OzVMX Forum
Clubroom => Tech Talk => Topic started by: YZ250H on September 05, 2010, 12:52:46 pm
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Hi Guys,
Just putting the bottom end of the latest project together. Now that I have the case halves back together the crank is tight :o. I assume this is not right ::)
The crank turned freely when installed in half a case (if that makes sense). Now back together and very stiff. Still able to be turned, but way too tight for what I think it should be. Ideas ?? Wrong size bearing on the second half ?? Pretty sure they are right. Got me buggered. Gearbox shafts all turn nice and freely. Gears seem to shift OK.
Cheers
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did you fit a new rod kit to the crank?
and if so, was the crank pressed back together to the correct measurement?
is the crank balanced correctly?
if it's out of balance, it'll usually go, tight,free,tight,free when rotated {keep it clean folks}.
sure your gonna handle that big bore 50 Tony?
be mindfull of the gearlever also :D
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Hi Guys,
Just putting the bottom end of the latest project together. Now that I have the case halves back together the crank is tight :o. I assume this is not right ::)
The crank turned freely when installed in half a case (if that makes sense). Now back together and very stiff. Still able to be turned, but way too tight for what I think it should be. Ideas ?? Wrong size bearing on the second half ?? Pretty sure they are right. Got me buggered. Gearbox shafts all turn nice and freely. Gears seem to shift OK.
Cheers
Hi Tony,
give the crank a decent tap with a rubber or plastic mallet directly on each end and it will free up, the crank will be firm up against one of the crank bearings making it harder to turn. I would suggest hit the right hand end first and then check the movement of the crank again. It won`t need much to centre the crank.
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I wish I lived next door to you Billet :-*
Mick, I didn't rebuild the crank as the bigend was good. There's probably a whole topic on wehter that is wise or not but .....
It is tight all the way around, so I'll just duck to the garage and give it a wack (the bike that is) and let you know.
I love this forum. You guys rock.
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Hmmm No good. I think what you are saying is right thought Peter. I don't suppose it would right itself when it is running. I am imagining a seizure and a lot more work. Better to put the work in now :-\
It's a bit odd - the cases went together fairly smoothly. Only needed a bit of a firm tap with the rubber hammer. As I said I can turn it by hand, but it is ceratinly not running freely like I think it should.
Should I give it another wack, or just go and have a beer (it's only 11 am over here)
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G'day Tony,
no it won't come good when running.
did you install new Main bearings? if so did they go all the way up to the crank shoulder.
if not, give it a few more wacks each side and check after each one. may need a deadblow hammer (heavy soft face hammer). if you don't have one use a piece of soft aluminium or copper between the shaft and a steel hammer
does it feel like its rubbing on the crankcase anywhere?
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Yes, new mains Hoony. I'll give it a few more hits with the deadblow. I've got a little butane torch, would a bit of gentle heat help you think ? If that doesn't help I might have to split the cases and have another look. The LHS main was definitely pressed in nicely. The RHS I can't be certain. :-\
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assuming the seals are in case don't use heat. are they genuine bearings or aftermarket?
i have seen some crank bearings have a large radius on the ID ( to mate to the radius on the crank) where aftermarket ones don't.
does it feel like its rubbing on a crankcase half?
i would pull it apart and check at this stage.
I never press bearings in, i use a small torch to gently heat the case and drop them in. same when i remove them i heat the case as alloy expands faster than steel and tap the case onto a block of wood the shock drops them out.
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Aftermarket bearings. Could be my downfall :-\
Doesn't feel like it is rubbing.
Will pull it apart again and see what's up.
Thanks for your help guys. 8) 8)
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no worries. i hope you have used C3 clearance bearings for the tolerance due to heat.
Where in WA are you ?
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While it's still together ....spin the crank slowly while applying some duct tap or electrical tap thru one revolution ... and then the other side. This will give an indication of crank binding with cases.
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Yes C3 bearings Hoony. Based in Perth now, been here since beginning of July. Just in time for the coldest July on record :o Already trying to work out how to get a bike to CD8.
That is a great tip thanks Stew. Unfortunately the manuals only show you what to do when everything goes right. I am not an experinced mechanic (as you all know), but I get there eventually. I learn a lot as I go along too (what life's all about really).
I'll give it a go. I have parked it up for later. Time to get things a bit organised.
I will let you know how I go, as it is a bit odd :-\
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Tony,
Sorry if i have asked the obvious, but i thought better to ask than not to !
