bottom end seized, again!

well, i went out to glamis this weekend and seized my bottom end, again! i just put it back together last weekend and this was my first time out with it. i broke it in really easy. rode it for about 15mins at my house around the block a couple times, really easy. then out there, i went for about a 30min ride by myself, really easy on it, just breaking it in and all. then after that, went out for 3 rides. on the third ride on the way back to camp it locked up. just before there was a lot of noise coming from the bottom of the motor. it's full of coolant, never ran hot, not too lean either. full of oil. when i emptied the oil there was a lot of metal shavings in the filter. not the normal little shavings either. a lot of bigger ones. what could be causing this. is there an oiling problem? not getting enough oil to the crank? im really thinking of just fixing it and getting a 450 but i like my bike. i know my bike. i dont want to get rid of it. how can i find out if it is an oiling problem? if its not an oiling problem, what could be causing this?

thanks for the help guys.


First you'll need to tear into it and find the point of failure. While it's apart, inspect the entire oiling system (pump, all screens, clean out the frame, etc.) Inspect the cam saddles. Blow air or use a plastic squeeze bottle to force oil through all the oil passages (you can find out where they all are in the manual). Once it's running again, check for good oil delivery by loosening the small bolt near the top oiler at the head.

i had good oil flow. i loosened the bolt at the top of the oil gallery and had good oil flow. i did that when i first fired up the engine. could it have got clogged and stopped the oil flow? when it was put back together last time EVERYTHING was cleaned. the cases, the cylinder, the head, the frame, all oil lines, everything. there was no old oil left in there. when i reassembled it all the bearings where oiled. the crank, piston, cams were lubed. also, if there wasnt sufficient enough oil flow then how could all of the metal shavings have made it to the oil filter? im pretty sure that it is the bottom end again. the big end of the rod. that is what happened last time. i was told to inspect the check balls in the cases. they seemed fine. could this have been part of the problem? ime going to start to pull the motor apart this week, hopefully. im pretty sure i can do it in an evening, after all, i just did this not even 2 weeks ago :) . oh well, thanks for the help so far. if anyone can think of something else that it could be, please help me out with this one. thanks again.

also, does anyone know of a good shop that can rebuild my motor, like if i took it out of my bike and gave it to them? im in southern california, near long beach.

I'm out of your area, so I can't help with that. You need to find out what it was that failed, and what kind of problem may have caused it.

Your oiling system has two major branches beyond the oil filter. One feeds the crank, and the other goes out to the external oil line and branches again to feed the trans and the top end. There is a seal in the right engine cover that seals in oil passing from the cover to the crank. It's possible this has failed, starving the crank, but the fact that you had oil pressure at the top seems to suggest it hasn't, because such a failure should drop the oil pressure system-wide. Check it anyway. Be sure you can flow oil all the way through all the elements of that circuit, including the crank itself. Make sure that the crankpin has a drilled bore plug in it on the left side. If the bike had a repeat failure, there's a problem in there somewhere. You just need to find it.

Good Luck!

Also check the oilscreen in the bottom of the frame reservoir.

Whatever you do, do not reassemble it until you have found and fixed the problem. It sounds like last time around you fixed the symptom (bad rod bearing) but not the cause.

Some ideas on what to look for: oil pump parts out of spec (get out the feeler gagues and check all parts for spec), partially plugged oil lines, a leak in an internal oil passage causing the pump to suck air on the suction side or loose pressure on the pressure side, clogged filter or screen, bad internal seal or parts worn out of spec (which could cause low oil pressure to areas such as the crank pin), etc.. Also have you done any fiddling with the CDI? If so, your rev limiter may be faulty and you may be overrevving it without knowledge. Not sure what equipment you would use to test the rev limiter without a running motor. hmmm... can't think of any other ideas at the moment, but basically disassemble the entire motor and check every little part to make sure it's in spec. Let us know what you find!

should i just replace anything and everything that has to do with oiling? pump, lines, etc.. then check all the passages for a clog? the filter was brand new and wasnt clogged when i pulled it apart and the screen at the bottom of the frame downtube was fine too. i havent really messed with the cdi besides the blue wire mod. i dont think i was overrevving it. i might have hit the limiter once or twice but not enough to cause any damage.

i can turn it over again. i broke it loose with a socket and ratchet on the nut on the crank. wasnt that hard. now i can spin it with the kickstarter and the plug out easily. im thinking about tearing it apart, sending out the crank and whatever else needs fixin, then having a shop put it back together that way they can go over it and they can warranty it.

If you do take it to a shop, fill them in on the whole history of the situation. That way, they'll know what they're working with, and be less likely to overlook something.

Don't just start replacing parts or you'll end up back in the same boat again very soon. You need to actually figure out what the cause of the problem is so that you are sure that the cause gets fixed. My personal advice is either keep looking until you find the problem, or send it to a builder and as said above give them the entire story so that they can go through the motor carefully. Best of luck and let us know what you find!

thanks for all the help guys. ima going to try and tear into it this weekend if i have time. ill let you know what i find when i find it.


People sometimes forget that the oil pump although "pumping oil" may not be pumping at "required" or "system" pressure. PRESSURE AND FLOW ARE BOTH REQUIREMENTS FOR PROPER LUBRICATION.

