TRX250R.ORG
Workshop => Engine and Bottom End => Topic started by: JoePA on July 23, 2013, 09:37:26 PM
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My engine started making a wierd noise earlier in the season. Didn't think much of it at the time but it only is getting worse. So, tonight I decided to do some investigating. I checked my counterbalancer and found one of the ears broke off on the bearing holder when I pulled the stator cover. OK no biggie that must have been it. But I figured I would check everything while I was at it. I grabbed the flywheel and went to try to move it and noticed i had side to side movement, quite a bit. So I pulled the clutch cover to make sure nothing came loose and all good under there.
My question is why the side to side movement? I replaced the crank and new bearings two years ago with a Hotrods crank and cr500 bearings. Could it be the bearings are shot already? I did have a head gasket go and burned up some antifreeze but not a lot. Any other ideas?
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This seams odd like maybe the bearings are slip fit on the crank or hopefully not the bearings loose in the cases.
The crank bearing would have to have allot of wear to make much movement I would think
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Wouldn't it have to be the bearings loose in the cases? Unless the bearings are very worn? On the right side the the bolt that goes into the end of the crank pulls the crank, bearing, sleeve, and primary gear all together correct? This should leave no side to side play unless the bearings are moving?
Trying to picture this in my head. I could be totally wrong......been a while since I was in my cases.
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there is a very slight amount of horizontal movement
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I'm going to tear into it tonight. there is about 3mm of movement. and I think the problem is I have the machined inner race bearings and that is allowing it to move. It may the cases are worn as well but won't know till I dig.
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I like 1 bearing machined for a tight slip fit and 1 normal tight fit bearing that way the crank does not float side to side but does allow for the crank halves to seek its own center with no bind.
I normally put the tight bearing on the transmission side and let the stator side float
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This must be where my issue is as I have two floaters in there!! That didnt sound right! LOL I'm going to spilt the cases tonight and see if thats the issue. Once agian thank you for the excellent input.
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joe ,I saw on the other site were both bearings are machined different sizes for the larger hotrod crank journals.is it possible that the larger i.d. bearing is on the stater side.never messed with a hotrod crank ,so I really don't know
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Yes, I wasn't sure why they were machined but then I was reminded why. I think either the bearings are bad or the cases are shot. Now that i think of it, Why would the HotRods crank be larger than OEM? It was my first crank replacement at the time so I think thats why I went with those bearings. Frustrating when you sink a bunch of money into it so it will last then only get two years out of it unless its the cases then thats understandable as they have 20+ years on them.
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for some reason hot rods cranks have a hair bigger O.D. on the bearing shoulder of the crank, I thought BDT sized those so they were still a slight press fit like the OEM are, maybe they were sized wrong?
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I think they might have been sized wrong cuz those case halves slid together like butter. I'll know tonight when i get them split.
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Keep us posted mine has to side play too. So I'm curious I always thought side to side ok up and down no go. Both 250r's ive owned as of recent have had some side to side play.Thanx
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If I remember correctly side to side is only one thousanth
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Even if the bearings are slip fit on both sides of the crank the only play you should have left to right is the play in the bearings. Which should be basically nothing. I think your going to find upon inspection that your bearings are loose in the cases. You can use bearing retaining compound for a temp fix it they are not to bad, but it will not last.(tried it on mine) Either replace the cases or have Pete at Hybrid put some sleeves in for you would be my recommendations.
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Even if the bearings are fixed and stationary ,the i.d. on the bearings being to big could allow the crank to slide a little back and forth.I think thiss is why whats his name wants joe to send the bearings back to him
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Joe you got that thing split yet? No rush haha.
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It's apart!! Ok, I found the problem/s. The first thing is the bearings. They are worn out and not sure why. The second thing is the bearing is loose in the right side case. This is where the side to side play was coming from for sure and the bad bearings just made it worse. So new bearings and seals are a must but that right side I'm not sure. That bearing retainer stuff might work as the bearing didn't fall out it had to be tapped with a hammer. **** like this happens every time I'm broke!!! LOL
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I did not have good luck with the retaining compound. Worked for a couple rides and then broke loose. Don't think it's meant to be hammered on like happens in a motor.