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Nothing is ever too obvious when you are talking to me Hoony ;D ;D ;D
Always good to have all bases covered. It is usually the most obvious thing that gets forgotten ;)
Thanks for your constant help :-* (my missus made me put that in )
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I have come across a similar problem rebuiding wr/dt200 motors,The genuine yam bearings are a poofteenth narrower than aftermarket jobs,although the i.d & o.d were the same! It had me knackered until i measured them,the crank turned fine until you done the case screws all the way home! I,m not saying that is your problem but it,s worth checking! Instead of splitting the cases to check measure the old bearings & then go to the bearing shop & ask to measure the same bearing they supplied to you or i think you can get bearing dimensions on the net,but dont know where.cheers smed
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actually, there's an idea right there!
just back the case screws off a tad to relieve any possible compression on the crank/bearing and see if that makes a difference before you just go ahead and re~split the cases.
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I have come across a similar problem rebuiding wr/dt200 motors,The genuine yam bearings are a poofteenth narrower than aftermarket jobs,although the i.d & o.d were the same! It had me knackered until i measured them,the crank turned fine until you done the case screws all the way home! I,m not saying that is your problem but it,s worth checking! Instead of splitting the cases to check measure the old bearings & then go to the bearing shop & ask to measure the same bearing they supplied to you or i think you can get bearing dimensions on the net,but dont know where.cheers smed
I doubt this to be true. A bearing number is a industry standard, unless the manufacturer puts a unique number on the bearing. A 6206 for example is exactly 30 X 62 X16 from both OEM and aftermarket. If they are I would be very surprised but I have never found this to be the case and I rarely use OEM bearings.
Check the cases have not been welded that had me in the same dilema once.
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G,day Lozza,Yes I agree a 6206 is a 6206, I never said anything about bearing numbers,what i said was wr/dt200 motors run a narrower main bearing than whats available aftermarket but has the same i.d. & o.d as a commonly available bearing,it was years ago i came across this problem so i cannot recall what the original bearings had written on them,I must have measured the i.d & o.d & grabbed the bearings off the shelf that matched & of course they fitted o.k, until it came time to assemble the cases & torque down the screws,the crank would not turn,after careful inspection & going over everything again i realized the new bearings were wider,i rang the local yam shop & quized the mechanic & he confirmed that was the case & he had also been caught out himself! Honda sometimes run strange size bearings in there motors,G,box especially & you cannot buy aftermarket,genuine only.cheers Smed 8)
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SMED ,s reply is interesting. I had the same issue with my yz125. Was tight when i put the cases together, I also used aftermarket bearings. I ended up taking 0.5mm off the thickness of the outer race. The aftermarket must be wider , very strange.
You are better off doing something about it as it will not fix itself. Hope this is a help.
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That will be something I'll be interested to check next time smed ,thanks for the tip. I assume you surface ground them down?
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I think from memory i got some genuine ones Lozza & chalked it up to experience,the next time i rebuilt one of those motors i found Bruce from yamwreck in vic had allready had some surface ground so i got a set off him as they were heaps cheaper than yam jobs, cheers Smed.
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Try checking the big end end float as it has a tolerance (the manual will tell you what it should be). If it is at the high end you could just press the crank together to the low end - might save you having to surface grind the bearings or buying new genuine ones. Sounds like it's only going to be a few thou and you are going to have to split the cases again either way so it might be worth checking. Don't forget to make sure that the wheels are true after you press it closed.
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Thanks for all the advice here lads. I will have a crack at it tomorrow night.
I'm not sure if I kep the old mains or not. I'll have a look.
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Bearings will bind and seem tight if they are assembled with preload, in otherwords if the OD of the bearings are a neat fit in the cases ie you had to heat the housing or press the bearing into the cases and the ID is also a similar fit (ie not a sliding fit) on the crank shaft then I suspect when the two cases were assembled the bearings may have some axial preload present hense giving the tight feel.
If this is the case, I would suggest removing the left hand seal and giving the inner race of the bearing a slight nudge under a press to remove any axial pre-load that may exist as a result of tightening the two case up. If you study all the workshop manuals they all recommend using special pullers for removal and re-assembly of cases, cranks etc so this does not happen. Unless you are experienced in bearing fitting procedures, these little obstacles sometimes present themselves.
