WR400 seized, what to look for...


28 replies to this topic
  • JJHayesIII

Posted June 08, 2006 - 10:49 AM

#1

Trying to figure out what happened...any ideas?

initially, the motor just stalled mid-corner, locking the rear up...after letting it sit for a while, I was able to kick it over again, and go for a few more minutes, but then it just locked up chugging down a straight, so I decided it was time to try and limp home...got it running again for a few more mins and headed back...but then, same thing...

Right before it died, it was kind of surging, basically like it wanted to stall, but kept going for another rev or two before it did...

Coolant level was normal, but it could be heat-related (dead water pump?)...

It definitely seemed harder to kick over, and felt like the piston wasn't moving as smoothly as normal, but that could've all been in my head...

I've taken the head off, and I haven't found anything bad yet, things look pretty good, other than finding that my slide had cracked, and possibly droppped a tiny piece into the motor, which I'm guessing went out the exhaust, since i haven't recovered it from the top end, and there's no scarring or any other marks.

The top end on this bike was done 2mos before I bought it, so most of the stuff should be pretty fresh. I've never torn down a motor before, so I really don't know what else I should be looking for.

Thanks guys!
- JJ

  • BIGMatt

Posted June 08, 2006 - 12:48 PM

#2

Maybe the problem is deeper inside.
Bad crank or tranny bearings??

That is a weird symptom, especially if there was no scoring on the cylinder wall. Even with no cylinder wall damage, that doesnt mean the piston is OK. Id check the piston and rings just in case!

  • JJHayesIII

Posted June 08, 2006 - 03:26 PM

#3

I'm hoping it's neither of the first two...

I didn't spin the crank after I got the head off, I should probably do that tonight...

Other than checking for obvious gouging, is there something I should look for on the piston/rings/cylinder?

It was shifting pretty good, and still seems to shift fine...any way to check the bottom end without splitting the cases?

Thanks for the help! I'll report back with some pictures tomorrow....

  • JJHayesIII

Posted June 09, 2006 - 07:50 AM

#4

Took some pictures last night:

cracked carb slide (vacuum release plate):
Posted Image

Head:
Has some noticeable damage, looks like it might have been chomping on some metal for a bit...but valves still seat fine and hold liquid with no leaks...I'm guessing it's all just superficial, and should hardly have any effect on performance...
Posted Image

Cylinder:
Noticeable scarring on the front and rear of the cylinder. On the front side, the gouges are deep enough where I can feel where something must've been caught there, the rear of the cylinder isn't nearly as bad, but still shows wear in the same fashion, no gouging though...and, is the top of the cylinder supposed to have that bronze color all the way around?
Posted Image

Piston:
This is the front of the piston, you can feel the up and down gouges, also, there are noticeable pits in it (once again, I'm guessing some metal got stuck there?)...the rear of the piston shows up/down wear, but nothing deep enough to really feel...
Posted Image

Piston closer up:
Posted Image

So, my thoughts now, are that something came up from the bottom end and got lodged between the piston skirt and cylinder wall. The binding would've caused the piston to rock back and forth (hence, the wear on both the front and rear piston and cylinder walls, and pitting on the one side).

Does this warrant pulling the bottom end and splitting the cases to see if
there's something else damaged? This is my first time pulling apart a motor, so I'd kinda want to avoid that if possible. If so, are there any non-obvious things to look for?

From an ordering parts standpoint:
If I do split the cases, would I be better off upgrading to the WR426 Crank and con rod as others have done here? Should I just send the cylinder to Luke's Racing for the big bore kit and leave the crank alone? I'm not necessarily going for performance, I'd much rather have reliability...and I'm definitely willing to drop some money as needed...

Thanks for reading!
- JJ

  • 5valve

Posted June 09, 2006 - 11:22 AM

#5

If going for reliability, keep the bike original.
Head doesnt seem to be damaged, just used over years. if compared to mine, just asembled 3 weeks ago. (check my avatar for 3 years or more not cleaned head and the same head cleaned)
Cylinder colour at top is I presume normal, since this is the part, that isnt brushed by piston rings.
Cylinder scarrs are seen just as normal wear throug time at the correct area, front and rear, because thats where the pistons hits with skirt going up or down.
Would recommend recoating cylinder, if scarrs are deep, because compression can blow by, which you can see in quickly darkening oil and oil coming out of the breather tube.
Also replacing the piston with rings should follow the reconditioned cylinder. (in my area, the shop repairs your cylinder after you give them new piston, so the piston to cylinder clearance is matched correctly)
Long marks on piston skirt are normal for prolongued use, but I wouldnt know about those dots, still i believe they werent made instantly but in longer period.
About throtthle slide plate..I believe that is the cause of your engine stall, If all other parts are running OK (like conrod and crank bearings)
Why? because it disrupted correct mixture delivery to the combustion chamber.
You are lucky it didnt break and get sucked into the cylinder as it already was the case.
I might be wrong on the last one, but that is generally my opinion.

add: also check for out of the ordinary size and quantity metal particles in oil and mostly in oil filter as that would as stated indicate probable bearing or other inner part abnormal wear.

