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Every time I ride it shows oil dripping out of the breather tube and usually is below sight glass level after 30 miles of riding and have to fill it back up to a safe level. Also it seems to be smoking a lot even after its warmed up. The premix i'm running is 50:1 golden spectro oil and have been running it since I bought it last spring. I'm starting to think there's a seal leaking and pushing the gear oil (10w-40 motorcycle oil) out of the case and is also sucking it in to the engine as well and burning it? I've also tried heavier weight motorcycle gear oils like 85w and they haven't helped.

You might try doing a leak down test to see if the seals hold pressure.

Kind of involved I know, but if this shows leakage there's no guesswork about your crank seals needing replacement.

Hows the bike run generally, and is there any unusual spooge or smoke?

pumpguy wrote:You might try doing a leak down test to see if the seals hold pressure.

Kind of involved I know, but if this shows leakage there's no guesswork about your crank seals needing replacement.

Hows the bike run generally, and is there any unusual spooge or smoke?

When you mean leak down test are you talking as I would do a compression test as well? The bike runs great, but it smokes a lot even when its warmed up. Not much spooge comes out that I can see, just a little bit of oil around the tip of the pipe. Also its not losing coolant, burning it or getting into the crankcase.

You can't have both things happening from a bad crank seal. When the seals start leaking you will either run lean due to sucking air (stator side), or you will have excessive smoke and plug fouling, and loose trans fluid due to it being sucked into the clutch side crank seal. But it shouldn't push it out the vent too, that just doesn't make sense. If I fill my trans up all the way in the sight glass, it will blow out the vent. I keep it under the half way point in the window and don't have an issue. And 'smokes a lot' is kinda subjective. It's a 2 stroke...it's going to smoke. And if it's not blowing it out the tail pipe, I don't think you are sucking it out of the transmission.

david wrote:You can't have both things happening from a bad crank seal. When the seals start leaking you will either run lean due to sucking air (stator side), or you will have excessive smoke and plug fouling, and loose trans fluid due to it being sucked into the clutch side crank seal. But it shouldn't push it out the vent too, that just doesn't make sense. If I fill my trans up all the way in the sight glass, it will blow out the vent. I keep it under the half way point in the window and don't have an issue. And 'smokes a lot' is kinda subjective. It's a 2 stroke...it's going to smoke. And if it's not blowing it out the tail pipe, I don't think you are sucking it out of the transmission.

It hasn't fouled a plug once, but it just seems like a lot of smoke for running 50:1. It might be jetted high because it does get pretty crappy mileage. I've been around enough two strokes and mine sure as hell is blowing a lot of smoke compared to others two smokers that I ride with. I usually don't fill the crank case with more then 3/4 way up on the sight glass. Even when I ride the bike around the block and stop back at the house its dripping oil from the vent. A couple days ago I put the vent hose facing up and it still spit out some gear oil. Last night I got a longer hose and its running from the motor all the way up to the back of the seat and back down by the brake lever. About to take it out for a ride and I'm hopping gravity will work and keep that oil from spitting out.

How about running it up to the airbox like stock??

No, a leak down test is not like a compression check. A leak down involves blocking off the intake and exhaust while applying pressure to the system to watch for a drop in psi over time. It's also a good idea to do the same while pulling a vacuum. Keep the numbers low (6 psi or so) to make sure you don't damage or blow any seals). Every avenue of escape (spark plug, kips cover, intake, exhaust port, etc) must be sealed and if your psi drops, you need to find the leak. Soapy water works good. That will let you know what condition your engine is in.

G22inSC wrote:No, a leak down test is not like a compression check. A leak down involves blocking off the intake and exhaust while applying pressure to the system to watch for a drop in psi over time. It's also a good idea to do the same while pulling a vacuum. Keep the numbers low (6 psi or so) to make sure you don't damage or blow any seals). Every avenue of escape (spark plug, kips cover, intake, exhaust port, etc) must be sealed and if your psi drops, you need to find the leak. Soapy water works good. That will let you know what condition your engine is in.

Well... I think I blew part of the gasket on the bottom end of the engine and the kips valve shaft on the right side of the engine. Its leaking tranny oil and i think its due to what I did on facing vent tranny hose up. Quote below on what I did. Had a blast riding central oregon, but my bike was bleeding by the end of the day.


"A couple days ago I put the vent hose facing up and it still spit out some gear oil. Last night I got a longer hose and its running from the motor all the way up to the back of the seat and back down by the brake lever. About to take it out for a ride and I'm hopping gravity will work and keep that oil from spitting out."

skycruiser100 wrote:Its leaking tranny oil and i think its due to what I did on facing vent tranny hose up.

Re-routing the vent line did not cause that problem.

I would bet at the very least your clutch side crank seal is leaking.

Tedh98 wrote:

skycruiser100 wrote:Its leaking tranny oil and i think its due to what I did on facing vent tranny hose up.

Re-routing the vent line did not cause that problem.

I would bet at the very least your clutch side crank seal is leaking.

And that would cause the bottom end of the cylinder to start leaking? I put a clear line on tranny vent so I can see if there was oil rising up. When I was riding I would take a look at it and could see oil rising and air bubbles from the pressure in the case building up. Once in awhile the oil would spit out of the vent. Its kind of coincidence that this all happen after re-routing the vent tube up.

It was happening when the line was routed down.

The stock routing is vertical up to the airbox. That much pressure in the transmission isnt normal.

david wrote:You can't have both things happening from a bad crank seal. When the seals start leaking you will either run lean due to sucking air (stator side), or you will have excessive smoke and plug fouling, and loose trans fluid due to it being sucked into the clutch side crank seal. But it shouldn't push it out the vent too, that just doesn't make sense. If I fill my trans up all the way in the sight glass, it will blow out the vent. I keep it under the half way point in the window and don't have an issue. And 'smokes a lot' is kinda subjective. It's a 2 stroke...it's going to smoke. And if it's not blowing it out the tail pipe, I don't think you are sucking it out of the transmission.

Let's think about what is happening in the bottom end of a 2 stroke under operation. As the piston is rising, negative pressure in the bottom end is pulling fuel mix in through the reeds into the crankcase, right? That's when the RH crank seal would be leaking trans fluid into the crankcase. Now take the opposite, as the piston is dropping, it is creating pressure in the bottom end which will eventually force the compressed air / fuel mix into the combustion chamber up top. While we have positive pressure in the crank case, that same leaking seal will be leaking the compressed fuel/air mix out into the trans. Generally failed crank seals don't leak in only one direction.

You're completely right...
But about the oil spill through the vent, i have noticed that you have to have the right amount of oil in the tranny ( 750 ml i think) or it will blow it out...

A friend had a 1997 KDX220R. He overfilled it and it blew out the vent. When he lowered it to the middle of the glass it stopped. Make sure you have that going before checking further, but a vacuum / pressure test will also confirm. Read, read, read on how to do it before getting started.