wr 250 oil breather

[steve192]

Hello everybody this is my first post. Great site here and very helpfull.

I hope someone can help me out a bit more. I've a 01 wr250 and the last day i had it out it spat oil out the breather pipe from the head. The bike was running fine and i just stopped it as normal. I'm no bike machanic but i was thinking it was the piston and rings so pulled it apart and it looks ok.

There was quite a lot of oil, it had went up over the shock and back wheel.

A guy said to leave it in and get the piston and barrel checked, but if someone could say it needs a piston it would save me time and i'd just go and buy one.

Do you think this would be the cause?

Thanks Stephen

[Swede73]

Oil out the breather is an indication of blow-by but could also be a result of too much oil(most common). Blow by is what happens when the rings and/or piston is worn out and gases from you combustion chamber blow by the rings. Have you changed the oil recently and accidentally put too much oil in? How many hours are on the piston? If the piston and/or rings are bad, inspect the cylinder really good. If you have the engine apart and post pics of your piston and cylinder we can look at it for you and see if somebody can notice something bad or not

[steve192]

I dont think i put too much oil in. The bike was using a bit of oil the last couple of times out.

I don't know when the piston was last changed cos i have'nt had the bike that long but i'm selling it now after i bought a wr450. I just want to get it fixed now to sell on.

I'll try and get some pics up later.

[steve192]

I got some pictures, i think the pictures make the scores and over all condition worse.

[Swede73]

Can you catch any scrapes or gouges with a fingernail in the cylinder? If not you might be able to get away with a re-hone. Do a search on it because there is a certain way of doing it because of the coating in the cylinder.

[nuity5]

What is condition of the top ring? In the second piston picture it looks suspect however that could be reflections, lighting, etc. The land above the top ring looks like debris has been going through it and I'm assuming this is the intake side in the second pic. Have you had any air cleaner issues in the past - find any dirt in the air box boot, in the entry to the carb, etc.? Clay

[steve192]

I had another look and you can't catch any of the scrapes in the cylinder with a finger nail.

The top ring looks not to bad, i think it just came out like that in the picture.

I always kept the filter clean and oiled. And just checked the boot before the carb and inside of filter and its all clean.

When i took the cylinder off the oil was still in the bike, quite alot of oil spilt out onto the floor! Does the oil usually be right up past the crank?

Is there anyway the engine can have too much oil in it when it shows ok on the dipstick?

Thanks for the replys.

[nuity5]

Definately sounds like too much oil in there. I'm new to the YZ/WR engines in particular but a YZ takes a little over a quart and I'm assuming that a WR is the same. How are you checking oil level? Generally on a dry sump setup you have to crank it up first to get the sump scavenged and everything in the oil tank for checking the level. As engines get older there is a check valve that will start leaking sometimes and some or most of the oil will leak out of the tank into the sump. If you fill the tank up without starting it up first you can overfill the tank. Other than that it would be a pump or screen problem. Pump is pretty easy to access and check, screen isn't. However I would think if you had a screen problem as far as debris plugging it, there would be crap everywhere you could see. Clay

[matt4x4]

looking at it tells you nothing, I'd say put all new rings on that piston, get the cylinder deglazed (run a hone through it REALLY briefly) and you're good to go, but to be sure, take the top ring off and set it in the cylinder and measure your endgap, the manual has a limit for new rings to make sure your cylinder is in spec, but it's also a good way to check the wear on used rings because the endgap grows as the rings wear. Since you got it apart, it's good insurance and you'll know you're good for 50+ hours before the new rings are gone again at which point you'll need to do a piston.

When you put it back together, set your timing to YZ timing, there's threads on how to do it but basically you just advance the intake cam one tooth.

[steve192]

Hi again, i got a local engine builder to look at the piston and cylinder and he said it would be ok with new rings (like you guys said)

So i got the new rings, gaskets and the cylinder and head on and all torqued up with the timing set and the head cover on. Then i decided to turn the engine over. I can turn it over with my hand! surely this can't be right, before i could'nt turn it over with a kick unless the decompression lever was used.

I stopped working on it for today, i'm not sure what to do now!

