excessive oil from exhaust yz250 2000

[yamahootin]

Hey all,
My bike has been blowinga little white smoke and leaving oil on the swingarm for about 6 mnths getting heavier as time goes by. I checked the gear oil and found that 650ml was missing leaving only about 100ml in it. Suspecting the crank seal is shot I have just finished replacing the right crank seal and I rode it in my 30 by 30 foot front yard for about 4 mins in first gear and the bike is now more smokey than ever and is spewing even more oil via the exhaust, even to the point that it "drips" out of the power valve linkage cover aswell. I removed the exhaust pipe to guage how much oil was coming out and started the bike. oil was spitting all over the front tyre.

Q: Is it common for a new crank seal to take time to seat itself or should it have fixed the problem immediately if it was a worn seal that was causing the problem?

Q: Is it common for a crack to appear between the gearbox and the crank case allowing gear oil in to the crank case?

Q: Are there any other ways gear oil could be getting in to the crankcase?



Any advice would be appreciated and thanks for your time,
Cheer's

[MXtras]

Lots of questions here, but I will take a stab.

The new seal should seal immediately. There is not run-in time. From the moment you put it in it should seal like a champ.

If your bottom end bearings are cooked and sloppy, the seal might not have stand a chance at sealing properly.

It is NOT typical for cracks to develop without influence - like a rock or other impact - possibly internal. The cases are pretty robust and don't just crack out of the blue.

Have you had any recent changes in the way your tranny sounds or shifts? It's also possible you have lost a tooth or two on one of the gears and it has popped a hole in the case while it was circulating in the oil - I have seen this happen quite a few times and it was a relatively common problem with Yamis from about 1998-2001. Apparently, they were having heat treating/material issues with their gears and shift forks - I reacall hearing this anyway. Their gears were not tempered correctly and were too brittle (not tough) and their shift forks were weak and would bend easily. I have first hand experience with this problem on three of my own bikes.

There is really only two other places the gear oil could be entering the crank area other than through the seal and that would be between the case halves or past the primary drive gear. To properly repair a leak between the case halves requires splitting the cases - not really a huge job but it can be a challenge if you have never done it before. It can be done without any special tools, and it is not exactly rocket science BUT you can screw things up if you have a heavy hand.

The possibility of leaking past the primary drive gear is there, but it's not a very likely thing to occur. I have never seen it - let's put it that way, but it is a potential entry point. It's been a few years since I have been inside of a 2000 but I think there is a hub behind the gear that the seal runs on on your bike and it is possible this collar has come loose somehow. Like I said - I doubt it, though. Plus you would likely hear or feel abnormal gear noise.

Another consideration is that the bike is just running excessively rich - maybe a loose main jet or a puked out air filter. BUT - you did say the gear oil level was way down, so I am giving that info a lot of weight in this online, sight-unseen diagnosis.

Scott

[yamahootin]

Thanks MXtras, you have been a great help and really know your stuff!

The main jet is tight and the air filter is freshly cleaned and oiled. It seems strange that only after the seal was changed the problem became twice as bad.
I havent noticed any changes in the tranny to mention. I am leaning toward it being gear oil related also but am unsure of how full the tranny oil was when i purchased the bike 7 months ago and cant really guage the rate at which it has lost the gear oil or if it was full to start with.

I have pulled the primary gear and the seal still looks good with springs intact. The spline was dry and looks that the primary gears are sealing sufficiently. I will replace the collar as the one on it has wear grooves and will eliminate that as a possible contributor and see if it makes a difference.

Q:Could a couple of thou wear be enough to make the new seal fail more than the one that was in it? I noticed that the new seal doesn't run in the same grooves as the one it replaced also.

Cheer's

[MXtras]

Originally Posted by yamahootin

...I will replace the collar as the one on it has wear grooves and will eliminate that as a possible contributor and see if it makes a difference.

