KX Riders
Maintenance & Technical => KX500 Original => Topic started by: tschisi on November 15, 2011, 04:17:53 AM
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Hi!
I?m in the middle of my bottom end rebuild, but now i?m facing a big problem.
My crank was worn.
A well-known honda machine shop which owns a race team itself, repaired it.
I?ve already got the seals and bearings in the cases, and the crank in the right case.
Now i noticed that i can slide the left main bearing, which is not installed yet, onto the crank and remove it again!
:-o
I called the shop and they told me that in some engines the crank is designed in a way that one crank-side is "thinner" for assembling and dismanteling reasons.
I never heard of something like that in k5 engines. :-(
They sent me some kind of loctite (in fact it?s Honda Lock 3, a threadlock from honda) to glue the bearing onto the crank while putting the left case on it (and hope that enough of the glue stays between shaft and bearing instead of getting wiped onto the seal).
It?s supposed to last 100hrs, which wouldn?t be shorter than the mains or conrod i think.
What do you think?
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Hi. It's a worry that they'd recommend doing that. It's not good/reliable. There's probably new cranks available for a reasonable price in America. Mrcycles seems to do an alright deal on OEM parts if you're not keen on a cheaper hotrods kit.
I'm in New Zealand and have recently had both sides of my crank ground down, hard chrome plated and then ground to factory spec again. The surface is very hard then and should last forever. Have had it done on other bikes and it worked well.
Unless you've got high compression or crank is out of balance/align I would expect the bottom end to last a lot more than 100 hours if done right.
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yes that is correct 1 side of the crank is a micron of so less, that is why when you split the cases 1 bearing almost always stays on the crank and 1 in the case. if you crank is worn on the journal you have a problem and it needs sorting properly. imo there is no glue known to man that could with stand the abuse a k5 crank gets and i would not be using it. just my opinion anyway. p.s the main bearings should go in the casing first not on the crank
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IMO, both the above replies are on the money.which saved me a sh&tload of typing.Nice :-D
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1 side of the crank is a micron of so less
But not so much that i can slide the bearing just onto it, right?
if you crank is worn on the journal you have a problem
It was worn, that?s why i sent it to the "machine shop"
the main bearings should go in the casing first not on the crank
That?s what i wanted to do, i just tried to slide the bearing on casually.
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Hi!
I?m in the middle of my bottom end rebuild, but now i?m facing a big problem.
My crank was worn.
A well-known honda machine shop which owns a race team itself, repaired it.
I?ve already got the seals and bearings in the cases, and the crank in the right case.
Now i noticed that i can slide the left main bearing, which is not installed yet, onto the crank and remove it again!
:-o
I called the shop and they told me that in some engines the crank is designed in a way that one crank-side is "thinner" for assembling and dismanteling reasons.
I never heard of something like that in k5 engines. :-(
They sent me some kind of loctite (in fact it?s Honda Lock 3, a threadlock from honda) to glue the bearing onto the crank while putting the left case on it (and hope that enough of the glue stays between shaft and bearing instead of getting wiped onto the seal).
It?s supposed to last 100hrs, which wouldn?t be shorter than the mains or conrod i think.
What do you think?
your engine builders comments are correct. Many race shops emery sand the crank stubs to allow a precise "slip fit" between the crank and bearings. OEM is always a press fit. My 12,500 rpm Honda CR125 shifter kart engine has been modified for "slip fit" removable bearings. Slip fit bearings makes for an easy, trouble free dissasembly. The engine builder probably noticed some wear on the crank bearing surfaces, then just machined them to the "slip fit " dimensions. You won't have any negitive effects running a slip fit crank.