With that said, our pumps are a two stage pump. Stage 1 is the scavenge pump for returning oil at high volume and low pressure back to the frame. Stage 2 is the low volume high pressure section that pressurizes the entire engine. If there has been debris chewing at the lobes of the high pressure gerotor you can pretty much bet that it's losing a significant amount of "pressure" but it will still "flow". The high pressure gerotor set is behind the backing plate in the pump casting (it can only be seem by disassembling the backing plate form the casting). The larger gerotor that you see when you remove the pump assembly, as a whole, is the scavenge pump. If the scavenge pump has scoring inside (between the inner and outer element) then you probably have the same on the high pressure side as well. When in doubt, or you see any signs of scoring, REPLACE BOTH.

The RH crank shaft end is sealed thru a lip seal to the RH side cover (hence where it gets is pressurized oil from to lube the whole bottom end). Have you checked it for damage and or leakage.

Also do thread search for "yzf oiling system in detail" for a more detailed breakdown I posted afew months back.

As the saying goes...Been There Done That :)

its unlikely, but so is your 2 engine failures. one time, one of the torx screws came out of the CB gear and got smashed up in my bottom end. it mostly ended up on my mag drain plug (you were using one, right?), but some bigger than normal chunks of metal ended up in my oil filter.

in my case it didnt sieze the motor, but i bet that if it got stuck just right it could sieze the engine.

this is just one possiblilty, and i have no idea about the oiling sytem. but, everytime i have the engine apart i re-torque those stupid little screws

hopefully for your sake it was something small like this.

ok, so i finally started to look into my problem. i pulled the clutch cover off and found some metal shavings on the inside. not a surprise. so i start to pull the plates out and i noticed that something looked funny. then i saw it! 6 fingers were broke off my clutch basket! so i pulled everything else off and pulled the sidecase off. not pretty. the basket is torn up. i havent yet pulled it off because im waiting for my buddy to bring me a 30mm socket to take it off. it is 30mm right? im pretty sure that the finger/fingers were the noise that i heard coming from the bottom right of the engine just before it seized. its also, HOPEFULLY, not the crank bearing like last time. im goin to try and get a hold of my engine guy to see what he says. if anybody else has some info/help for me i would really appreciate it. thanks again guys.


I have a 2001 YZ426 Motor complete swap for sale with Hotcams....PM me for more info

You're on the right track. Keep taking it apart. I would put my $1 on the source of the seisure being in the gearbox, probably from chunks of your clutch basket. Not sure if that's better or worse than a crank bearing, gearbox and clutch repairs are not free. Keep us informed what you find and good luck!

the motor is not locked up now. after i pulled the basket out and got the chunks out that i could i can turn it over with the kickstarter. would it be possible for me to clean it up as good as possible then fill it with oil, start it, run it for like 30 secs., then shut it off and drain the oil, and do this 2-3 times? would that be ok? or should i pull it apart to completely clean the inside? also, when i finally got the basket off, it was worse than it looked. it was cracked in half. if i can get pictures up i will. thanks again for the help.

the motor is not locked up now. after i pulled the basket out and got the chunks out that i could i can turn it over with the kickstarter. would it be possible for me to clean it up as good as possible then fill it with oil, start it, run it for like 30 secs., then shut it off and drain the oil, and do this 2-3 times? would that be ok? or should i pull it apart to completely clean the inside? also, when i finally got the basket off, it was worse than it looked. it was cracked in half. if i can get pictures up i will. thanks again for the help.

Mine wasn't cracked in half but lost a few fingers. Some broken pieces got stuck between the basket and sidecover locking the engine. Like you I was tempted to flush out the engine but knew that was not the best thing to do. I completely stripped mine and there was metal everywhere. Lots of big and small chunks and filings ground up by the gears. There was a lot of small filings in the oil screen pickup right in the bottom of the engine and there was even metal inside the flywheel around the stator.

Check all your gears too, clutch basket, primary and transmission. I found bits of metal pressed in between gear teeth on the clutch and tranny and had to dig it out with a screwdriver. The metal is too soft to hurt the gears but it will eventually come out into the oil and could cause strain on the shafts when the tooth hits the metal and pushes the shafts apart.

I also had a few dings in the outer edges of the metal clutch plates so I replaced everything, again! :) . I had just installed new plates and a new paddle tire and I think the extra grip of plates and tire put too much pressure on the old weak basket. The first day out I fell and snapped the clutch lever. I rode home without the clutch, not a big deal since I rarely use it anyway, but that's when it came apart.

that really sucks. it wouldnt be so bad if i hadnt just had the motor apart 2 weeks ago. oh well, im goin to talk to my motor guy today and ill see what he has to say about it all.

No no no, take it apart! You may have lots of pieces floating around in there that won't come out with an oil change. Not only can the pieces themselves cause some damage, but if one or more of them gets sucked up by or clogs the pickup for the oil pump then you really could be in for an expensive ride. I know it sucks, but take it apart and clean it out.

Along the same (oil) lines..How much pressure should be in frame while a '01 YZ250F is running?? I was changing and flushing oil last night when I decided to see if oil was circulating by opening filler plug in frame and POW! oil everywhere! I didn't expect that much pressure in the frame. Any experience on that? I'm thinking I may have a clog in a return line to the motor. Wanted to race tomorrow, but, now i'm hesitant untill I can verify if this is normal or not. I just bought this bike.

Sorry to hear about your motor, bummer. If you take it to a shop, they would probably like to disassemble it, diagnose it, and do the rebuild from A to Z as necessary so they can be confident about the problem finding and giving you some kind of warranty on it. As opposed to receiving the motor in parts.


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