WR 426 Loud Intermittent Rattle From Right Side


22 replies to this topic
  • nnamssorxela

Posted September 11, 2012 - 04:20 PM

#1

Hey all,

Note that this bike is a 1998 WR 400 with a 426 top end. I haven't run my bike in a while (lots of repairs) and I just started riding it the other day. I've always read that the yz/wr models are notoriously loud bikes, but I noticed an intermittent rattle that seemed out of place. It seems to be coming from the right side, particularly around the header bend. I've seen similar videos on youtube and there have been many opinions from water pump to air leaking around the header. I put on a skid plate yesterday and now the sound seems extraordinarily loud (obviously due to sound reflection) but I'd like to find the issue.



The video sound is off (and I think it was a bit loud for my camera), but you can hear the sound throughout the video, particularly when I rev it up a little bit. Any suggestions?

-Alex

Edited by nnamssorxela, September 16, 2012 - 09:32 AM.


  • nnamssorxela

Posted September 12, 2012 - 04:35 AM

#2

The cam chain, cam chain guides, valves, piston, cylinder, and tensioner (manual) etc. are all new, though I recall it making this sound a little before, though not quite as bad, I also didn't have the skid plate on. Let me know if there is any more info I can give.

  • allterra

Posted September 12, 2012 - 05:03 AM

#3

I would use a screwdriver as a stethascope (sp?) To try to pin point it or at least narrow it down. I could not hear it on the vid but if I had to make a wild guess I would check the pump for debris.

  • armpit

Posted September 12, 2012 - 11:38 AM

#4

stethoscope

ftfy

Spray some carb cleaner around the header to see if there are any changes in the idle

  • nnamssorxela

Posted September 12, 2012 - 03:30 PM

#5

I've been mulling this over all day and I just went out and listened to it again, and grabbed a friend for a second ear. We confirmed that the sound appears to be coming from the front, right, lower section of the motor, so I'm hoping it's as easy a fix as the water pump.

Is it common for these things to chew up impeller bearings? I've read about the '99 model having a slightly improved shaft and I'm hoping that solves my problem. This bike has never lost any coolant if it makes a difference.

Any more suggestions?

EDIT: Looks like I have to split the case to replace that bugger...

Edited by nnamssorxela, September 12, 2012 - 03:38 PM.


  • MANIAC998

Posted September 12, 2012 - 05:48 PM

#6

Nope, you don't have to split the cases to fix the waterpump! Just the right side engine cover.
Maniac

  • nnamssorxela

Posted September 13, 2012 - 06:19 AM

#7

That still looks like a bit of work, I guess more of just a bummer since I just filled it up with fluids...again. Will I be able to feel any play in the impeller if I just pull the pump cover off, or do I have to pull the side cover off to diagnose if the shaft/bearing are toast?

Also, is it most likely that it is the water pump bearing/shaft, or should I be looking at the counter balancer bearing?

Thanks for the input guys!

Edited by nnamssorxela, September 13, 2012 - 06:20 AM.


  • Birdy426

Posted September 13, 2012 - 12:30 PM

#8

very similar sound on my '01 WR a few years back. Turned out that the nut that holds the primary drive gear onto the crank had worked loose, and the gear had worn the splines on the crank. New gear quieted it down for a while. I ended up replacing the crank after a while just cuz I didn't "trust" it, not because it got worse again...

  • nnamssorxela

Posted September 14, 2012 - 10:35 AM

#9

Hopefully this is something simple that doesn't require a new crank!

So I pulled the water pump cover off to inspect the impeller.

Should there be any play at all?

I can definitely wiggle it back and forth, but it doesn't "rattle" back and forth. Also if I spin it in either direction, it has a bit of free play before it engages and I feel resistance like I'm spinning something back there.

Input?

-Alex

  • nnamssorxela

Posted September 14, 2012 - 01:32 PM

#10

Ok guys, bear with me. I've never been inside one of these engines, so I'm not sure what does what. I'm really not sure what gears are supposed to have play in them, but I was a bit overwhelmed when almost all of them did...

Any pointers?



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  • Birdy426

Posted September 15, 2012 - 08:48 PM

#11

Ok guys, bear with me. I've never been inside one of these engines, so I'm not sure what does what. I'm really not sure what gears are supposed to have play in them, but I was a bit overwhelmed when almost all of them did...