[nuity5]

Hopefully you just left the plug out:). Simple is good. As has been said on here many times, check the obvious first. Cam timing, valve adjustment, decompressor adjustment, etc. If this turns up nothing, my next step would be to make an air adaptor to put pressurized air into the cylinder. This will give you an audible clue as to where compression is being lost and then you can go after it. I usually make air adaptors out of old plugs if it's something I don't have (I have mostly automotive adaptors). It might be just as easy to pull it back down to look at the rings though. Clay

[Swede73]

Are the rings installed so the gaps aren't lined up? You didn't happen to instal auto decomp cams did you? Like nuity mentioned, check your cam timing and spark plug

[steve192]

Hi i wish it was just the plug left out:) I checked the timing, valve adjustment and the decompressor and its all good.

The rings also look like they have been put in right as per manual.

And i have'nt put the auto decompession cam in.

Its only now i held the cylinder and head pushed together with no gasket up to the light and it looks like something is warped. Its tight on three corners and not quite tight on the other corner.

Looking back now the bike probley did over heat on an enduro, i let my mate use the bike on a few weeks ago. I was on a wr450 i had just bought and it was running really hot due to muddy boggy conditions. I did have the 250 out for a run on the roads after that and it started and ran as normal ,its only when i stopped after 30 mins i noticed the oil had come out the breather pipe.

Im going to go back the machanic and see what he thinks. Looking at the warp i'm pretty sure thats the problem.

If the head is warped is it possible to skim it? i'm guessing not i don't think i'd get away so handy.

Thanks again for the replys and being so helpful.

[nuity5]

If it's a head gasket problem due to warpage I would think you should be able to hear it leaking while you're turning it over and it really should still have some compression. You could put the cylinder and head on something flat and probe with feeler guages. Of course a surface plate is ideal but anything like a piece of glass, piece of granite (countertops), etc. will give you an indication - not the exact amount of warpage but they'll get you close enough to find out where the problem is. I haven't messed with these bikes enough to have ever checked piston - valve clearance but I can't imagine that would be a problem if you are running factory cams. Cam chain tensioner should easily take up the slack in the chain since you will be taking off minimal material. Milling the head shouldn't cause any other problem other than a very slight bump in compression but it seems like that shouldn't be a problem either from what I have read. I'm really impressed with the compression ratio's these bikes can get away with on pump gas. Clay

[Swede73]

Yeah depending on how much they have to take off of the head to resurface it flat again you can run into compression issues or too much taken off and the wrong piston the valves can hit the top of the piston

[longerdeeper]

you mght get away with rubbing your head and cylinder on wet&dry sand paper- about (400grit) paper on a very flat surface glass granite as above ( I hold the edges down with double sided tape). to get it back flat,

-you will see when alll areas are making contact,

-might take 1/2 hr but it will be the way to remove the least amount of material.

[steve192]

I got my brother to leave it in to get skimmed. Although he did'nt say if it would be 100% succesfull or not.

I think there was a bit much for the wet and dry paper.

I should have got a picture for you's to see but never thought.

I'll let you's know how i get on when the head comes back.

Thanks Steve

[steve192]

Hi, i got sorted at last i hope. Got the head skimmed and all built up again and then could'nt find one of the little clips goes on a pipe on the head cover.

I was afraid it had dropped in the engine, i tried my best to find it with a little magnet but nothing showed up, so left it in to get the bottom half split and turns out it was not inside.! But sure better safe than sorry.

So tonight all built up again and she started second kick with what feels like good compression.

Only thing is once it started to get warm it started smoking and got worse the warmer it got. So let it cool down and it was smoke free until it warmed again.

I'm going to go out tomorrow and see if it clears cos i'm hoping its just oil in the exhaust from when i first had problems with the bike.

Thanks again for the help.

[steve192]

Right not so good, took the bike out and after about one minute it felt like it was going to seize, the back wheel started to drag a bit so i stop the engine.

I turned it over with the decompression lever pulled and it felt tight.

I took it apart again fearing the worst and the piston and cylinder looks as good as it did before. I thought the oil rings had been put in wrong and they where ok when taken apart. The oil level was right on the dip stick when warm.

I really don't know what to do now has anyone got any ideas??

[nuity5]

I have read on here these are prone to seizing the cams in the head if the blocks are overtorqued (especially the intake cam I believe). I would pull the cam caps first and look there. Just thought - if you looked at the cylinder you already looked at them most likely. Did you verify oil flow to the head when you cranked it? Clay