  • JJHayesIII

Posted June 09, 2006 - 12:21 PM

#6

Thanks for the response!

I'm thinking that the scars on the cylinder/piston are not normal wear, because the piston is only 2 months old (along with rings, valves, springs)...

Could the increased air from the cracked slide have caused the bike to run lean enough where heat would become an issue? The first time it stalled, it literally felt like the piston had frozen in the cylinder. I was able to wait a little while, and start it up again (after it had cooled?), but it seized again a couple minutes down the road...

The reason I asked about the big bore was that I've heard getting the cylinder recoated would cost close to $300, where I can get the big bore, with a cylinder swap, for about $400 (http://www.lukesraci...uksr/yz400f.htm)...

I haven't been able to pull the piston (need something to get the piston pin out), but it didn't feel like the con rod had any play...

As for the filter, it did have a lot of metal in it, all the particles were similar sized, didn't look like anything too large, just shavings, but I figured that had something to do with the top end being replaced recently...

  • 5valve

Posted June 09, 2006 - 01:39 PM

#7

They take old cylinder, rebore and renew it and sell it as new in a set.
It actually isnt so expensive and a 20cc isnt a big raise, however, Id stick with 12,5 compression, since ive seen issues when using 91 octane on 13,5.

At my place, new nikasil would cost me 75-100$, depends if welding would be needed.

It is for sure not OK, for the 2 moths old piston to look like that.
Did you have the cylinder honed, before assembly, to ensure smooth running of the new piston?
Did you measure the piston to cylinder clearance, it might've been too small piston for the bore or maybe too big! http://www.pro-x.com....asp?No=01.2418
If the throttle slide plate would affect the combustion to be very hot, your plug should be white as a bone, left on the sun.

Sticking piston is for sure heat related, it happened to me once on a diesel car, bent head, loosing water, engine stalled, waited a while, refilled water, car restarted normally.

So probably you've had too loose or too big piston, than your plate broke, heat rose, damage occured. (speculation)

  • JJHayesIII

Posted June 09, 2006 - 02:08 PM

#8

I guess I should check out what the price at my shop (gotta find one first) is going to be for the nikasil, because it looks like I definitely need to do something about that cylinder wall. I agree with sticking to 12.5:1 compression, I don't want to worry about the motor popping, I just want to ride it...

I bough the bike knowing it was going to need work, and the previous owner is the one who did the top end. He said he used all stock parts, so the piston should be the right size, no? I didn't check the clearance (I don't know how)...

I checked the plug by running it somewhat hard and pulling the plug right after....it was only slightly white on the very top...

So, my next steps should be to have a shop check out my cylinder and piston, to make sure the clearances are ok?

  • Yamahondaha

Posted June 09, 2006 - 02:53 PM

#9

I had the same or similar symptoms with my 99 WR400F. After putting auto decompression cams in it the motor would run fine till it got hot and would lock up (I didn't break in the new cams right), once it cooled it would start back up. I saw metal particles in the oil that must have made it to the rod bearing causing it to fail next. I talked to several motor builders and they said that rod failure was common on the 400 but the 426 was an improvement even over the 450. Good news, you can rebuild your 400 with 426 parts. The crank (with drive gears), rod, piston & cylinder is all you need. The 400 and 426 heads are the same except for the hot start air inlet port near the carburetter intake. The same builders also said that the stainless valves in the 400 are more reliable than the 426 ti valves so if you want reliability, build your motor up with the 426 crank and jug.

  • JJHayesIII

Posted June 09, 2006 - 03:20 PM

#10

Good info...I think I remember reading that here. Do you happen to have a price/parts list that you used? How tough would this be to do on my own? Something I can do in the garage, or do I need a lot of special tools? As it is, I can't get my damn piston off because I need something to remove the pin...

Have you had any issues with the motor since you changed everything out?

Was your rod bearing causing it to seize up, or did you just find that problem while you were taking everything apart cuz of the cams?

Thanks for the help, that sounds like the route I should head, but I want to make sure this issue doesn't pop up again after all the work...

- JJ

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  • Yamahondaha

Posted June 09, 2006 - 04:00 PM

#11

Good info...I think I remember reading that here. Do you happen to have a price/parts list that you used? How tough would this be to do on my own? Something I can do in the garage, or do I need a lot of special tools? As it is, I can't get my damn piston off because I need something to remove the pin...

Have you had any issues with the motor since you changed everything out?

Was your rod bearing causing it to seize up, or did you just find that problem while you were taking everything apart cuz of the cams?

Thanks for the help, that sounds like the route I should head, but I want to make sure this issue doesn't pop up again after all the work...