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I personally would not fit a slip fit bearing in a kx500, i think there is too much side clearance on the kx crank , it will damage the seals , the vibration of a 500 crank #[far more than a 125]will also make a slip fit a looser fit afer a while
as for the honda [cr500] you may get away with slip fit due to a tighter side play
and the main bearing on clutch side is locked to the crank by primary gear and seal sleeve
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its the left journal that is slightly smaller.with the right side having the primary/clutch relationship to give something to stop this side of the crank deflecting, it would make sense to me to have them hard chromed when worn, and do them both to the right side spec. if you would rather have one looser for ease of disassembly, have the right looser and the left tight as having flywheel mass and nothing to assist against deflection means the left side bearing (therefore seal too) has to work harder, without the benefit of an oil bath in case of the seal. when I pulled mine (previous owner could pick his toenails without bending down) (thats a neanderthal themed funny, laugh or I'll club ya!) the first thing I noticed when I pulled the crank was the left side bearing had WAY more play than the right.I think the above is the reason.K.
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some guys also use a spot of blue loctite on the journal/bearing face, but usually when having normal tolerances, not to fix an issue. it may be akin to taking aspirin as a cure for decapitation. not heard of the slip fit method before so cant comment on its reliability, but when I think of the mass of the K5 crank at full tilt I'd rather use the hard chrome route. I know your build has been a steep learning curve, and like many of us around the globe, money isn't easy to come by.Play safe and hard chrome is my advice.K.
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In my motor build thread,.. It lists the loctite you need to fix your problem.
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slip fit hmm :| i would like to know the result of this experiment. unfortunatly my 500 motor is built now so i cant try it in mine, what a shame :-D i found some pics dont mean to worry any one :lol:
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Uh hmm. :-o thats what I'm talking about.K.
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slip fit hmm :| i would like to know the result of this experiment. unfortunatly my 500 motor is built now so i cant try it in mine, what a shame :-D i found some pics dont mean to worry any one :lol:
That motor didnt fail due to a slip fit bearing.... Or any kind of main bearing issue from what I see in those pictures...
My Personal vote.... Cast piston strikes again
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slip fit hmm :| i would like to know the result of this experiment. unfortunatly my 500 motor is built now so i cant try it in mine, what a shame :-D i found some pics dont mean to worry any one :lol:
That motor didnt fail due to a slip fit bearing.... Or any kind of main bearing issue from what I see in those pictures...
My Personal vote.... Cast piston strikes again
i know, just making a point. there are some big pieces of metal moving very fast in there and when things go wrong it can get messy and expensive. motorad, did you use a slip assembly on your motor, i have never heard of it but must say i am a skeptic
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1 side of the crank is a micron of so less
But not so much that i can slide the bearing just onto it, right?
correct
if you crank is worn on the journal you have a problem
It was worn, that?s why i sent it to the "machine shop"
why did they not fix it
the main bearings should go in the casing first not on the crank
That?s what i wanted to do, i just tried to slide the bearing on casually.
sorry i miss understood
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slip fit hmm :| i would like to know the result of this experiment. unfortunatly my 500 motor is built now so i cant try it in mine, what a shame :-D i found some pics dont mean to worry any one :lol:
That motor didnt fail due to a slip fit bearing.... Or any kind of main bearing issue from what I see in those pictures...
My Personal vote.... Cast piston strikes again
In my 25+ years of using cast OEM piston's i've never seen one fail for no reason. I have seen many cast pistons (and forged) fail due to excessive wear and "skirt slap" against the cyl walls.... I personally have much respect for the consistant relibility of OEM cast pistons. One things clear in the pic is that that engine failure was a WFO, catastrophic piston granade to do that much extreme damage.. (strictly just my opinions)
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if you crank is worn on the journal you have a problem
It was worn, that?s why i sent it to the "machine shop"
why did they not fix it
Well, they did something.
I had a worn journal of the left main bearing.
It could be felt with the fingernail.
(http://img690.imageshack.us/img690/2136/99353779.jpg) (http://imageshack.us/photo/my-images/690/99353779.jpg/)
Now the area is shiny, maybe just polished or so.
The notch is still there, but the bearing also slides over the seal-area which wasn?t damaged?!
