Jump to content
Sign in to follow this  

YZ250 '99 issue with bottom end? HELP 2012 yz250 fork seals

Recommended Posts

I recently bought a 2012 yz 250. My old one however is having some issues that make me question if I shall fix it or part it out. Bike has a lot of hours on it. It started making a rattling noise that I thought was probably just piston rattle/slap. But when I would stop sometimes I would hear a metal on metal clunk that didn't sound good at all. The sound went away so i continued to ride it. I wanted to sell it but didnt want to dump a bike that was going to break on someone. A few weeks later I rode it again and it would not shift into neutral while i was riding it. Started it again a few days later in neutral and it instantly went into gear as the rear wheel sprayed rocks all over my neighbor's driveway then shut off. Some people have said it is a clutch issue however if it were I think that neutral would still work fine. If anyone good mechanics out there know what the problem could be let me know. And I would also appreciate any opinions on what to do with it like part it out or fix and sell or maybe even fix it and keep it as a dunes bike. My 2012 yz250 is an absolute beast has only had about 3 or 4 tanks ran through it. However my left fork seal already went out. Could be from dirt getting in there.. But I am just wondering if it could be from the suspension bottoming out and if stiffening it up would make a difference and help prevent that. I am 180 lbs. and the suspension is stock . However I should probably turn the adjusting screws all the way in then back them out to make sure it is set correctly. I am the 2nd owner and who knows if the guy before me adjusted that. I know that I am supposed to let the air out before and after every ride. Which I did not do immediately after my last ride. Could forgetting one time cause them to leak. I pulled down the dust seal and cleaned the area best i could and it seemed to stop leaking, but who knows until I actually ride at the track. Fork seals are a pain to do myself. And very expensive to have a shop to do. I think from now on I will make sure to always let the air out, and pull the dust seals down, clean the area and put a little grease above the dust seal. I should also invest in some of the little protectors that help prevent dirt from getting in there and cover the area where the dust seal is..Thank you for your advice guys!

Share this post


Link to post
Share on other sites

For the '99, pull off the clutch cover and have a look at your shifting mechanism. On my '97 there's a series of levers that turn a plate that has springs and stoppers in it that sits in a grooved cup thing. That "plate and cup" assembly regulates how for the shift drum moves per movement of the shift lever. That assembly could be screwed up, preventing the "half click" that gets you into neutral from happening. If that whole assembly checks out, crack the cases and take a look at the shift drum and shifting forks. Also check out the dogs that the forks ride on.

If it's not anything that I've already pointed out, you'll have found the problem anyways by the time you got the cases split. It's also a good time to replace crank bearings, seals, and inspect the crank for out of tolerance movement. (You stated many hours, so I'm assuming that you haven't rebuilt the engine lately). Also, you'll be staring right at your clutch when you remove the case section, so you can inspect that and make sure that it isn't causing any problems.

Sounds like a good candidate for a dunes bike to me, since you already have a much newer bike for racing. Parting out is such a hassle, and passing on a bad bike is bad karma (the previous owner of my '97 yz250 is probably hating life, if karma is real) and nobody needs bad karma.

Share this post


Link to post
Share on other sites

Exactly, I believe in karma so it is a good thing that I did not sell it. My friend tried telling me its not worth fixing it but he doesnt know shi7. It does go into neutral fine when the bike isnt running. But ill tear it apart and check it out. I have never split the cases on a bike sounds a little intimidating but I should be fine if I get the manual. What do you mean  check out the dogs that the fork rides on? Ill see what you mean when I tear it apart i guess..

Share this post


Link to post
Share on other sites

You'll see what the shifting forks ride on when/if you tear it apart. Definitely get a manual, though! Clymer treated me pretty well with rebuilding my '97 250 engine. And consider rebuilding the older engine practice for when the newer one needs work! Splitting the cases isn't that hard at all. My first time doing any sort of engine work involved replacing a "repaired" transmission case half on my yz. Took a couple weekends in a buddies garage and a lot of patience, but I now have a perfectly running engine and piece of mind knowing that everything is good in the hood as far as the lower end of my engine goes.

I haven't heard of not being able to shift into neutral with engine running before.... You'll definitely figure it out once you get into the engine, though. The manual will have guides on how to inspect every little part and assembly that can wear out. It's likely that you won't have to get into the transmission, but it definitely doesn't hurt to split it open and make sure that everything is in spec.

"Nothing ventured, nothing gained" is the outlook you gotta have with your first time doing engine work. My dad actually wants me to tear apart his 2-stroke roto-tiller for him and make it run, now that he sees my dirtbike running again haha.

Share this post


Link to post
Share on other sites

sweet man thanks for the help. I will get a manual and get to work! nothing ventured nothing gained. great words of advice. and your right it is probably still quite similar to the 2012 model i know they didnt change a whole lot! but I will defidently have to get the '99 manual. i already have the 2012 manual. Do you think that fork seal being blown could be a result of my suspension being too soft and bottoming out . I have had to do fork seals like 10 times on the '99 i DO NOT  want it to be like that on the 2012.. the '99 may have had an imperfection on the bottom part that was causing the seals to go out though.

Share this post


Link to post
Share on other sites

Someone else will have to comment on the suspension. The only thing that I've done with that stuff is unbolt my rear shock from the linkage so that I could remove the swing arm and engine :p

Glad to hear that you're gonna try and fix it yourself! Good luck, If I can get basically the same engine down to the bare cases and back together in a functional form, pretty much anyone can haha. The internals of these engines are crazy simple. Just make sure to use the torque wrench for assembly!