If either the OD or ID were loose sliding fits then disregard the above and go back to clearence issues.
P.S. Talk of grinding bearings to suit is a recipe for disaster. Unless the bearings are throughly cleaned (and I mean cleaned, cleaned and cleaned some more) of all grinding residue, your bearing will have a short life.
Hope this helps
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I had the same prob with the 465 so i heated the case halves really hot. you think they are going to melt but thats when the clearances are enough to let the bearings slip in without them getting side preload. as the bearing is forced into the case the inner shell is being pushed opposite to the outer shell causing preload. After i heated the fu*& out of them i had to use an old tee shirt to hold them and rest the cases on. After tightening all the screws i lifted the engine up only to find the tee shirt hanging from the bottom of the engine. Got pinched in the case halves joint. I wasnt going to pull the barstards apart again to i ran a stanley knife ofer the joint trimmed the tee shirt off and she has never leaked in 3 years ha ha :D
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I had the same prob with the 465 so i heated the case halves really hot. you think they are going to melt but thats when the clearances are enough to let the bearings slip in without them getting side preload. as the bearing is forced into the case the inner shell is being pushed opposite to the outer shell causing preload. After i heated the fu*& out of them i had to use an old tee shirt to hold them and rest the cases on. After tightening all the screws i lifted the engine up only to find the tee shirt hanging from the bottom of the engine. Got pinched in the case halves joint. I wasnt going to pull the barstards apart again to i ran a stanley knife ofer the joint trimmed the tee shirt off and she has never leaked in 3 years ha ha :D
I betcha the next bloke who pulls it apart will get a bit shirty. ;D ;D ;D
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How did the 50 end up? I had a similar experence today with my rmx250 i had big trouble fitting the crank to the lhs case even after heating the case and freezing the crank it still wouldn't go and in the end I had to use a old socket and hammer to hit it home ( I know it's wrong but I don't have a case puller). Anyhow when I fitted the rhs case and tightened it up the crank started to stick so I gave it one more firm tap and it came good I think the combination of pulling the cases with bolts and a tap with hammer was enough to do it. Forgive my mechanical ignorance I'm a plumber not a mechanic!
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Didn't get to it during the week and most saturdays are working these days :'(
Tomorrow is play day ;D
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Know the feeling I snuck home from work at 1pm for a couple of hours quality time in the garage before the Family gets home :)
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OK - pulled the little sucker apart. As suspected once the pressure was released from the screws surrounding the crank and the cases separated by a hair thickness it all freed up again. It is just that little bit of pressure at the end that does it, so there must be only a poofteenth in it. A bit frustrating >:(. The LH bearing seems pretty solid on the crank and stayed on the crank when I separated the cases. Do you think perhaps it is pushed onto the crank too far ?? Maybe the bearing on the other side isn't far enough in ?? FIIK
There is a minor mark on the LH case where it looks like it has been dragging.(http://i202.photobucket.com/albums/aa49/tbarsby/006.jpg)
It runs free in one case (as before). Picture coming. Also some minor marks on the crank.(http://i202.photobucket.com/albums/aa49/tbarsby/008.jpg)
Don't worry WMC83 - I am an enjuneer not a mechanic (obviously ;D).
Should I just admit defeat and take it to Mr Yamaha at $1000 an hour :-\
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i can see the problem in the first pic, typical Yamaha basket woven crankcase :D
(http://i202.photobucket.com/albums/aa49/tbarsby/006.jpg)
seriously, it wont be a problem of pushed on too far as this cannot happen due to the shoulders, it will be its not pushed on far enough, more likely
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Yes, all these dramas I seem to have all the time (through lack of knowledge) have driven me to basket weaving in my spare time ;D ;D ;D ;D
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the wear marks at "A" are small while the wear marks at "B" are more noticable.
i'd be wanting to check the crank for balance to see if it's running parrallel with itself. looks like it's got a case of the wobbles.
a balance check will answer that easy enough. if it's in balance, then we move onto another idea. if it's out of balance, could be problem solved.
did you by chance drop the crank at any stage? was it stored in a box for sometime with a possibility of being knocked?
(http://i1035.photobucket.com/albums/a438/vandy010/ozvmx%20stuff/YZ50problem.jpg?t=1284271289)
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I know it's been said before but is the bearing the correct width? Maybe yamaha over machined the bearing retainer in the case did you try tapping the crank to bring it back off the case? (unlikely I know just a thought)
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Yeah. I did give it a heap of good wacks from both sides to no avail. I think I will press the crank out of the RH case and do some measuring. I didn't fully measure it up before I put it back in - just made sure the big end was sound. Probably my downfall at the end of the day :-\.
