OldnBroken wrote:

Look at the crank from the top and check if the crank is offset to one side or the other. Sometimes when the cases are ...more

FWIW OP, I had to do exactly this with a Kx250f engine, everything was perfect after wards.

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12/24/2018 5:25 AM

This whole thread here is why im sceptical of any second hand bikes lol

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