Case of the missing gear oil

[honxl]

I bought an 05 kdx 200 a month ago or so and have bought a crap load of hours on it. I have swapped the gear oil (honda HP) about three times now and its always pretty clean and no metal. However after everyday of riding I have to top off the gear oil ~20-50ml. There are no leaks and my compression is 145 (local dealer said 90-150 is acceptable) which would tell me my rings arent worn out and oil getting passed.

Is this a KDX problem? Or just mine? and if so, what should I check???
Appreciated the help

[MXOldtimer]

Ring compression has nothing to do with the tranny oil loss. The tranny oil is separate from he combustion chamber/crankcase.

If your sure you have no visible leaks (exterior) they need to do a leak down test. You might have a leak between the tranny & crankcase. If so your burning the tranny oil.

[canyncarvr]

Re: 'There are no leaks...'

One more vote for what he said....

Re: '...my rings arent worn out and oil getting passed.'

MXOldtimer answered this, too. Take the time to understand what he said about it. Not only is the transmission oil separate from the crankcase, but the crank has nothing to do with being oiled from transmission oil, neither! That's one reason why your fuel is a gas/oil mix.

What do you understand the differeneces to be between 4-stroke and 2-stroke engines? Owning a 2-stroke, it would be beneficial to gain that understanding.

Do you have any transmission oil in your airbox? There is a drain on the bottom of your airbox (that is supposed to have a one-way vent on it). Is there oil 'leaking' from that drain?

I wouldn't have thought this a possibility...but rode with a KDXer a couple weeks back that had a considerable amount of transmission oil coming out of that drain....happened every time the bike got topsy-turvy. I've never seen oil come out of my airbox like that..and that sure ain't 'cuz my bike is never upside down!! There is a transmission vent tube on the RH side of the bike just behind the kick lever. Turn the bike upside down, and oil WILL come out of that vent.

So..considering there to be no leaks visible..if the oil is NOT dumping into the airbox, you DO most likely have a crank seal leak on the RH side.

[OLHILLBILLY]

One last place to look for a leak. Do you have any oil coming out the weep hole under the water pump housing? If so, the oil seal on the water pump drive shaft is leaking. Long shot, but it's possible.

[tcat992]

Another spot is the output shaft, behind the front sprocket. If its not leaking badly its hard to tell its leaking because it runs to the sprocket and chain, and ends up looking like chain lube(to the untrained eye).

[threestroke]

The one way valve under the airbox is functional, but there is no oil in the airbox. There is nothing coming out of the weep hole. I will check the output shaft first, but I think I need to do the leak down test. How is the crankcase and tranny separated? Is it seals or gaskets? Is there any way to replace these besides splitting cases?

Appreciate the help guys. I rode a goat trail with three 450's yesterday and was the fastest hands down in the tight sections and held my own on climbs. I love this KDX. I never have liked my dirtbike so much before. cheers

[canyncarvr]

Check out some basic 2-stroke theory on the web..that will answer a lot of questions.

Kind'a like THIS!

How are they separated?

Seals..at the crank bearings. More correctly the RH seal. The LH seal doesn't keep out transmission oil/fluid. It keeps out air, keeps IN air/fuel mix.

Without splitting?

No.

[danfree]

I have this Jeff Fredette video with KDX helpful hints on set up and such. He mentioned a problem with the case casting right behind the stator ass'y that apparently leaks on some bikes. He even goes into a JB weld fix he uses whether it is leaking or nor. I don't know if it is specific to certain models or not (i.e. E model vs H model). The point is that, in his demonstration, it isn't a shaft seal. It is a weakness in the case. Though it may not be your problem. But it may be a simple matter to just pull the cover and have a look-see.

[Colorado Mike]

It's seperated by the case casting, with thin sealant between the two halves. There is no way to replace that sealant without splitting the cases. It's not usually the problem though. By far, the most common way tranny oil gets into the crankcase is by a bad crank seal on the clutch side, like CC said. The only other way is if the crankcase is cracked or wasn't sealed/assembled properly.

[KarlP]

I gotta ask, just because I have been known to misdiagnose problems and go far down the wrong road.

How are you measuring an oil loss of 20 to 50 ml in the transmission?
Does it seem to be smoking excessively?
Does the exhaust smell like burning transmission oil?

If you put a full quart in the tranny it wil bring the level well above the top of the sight glass. How long do you ride before the oil level starts to appear in the sight glass? How much further can you go before it gets near to the bottom of the sight glass? there is a lot of oil between those two points.
If it is leaking I think you'd notice. If it is burning I think those 450's would have told you so.

I was riding with a buddy a couple of years ago. He was on a KX250 and complained his bike wasn't shifting well. By the end of the ride it wouldn't shift at all unless the motor was off. We took a look and he had practically NO tranny fluid. He said "Heck, I changed it a couple of years ago. I wonder where it went?"
Put a quart in and he was good to go.

[threestroke]

I know I am losing 20ml to 50ml of gear oil because I keep track of what I am adding in. I am currently running maxima pre mix at 40 to 1 (which im switching to AMSOIL) and it does not smoke too much, just first at start or when the bike and I go down. The I have not noticed that the exhaust smells like gear oil, but I will take a closer more directed sniff.

I always start the ride with gear oil in the upper level of the sight glass and can ride most all day. If I have to come back to the truck to fill up I will top off gear oil again. The tranny operates and shifts smoothly at all times.