Any pointers?

http://www.youtube.com/watch?v=JlcsjBGsunQ&feature=youtu.be


the small gear on the end of the crank (at about 17 seconds into the video) is the one I'm talking about. by the way, is yours a 2000, or an '01/'02?

  • nnamssorxela

Posted September 16, 2012 - 04:37 AM

#12

Mine is a '98. Should any of those gears/shafts have play?

-Alex

EDIT: I thought I mentioned that this was a WR 400 with a 426 top end in the original post, but it appears I didn't. I will add that in now.

Edited by nnamssorxela, September 16, 2012 - 09:31 AM.


  • Birdy426

Posted September 16, 2012 - 04:58 PM

#13

Mine is a '98. Should any of those gears/shafts have play?

-Alex

EDIT: I thought I mentioned that this was a WR 400 with a 426 top end in the original post, but it appears I didn't. I will add that in now.

Alex-
If you pressed a 426 rod inbto the 400 crank, you have a keyed gear instead of a splined gear. Replace the gear and key and I bet your noise goes away. If you used an entire 426 crank, the gear is splined. Replace the gear and that should also quiet it doen.

  • nnamssorxela

Posted September 16, 2012 - 05:19 PM

#14

Birdy,

Thanks a ton for the input. The PO did the 426 conversion, so I'm unsure which is the case. Does the play in all the other gears seem normal? I'm becoming super paranoid.

Also, you're saying that the smaller gear on top is the culprit? That it should not move in and out on the shaft?

On a final note, the rectangle hole that turns the water pump is not perfect...is that an issue as well (I'm worried that it is a bit wallowed out and in need of replacement, I can get a picture if that helps)? The water pump shaft seemed to have play, so I'm going to pull it out and see if I can feel it in the bearing itself, and if there is not, I'll assume it's normal.

  • Birdy426

Posted September 16, 2012 - 09:57 PM

#15

Birdy,

Thanks a ton for the input. The PO did the 426 conversion, so I'm unsure which is the case. Does the play in all the other gears seem normal? I'm becoming super paranoid.

Also, you're saying that the smaller gear on top is the culprit? That it should not move in and out on the shaft?

On a final note, the rectangle hole that turns the water pump is not perfect...is that an issue as well (I'm worried that it is a bit wallowed out and in need of replacement, I can get a picture if that helps)? The water pump shaft seemed to have play, so I'm going to pull it out and see if I can feel it in the bearing itself, and if there is not, I'll assume it's normal.


Alex-
As far as the waterpump shaft, if you're the least bit nervous about it, replace it. They are pretty cheap, and eventually need to be replaced because the seals wear into the shaft and they start to leak. As far as the gear, it's the smaller of the two gears on the end of the crank. The one that you said you could see a little bit of motion in the video. All the other stuff looks normal (nice clutch basket, by the way...Barnett, and really good stuff), but that gear shouldn't move axially onthe crank at all, nor clockwise/counterclockwise very much. Pull the gear off, and have a look. If it's splined, get a gear from an 01/02 426, along with a new lock washer and nut. If it's held with a square key, get a gear from a 400 along with a new key, new washer and nut.

If you do end up replacing the waterpump shaft, replace the seals as well...just to be safe.

  • nnamssorxela

Posted September 17, 2012 - 04:21 AM

#16

Thanks again for the help! I'll be digging into it this weekend when I have some free time. I'll probably throw up a picture of the water pump drive "slot" to get an opinion on that as well.

And thanks, that basket was the cheapest I could find, and the fact that it had steel inserts to prevent the notching issue was certainly a plus. When I installed it (quite some time ago) I remembered it being a little bit more solid though, or is it supposed to have some play as well? I'll probably pull it to double check since I'm this far already.

-Alex

  • nnamssorxela

Posted September 22, 2012 - 02:11 PM

#17

Video referenced throughout post:

Ok guys, I had some time to dig into this today and I have tons of questions.

So first things first, the water pump shaft was all sorts of worn, so I will be replacing that with the "updated" shaft from a '99 with bearings, seals, etc. and using the original impeller as it looks fine.

