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A long list of questions need answering

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Hey guys I have a 04 yz250f and I've been having tons of problems lately.

I have a long list of questions, so hold on!

First off, it's running very lean and overheats quickly, so I ordered a FMF jet kit (I ordered one before and lost it last winter) that should solve that problem.

Its burning oil (it has been for a while) so I ordered new piston rings cam chain, valve seals and springs. Should I replace valves too? Ive had the bike over a year an it never needed re-shimming. I will check clearance later.

Next off, once it overheats, it stops running and will not start.

And this is my mystery; when I check the oil while bike is cool, it overflows with clean oil like it has too much, then when I ride and check it, it barely had any and it looks TAN-WHITE! When hot, white oil drips from the heads breather tube. I'm running yamalube 10w-40, should I use a full-synthetic?

It runs low on coolant too. It may be from it boiling over, or it could be leaking into the oil.

Here are my main questions:

1. Should I replace my valves while Im in there?

2. When replacing valves, do I have to take my head to get the valve seats cut?

3. When doing the head rebuild, what else should I do?

4. What is causing it not to start when hot?

5. If the coolant IS leaking into the oil, where the hell is it coming from??

6. Could anything else be causing the oil to turn white?

7. Is there something Im just not seeing?

I know it's a lot to ask, but you guys have always had perfect answers. Thank you in advance!

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Will replacing the head gasket solve my problem with the oil burning also?

No that is probably due to a worn oil control ring and/or valve seals.

Edited by alligatorman

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If you have milky white oil then it could be-

Water pump seals (check for coolant coming out from under the water pump drain hole).

Head gasket.

The reason it could have done this is that the jetting was too lean, the timing was out causing it to overheat (it would have ran poorly and backfired a little). or the valves need shimming. If you have shimmed once, it is time to buy the valves as replacing them will be not ''too far down the track'',

If you are blowing smoke when the bike is cold but decreases when warm it suggests that the valve stem seals are worn. If you continue to blow smoke the oil control ring is not sealing. This can be because the oil control ring is worn or incorrectly fitted or the cylinder is out of round.

Make sure your jetting, timing, valves are all spot on before riding!

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If you have milky white oil then it could be-

Water pump seals (check for coolant coming out from under the water pump drain hole).

Head gasket.

The reason it could have done this is that the jetting was too lean, the timing was out causing it to overheat (it would have ran poorly and backfired a little). or the valves need shimming. If you have shimmed once, it is time to buy the valves as replacing them will be not ''too far down the track'',

If you are blowing smoke when the bike is cold but decreases when warm it suggests that the valve stem seals are worn. If you continue to blow smoke the oil control ring is not sealing. This can be because the oil control ring is worn or incorrectly fitted or the cylinder is out of round.

Make sure your jetting, timing, valves are all spot on before riding!

thanks for the info, a lot of inspection as well as head gasket and ring replacement is on its way

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Hey guys I have a 04 yz250f and I've been having tons of problems lately.

I have a long list of questions, so hold on!

First off, it's running very lean and overheats quickly, so I ordered a FMF jet kit (I ordered one before and lost it last winter) that should solve that problem.

Its burning oil (it has been for a while) so I ordered new piston rings cam chain, valve seals and springs. Should I replace valves too? Ive had the bike over a year an it never needed re-shimming. I will check clearance later.

Next off, once it overheats, it stops running and will not start.

And this is my mystery; when I check the oil while bike is cool, it overflows with clean oil like it has too much, then when I ride and check it, it barely had any and it looks TAN-WHITE! When hot, white oil drips from the heads breather tube. I'm running yamalube 10w-40, should I use a full-synthetic?

It runs low on coolant too. It may be from it boiling over, or it could be leaking into the oil.

Here are my main questions:

1. Should I replace my valves while Im in there?

2. When replacing valves, do I have to take my head to get the valve seats cut?

3. When doing the head rebuild, what else should I do?

4. What is causing it not to start when hot?

5. If the coolant IS leaking into the oil, where the hell is it coming from??

6. Could anything else be causing the oil to turn white?

7. Is there something Im just not seeing?

I know it's a lot to ask, but you guys have always had perfect answers. Thank you in advance!

#1 Valves are a judgement call. If you've reshimmed you may want to pull the trigger on a new set.

#2 I don't get the seats cut but I do make sure to lap the valve in.. a minute or two with coarse then same with fine.

#3 Depends on $$

#4 Not sure could be a lot of things

#5 Its usually coming from the head gasket. Sometimes it is normal to have a little milky oil flow from the tube b/c it will build condesation inside and when a little oil passes thru the tube it gives you the "oh snaps my head gaskets blown" milky oil drip.

#6 Read #5 but also if you're losing coolant and have no noticable drips then change the oil and that'll tell you.

