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Wet seal finally gave out

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Been experiencing a bit more plug fouling lately and a little bit less go in the motor of my YZ250 (2005). I've suspected it had leaky seals for a long time, even though it passed the leak down test. My understanding is that seals can check good when the motor isn't running but leak at specific RPMs. Top end with new cylinder has about 6 hours on it but have had an issue of fouling plugs with excellent jetting since before doing the top end.

Today with a warm engine I get lots of smoke at WOT and she isn't running very well. Below that it's pretty good. Can't say positively leaky seal is the problem, but I've wanted an excuse to change them for a long time and am finally committed to getting it done. 

First time for me, so looking forward to learning something new. 

QUESTION: What parts will I need? Gaskets, bushings? I'll follow the manual, but just looking for tips and tricks. I do have a bearing puller tool (claw looking beast).

 

EDIT: Will definitely run a compression test before I do anything.

Edited by LSHD

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5 minutes ago, LSHD said:

Been experiencing a bit more plug fouling lately and a little bit less go in the motor of my YZ250 (2005). I've suspected it had leaky seals for a long time, even though it passed the leak down test. My understanding is that seals can check good when the motor isn't running but leak at specific RPMs.

Today with a warm engine I get lots of smoke at WOT and she isn't running very well. Below that it's pretty good. Can't say positively leaky seal is the problem, but I've wanted an excuse to change them for a long time and am finally committed to getting it done. 

First time for me, so looking forward to learning something new. 

QUESTION: What parts will I need? Gaskets, bushings? I'll follow the manual, but just looking for tips and tricks. I do have a bearing puller tool (claw looking beast).

Be very carefull with that that you don't scrape the case surface at seal.

I prefer to drill a small pilot hole and run a tech screw in, pull seal with needle nose plier. 

With the seal experiencing this, at heat and running, I would suspect a main bearing might be part of the equation. So, check for any play when you get there. 

Seals, maybe outer case gasket, coolant, oil, and you should be good. If you haven't replace in a long time (all the seals) would be a good start.

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1 minute ago, LSHD said:

Thanks Doc! Bottom end only has 21 hours on it. Hope THAT isn't bad. That's a case split, right?

Bearings yes, seals no. This is not a Kawk! :thumbsup:

What bearings did you use? Hope not HotRods. 

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4 hours ago, LSHD said:

Previous owner had it done. I've got the receipts somewhere, but I think OEM. We'll see.

While the seals are out, check for play etc.

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Checked compression. 225 psi - Exactly the same as 2 hours after the rebuild. Happy about that. Strangely enough when I warmed it up (by riding around my work like a mad man, AGATT) yesterday to get ready to dump the oil it ran very well with minimal smoking but a little more spooge than usual. No matter what I am changing the seals, but I sure hope that is all I do.

Found a little metal on the magnetic plug. Not a lot, but a little more than in the past. I sure hope that Doc is not right regarding the crank bearings. We'll see. It looks like a heck of a lot more in the photo than it was in person. Note that I did a top rebuild, including cylinder, about6 hours ago.

20171106_162814.thumb.jpg.71f649ad6ca953ffdb7c6adb8b043ba0.jpg

Edited by LSHD

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Completed left side today. Had to leave the shop before starting the wet side.

QUESTIONS:

1. What do I have to remove to get to the wet side seal?
Manual is confusing on this to me. I think it is just clutch, brake lever, kick starter lever, and radiator hose. Anything else?

2. Do I grease the outside edge of the seal or only the inner lip?

Many thanks to all.

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9 minutes ago, LSHD said:

Completed left side today. Had to leave the shop before starting the wet side.

QUESTIONS:

1. What do I have to remove to get to the wet side seal? Complete right side of engine case and everything to get there, clutch basket, primary gear stack, seal keepers. So, coolant, oil, brake leaver. Might as well replace water pump seals while you are that far. 
Manual is confusing on this to me. I think it is just clutch, brake lever, kick starter lever, and radiator hose. Anything else?

2. Do I grease the outside edge of the seal or only the inner lip? I only grease the inside lip with the lithium white soap base. Important thing is drive it straight so you don't cut the inner lip on the crank.

Many thanks to all.