Share this post


Link to post
Share on other sites

As for your suspension, I see no way that "excessive bottoming" could cause the seal to blow out. I guess it could, but seems highly unlikely.

 

Typically, it's caused by some foreign object (sand) holding the seal slightly away from the sealing surface which allows it to leak, or some type of damage to the fork tube (scratch) which destroys the sealing surface of the seal.

 

You have to remember that those seals are engineered to barely seal that surface, that way they have as little stiction as possible, so it doesn't take much at all to cause them to leak. Most of the time, you can just clean the sealing surface with a "seal doctor" or similar small, thin piece that you slide underneath the seal and "work" the debris out from underneath it.

Share this post


Link to post
Share on other sites

I am absolutely torn apart right now . my 2012 yz 250 started making a screaching noise. the thing has only 15 hours on it tops . my gear oil was slightly low but i dont think it wud casue this.. it is very loud when in neutral . when it is in gear it is making the noise but not near as loud. i can hear the screach when i even push the kicksarter down. i am freekin out right now just got this bike.then when i was trying to shift from neutral to first it was like halfway in gear half in neutral. i first heard the noise while i was just cruising along in 5th gear it almost seemed like it went away when i was in 4 th gear

Share this post


Link to post
Share on other sites

I am absolutely torn apart right now . my 2012 yz 250 started making a screaching noise. the thing has only 15 hours on it tops . my gear oil was slightly low but i dont think it wud casue this.. it is very loud when in neutral . when it is in gear it is making the noise but not near as loud. i can hear the screach when i even push the kicksarter down. i am freekin out right now just got this bike.then when i was trying to shift from neutral to first it was like halfway in gear half in neutral. i first heard the noise while i was just cruising along in 5th gear it almost seemed like it went away when i was in 4 th gear

Anything come out on your drain plug magnet aside from the normal clutch crap (assuming you have one, if not, get one ASAP)?

Take off the stator cover (left side roundish cover, probably secured by Phillips head screws) and give your crank a tug and wiggle. If a crank bearing went, you should be able to feel it moving and that would explain the screeching noise. If it is a blown bearing, consider yourself VERY lucky. Those things going out could ruin your piston and destroy the cylinder and/or head.

Share this post


Link to post
Share on other sites

Drain plug magnet? i just took the drain plug out and there was no washer.. not sure if there is supposed to be or not there..isnt the drain plug already a magnet? i took off right side already cuz i can tell its something with the kickstarter ( several people have said if you dont have enough oil in there its the kickstarter gear and that is the screach..  but your saying to take off right side and move the part behind there around a little? does that have to be replaced with a gasket? i will check that too i didnt know the crank was right there i dont think ive ever had to take off the left side.. we will see

Share this post


Link to post
Share on other sites

Yeah, search on amazon and find a magnetic drain plug for your bike. It'll catch stuff before it slips up into your trans or other parts and cause damage. Should come stock, but doesn't for whatever reason.

And I saw that other thread just after my last post. Sounds like you have it solved. The check holes are way wrong on the yz bikes. Measure out the correct amount of oil and ignore the check bolt like its your psycho ex girlfriend haha.

You don't have to replace the gasket if it's still in good shape. You can always use RTV instead of a gasket for that one if you don't want to go buy the proper gasket. It's good to check the crank for wiggle once in a while anyways. Takes 5 minutes or less to get at it on the left side. Just grab the flywheel and see if it moves around. If it does move, your crank bearings are shot.

Share this post


Link to post
Share on other sites

ok cool ill still get the gaskets for the right side though power valve and water pump gasket also have to be replaced whenever you take them off correct?

Share this post


Link to post
Share on other sites

including the crankcase and clutch cover gasket .. oh well didnt really need to take all that off.. hope fully the right amount of oil solves the problem it seemed like it was having trouble shifitng but that could have been wrong i was so freeked out about that sound i was even thinking straight it felt like

Share this post


Link to post
Share on other sites

Replacing the right side gaskets is a good idea. The left side doesn't hold any fluids, so it's not a huge deal to use RTV instead of the gasket. As long as it seals out the dirt and sand, you're golden.

Share this post


Link to post
Share on other sites

i just want to fix it now.. the right side gaskets are not damaged at all is it really neccessary to replace them

Share this post


Link to post
Share on other sites

better to be safe then sorry i am so just so anxious to see if the right amount of oil fixes the problem or if its too late and the damage has been done. i havent been riding it much though on low gear oil..


when in neutral though the rear wheel seems to want to move more than usual

Share this post


Link to post
Share on other sites

i put it all back together and started it with it on the stand. in neutral made a clank and went into gear tire started spinning. started it with tire on ground and made a bad screechin/clank sound. before i put it back together gear worked and i cud ride it but wud make a sound just dont want to ride it or start it anymore now that i put it back together  and it still isnt working

Share this post


Link to post
Share on other sites

Damn, that blows dude! This is the 2012 doing this?

I don't know what to tell ya other than tear it all apart and start looking through everything with a fine tooth comb. There isn't much to these engines, so it should be pretty obvious what the problem is once you get it visible.

Share this post


Link to post
Share on other sites

Sorry for the luck I feel your pain although both bikes at once is even worse than my luck. Hang in there you ll get them going again. Please post the results though for both bikes you have some interesting problems. You never know who might have the same problem in the future. Threads like this can really help others trouble shooting.

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  

×