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I honestly think the cases can only take so much over the years before they just can't hold the bearing tight anymore. Might want to see what it would cost for inserts vs a know good case half.
however if the crank was loose in the bearing it could of ruined the bearings and beat the cases. Of course the could of messed up the crank journals as well.
i know Pete does the inserts at Hybrid...not sure on cost though.
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Now I'm in need of bearings. Since the Hotrods crank is ever so slightly larger than OEM am I forced to purchase the machined bearings or can I get a standard OEM bearing to fit on the crank?
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it does not take alot of sanding on the crank to make them fit properly or to sand the inner bearing race of one bearing.
Allot of people just run them tight and it should be OK but the slip fit on 1 side is something most guys squeezing every last bit out of their motor will do.
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Once again thank you for excellent info. With funds on extreame empty I'm going to throw new bearing in, loctite the one side and park it till I can figure out a better plan and get some extra $$
Thinking of throwing in a long rod crank i have in to see if the power is any different.
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You can use the standard bearings. They are just a tighter fit which makes for slightly harder assembly. Do you have a crank install tool?
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Polonda,
Yes, I have an install tool. its a TUSK but should work.
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The Tusk crank tool is nice!
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Have the tusk my self. Buy some bearing retaining compound that is made for the clearance you have. Loctite has a coup
e different ones. Hope it last for you.
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hey joe I was wondering do the current bearing have a interference fit on the crank or do they just slide on
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The current bearing fit really well on the crank. You can't just slide them off and I did need a puller to split the case. So the inside diameter seems to be machined really well.
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good thanks for the reply
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Once again I want to thank everyone for their input as to what the crank issue was and how to fix it. It was apparent I had multiple issues but problem found. I hope this helps future member when they use the search button.
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No problem Joe. Let us know if you need anything when putting her back together!
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I learned some things On this post ,so thanks joe
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I just installed new OEM Honda 88-89 250R 8 Ball bearings (aka CR500 bearings) this spring and noticed right out of the bag the inner races could be tilted slightly by hand with respect to the outer race. I knew this would translate to some side to side play in the crank once assembled, which it has. But I think it is ok to have a little bit of end to end free play in the crank, it is the up and down movement you want to be tight, like the rod bearing. The slight end to end movement will allow the crank to find its neutral center position to the bore when running. If the crank were tight it could be in a bind and this is when things could break. Don't forget Neil's trick of relieving the preload on the crank after you install it by giving it a whop with a mallet on the clutch side, it should spin a little more freely then too. Also I used a hot rod stroker crank and sanded down the right bearing journal with emory paper carefully until it measured the same OD as an old Honda crank I had laying around. This allowed a slip fit with the bearing since I don't have a press.
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Frank, thanks!!! The side to side was a bit excessive as it would clunk when you did it. If it was just a little then ok but I had up and down movement on the stator side as well. So its keep it snug on the clutch side but a slip fit on the stator side?
When's your next race? I see you ran line mountain...that's one heck of a course.
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Factory is slip fit on the clutch side. However some do the opposite with the hot rods cranks. Not sure it really matters.
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Frank, thanks!!! The side to side was a bit excessive as it would clunk when you did it. If it was just a little then ok but I had up and down movement on the stator side as well. So its keep it snug on the clutch side but a slip fit on the stator side?
When's your next race? I see you ran line mountain...that's one heck of a course.
Slip fit is on the clutch side, stator side stays interference fit like stock.
Yeah line mountain was fun but it is rough, lots of rocks! I got first in the 2stroke class and 9th out of 73 quads and bikes overall so not a bad day for the old R. That might be my last race for a while its crunch time now getting ready for the little one to come around Labor Day! I do plan on going to the 2 stroke shoot out at Sleepy in September to watch, that race is getting bigger and better every year and I'm hoping their pro national team will be there too.