 

On 11/7/2017 at 5:11 AM, LSHD said:

 

Found a little metal on the magnetic plug. Not a lot, but a little more than in the past. I sure hope that Doc is not right regarding the crank bearings. We'll see. It looks like a heck of a lot more in the photo than it was in person. Note that I did a top rebuild, including cylinder, about6 hours ago.

20171106_162814.thumb.jpg.71f649ad6ca953ffdb7c6adb8b043ba0.jpg

No way for crank bearings to be the cause of the metel shavings. Looks excessive, so lets look at the pushrod end in the clutch axle when you get inside to engine. Could be doggs or gears or the shift stop also. You'll be able to inspect the stopper when you get inside.

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Thanks YZ Doc,

I only greased the inner lip on the dry side and used a big socket to drive it straight in. That side is easy as pie. Other side had me a bit intimidated, but I'll knock it out tomorrow, slowly but surely. Will also look around for a source of metal. There is actually not nearly as much as it looks in the photo, but still would like to nip any issues in the bud.

BTW, ZERO crank play up or down, right or left. Bearings look brand new. Dry side seal was driven in unevenly, which have accounted for a rare occasional lean surge at just the right RPM and case temperature. Looking forward to seeing how the wet side looks.

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Here is the photo of the old dry side seal. Notice how far it is sticking out at the top and how far it is tilted in at the bottom. Lame.

20171118_135110.jpg.6a9723998cee557b46342ce4842537e6.jpg

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7 minutes ago, LSHD said:

Here is the photo of the old dry side seal. Notice how far it is sticking out at the top and how far it is tilted in at the bottom. Lame.

20171118_135110.jpg.6a9723998cee557b46342ce4842537e6.jpg

Yah, that is dum messed up. Seal should be flush with case surface, and not deeper. Some run them in to the 1/16 or 1mm lip is shown. Looks like a lot of grit also.

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Not liking the metal in tranny is it slipping in gear at all? That's not aluminum ;)Are you splitting or just doing crank seal?  

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Shifts like a dream. Just crank seals for now. Honestly it isn't as much metal as it looks like. It was a tiny bit. Camera angle and oil magnified it. But I will check out what I can with the right side crankcase cover off. I do abuse the heck out of the clutch, so maybe pushrod end or related. I've seen those get pretty trashed/rounded off.

Edited by LSHD
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Had some free time and finished the seals. Bike starts and runs awesome. Old seals looked fine except for the crooked dry side. Will it fix my oil disappearing act? Who knows. Glad it's done because it would have bothered me forever. If not leaking externally, how else can oil go through the motor except for wet side seal?

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15 hours ago, LSHD said:

Had some free time and finished the seals. Bike starts and runs awesome. Old seals looked fine except for the crooked dry side. Will it fix my oil disappearing act? Who knows. Glad it's done because it would have bothered me forever. If not leaking externally, how else can oil go through the motor except for wet side seal?

Gremlins, those little bastards will syphon it out while you're not looking.  

No other way, besides the rear water pump seal, but that would run out the weep hole.  

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1 hour ago, 2 STOKE YZ DOC said:

Gremlins, those little bastards will syphon it out while you're not looking.  

No other way, besides the rear water pump seal, but that would run out the weep hole.  

Ha!

How much oil would you estimate you would measure if you changed it after 6-8 hours? I was consistently getting around 650 ml. Added 750 ml fresh each time.

Edited by LSHD

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1 hour ago, LSHD said:

Ha!

How much oil would you estimate you would measure if you changed it after 6-8 hours? I was consistently getting around 650 ml. Added 750 ml fresh each time.

100ml every time? No less? Does look like any comes out the breather at all? Weird that only 100 each time and no less if so. How long between? 

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3 minutes ago, LSHD said:

Zero oil on the ground. Maybe I'll make a vented drip can to see if any comes out of the breather. But fouling plugs lately. 

Giver some gas man :ride:lol jk. But ride them wide open they don't not foul. Id go all season on same plug forget to change it lol put new one on and never tell diferance.  Stock jetting 32:1 927 feul 50\50. Id ride new bike for season completely stock just springs. Then it got new everything and jetted.  Honestly I still did same with minor mods and jetted.  I don't know how you ride it but could just be using wrong premix for your type riding or need some jetting even. My bikes only ever seen mix tracks racing. Just trying to help :rolleyes:

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