Q:Could a couple of thou wear be enough to make the new seal fail more than the one that was in it? I noticed that the new seal doesn't run in the same grooves as the one it replaced also.

Cheer's

I think you have found the problem.

A new seal can compensate for "a few thou" but it's tension will be effected and could fail to seal properly. It's a potential issue, so I agree that the potential should be eliminated by replacing it. They are only around $15.

Try these guys for parts - they consistently have the cheapest prices on OEM Yamaha parts:

[Only registered and activated users can see links. ]

(I have NO affiliation with them, just a happy customer)

Also - make sure you drive that seal in straight and not deeper than needed! It's not a bad idea to 'press' it in place using the primary drive gear bolt and a stack of flat washers or a large socket. This way its straight and true.

Check your bottom end for vertical play while you are in there. ANY play (within reason - say more than .008MM (.0003")) and you should think about replacing the bottom end bearings before other things get ruined. Check your manual for the limits - I don't recall their maximum reccomendation.

Scott

[bitshifter]

Yamahootin, I am not sure about the 2000 but some bikes have an oil drain hole in the case between the seal and the crank bearing. Seals for this style have notches around the bearing side of the outer race that need to line up with this drain hole. If the seal is pressed in wrong or to deep it may be covering this hole.

Mxtras, I have a question that I am hoping that you can answer. I have an 89 yz250 that also uses crank oil and I have replaced the seal and the seal surface is new. I suspect that oil is getting past the primary drive gear because I can't see what keeps it out. The collar slides over the crankshaft and up against the inner race of the crank seal. The primary gear sandwiches the collar between the primary gear and the inner race but there doesn't seem to be anything that keeps the oil from passing between the crankshaft and the inner wall of the collar except the area of contact between the inner race and the collar. I was thinking of making a gasket ring to insert between the collar and the inner race. Does this make sense? Can you explain what keeps the oil from following the path I described?
I have been wondering if this is a design flaw corrected on later bikes or if I am just completely nuts.

Thanks

[MXtras]

Originally Posted by bitshifter

.... If the seal is pressed in wrong or to deep it may be covering this hole.

Not sure if this is an issue on this bike, but I don't think so. BUT - the seal should be pressed in no further than flush. THis is where using a stack of washers and the gear bolt will press the seal in flat and straight.

I suggest always finding a way to press in bearings and seals - using a hammer is just not contollable enough. It's a lot easier to screw up the component being installed - especially if it's a bearing. Seals can be easily distorted by an off-center hit.

Originally Posted by bitshifter

.... Mxtras, I have a question that I am hoping that you can answer. ... Can you explain what keeps the oil from following the path I described? Thanks

Nothing. Metal to metal. You can find a small diameter O-ring (diameter of the cord, not the physical ID or OD of the ring) that will fit into the ID chamfer of the collar and place it on the crankshaft after the collar is in place and then install the gear. The idea is to get an O-ring that will create a seal between the collar and the shaft and will be squished a bit when the gear is installed.

Beginning in 2001 (IIRC) they eliminated this collar and the seal now runs directly on the bearing journal of the crank. One less piece to screw with.

A leak in this area is not really that common from what I have experienced, but it is a possible entry point so I mentioned it since the OP was looking for ideas. I usually consider all reasonable options. The most common leak point is the seal and the second most common is the seam of the case halves - especially since Yamis don't use a gasket between the case halves.

I see a lot of people using silicone to seal the case halves. Personally I don't think it's a good idea. Silicone in thin sections doesn't have much strength. I recommend using Permatex Aviation Gasket sealer or OMC Outboard Motor Gasket Sealer to seal the case halves - not silicone. The Permatex and OMC sealers are pretty much the same except the OMC stuff is a bit thinner and has less body, or bulk. I prefer the Permatex stuff - NAPA has it. I am sure there will be a few people that will chime in and claim silicone is fine since the OEM seal is a silicone, but I don't think the aftermarket stuff you can easily get is the same - it handles/feels differently.

