A bad thing happened today

[jboomer]

I was at the track today and rode for about 4 hours. On my last lap of the day on the SX track, I came up short on a double and heard a pretty loud crack...I quickly gave it gas to clear the next double (of a 3 double rhythm section) and nothing happened but a high rev. I nearly went over the bars on the second double because I came up so short, but the suspension soaked it up pretty good and I rode it out. Well, the chain broke.....effectively taking out the case guard, plastic sprocket guard and the entire bottom of the compartment that holds the clutch arm. It completely tore the portion of the case that the bolts holding the case guard on out....you can't even screw a bolt into the spaces left....the bolts didn't break mind you, the case broke around the bolts. The hole under the clutch arm is bad enough that I'm fairly positive it's not fixable. It didn't blow oil out, but it seeped a couple tablespoons. I've got some pictures if anyone is interested in hosting them so everyone can get a peek. Looks like ServiceHonda can get me a replacement Left Case for $180...not bad considering I was guessing at least $250. Looks like I'll be splitting the cases myself (no way is the local Honda dealer getting my business). Question: anything in particular I should look into replacing while I've got this engine torn down? I know the valves have been troublesome to some, but thus far I've had no problems. The bike has probably 60 hours or so on it and I'm not hard on it, so there shouldn't be any excess wear on anything. Are there any special tools I'll need? I've got a friend that did a complete top and bottom end rebuild on his 99 YZ426 over the spring, that's going to help....so the process shouldn't be excessively difficult.

Well, I'm going to go sulk now. Thanks for listening....

Oh yeah, what I think happened. The track was pretty muddy today and I stopped to clean mud out of the case cover twice in that four hour period...it would pack in there pretty bad. I just adjusted the chain last night because I put on a new sprocket...so I know it wasn't too tight. Anyway, I also noticed a tooth broken off my new sprocket. So I'm guessing a rock got lodged in-between a link and once it hit the sprocket it pulled the chain too tight (breaking a tooth in the process). Well, I came up short on that jump and I think the combination of the two broke the chain. I found the masterlink (it's what broke) and it was twisted really bad and the riveted side is what broke. The retaining clip was still attached to the pins.
:(

 

[Hick]

Yuck.

Can you really buy just one case half? I thought they typically came as a matched set.

I would imagine that reusing the bearings out of the old case may not be a good idea, not sure if you can remove them w/out damage, so you should consider new bearings.

And don't forget all the gaskets you are going to need...


Sorry for your bad luck

 

[DRZ_Dad]

Dang boomer I hate to hear that ! but atleast it didnt cause you to have an abrupt get-off............

 

[dirt bike dave]

Can you really buy just one case half?

For Hondas, you usually can just buy one half, and it should have a crankshaft bearing already installed. Compared to other brands, prices on crank cases are very reasonable.

 

[jboomer]

Yeah, I was pretty suprised it was that low. First thing I told my buddy when I pushed it up was "Well, I just spent 300 bucks!" Glad to hear you can purchase one half....when I read Hick's post the hair on the back of my neck stood up! Fortunately I can do the work myself and save myself another $300. Guess if had to happen, now's the time. Almost too hot to ride. It sure does suck though! Don't know what I could have done differently to prevent this. I guess the end of the chain kind of "whipped" around the CC sprocket and took out everything in its way (or bunched up real quick until the case gave way). I'm sitting here at my computer desk right now with the plastic countershaft guard, metal case guard, and the piece of the case that the bolts screw into----still attached. Sickening sight.

 

[bclapham]

a good welder can Tig that up no problems- same thing happened to my YZ250, it took a rock through the chain guard.

remember to take all the electrics off and have at it!!!

 

[kelseybrent]

Ouch, don't know if this would have helped you or not. Good luck.
http://secure.srcinc.net/prodpage.c..._Selected=7&Product_Selected=0206&StartRow=11

 

[Detonator]

The fact that your leg was uninjured is worth whatever you have to spend. Your bike's chain guard did its job. Hope the repair goes quickly!

 

[jboomer]

a good welder can Tig that up no problems- same thing happened to my YZ250, it took a rock through the chain guard.

remember to take all the electrics off and have at it!!!

Bruce, would I still need to pull the motor to have this done? As far as disconnecting electrics....would disconnecting the ignition be enough or is there something else I'm missing? If repairing it would cost less than $100 I may consider this route instead of splitting cases and such. More info would be great thanks!

Did yours also break off the mounting pieces that the bolts thread into? Can they reweld something like that?

 

[truespode]

Boomer... drop Gomer a line. He has been through the cases on his bike several times and he can tell you what parts you can or cannot take off without having to remove the engine. He has some pics from the manual he can send you too to show you the specific pieces in case there is any confusion.

He doesn't check this forum often so if you have his number call him or e-mail him at highlordgomer AT bellsouth.net

Or e-mail me at truespode AT yahoo.com and I'll give you his cell number.

Ivan

 

[truespode]

I talked to Gomer and he said you do have to pull the engine. He did say you can bring it over to his house and he'll help you do it but you might as well bring some main bearings and a new piston to do at the same time.

Feel free to call him when you get a chance.

Ivan

 

[Jaybird]

As good an eye as I can get on your CS sprocket, your teeth show signs of wear. This would be indicative of a worn out chain that had elongated past limits.
It is very hard to break a chain that is not stressed by wear or maladjustment.
Also, mounting up a new sprocket with a chain that has been worn will accelerate the problems.

Not baggin on ya...just analyzing what I see.

 

[jboomer]

It's not a very good picture...the cs sprocket still looks nearly like new. If I get a chance after work, I'll go out there and pull it and get a better picture. Actually, I've only had to adjust the chain once or twice since I've owned it (6 months with only 3 of those ridden regularly). I'm certain the chain isn't worn, but it won't be used again after this. I can't take the chance of it having more fractures or anything in it.

