Right Crank Seal..Which direction????

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#1
OK, I'm replacing my right side crank seal on my 1980 RM250 because the bike couldn't go more than 20 minutes without fouling a plug and the jetting was actually a bit lean. Leakdown test showed a bit too fast of a pressure loss from 5 psi.

Anyway, the manual shows the seal with the open side facing the crank. When I got in there, the open side faces the crankshaft gear. Which is right? I know fork seals have the open side on the oil side, so maybe this is right, but I want to make sure before I put this in. Maybe it was installed wrong and that's why it is leaking.

So, Concave side faces inboard or outboard??

Please help if you know!
 
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#3
It't not, it's a Clymers manual. I haven't ever seen a factory service manual on a bike this old.

Anyone else?
 
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#4
The Clymer manual for my 2000 RM250 showed the open side towards the gear. When I got it apart, sure enough, the open side was towards the gear. On the flywheel side, the open side is towards the crank. For what it's worth, looking at the fiche for your bike on YamahaofTroy, it looks like they have the open side towards the crank. You could try calling your local dealer. Also, keep an eye out on Fleabay for the service manual. They pop up on there all the time.
 
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#5
On a 76 rm 125(with no rings)it has the seal open to the gear. the bearing is between the seal and gear,it gets lube from the tranny! My figuring says to match the other side,concave inward! So do the micro fiche's!
 
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#6
Yeah, the parts fiche is what is throwing me off. It looks like the open side goes inboard. Mine was leaking but the bearing feels fine and I thought maybe the reason it was leaking was that it was installed backwards.

Who knows? I hate to put the new one in backwards and have the same problem all over again. It's a pain in the buttocks. Bike runs great for one moto but it will not start again after that and the plug is totally oil fouled. Putting in a new plug every time I go on the track is getting to be a pain and getting expensive.
 
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#7
I do not believe it would hold a seal for long,that rm125 seal has springs on both sides of the seal lips! Installed correctly should solve your sparkplug issues!
 
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#8
Wait! I'm missing your point. Are you saying that I should install it with the open side inboard? My seal is outside of the bearing and accessable without splitting the case. There is no spring that I can see on the seal.

So are you saying mine is installed wrong?
 
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#11
i have went through this as well- almost all the bikes i have rebuilt have the spring/ open side to the oil- it gets lube this way-
also if the gear slides under the lip it will not fit properly the other way
suggestion- seal the centercase gasket while your in there-
 
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#12
chiro972 said:
...Mine was leaking but the bearing feels fine and I thought maybe the reason it was leaking was that it was installed backwards...
It was leaking because it was bad, direction had nothing to do with it.

Normally, the open side of a seal is installed towards the pressure side. Due to the design of the seal, added pressure on the open side will help press the sealing lips tighter against the shaft.

In your case, you're getting oil into the crankcase. In order for this to happen, the oil side must be at a higher relative pressure than the crank side. Because your seal had the open side towards the oil side, it should have been more effective in stopping the flow, not less.

Keep in mind the crankcase experiences both positive and negative pressure cycles so the seals have to work against both. Suzuki for sure has adopted the practice of installing the r/s seals with the lips facing the oil. They've been doing it that way for quite a few years now and there's been no indications that they fail any sooner than seals installed the opposite way.

I suspect whomever did the seals on your bike the last time installed them that way out of habit of working on newer Suzuki's. Since the fiche show the open side towards the crank, install it that way and don't worry about it. Provided the crank is in good condition, as long as the seal is installed square to the bore and not deformed during installation, it will be fine.
 

RM_guy

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#13
Keep in mind too that there is still oil present on the crank side from the fuel mixture so it gets lube no mater what.
 
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#14
With almost no exception, the open side of an oil seal goes towards the side or cavity holding the oil. I don't care if it is an axel seal in your pickup or a crankshaft seal in your dirt bike. Stator side seals go with the open side inboard toward the crankshaft, right side seals goes with the open side toward the gear case (location of tranny oil) closed side toward the crankshaft.
 
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#15
I say the open side goes towards the pressure, not the fluid. Lip seals work off of pressure. The crankcase sees the most pressure.