If one of the halves is a bit out of wack (just a bit) maybe it would have that effect. Maybe it's not the bearing getting tight at all but the crank rubbing on the case 'cause it's out of wack. Who knows - I don't ::)
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While you are at this stage ...what is measurement of crank webs left to right, is the crank pin flush with webs.
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The crank pin is a little bit proud on the LHS. Can't see the other side obviously.
I will do some meaurements. I assume you want a few measurements all the way around.
Edit - probably almost a mm difference between smallest and largest dimension. I'm only doing it with vernier calipers.
Seems like my crank needs some work yes ?? I've got another one - I'll have a look at it
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Is there a gasket in between the cases or just 3bond,hard to tell in the pics.
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i can see the problem in the first pic, typical Yamaha basket woven crankcase :D
(http://i202.photobucket.com/albums/aa49/tbarsby/006.jpg)
seriously, it wont be a problem of pushed on too far as this cannot happen due to the shoulders, it will be its not pushed on far enough, more likely
Hoony,
no disrespect but you need to stay away from this topic as i think what is confusing you is a set of crankcases that haven`t got a big hole in them. ;D ;D
(Shit i`m gonna regret being a smartarse when Hoony catches up with me.)
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Is there a gasket in between the cases or just 3bond,hard to tell in the pics.
Just threebond.
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Just another tip...When you sort the crank out & ready to put back together, warm the cases in the oven (my wife loves it!) & take the bearings out of the box & put em in the freezer-it shrinks them a tiny bit. When you take the bearings out of the freezer, make sure you grab them in the middle (stick your fingers in the hole) & they will just fall straight in,no hammering or force at all. You can do the same with the crank too.Hope this helps, worked heaps of times for me...
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Thanks for that Whitey. I am working on making one of those crank installer tools as well.
Strangely the bolt holes for the case splitter are a different dimension on the RH case than the LH. Have to modify my case splitter as well now. All these things take time.
I might take the crank to the shop to get aligned etc. If they have to take it apart I will get a new big end.
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Hope it goes well 4 u
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Hoony,
no disrespect but you need to stay away from this topic as i think what is confusing you is a set of crankcases that haven`t got a big hole in them. ;D ;D
(Shit i`m gonna regret being a smartarse when Hoony catches up with me.)
Hey Pete, i'm never going to be allowed to forget that one am i :D and with the amount of riding you do lately i doubt i will ever catch you mate ;)
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Hoony,
no disrespect but you need to stay away from this topic as i think what is confusing you is a set of crankcases that haven`t got a big hole in them. ;D ;D
(Shit i`m gonna regret being a smartarse when Hoony catches up with me.)
Hey Pete, i'm never going to be allowed to forget that one am i :D and with the amount of riding you do lately i doubt i will ever catch you mate ;)
It`s all good Hoony.
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Is there a gasket in between the cases or just 3bond,hard to tell in the pics.
Just threebond.
I'm not familiar with YZ cases...does that mean the YZ's ran no gasket in between the cases?
That might be the clearance you need.
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yes spot on monaro, this is the case with some yamaha's.
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OK, she's back together again and the crank turns freely. I tried a combination of things you guys suggested. At the end of the day I don't think either bearing was pressed into the crankcase enough. A little heating in the oven a bit of gentle persuasion with the dead blow and tongue in the right position and it all seems to be good now. I don't think it is dragging at all now as it turns quiet freely. I didn't buggerise around with the crank as I measured it properly with a dial guage and it seemed to be OK.
BUT.. now the shaft that the clutch basket bolts to (main) has about 1.5mm of end float. Is this right. The gearbox diagram on the Yammy website doesn't show any washers or spacers between the last gear and the LHS crank case, so I assume it's all good. I would hate to get the whole thing back together and have to start again >:(.
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My 125j had quite a lot of end float and you could move the primary drive around a fair bit. The clutch plates and presure plate seemed to tie it all together once it was assembled if thats any help
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so long as it selects all gears and feels nice and positive then the endfloat is acceptable ;) it is common
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Sweet, thanks guys. I will continue to put her back together 8)
Thanks for the help everyone. I will post photos when I get a bit further along ;)