Jump to content
Sign in to follow this  

2006 YZ250F pics: post-clutch plate explosion/bottom end teardown

Recommended Posts

After my clutch plate disintegrated, I decided to go ahead and tear down the engine. While I'm glad I did (there was a lot of junk, as you'll see in the below pics), the engine design did a good job of trapping everything appropriately.

Also two of the tranny bearings felt pretty rough -- really rough, actually -- while they were in the cases. Funny thing, though. After I knocked out one and pulled out the other, they felt smooth once outside the case.

Also, check out my trick custom crank puller (pusher?).

Any opinions/advice/comments on the condition, etc., based on the below images are welcome. So far, my plan is to replace crank bearings, the external seals, the bearings I knocked out and clean everything really well.

I think the crank is good. There's no detectable vertical play in the rod and very little clearance between the crank lobes.

The head is boxed up and going to Eric Gorr for stainless valves, cut seats and a rebuild. He's diamond honing the cylinder, as well. I'll also install a new Wiseco top end and a new cam chain -- and a new clutch, obviously.

FWIW, this was my first YZ250F bottom end, and it was very easy to work on compared to other bikes I've done. It seems very well designed. If you find yourself in the same situation I was in, I wouldn't hesitate to tear into it and make things right. I did the teardown last night. If the local shop has the parts I need, I hope to have it buttoned back up this evening.

2006yz250f-1.JPG

2006yz250f-2.JPG

2006yz250f-3.JPG

2006yz250f-4.JPG

2006yz250f-5.JPG

2006yz250f-6.JPG

2006yz250f-7.JPG

2006yz250f-8.JPG

2006yz250f-9.JPG

2006yz250f-10.JPG

2006yz250f-11.JPG

2006yz250f-12.JPG

2006yz250f-13.JPG

2006yz250f-14.JPG

2006yz250f-15.JPG

2006yz250f-16.JPG

2006yz250f-17.JPG

2006yz250f-18.JPG

2006yz250f-19.JPG

2006yz250f-20.JPG

(more images in next post due to limit...)

  • Like 1

Share this post


Link to post
Share on other sites

The crank remover plate you have is neat. I thought about doing that also, but was afraid I would strip the case thread holes or unevenly remove the crank causing possible bearing twist in the races - it really doesn't matter though, almost certainly they (main crank bearings) are going to be replaced anyway in a rebuild. I have that style of bearing pullers also, and was wondering what you rested on the case half to pull them? I was also wondering if the bearings are removed with a puller, is it possible to reuse them if nothing is wrong with them? The reason I ask, is because when you set a bearing, the rule of thumb is to make contact with the outer part of the race only. Well, the problem is, the only why to remove them is knocking or pulling them out by using the inner part of the race because of the case design. Oh, by the way, nice work and layout of the rebuild so far, can't wait to see more :smirk:.

Share this post


Link to post
Share on other sites

Thanks! It took awhile digging around the garage, but I finally found a plate with the holes in the right place to match up with a couple case screws. I had to swap in a few shorter different bolts as I tightened it down because of the lack of depth in those particular holes.

It doesn't take much pressure at all to press out the crank, so there is no concern about stripping out the threads. The reason for the press isn't to generate force. It's to generate even/steady force to protect the crank (and rod bearings) from shock.

On the tranny bearing, I cranked the center bolt down against a large Crescent wrench that I laid down across the case half with some rags protecting the case (you can see it lying there in one of the pics). The Crescent wrench was handy because the words forged in the handle gave the point of the puller something to center into. It took quite a bit of force to remove this bearing, and it came out with a sudden "pop." As you can see, the puller arms were a tight fit. I had to disassemble the puller to get them in there.

I'm no expert, but I wouldn't re-use a bearing that has been pulled or pressed out, especially ones that are so time-consuming to get to.

Oh yeah...I got to the shop and they had one seal, so this won't be going back together this weekend. Should have called first!

Share this post


Link to post
Share on other sites
On the tranny bearing, I cranked the center bolt down against a large Crescent wrench that I laid down across the case half with some rags protecting the case (you can see it lying there in one of the pics). The Crescent wrench was handy because the words forged in the handle gave the point of the puller something to center into. It took quite a bit of force to remove this bearing, and it came out with a sudden "pop." As you can see, the puller arms were a tight fit. I had to disassemble the puller to get them in there.

I'm no expert, but I wouldn't re-use a bearing that has been pulled or pressed out, especially ones that are so time-consuming to get to.

