Yz125 crank not turning

yz8103
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yz8103
Edited Date/Time 12/24/2018 5:25am
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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pkiczuk
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pkiczuk 12/20/2018 3:36am
12/20/2018 3:36am
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?
yz8103
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yz8103 12/20/2018 4:01am
12/20/2018 4:01am
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 did you...
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?
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
pkiczuk
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pkiczuk 12/20/2018 4:21am
12/20/2018 4:21am Edited Date/Time 12/20/2018 4:26am
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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yz8103
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yz8103 12/20/2018 4:35am
12/20/2018 4:35am
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 odd that...
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.
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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jdj727
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jdj727 12/20/2018 10:00am
12/20/2018 10:00am
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..
loftyair
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loftyair 12/20/2018 10:07am
12/20/2018 10:07am
Might be an added wrong piece, or a piece missing for case halves to 'bind' on torque. Something is 'amiss'.
loftyair
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loftyair 12/20/2018 10:11am
12/20/2018 10:11am
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.
OldnBroken
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OldnBroken 12/20/2018 10:15am
12/20/2018 10:15am
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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OldYZRider1
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OldYZRider1 12/20/2018 10:17am
12/20/2018 10:17am Edited Date/Time 12/20/2018 10:20am
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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DynoDan22
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DynoDan22 12/20/2018 10:21am
12/20/2018 10:21am
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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kb228
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kb228 12/20/2018 10:23am
12/20/2018 10:23am
Make sure you installed the bearing straight. If its crooked or your crank isnt centered its not going to work
OldnBroken
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OldnBroken 12/20/2018 10:50am
12/20/2018 10:50am
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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lostboy819
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lostboy819 12/20/2018 1:29pm
12/20/2018 1:29pm Edited Date/Time 12/20/2018 1:52pm
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…

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yz8103
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yz8103 12/20/2018 2:48pm
12/20/2018 2:48pm
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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yz8103
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yz8103 12/20/2018 2:51pm
12/20/2018 2:51pm
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
lostboy819
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lostboy819 12/20/2018 5:40pm
12/20/2018 5:40pm Edited Date/Time 12/20/2018 5:44pm
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 turning perfect??
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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slipdog
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slipdog 12/20/2018 8:21pm
12/20/2018 8:21pm
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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OldnBroken
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OldnBroken 12/20/2018 8:47pm
12/20/2018 8:47pm
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 turning perfect??
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...
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
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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WEAL
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WEAL 12/21/2018 1:55am
12/21/2018 1:55am
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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psg119
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psg119 12/21/2018 1:33pm
12/21/2018 1:33pm
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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mattyhamz2
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mattyhamz2 12/21/2018 1:42pm
12/21/2018 1:42pm
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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yz8103
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yz8103 12/21/2018 3:42pm
12/21/2018 3:42pm
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 turning perfect??
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...
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
Thanks man!
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Spudnut 12/23/2018 10:52am
12/23/2018 10:52am
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 assembled...
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.
FWIW OP, I had to do exactly this with a Kx250f engine, everything was perfect after wards.
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slammedmind 12/24/2018 5:25am
12/24/2018 5:25am
This whole thread here is why im sceptical of any second hand bikes lol

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