What does everyone use? (just out of curiosity)

Make sure you wipe a film of oil on the sealing lips oil of any seal before installation, or use a very thin grease. A small film of sealer on the OD of the seal is OK (NOT in the bore unless it is super thin - it can plow into the bearing!) if the seal has a retainer that keeps it from popping out - the sealer acts as a lubricant until it is set so the seal can slip out if it's not retained before the sealer is set which takes about 1/2 hour.

I hope this helps.

Scott

[yamahootin]

Cheer's guys!

Bitshifter, I can now see the hole you speak of and as long as i seat the seal flush it wont block the hole on the 2000 yz250. Thanks for learnerin me about that hole :-).

Mxtras, I pulled the new seal out as it did go a little skewiff when i hit it in with the "not so" ubeaut tool i made up and there was a nice little puddle of new tranny oil sitting up against the bearing ready to get sucked up.

Ill grab another new seal and press it in as you suggested. Using your washer set up idea i was thinkin on putting the new seal followed by the old seal followed by the large primary gear and press it in using the primary gear bolt and washer. This will drive the bearing half way in and has no option but to go straight in as there is no twist at all in the fit between the spline and gear. Adding the smaller gear to drive it the rest of the way may be a drama though as its a tight fit to get on the spline while tightening so i will add a couple of washers to get it that extra 4mm odd to flush. That should work hey as long as i stop at flush? It can only go about 1mm further before the gear tops out on the spline anyway so i cant get in to too much trouble....maybe

[yamahootin]

P.S. I just realised that once the gear has topped out i can turn it around and repeat the process, which will give me the extra 4mm odd and seat the seal flush due to the gear being off centre and have no need to find extra washers.
Also realised i put a small dint in the seal wall edge while levering the seal out. This created a small raised spot in the seat so the seal wouldnt make contact properly and leaked like a seive . After sanding the high spot the best i could , i guess i will have no choice but to use a little silicone sealant on the OD of the seal before pressing it in.

[MXtras]

Glad to hear you are back in the hunt.

Let us know how it turns out and if this solved your problem!

Scott

[yamahootin]

I wont rest till my butt is back on the ol girl.

I will be sure to share the outcome and maybe someone else will stumble over this thread and learn from my mistakes.

Thanks again fellas!

[MXtras]

Originally Posted by yamahootin

...Also realised i put a small dint in the seal wall edge while levering the seal out. ...., i guess i will have no choice but to use a little silicone sealant on the OD of the seal before pressing it in.

I think you are saying that you gouged the bore when you extracted the old seal - is this right?

Please clarify - you are not re-using the old seal you pulled out, are you? Please tell me no!

Scott

[yamahootin]

No im not going to use the old seal, it was destroyed when i pryed it out and have a new seal and collar on its way.

I was careful not to score the bore with the business end of the screwdriver while removing the seal. What i meant is that when i pryed the old seal out the shaft of the screw driver slid off the wooden pole i was using as a leverage point and dinted the outer edge of the seal recess, the same place where your washers would top out/make contact when you press in a seal. By compressing the alloy it created a raised lip inside the recess on the actual bore/seat, which i had to lightly sand out so the seal can make contact around its whole circumference. The high spot seems to have been removed by wrapping wet and dry sand paper around a cylindrical pole and lightly sanding but i think i will need the sealant just to be sure as i dont have the tools to make sure that the ID of the seal bore are perfectly round to create a perfect seal.

Q:Will i have much trouble removing the seal later on if i use a light smear of silicone sealant on the OD of the seal before pressing it in? If so should i very very lightly smear transmission fluid on the bore so the silicone only adheres to the seal surface to make it easier to remove later...but still fills any low spots?