Next are the 2 "idler" gears. Note that in the video I have removed the circlips, so they are not actually missing. The gear ~2 seconds into the video has a little bit of play and the below image is what the bronze(?) bearing (journal?) looks like. You can see the little divots in the surface are still there. Should this be replaced? And can I get those bronze inserts separately and drive them in?

Posted Image


The oil pump drive gear (I am calling this the 2nd "idler" gear) is in much worse condition. You can see where the gear has so much play (~6 seconds into the video in this post) that it has hit the case. You can also see in the below image that the divots in the bronze piece have completely been worn past (if they were even there to begin with). Obviously this should be replaced, but can I get that bronze insert separate? The shaft was shiny, but I could not feel any wear on it so I am assuming it is safe to reuse.

Posted Image


The clutch basket was the next piece I inspected. In my first video farther up the page you can see there is a bit of play in it as well. Again here there is a picture below of the bronze "bearing," and again I'm wondering if just the bearings can be purchased and driven into my existing gear, or if this amount of play is normal and I should just leave it alone.

Posted Image


The next issue was the 2 stacked gears on the end of the crank, and what I believe to be the source of my noise. I originally thought everyone was referencing the outer most gear as the problem causer. You can see in all my videos that there is a bit of "play" in and out on the shaft and that the splines on the shaft stick past the outer gear preventing the nut from applying pressure to the gear itself (~16 seconds in the video in this post), but rather the splines on the shaft. The metal lock washer is not thick enough to prevent this. The lock washer that was there was beat to hell and looked like #13 from the diagram, nothing like the thick #2 which is what it should be, is this an issue from the previous owner? Once I pulled that gear off, to expose the inner gear, the infamous CB gear key issue was apparent and you can see that the key is basically mangled, but the gear and shaft look fine. Can I get away with just replacing the key?

Posted Image


Below is a picture of the end of the crank. that shows the amount that the splines stick past the gear. As I mentioned before, the lock washer that was here was the thin metal type that you fold over the nut and was not thick enough to cover all of the splines. You can also see some scaring from what I assume is the messed up seal on the snout of the crank. I really hope that this is acceptable wear.

Posted Image


Below is a picture of the inner clutch basket. You can see that the basket is a little bit farther out than the splines. The nut also has a cut out portion along the inside diameter that makes me think that it was designed to clear the splines and still tighten down on the basket in the even that they did stick out past the basket. It seems like the crank nut should be similar, but this is not the case, and the crank nut actually looks like it has been modified/ground down (you can see this in the first video in one of my previous posts).

Posted Image


-Thanks again,
Alex

Edited by nnamssorxela, September 22, 2012 - 02:14 PM.


  • nnamssorxela

Posted October 03, 2012 - 01:42 PM

#18

Well I have a small update for anyone that searches for this later. I got my parts today and found a couple things out on my own.

The oil pump drive gear is supposed to have dimples on the bronze "bearing" surface like the other gears. I replaced this gear and it still has a bit of play, but I think that is normal for that style of bearing.

The main issue was the nut that was on the end of the crank. It had been modified and did not have the cutout for the splines that the clutch basket nut has. This was causing the nut to tighten against the splines and not the gears, allowing the in and out play you can see in the video, and I assume what caused the key to get chewed up as well. There was a tiny bit of play with the new key in place, but once everything was tightened it was solid as a rock.

I'm expecting the motor to sound a lot quieter next time it starts up.

-Alex

  • GuyGraham

Posted October 05, 2012 - 07:08 AM

#19

The primary drive gear is, as you have discovered, supposed to be clamped tight by the nut - the nut will have a hollow section on it that fits over the spines that protrude past the gear in situ, so it clampes against the gears and not the shaft
Make sure you torque it up, and put some Loctite 271 on the threads whilst your in there, so it don't come loose

Clutch basket (outer), oil pump gears etc normally exhibit some movement
clutch basket inner, should also be clamped tight by its nut

Edited by GuyGraham, October 05, 2012 - 07:15 AM.


  • nnamssorxela

Posted October 06, 2012 - 06:32 AM

#20

Thanks for the input. I torqued everything to spec and used new "lock" washers, but no loctite. I have no idea why the previous owner modified the bolt, maybe too cheap to buy a new one, but the issue is fixed now. Filled up my fluids and hopefully today I'll be able to start it up and listen to that rattle free idle.




 
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