I had the same experience with the transmission bearings myself. I think you mentioned something about them being rough while in the case, and after they were pulled, they smoothed out. They were wicked tough to pull, and I have the tusk bearing removal tool. I can't believe that one picture where you have what looks to be a rivet to stop the gear cogs from rotating so that you could loosen the nut. Did that really work? I have seen guys destroy three pennies before one of those two nuts would even budge! After I had the bottom end all buttoned back up, I noticed what appeared to be a hairline crack on the inner race of the bearing just behind the front sprocket. I noticed it when I went to insert the collar that goes in there before you put the outside protector and sprocket on. I replaced everything in the cases, and I mean everything but the case halves themselves and the actual transmission gears. I thought how the heck could a brand new bearing have a crack in the outer race already, when I haven't even put any hours on it, and here it is after I tore it all back down, I discovered it is a heat crevice or oil line groove. I just had to make sure for piece of mind, that it didn't go through the entire race. That, and the fact that I have a lot invested in the bottom end right now. My entire top end is coming after the holiday. When I received the other new bearing that I am referring to (the one behind the front sprocket), it had the same crevice; but, when in the case, looks or appears to be a hairline crack. The reason I had to order another one, is because I had nothing to compare the new one in the case to. The old one had already been gone for a month, and the only way to make sure that it wasn't a hairline crack that was going to propagate all the way through the bearing, was to disassemble the whole bottom end in the meantime anyway. That was the third and final time I split the cases, when in reality, it should have only been once to begin with. The second split was due to doubting myself about applying Locktite® to a particular set of bolts. I guess I needed the practice. :smirk:.

EDIT: I forgot to ask: What do you think personally was the cause of the clutch plate failure/explosion?

Edited by nokickstandsallowed
Added question.

Share this post


Link to post
Share on other sites

It came near the end of a long day of mud riding, getting stuck a lot and abusing the clutch. The bike overheated either just before, during or right after the clutch went. (My son was riding the bike, so I'm not sure.)

It was pretty low on coolant, so it may have started off with the deck stacked against it (my fault), or the missing coolant could have been what boiled off.

What bugs me is that was a relatively new clutch. I put it in last fall. The first (stock) one lasted an amazing four years (since the bike was new). The second aftermarket one lasted around half a dozen rides.

Share this post


Link to post
Share on other sites
What bugs me is that was a relatively new clutch. I put it in last fall. The first (stock) one lasted an amazing four years (since the bike was new). The second aftermarket one lasted around half a dozen rides.

You missed or forgot to answer my question in post #5 about the rivet :smirk:

I just stacked my stock clutch pack next to my replacement aftermarket clutch pack to see which stack would be taller with steels and friction plates. They were both the identical height. I wanted a quick comparison to tell me that I didn't spend my money foolishly again. Then I broke out the digital calipers to find that every single friction plate from my stock pack of three and a half years lost virtually no friction pad thickness. The springs in comparison from stock to aftermarket, did differ dramatically in their free lengths. I guarantee my stock springs were worn to the bone; but, could not believe for one second that my friction plates thickness was not altered in any way. I looked in the manual to discover that they were well within specs and had another 3 years of life left to them. Mind you not, and I am not making this up either for kicks, the stock clutch pack has 1260 hours of use/not abuse on them. I was still probably correct for replacing the stock pack anyway, or risk the chance of having one explode or disintegrate also. To give you a rough example of how much of a clutch perch abuser I am myself, I have went through a clutch cable a year just from them wearing out. In the course of one ride on my two acre single short track, I calculated that I shift no less than 10 times in the course of one lap. I do a good 75 to 100 times around it before I am even starting to get a twinge in the clutch hand.

Edited by nokickstandsallowed

Share this post


Link to post
Share on other sites

Sorry about missing the question! I've used pennies for this purpose before, but wanted to find some aluminum. Stumbled on a drawer of rivets and it worked great.

Share this post


Link to post
Share on other sites
Sorry about missing the question! I've used pennies for this purpose before, but wanted to find some aluminum. Stumbled on a drawer of rivets and it worked great.

No problem - I wasn't sure if that rivet was aluminum or steel and figured the aluminum would just fold right through the tooth and tooth wedges. I never tried one, so I had to know, because next time I might not have the luxury of having a Motion Pro gear wedge. Plenty of rivets though :smirk:. I saw my buddy get some bloody knuckles trying the penny approach and he opted to go with a different gear jamming mechanism - another penny - and guess what, that one went completely through the gears also. Since he was done putting his 2 cents in - no pun intended - yeah right :prof:.... I showed him how to properly wedge a penny in there. There is a technique of placing it properly in there before the actual meshing of the tooth and tooth wedge (It is the off camber technique) - he was putting them in there where the blunt point of the tooth was just causing the penny to shred like aluminum foil and causing it to come out the other side almost in two pieces. In other words, he wasn't using the edges of the penny (like I showed him), he was feeding it directly into the cogs like feeding a tree limb into a wood chipper. Wasn't pretty :smirk:.

Share this post


Link to post
Share on other sites

yzmuddereffer,

just wanted to say .... some of the best pics i've seen in a long long time!

very nice job!!!

what brand of clutch components are you putting back in?

Share this post


Link to post
Share on other sites
yzmuddereffer,

just wanted to say .... some of the best pics i've seen in a long long time!

very nice job!!!

what brand of clutch components are you putting back in?

Thanks, SUnruh. I have a Rekluse Core EXP 2.0 waiting for install. The kit doesn't come with fibers. For the fibers, I'll use either Rekluse's brand or stock. Leaning toward stock, but I don't know? Opinions are welcomed.