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#1 Valves are a judgement call. If you've reshimmed you may want to pull the trigger on a new set.

#2 I don't get the seats cut but I do make sure to lap the valve in.. a minute or two with coarse then same with fine.

#3 Depends on $$

#4 Not sure could be a lot of things

#5 Its usually coming from the head gasket. Sometimes it is normal to have a little milky oil flow from the tube b/c it will build condesation inside and when a little oil passes thru the tube it gives you the "oh snaps my head gaskets blown" milky oil drip.

#6 Read #5 but also if you're losing coolant and have no noticable drips then change the oil and that'll tell you.

Not to start an argument but..

(N2.) The 04 YZ250f has Titanium valves. You are not supposed to lap the valve or you wear the protective coating off so the seat must be cut.

(N5.) It can also mix with the oil and leak from the water pump. See post above. Then the head gasket is the next venerable.

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I've heard about all the titanium coating deal but the manual says to lap so I lap. Nothing crazy just real light pressure enough to see the seating ring is smooth. Idk it works for me.

And yes the head gasket issue can go both ways and either issue isn't necessarily a for sure tale that that's the issue

Edited by squintz

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So, what is the update on this post? I have the same thing going on with my 2003 WR450F after installing a new piston and ring set along with gaskets. I torqued the head bolts to spec of course but did not recheck them after doing some riding. I noticed oil coming out of the head gasket area at the front of the motor. I was not that far down on the dipstick too bad but  I added oil instantly. I rode about a total of around 30 miles after first notice of this but I did keep a keen eye on the oil level. When I did get an opportunity to further check into the situation, I noticed that I too had lost all coolant from the radiator. Not a drop in there at all. There was no leak at the water pump weep hole so I knew that it was a situation like yours where it is leaking into the motor. I never got a chance to notice anything out of the ordinary from the exhaust like you did but I noticed my fresh clean oil has turned black due to the motor getting hot from the lack of coolant and therefore heating the heck out of the oil. The oil was not milky at all like I was expecting it to be but I figured it had all evaporated from the motor. The bike ran strong and I was lucky to have added oil when I noticed the leak. I completely removed the motor from the bike a couple weeks ago and cleaned the oil from the exterior of the motor. I have not touched the motor yet since cleaning it. 

Please, anyone, answer this....

1. Is it possible to reuse the same new upper/lower gaskets that I just put in but put a tiny bit of Permatex high temp red on them this time? Any thoughts on this?

2. Has anybody actually had to recheck the torque specs after doing a piston/rings/gaskets rebuild to find out that they went out of spec after the initial break-in ride? Do they often need to be rechecked due to the heat cycles after break-in?

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So, what is the update on this post? I have the same thing going on with my 2003 WR450F after installing a new piston and ring set along with gaskets. I torqued the head bolts to spec of course but did not recheck them after doing some riding. I noticed oil coming out of the head gasket area at the front of the motor. I was not that far down on the dipstick too bad but I added oil instantly. I rode about a total of around 30 miles after first notice of this but I did keep a keen eye on the oil level. When I did get an opportunity to further check into the situation, I noticed that I too had lost all coolant from the radiator. Not a drop in there at all. There was no leak at the water pump weep hole so I knew that it was a situation like yours where it is leaking into the motor. I never got a chance to notice anything out of the ordinary from the exhaust like you did but I noticed my fresh clean oil has turned black due to the motor getting hot from the lack of coolant and therefore heating the heck out of the oil. The oil was not milky at all like I was expecting it to be but I figured it had all evaporated from the motor. The bike ran strong and I was lucky to have added oil when I noticed the leak. I completely removed the motor from the bike a couple weeks ago and cleaned the oil from the exterior of the motor. I have not touched the motor yet since cleaning it.

Please, anyone, answer this....

1. Is it possible to reuse the same new upper/lower gaskets that I just put in but put a tiny bit of Permatex high temp red on them this time? Any thoughts on this?

2. Has anybody actually had to recheck the torque specs after doing a piston/rings/gaskets rebuild to find out that they went out of spec after the initial break-in ride? Do they often need to be rechecked due to the heat cycles after break-in?

I finished my bike a couple days ago and I believe my problem is gone. I addressed everything (besides valves) that needed to be done and its running perfectly. I initially thought more coolant was getting into the oil when I ran it for the first time but I'm pretty sure it was coolant that was sitting in my engine from before. So I'll have to ride it and watch very closely, then get another update on here.

As far as your problems, it doesn't sound very much like my problem. It sounds like you have an external coolant leak, not internal. Its a lot harder to test that theory without the motor on the bike but I'd go rent a radiator compression check tool and go from there. As for the gaskets, get new ones. It doesn't seem like your in a hurry so you might as well spend the $30 now instead of later.

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