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Bike is a 1999 Suzuki RM125.  I had the crankshaft rebuilt, so during the install I had put in new crank bearings, new crank seals, new case gasket, new reeds, and a new top end.  I also cleaned the carb and put in the recommended jets for my exhaust and elevation/temperature.  I run 32:1 fuel mix.  I also put in a new primary gear, which is what contacts the oil seal.  I put axle grease into the seal before inserting the primary gear.  The bike smokes more than it should, and I'm pretty sure the cause is that transmission oil is leaking into the crankshaft area and eventually getting into the cylinder.  I would top off the oil and check the level with the little bolt on the side of the clutch cover.  After a while of riding I would take the bolt out and I would have to tip the bike quite a bit for anything to come out.  I don't understand why it could leak.  I also topped off the coolant, and the level stayed the same, so that's not leaking.  Do you think its still getting in through the seal?  If not, where could it get in from?  There was quite a discussion as to the orientation of the seal itself here, but since that post I have installed a new seal with spring side out (which is different than most bikes, but I think that's what the manual says).

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Hopefully, it's not a leak into the crankcase at the center case gasket. Before tearing down your engine, you can try this to confirm oil usage; Fill oil to the correct level. Now drain that oil as completely as possible that you have in it now and measure how much was drained. Re- fill the gearbox with the recommended amount of oil, but use a measuring cup to determine how much you put in. Ride like you normally would. Now drain the oil again and measure how much oil drained. You can now determine how much oil you're actually using while riding. If still unsure, you can repeat this process a 2nd time.

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Thanks 76xtdrvr,

Well, I took the oil fill cap and actually was able to see using a flashlight what the oil seal looked like.  I will try and post a picture later, but it didn't look like it was sealing the way it should.  I was very gentle when installing it and tapped it in gently with a large socket.  I tapped on the socket gently until it made contact all around with the case material, so the seal was nice and flush with the case.  This was before the crankshaft was even installed.  Thankfully the primary gear comes out providing more room to work with.  I hate to have to remove this seal, which is brand new and replace it to have the same thing happen again.  I will tear into it soon and get a better understanding of what happened.  Maybe I can just tap the seal back into place, but from what I've seen it looks as if its still in the right position, but the spring around the lip might not be seated properly.  Anyway, will get a pic out soon.

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You could always try a leak down test if all else fails.

When you say you had the crankshaft rebuilt, what was done and who did it?

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I shipped it off to some place that does that does crank rebuilds and other bike engine machining.  I've sent my 1997 CR125R there too and its been great.  Basically what I mean by rebuilding the crank is separate the two halves and install a new rod kit, as well as balancing and inspection.  Is there a way to do a leak down test without special equipment?  I mean could I rig something together that would work?  

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You can Google search "2 stroke leak down test" for lots of info on it.  

Your 2nd post said the seal was installed in the case before the crank was installed. It's possible you nicked the i.d. of the seal during assembly. 

How does your sparkplug look? With a lot of gearbox oil consumption you s/b fouling plugs. 

At 32:1 you will be getting a lot of smoke without any seal leakage.

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Just saw the post in your other thread, apologies for not being on here in a while. Figured I'd just post this here. Here is the procedure for installing the crank seals according to my service manual:

1. Pry out old seal, protect case from damage. When prying, do not allow the end of the tool to touch the seal bore or snag the oil hole in the bore. Scratches in the bore will cause leakage and heavy-handed prying can break the casting.

2. Clean the oil seal bore. Pass a narrow object through the oil hoe and leave it there until the new seal is installed.

3. Pack grease in to the lip of the new seal.

4. Start the seal into the bore, with the closed side of the seal facing out. The seal must be square to the bore.

5. Carefully drive the seal. The seal must be installed so it is slightly above the top edge of the bore. Do not drive the seal flush with the bore. Installing the seal too deep can block the bearing oil hole, causing bearing failure.

6. Move the object placed in the oil hole and verify that the hole is uncovered. Remove the object from the hole.

This is all it says, so I assume the procedure is the same for both crank seals.

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On ‎7‎/‎23‎/‎2017 at 4:26 PM, criggs88 said:

Just saw the post in your other thread, apologies for not being on here in a while. Figured I'd just post this here. Here is the procedure for installing the crank seals according to my service manual:

1. Pry out old seal, protect case from damage. When prying, do not allow the end of the tool to touch the seal bore or snag the oil hole in the bore. Scratches in the bore will cause leakage and heavy-handed prying can break the casting.