Cheer's

[yamahootin]

Mxtras, I picked up my new seal today and smeared a fine film of oil on the ID of the seal bore and lightly wiped it away leaving the lightest hint of oil so the silicone would have a weak spot the break when it comes to take it out later. I pressed the new seal in using the old seal followed by the large primary gear then washer and bolt. I tightened the primary bolt and the seal slid half way in and then i turned the gear around and tightened the bolt until it topped out and began to spin the crank. This left the seal sitting perfectly flush with the outer edge of the seal
I filled the v-shape channel that is formed where the chamfer on the edge of the oil seal and the edge of the aluminium recess meet with silicone so there is no way oil is getting past the OD of this seal! maybe a bit extreme but i really need to eliminate this as a problem area.
Im hoping that when the new collar arrives it will put an end to this issue and spare me the torment of a new hunt to the sparce nether regions where the left case meets the right
Thanks for the idea to use the primary bolt to press the seal in and all your support, your a champion!

[MXtras]

Excellent!

I was fortunate to have a father at an early age that taught me a lot about how to mess with large, precision mechanisms and my career allows me to refine my knowledge and skills daily. I have no issue passing on what I have learned even though a lot of people think I come across as an egotistical know-it-all. Oh well.

I am glad I could help. That's what this forum should be all about!!!

Scott

[yamahootin]

It takes a wise mind to interpret and receive the constructive content from a lesson.

Those that dwell on the method of delivery are destined for an ardous path.

Keep up the good work Scott

[yamahootin]

Scott (Mxtras),
After replacing the crank seal and primary collar it Seems this wasnt the whole problem and it is still leaking a heap of oil and blowing white smoke. With the crank seal eliminated as a possible contributor would leave a possible leak between the tranny and crank case as you mentioned.

Im thinking that the reason why it is now worse than before i pulled it apart is because it originally had a very low oil level with only 100ml left in the tranny. Maybe the leak is in a higher point of the case, which is now flooded by having 750ml of oil in the tranny and a higher oil level allowing an increased flow into the crank case?

Would my next step be to pull out the tranny gears and inspect it for missing teeth and punctures?

Also out of interest, what effect would running a bike with an overfilled tranny have on an engine? Ex: Would it build pressure when it heats up and be forced through the weakest point?

Cheer's

[MXtras]

Well - this is tough to diagnose internet style. Five seconds of seeing, smelling, feeling and tasting would likely develop a better diagnosis.

I notice you say white smoke? This could be coolant - like from a blown base or head gasket. A pressure test of the cooling system is in order. This would not explain the low transmission fluid level, though unless you have two problems....

As far as your other questions - an overfilled tranny will not really cause any of the issues you are describing. There are not many detrimental effects of an over full transmission that I am aware of except for maybe some discharge from the transmission vent tube and a lot of clutch drag. The tranny and the crank are in seperate chambers completely and the tranny is vented to atmosphere so pressure build is typically not an issue - unless the vent tube is plugged. I am not advocating overfilling the transmission.

I would investigate the cooling system. If this is good, then it might be in your best interest to split the cases and search for an internal cause.

Scott

[yamahootin]

Well it looks like there is only way ill be stopping this oil spewing from my exhaust and hope to catch you all in my next "HELP!" thread while splitting the cases.
Scott, Ill replace the base and head gaskets to eliminate coolant as a contributor to the white smoke after splitting the cases.

Thanks for all your help in this thread fellas.

Cheer's

Scott

[yamahootin]

Back again fellas, After filling the tranny with 650ml and riding the bike for a total of 8 hrs it managed to chew through 200ml of tranny oil and my worst fear is realised.

Looks like the cases are coming apart and i bet that you hit the nail on the head mxtras due to the probs i have selecting gears.

If this is the case can a puncture in the crankcase be welded up being that the cases are cast alloy? If so is welding recommended?

Thanks,

[MXtras]

Yes - it can be welded. The cases are actually very good material but they do contain a lot of silicone, so tell your welder to keep the weld hot and short. Soaking with heat will draw the silicone to the surface.

Scott