That fredette video is of interest to me......But it sounds like I have a RH seal going on the crank. When I get back home, I will pull my cover and inspect. How do you preform a leak down test on a two stroke?

Thanks for the help and the links guys.

[canyncarvr]

Re: 'I know I am losing 20ml to 50ml of gear oil because I keep track of what I am adding in.'



You do realize that does not answer the question...right? Honestly..at this point I don't know if this is The State of Obtuse...or you're a troll.

Re: 'How do you preform a leak down test on a two stroke?'

Honestly? Having presumed a compression test to have proved your rings to be in good shape...and therefore not passing/using/burning oil, I'm quite sure such a test is well beyond your ability and likely capability.

Basically, having blocked off the intake and exhaust you pressurize the crankcase with a two gauge set-up. One gauge reads the pressure applied, the other reads the pressure in the crankcase. 100psi applied, 97psi in the crankcase is a 3psi loss..3%.

You can make one...you can buy one:



A write up on the MotionPro product HERE!

I found the above information using Google. That will work for you too, I'll bet!

Uh....I used 100psi as an easy math example. No way you're going to pump 100psi into a 2-stroke crankcase. I guess 10psi would'a worked just as well, 'eh?

[Colorado Mike]

I don't think you want to put that much pressure in a 2 stroke crankcase, but I could be wrong. I rigged up a 2 stroke leak down test kit out of plumbing and air tool parts available at home centers and Harbor freight. It consisted of a piece of PVC that I turned to the proper diameter to fit the carb boot, with an end cap glued on. this I threaded to accept a NPT tee that I mounted a cheap 30lb pressure guage and a schrader valve to. Then I sealed off the exhaust opening with another end cap, round side "in" with a hunk of inner tube over it to seal. I used a big woodworking clamp to hold it in place.

I then pressurized the cylinder to about 15 PSI, and from my reading was told this should hold close to that for 6 minutes. I don't know why it's not 7, or even 5 (unlest thou proceedeth to 6) but I read 6. Anyway, it held forever (well, I got bored after 20 minutes, seemed like forever).

I know car leak-down tests use much higher pressures to test the valve seating. Since the crank seals on the yamaha I was working on go in from outside the case, I would be concerned 100 psi would move them. But, I don't know what kind of pressures those seals see in normal operation. I think it is much lower than that though.

<edit> I dunno what kinda time warp I fell into. I read CC's post without seeing any picture of the kit or the disclaimer on the pressure. Sorry.

[canyncarvr]

Re: 'I don't think you want to put that much pressure in a 2 stroke crankcase..'

Me neither..which is why I said that.

We are posts passing in the night.....:sigh:

Not to worry. Nothing was missed. I posted my smarmy response first..then went looking for information, edited it later. Edit turned into a problem (sticky keys turned on and I didn't notice it..no key then worked the way it was supposed to..took a few minutes to get it sorted out).

What you read..and responded to..was the half fast and not completed post.

Why did I say any of that? It would be MUCH better that CM think he was lost in space....it's not like he's called ME stoopid any time recently..



..which I was...but that's not the point!!!

<disclaimer> I don't own a leakdown tester, have never used one. I don't see two gauges in the MotionPro tool. I may be wrong about that part. Don't think so, but I'm not going to bother proving or disproving it. The idea remains the same.

[Colorado Mike]

I never said you were stoopit. I said you didn't remember your enlightenment. Thanks for explaining, I'll stop researching Alzheimer's medication now.

[canyncarvr]

I'll stop researching Alzheimer's medication now.

I don't know about that!. Let's not be HASTY!

(stoopit? No, you didn't. That was merely poetic license on my part..........).

Now....where's MY Aricept....I'd take it if I could FIND it!!!

[KarlP]

Back to original guy, who started out as 'honxl' and turned into 'threestroke' - I don't think you have a problem, at least not yet. I'd keep riding it until you started doing some serious mosquito control.
I have never made things better by taking stuff apart that was working O.K.

[MXOldtimer]

Before I bought a leak down tester I'd call the local shop and ask what they'd charge. More than 20 bux I'd then do what Colo Mike did and make one from goodies at my local ACE hardware store.

[IdahoCharley]

FWIW - I am with CC. I would not use more than 10 psig on a 2 stroke engine leak down test. Don't want to push your cranks's seal lip out an create a problem you did not have. IMO it it holds within a couple of psig of your 'set pressure' for 5 minutes you should be go to go as far as the leak down test goes. If it is leaking pass the crank seal you should feel it at the transmission vent tube. (Maybe just plug the tube with your thumb and see if the pressure loss slows significantly. )

I seem to recall it being about 750 ml to the middle of the sight glass and about 800 ml to the top of the sight glass. (I could be wrong maybe it is 700 to the center of the sight glass) Seems than after one adds oil 3 or 4 times to bring it back up to a predetermined level and doesn't have an apparent leak - the chances are - the RH seal is on it way out.

[MXOldtimer]

I have never made things better by taking stuff apart that was working O.K.

"Tim the tool man" would super glue your crescent wrench wheel, grease your hammer handle and spit in you measly lil under stuffed tool chest for talk'n like that.

Real men disassemble........................ then ask questions.

Owwwwwwwww Owwwwww Awwwwwwww Awwwwwhhhhhhhh OWWWWWWWWWW!!!!!!