2. Clean the oil seal bore. Pass a narrow object through the oil hoe and leave it there until the new seal is installed.

3. Pack grease in to the lip of the new seal.

4. Start the seal into the bore, with the closed side of the seal facing out. The seal must be square to the bore.

5. Carefully drive the seal. The seal must be installed so it is slightly above the top edge of the bore. Do not drive the seal flush with the bore. Installing the seal too deep can block the bearing oil hole, causing bearing failure.

6. Move the object placed in the oil hole and verify that the hole is uncovered. Remove the object from the hole.

This is all it says, so I assume the procedure is the same for both crank seals.

What do you mean by the closed side of the seal facing out?  This first pic is how the bike came when I got it.  The second pic is the way I installed the seal, according to the manual (third picture).  Both bikes seemed to smoke the same.  Like I said, fuel mixture could cause smoke, but I don't think that's the issue, and right now I KNOW that that my oil level is going down, so that's what I want to address.

 

5977a1f68d208_OLDSEAL.jpg.cc055b7fa210e77c6ac4b03ee308fa8d.jpg5977a0feb96db_20170722_1704221.thumb.jpg.64dfb0de36913de6b63ddd8a96c71942.jpg5977a26aec0d2_SealManual.thumb.png.8154c648341eabe8bdab19e26ab72bf7.png

 

 

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the manual is wrong ,

there is no way that seal has a chance to seal the crank pressure in with the spring facing out

if the bike smoke heap before the rebuild the problem was poor jetting and tuning , warn top end and high flash point pre mix oil loading plug up at idle

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10 hours ago, kxrob said:

the manual is wrong ,

there is no way that seal has a chance to seal the crank pressure in with the spring facing out

if the bike smoke heap before the rebuild the problem was poor jetting and tuning , warn top end and high flash point pre mix oil loading plug up at idle

Maybe it is, who knows.  The jetting is right, the top end is new, and like I said, the gear oil is going down, so its definitely escaping somewhere.  I think the only two places it could be are RH crank seal (which is new), or case gasket (which is also new, and cleaned the gasket surfaces very well), or legit leak but there is no sign of oil on the external of the engine.

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It is my understanding that there are pulses of alternating pressure and suction in the crankcase of a 2 stroke.  And that overall there is more suction than pressure.  The seal is to keep transmission fluid from being sucked into the crankcase. Therefore the lip of the seal should be toward the transmission oil.

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In the picture you took, it looks like there is a hole in the case below the seal.  Or is that a spot of gasket sealer? The pictures in the instructions show no hole there.  If that is actually a hole, that is likely the problem.  A hole that size would suck the oil out of the transmission in a hurry.

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On 7/25/2017 at 3:58 PM, kevelev said:

What do you mean by the closed side of the seal facing out?  This first pic is how the bike came when I got it.  The second pic is the way I installed the seal, according to the manual (third picture).  Both bikes seemed to smoke the same.  Like I said, fuel mixture could cause smoke, but I don't think that's the issue, and right now I KNOW that that my oil level is going down, so that's what I want to address.

 

5977a1f68d208_OLDSEAL.jpg.cc055b7fa210e77c6ac4b03ee308fa8d.jpg5977a0feb96db_20170722_1704221.thumb.jpg.64dfb0de36913de6b63ddd8a96c71942.jpg5977a26aec0d2_SealManual.thumb.png.8154c648341eabe8bdab19e26ab72bf7.png

 

 

Top pic is the right way. Told yo that i think few times when your doing it couple months ago. Spring side has to be in on the Suzuki crank seal as wezer says. The gold always faces out on Suzuki :thumbsup: keep burning tranny oil it will eat the rings up

Edited by Motox367

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2 Strokes r supposed to smoke. U don't want no smoke cause u wanna b rich. If ur lean u will blow up ur engine. The more smoke the better!

Sent from my SM-G955U using ThumperTalk mobile app

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One thing about getting advice on a forum.  You can get all kinds of suggestions, and take your pick as to which one to follow.  Or none of them!

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12 hours ago, Dawson said:

2 Strokes r supposed to smoke. U don't want no smoke cause u wanna b rich. If ur lean u will blow up ur engine. The more smoke the better!

Sent from my SM-G955U using ThumperTalk mobile app
 

 I Hope you are joking 

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On ‎7‎/‎28‎/‎2017 at 9:15 PM, Weezer the Geezer said:

In the picture you took, it looks like there is a hole in the case below the seal.  Or is that a spot of gasket sealer? The pictures in the instructions show no hole there.  If that is actually a hole, that is likely the problem.  A hole that size would suck the oil out of the transmission in a hurry.

There is no hole.  That was grease I used to pack the crank seal with before installing.

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