Share this post


Link to post
Share on other sites
I have a Rekluse Core EXP 2.0 waiting for install. The kit doesn't come with fibers. For the fibers, I'll use either Rekluse's brand or stock. Leaning toward stock, but I don't know? Opinions are welcomed.

I would go for stock. Why would "a kit" be called a kit, if it didn't come complete with fibers? That one always baffled me about certain things we buy for our bikes. SUnruh pointed out something about your photos, and I couldn't agree more. They are of digital enhanced clarity, and I'm starting to wonder about the Sony digital camera that I'm using. I can't tell the difference in my photos' clarity between using my Generation Four I-Pod or that $1200 Sony digital camera I'm using. You see, normally when a photo is taken of metal on a square dead on angle, (such as some of your photos) light is reflected back to the photo lens and distorts the photo. Are you having NASA digitally enhancing your photos? :ride:. I haven't seen clarity in photos like that where you can have two points of reference in focus at the same time. Example being, how did you get the clarity of what is in the background to be almost as "in focus" as something that is in the foreground? No, seriously though, great photos. But what kind of photo taking device are you using?

Share this post


Link to post
Share on other sites

Nikon point and shoot. There's no trick. Just hold the camera steady, provide as much natural light as you can, give it time to focus and make sure you use the macro setting for extreme closeups.

Share this post


Link to post
Share on other sites

Time to start putting this back together.

Cases, cleaned and ready...

yz250frebuild1.JPG

In the oven they go. I went for 275-degrees for 20 minutes. The bearings were in the freezer for several days. This helped, but I still had to press the bearings in to get them fully seated.

yz250frebuild2.JPG

Make sure you install the crank bearings with the lipped edge facing in!

yz250frebuild3.JPG

A couple small pieces. Oil strainer -- this little puppy saved a lot of junk from being sucked into my engine! Torque to 7.2 lbs.

yz250frebuild25.JPG

New countershaft seal and this cover/retainer thing...

yz250frebuild26.JPG

Linkage greased...

yz250frebuild28.JPG

Frame cleaned and waiting...

yz250frebuild27.JPG

Next: Transmission!

  • Like 1

Share this post


Link to post
Share on other sites

For most people who don't do this for a living, installing the tranny is probably the most intimidating part of reassembling a dirt bike's bottom end. Maybe these pics will help.

Note that I'm still waiting on new screws for the retaining clips, so this is a "dry fit," I guess. In other words, yes, I'm aware some of these bearings are missing their retaining clips! I did this for practice/demonstration.

It may seem obvious, but you'll need to elevate the case to allow for the countershaft sticking out the other side. I used this small Motion Pro plastic toolbox I found under my workbench, but it's easier to work on a small box built out of 2x4s if you have the wood and woodworking tools handy. I didn't.

yz250frebuild4.JPG

There are ways to install the transmission as one working unit, but I'm too clumsy to get that to work. This installs each major piece individually. First, oil everything up real nice so it will turn/insert smoothly.

Here's the driven shaft going in, with the fork already in place. If you're confused about which fork goes where, don't worry. There's only one way they will go in and still have the pins point toward the shift drum...

yz250frebuild5.JPG

yz250frebuild6.JPG

Tranny drive shaft is next. You can slide off the top gear on the driven shaft to make this easier...

yz250frebuild7.JPG

yz250frebuild8.JPG

Stick on the other shift fork. Simply raise up the gear it slides to lift it into place...

yz250frebuild9.JPG

yz250frebuild10.JPG

The shift drum has a groove for each pin on the shift forks...

yz250frebuild11.JPG

This next step could take quite a bit of finessing. You will need to slide the shift drum into its home while simultaneously raising and/or lowering the pins to fit into their grooves. Be patient and try rotating different sides (does a cylinder have sides?) of the shift drum toward the pins...

yz250frebuild12.JPG

yz250frebuild13.JPG

yz250frebuild14.JPG

yz250frebuild15.JPG

yz250frebuild16.JPG

All in...

yz250frebuild17.JPG

Next, you need to make sure everything works correctly...

  • Like 1

Share this post


Link to post
Share on other sites

If everything went together correctly, you should be able to shift the gears by rotating the shift drum. Between gears, you'll need to spin the transmission.

This is probably overkill on the pics, but here's a shot of the shift drum through the gears...

yz250frebuild19.JPG

yz250frebuild18.JPG

yz250frebuild20.JPG

yz250frebuild21.JPG

yz250frebuild22.JPG

yz250frebuild23.JPG

yz250frebuild24.JPG

Share this post


Link to post
Share on other sites

+3 on a couple of my transmision bearings feeling very rough and then completly smooth once I removed them.

Share this post


Link to post
Share on other sites

Nice pictures!

I use Honda CRF250 fiber plates in my bike. They have more area and you can start the bike in gear with them. 1 plate needs the ID opened up in a lathe or you can use the stock Yamaha plate.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×