- JJ

I am assuming you are talking to me, I spent $1,100 on all the parts including the head rebuild with kibble white stainless valves. I got my parts from www.partswarehouse.com

I did all the work myself in my shed and didn't use any special tools, I improvised a flywheel puller with a three way pully puller, to pull the crank I used the same puller tool in reverse and to reinstall the crank I just used a pipe long enough to take up the space between the flywheel nut and the main bearing (it needs to be slightly wider than the crank taper) I jamed an aluminum plate between the drive gears for all shaft mounted nuts that required torque wrenching instead of using a holding tool (as shown in the repair manual for torquing the counter balance shaft nut, however the SAE torque value was incorrect but metric was right)

I sold the bike after 4 or 5 months but up till then the motor ran great, it was a great learning experience and my WR450 is so similar to the 400 that I know I can tear my 06 Yamaha down when the time comes...

Good luck and PM me if you want the pix I took from the rebuild

  • JJHayesIII

Posted June 12, 2006 - 02:01 PM

#12

I am assuming you are talking to me, I spent $1,100 on all the parts including the head rebuild with kibble white stainless valves. I got my parts from www.partswarehouse.com

Good luck and PM me if you want the pix I took from the rebuild


Thanks for the info! I've decided that this is probably the best way for me to go...Any tips on what to look for when I open it up? I'm assuming I should check all the bearings, and make sure there's no more metal shavings kicking around in there...

  • 5valve

Posted June 13, 2006 - 06:51 AM

#13

Rather than check, replace them.
Its fairly old bike, and those arent expensive. no need for original parts.

  • JJHayesIII

Posted June 13, 2006 - 10:21 AM

#14

Rather than check, replace them.
Its fairly old bike, and those arent expensive. no need for original parts.


Any suggestions on where to get them? How about which ones I'd need?

  • JJHayesIII

Posted June 13, 2006 - 11:03 AM

#15

Looking at this site, it shows the parts needed to convert to a 426:
http://www.powroll.c...A_YZFWR426F.htm

Would it be safe to assume I could order the whole WR426 Crank Assembly (5JG-11400-20-00) to avoid having to rebuild the crank? Then I would just be able to order the 426 piston and cylinder and be done with it, no?

  • MN_Kevin

Posted June 13, 2006 - 01:47 PM

#16

Be sure you pull the cams and verify the journal surfaces are good.
I had seized my cams due to a lack of lubrication.

A guy in CA repairs the journals. He is the only one I know refurbs heads.

When I had scrapes in my cylinder, Eric Gorr did the work for me, although all he did was PREP the cylinder. He sent the cylinder and my WISECO 420cc piston to [ the place whose name escapes me >> they are in Wisconsin...something "Chrome" maybe??? ] have the cylinder bored and replated.

Feel free to PM me if you have any questions!

  • JJHayesIII

Posted June 14, 2006 - 09:35 AM

#17

Kevin, the cams looked pretty good...how come yours weren't being lubed? clogged oil jet or something?

Got my motor out, and removed the piston finally (just needed a little persuasion)...

How much play is the rod supposed to have? It definitely feels like the big end bearings might be going bad...but I the top of the rod will only move a mm or two back and forth...and I doubt that'd be enough to cause the motor to seize up...

  • Solo

Posted June 14, 2006 - 12:33 PM

#18

My guess is the guy who sold you the bike didn't rebuild it as he stated. Did he have reciepts?

The wear you have in the photos and your discription of the symptoms SCREAM of being heat related.

Since I've never been into one of these motors I can't speculate where your problem could have started but it's definately rebuild time.

  • JJHayesIII

Posted June 14, 2006 - 01:06 PM

#19

My guess is the guy who sold you the bike didn't rebuild it as he stated. Did he have reciepts?

The wear you have in the photos and your discription of the symptoms SCREAM of being heat related.

Since I've never been into one of these motors I can't speculate where your problem could have started but it's definately rebuild time.


He's a reputable guy, but I didn't ask for receipts, this is what was said to have been done:

Valves/springs
piston/rings
cam chain/tensioner
water pump
oil pump

and you're right about rebuild time...If I don't find any major damage, I'm going to pray it was just a combination of the cylinder and the big-end bearing being being worn, so replacing those will be the fix...

  • JJHayesIII

Posted August 17, 2006 - 01:29 PM

#20

So, this is still going on....I finally received some parts, and got to work.

Stripping the motor was pretty easy with some help from the manual. I made sure to put every sub-assembly into it's own ziploc bag, inspecting things as they were removed.

My tranny looks to be in great shape, so I'm not planning on changing any of that out. I'm definitely going to be doing all of the bearings, and I've decided to convert it to the 426 crank and cylinder/piston. I'm hoping the new crank solves my issues, as everything else seemed to be in real good condition.

Getting the new bearings pressed (and the old ones removed) was the biggest pain in the ass so far, I saw the best results using the freezer, some sockets as drivers, and a hydraulic press.

I also ended up buying some special tools (nothing too pricey though), something to pull the crank (used the same thing to install it) and a pilot bearing remover...definitely helped out.

So far, I've installed all my new bearings, tranny, crank, oil pump, primary drive, kick start and balancer, so my motor is a good portion re-assembled. I ran the tranny through all the gears, and it seemed to work fine, I'm hoping that the cases will hold oil, so I don't have to re-seal them. Any ideas of what else to look for/think of before I get it ALL together and it doesn't run?




 
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