Thanks for the heads-up Ivan! I think I'm just going to get the new case half. If I run into any hang-ups I'll definitely get ahold of Gomer!

 

[Jaybird]

I took a closer look and enhanced the photos. The chain was definately worn. That is what deforms the tooth profile the way it is. When the pins and bushing wear, it places undue stress on the sidelinks.
If you measure your chains proper, you can change them out before they reach 2% longer than new. This will keep your sprockets from ever deforming, and probably keep chains from ever breaking.

If you only adjusted twice in six months, I would bet money it was too tight during the adjustments.
If your chain measures out now to within spec (<2% growth), then I'm positive that the chain was too tight.
Tight adjustment and elongated chain are the only two things that can deform the CS sprocket teeth uniformly like that.

 

[Ol'89r]

Bruce, would I still need to pull the motor to have this done? As far as disconnecting electrics....would disconnecting the ignition be enough or is there something else I'm missing? If repairing it would cost less than $100 I may consider this route instead of splitting cases and such. More info would be great thanks!

Did yours also break off the mounting pieces that the bolts thread into? Can they reweld something like that?

jboomer.

If you can find a good tig welder in your area, take Bruces suggestion. Drain the oil and disconnect the cdi box. The high frequency used in tig welding of aluminum can damage the cdi box if left intact.

A good welder should be able to repair it while it is still in the frame and build the bosses for the chain guard back up. If you can't find anyone in your area to do it. We could do it here but, you would have to remove the engine and box it up in a sturdy wooden crate and ship it here. We will use the same crate to ship it back so make it strong.

From looking at the pictures, I would guesstamate somewhere under $150.00 to repair. How far under is hard to say without actually seeing the engine.

Let me know if we can help. :cool:

Ol'89r

 

[jboomer]

I got your PM and thanks for the suggestions! I may just go ahead and replace the case half, I don't want that hurting me in the long run when I decide to get rid of the bike.....although my wife controls the money and may tell me to look for the cheapest alternative, so we'll see in the next couple of weeks.

 

[Studboy]

Last May we were at the sand dunes, and the same thing happened to my friend's RMX250.
We were jumping and the masterlink broke in half (DID X-Ring), bunching the chain up into the guard which worked and saved his cases. We determined that the cause was due to this equation: too little slack in the chain+jumping=broken chain. :) :) :)

 

[SpeedyManiac]

I would recommend getting a case saver once you replace the case. Any offroad oriented company should sell them, other people on drn can probably recommend one.

 

[KawieKX125]

Your chain was too tight I bet, that is the only time I have seen them break. I like the chains on my bikes on the very loose side, doesnt hurt anything but the chain slider, which is a nice cheap part.

 

[jboomer]

Actually, it was adjusted the night prior (I had the wheel off changing out the rear sprocket). I've always adjusted according to the manual....bike on the stand 1 1/4" of play at it's tightest point. Like I mentioned in the original post, it was really muddy that day. Not to mention the track had added a bunch of sawdust to try and absorb some of the water and to "loam out the track" a little. That stuff is like particle board once you add copious amounts of wet mud. It was packing under the plastic case guard really bad and I had stopped and cleaned it out once half way through the day. The conditions were just right for breaking a chain.

It's a bad idea to run these chains on the loose side on the CRF's. They chatter really bad and eat up your swingarm and the aluminum down spar just behind the cc sprocket. Of course you can't run them tight either, the only answer is to frequently check the adjustment and correct it if it's wrong.

Also, they come stock with a case saver, if you remove the plastic cc sprocket cover, it's located underneath it. But, one thing I've learned from this....I'll always have a short pair of bolts in my toolbox so when it's really muddy at the track, that plastic cover is coming off so the mud doesn't pack.

 

[Treejumper]

When i had a chain take out my case on my 86 YZ250 i couldnt find a case. So i had a local welder/rider split the case, install a new shifter shaft (bend mine), redrill the hole for the shifter shaft and put the motor back together for $100. Then all i had to do was put the motor back in the bike. You cant even tell it was broke.

 

[jboomer]

My wife is encouraging me to take it to a local welder to see if they can fix it. It'll save a little money but a lot of time. I don't plan on getting rid of the bike for a couple years at least, so this may be the best option. I am curious though, Ol'89er where is it that I need to unplug the CDI? I haven't looked at it, but I'm guessing there's a plug up near the box...is this enough?

 

[PINGERS4LIFE]

yeah man i would consider ur lucky the same thing happened to my but mine is a cr125 chain got wedge on the shifter and put the shaft down threw the case no weld job for sure so i am thinking on trying to find a 96 or 97 bottom end they have the same gasket kit and cylinder as mine so that would mean that it just might work is the only reason i want to do this the 96 and 97 are 6spd and mine is 5spd

the same thing that happened to urs happened to my fathers 99 rm250 he used jb weld and let it set up for a lil and pulled the clutch once in a while works great it was a 5dollar fix so that might intrest u 2

 

[Treejumper]

Pingers4life,

You can still have your case welded. It will just have to be redrilled for the shifter shaft. I had the same thing happen to mine. Here is a picture after it was welded up. Basically the lower half of the of the shaft housing was missing and about 2" of the bottom case. The welder said it would of been easier if had found the chunk of the case that was knocked out.

 

[fatherturtle]

On my KX I adjust the chain so it is 2.5 -3.0 inches in chain slack like the book says. If you have to tighten the chain to get the side to side play out the chain, you need a new chain. I was always told if your chain starts to chew up your mud flap with the proper chain tension your chain is worn out...I don't own a CRF so I don't know your circumstances.

Also sorry to hear about your problem I think I am going home tonight and I am going to check my bike for wear and tenshion. ouch