(http://img522.imageshack.us/img522/8641/pb160021.jpg) (http://imageshack.us/photo/my-images/522/pb160021.jpg/)
The bad thing is that i just didn?t have a close look at the journal after the "repair", was blinded by the shiny surface.
Removing it again will damage the right bearing...
Motorrad,
How much play did your bearing have?
Was it a k5 (so you had to glue the bearing and insert crank into seal at the same time)?
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tschisi, how did you resolve your seal seat damage?
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No fixing needing.
As the seat itself is undamaged, and only about 1/5 of the stop is broken out, this doesn't effect the sealing function.
Confirmed by a kawi-mechanic.
The stop just prevents the seal from getting pushed out...
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your lucky.dont forget to use case sealer round the out side of seal.K.
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if you crank is worn on the journal you have a problem
It was worn, that?s why i sent it to the "machine shop"
why did they not fix it
Well, they did something.
I had a worn journal of the left main bearing.
It could be felt with the fingernail.
(http://img690.imageshack.us/img690/2136/99353779.jpg) (http://imageshack.us/photo/my-images/690/99353779.jpg/)
Now the area is shiny, maybe just polished or so.
The notch is still there, but the bearing also slides over the seal-area which wasn?t damaged?!
(http://img522.imageshack.us/img522/8641/pb160021.jpg) (http://imageshack.us/photo/my-images/522/pb160021.jpg/)
The bad thing is that i just didn?t have a close look at the journal after the "repair", was blinded by the shiny surface.
Removing it again will damage the right bearing...
Motorrad,
How much play did your bearing have?
Was it a k5 (so you had to glue the bearing and insert crank into seal at the same time)?
Yes mine is slip fit on the Ignition side.
The Seal surface is supposed to be smaller than the bearing surface.
when putting together use the Freeze Heat method I have described In Chris 's KX60 section.. and elseware...
To use the loctite properly, you put a bead of it around the crank, on the leading face of the bearing surface.... and drop the case on... whala...
Just remember, if you ever want to take it appart again... that loctite I listed is EVIL STUFF.. you WILL BREAK THINGS, trying to get her back appart unless you use a torch to release the loctite.
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Use the heat/freeze method although the parts could be put together at the same temp (because of the slip fit) ?
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if your right side is done, use heat freeze to get the left bearing in case, if you have the clearance your left should slide into crank without, depending on your clearance.K.
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Use the heat/freeze method although the parts could be put together at the same temp (because of the slip fit) ?
that crank needs repairing{ probably both sides} your bearing journal diamater is smaller than seal surface,
you may be lucky with the lockite but i would not take a chance
I personally think the kx500 is the one motor that u have to have the journals as tight as possible
As i said on my lasts post, on a cr500 and other hondas the bearing is locked to the journal with the primary gear bolt, no chance of the crank moving sideways on the journals
A honda mechanic might not be the best person to get advice from
before i strip a motor i always check the crank for side movement, about 50% of kx5 motor i have either have the journal or cases worn
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Use the heat/freeze method although the parts could be put together at the same temp (because of the slip fit) ?
that crank needs repairing{ probably both sides} your bearing journal diamater is smaller than seal surface,
you may be lucky with the lockite but i would not take a chance
I personally think the kx500 is the one motor that u have to have the journals as tight as possible
As i said on my lasts post, on a cr500 and other hondas the bearing is locked to the journal with the primary gear bolt, no chance of the crank moving sideways on the journals
A honda mechanic might not be the best person to get advice from
before i strip a motor i always check the crank for side movement, about 50% of kx5 motor i have either have the journal or cases worn
+1 dave is right imo
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Oh man, more and more costs.
Anyone wanna buy k5 parts? :roll:
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that picture of the broken cases clearly shows the rod broke, not the piston.
I'd build up the crank or get another.
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Oh man, more and more costs.
Anyone wanna buy k5 parts? :roll:
dont quit yet, you have hardly got started :-D
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a couple hundred dollars now may save having to start again 6 mths down the line.Your call.K.