06 YZ450F Crank Seal...

WOW! Is all I have to say. Long story short Yamaha has just plain left out a few very important things in their service manual (Honda manuals are the best). Needless to say im very disappointed!

They dont even mention the oil pump check valve assembly (at least I cannot find it) and most importantly to me they dont mention the crank shaft seal assembly (in the right side kick start cover, very close to the check valve).

The seal is "red" on one side and I made the mistake of not paying close attention to its orientation when I removed it (red facing in or out, since I figured the service manual would at least mention its existence).

I can tell you this much, the marks left on the seal when I removed it looks like red was facing away from me which seems backwards to logic. Can anyone confirm orientation?

Justin,

The seal is of a conventional design in that it has an open side and a closed side, if you will, with the main, larger sealing lips on the open side. The sealing lips must face toward the fluid that they are intended to seal, and in this case, that is the high pressure oil being fed to the crank through the oil passage the seal sits in. Thus, the open side of the seal with the lips faces down into the bore of the oil passage to keep oil from leaking out around the crank instead of being pumped into it.

Thanks for the reply Gray. Thats what baffles me, I understand which direction seals are supposed to face. Like the water pump, that messes people up all the time, those seals "face" eachother. In the case of the crank seal, I am certain the motor has never been opened before (ive owned it since new) but I am also pretty certain which direction the seal was facing when I pulled it out since the hole is effectively "blind" and it would appear to me it was in backwards judging by the "damage" to the seal from me removing it. This means one of two things, you and I are somehow wrong and for some reason Yamaha wants the seal "backwards" to common usage, or (most likely) it was intstalled backwards by mistake on Yamahas part. Here is a pic so that you can see what I mean by the damage from removing the old seal to replace it:

DSCF3476.jpg

I've looked at this on both my own bikes, and in both cases, they are installed with your "red side" toward the crank, or "red side" out, as I suggested, and as we agree looks correct logically. In my case, neither of them are red, but that doesn't matter.

But it's interesting because even in the lube diagram on page 2-19 of the manual, it's illustrated as going in the other way. But that makes no sense to me at all, and would even make the seal prone to damage while assembling the case cover to the crankcase. I flat out would not install it like that.

This is a big deal, how they could leave out things like the oil pump check valve assembly AND the main seal from the service manual (in detail anyhow) blows me away. Im really concerned now as my bike has not had any lubrication issues and im convinced Yamaha HAD to have chosen to put this seal in "backwards" for a reason. Im wondering if they wanted some sort of controlled "leak"? The crank snout is heavily beveled so I doubt the seal would get damaged (it obviously didnt when Yamaha built my motor).

Can anyone confirm without a shadow of a doubt which direction this seal is put in by Yamaha? (would have to be a motor like mine that can be verified never opened since new)

Justin, I just pulled mine this morning and the red side faces away from crank.

This motor has never been apart until now, that is how it was installed from the factory.

Not sure if it is correct or not but thats how it came.

Justin, I just pulled mine this morning and the red side faces away from crank.

This motor has never been apart until now, that is how it was installed from the factory.

Not sure if it is correct or not but thats how it came.

It must be correct then, it just appears to be backwards from normal usage.

It must be correct then, it just appears to be backwards from normal usage.

I am not sure it is correct, this may be why my lower rod bearing went bad. Not enough oil due to seal being installed the wrong way.

I am headed to a yamaha shop tomorrow to get a new seal and I will ask them.

I doubt it, I have easily over 1000 (yes a thousand not 100) hours on mine and my rod and most of my other engine bearings are all tits. If you think about it, the big end bearing of a thumper and a 2 stroker are almost identical and ring dingers dont have any pressurized oil feed at all and last just fine...:banghead:

I would like to hear from someone with an 07 or 08 and see if the seal still faces the same way ours do. A few bikes with "backwards" seals is believable (slim chance tho that Yamamaha messed up that many) so im sure there is a reason they chose to do this. I wonder how they managed to miss putting this assembly in the Service Manual however!!

Anyone with an 07 or newer service manual? Please look and see if the crank seal assembly is mentioned and see if there is an explanation as to why the seal faces this way please!

It's not in the '09 or '10 manuals, either. And yes, the '10 has one.

But the crankshaft branch of the oil circuit doesn't need a lot of pressure, just an adequate volume. The oil that flows through that seal feeds only the crank pin, which is a rolling element bearing, and won't hold any oil pressure the way a plain bearing would, anyway. The oil thrown off at the big end is most of what lubes the piston. Look at the amount of oil a two-stroke rod bearing survives on, after all.

Besides, once the oil is pumped to the crank axle, the centrifugal force of the spinning crank will take it the rest of the way out to the big end. I doubt that the seal is that critical.

However, I've seen engineers decide some odd stuff before, and since it's not in the owner's service manual, the best source of info is apt to be either the technician's shop manual, or a tech himself, especially one who's attended some product training from Yamaha. I know we used to find out all kinds of undocumented stuff from GM all the time that way.

The oil thrown off at the big end is most of what lubes the piston.

I believe the piston "squirter" does more... :lol:

I doubt that the seal is that critical.

I agree that the motor would prolly be fine either way, but I also believe that Yamaha knows better then we do! My guess is they wanted a certain amount of oil to get by the seal to lube soemthing in that area like the primary gears or counter shaft, etc. The seal definately is made of a different material than the rest as it is a crimson/brownish red color.

However, I've seen engineers decide some odd stuff before.

Yamaha takes the cake there in my personal experience. I literally laughed my butt off when I read how they tell you to put the trans/forks/shift cam back in! Whomever designed the shift fork pinned to the shift shaft needs to be kicked in the shins! :ride:

I believe the piston "squirter" does more... :moon:
It does, but it's not on the same branch of the oil circuit as the crank, and it's directed at the underside of the crown, rather than the cylinder walls. :moon::p:smirk:

The seal definately is made of a different material than the rest as it is a crimson/brownish red color.
It's a high temp material designed to better cope with the extreme high speed of the crank and have low drag at the same time.

Yamaha takes the cake there in my personal experience. I literally laughed my butt off when I read how they tell you to put the trans/forks/shift cam back in! Whomever designed the shift fork pinned to the shift shaft needs to be kicked in the shins! :lol:
He was one of those engineers born with 4 hands. Seems to be a common characteristic of the species. It's really not quite as bad as you think, though.

I also believe that Yamaha knows better then we do!
You mean like the oil filter well drain? Lapping Ti valves? Replace the piston at 15 hours? (I guess that would be safe, though :ride: ) :D Next, you'll tell me there was a logical reason to put the sump drain behind the frame rail. :lol: And what about leaving this seal out of the manual? :bonk:
it's directed at the underside of the crown, rather than the cylinder walls. :lol::p:smirk:

Forgot about all those holes in the piston in the oil ring grove eh? :bonk::lol:

And what about leaving this seal out of the manual? :ride:

What about the oil pump check valve? :D

Dont get me started! :moon:

[quote=Justin Pearson;9094978

Yamaha takes the cake there in my personal experience. I literally laughed my butt off when I read how they tell you to put the trans/forks/shift cam back in! Whomever designed the shift fork pinned to the shift shaft needs to be kicked in the shins! :ride:

I was holding the trans just like the picture in the manual thinking YA RIGHT I'm going to get all six shafts into their holes without something slipping out.:lol:

Forgot about all those holes in the piston in the oil ring grove eh? :lol::ride:

No. Those are there to channel oil OFF of the cylinder walls as the rings travel down the bore, not to lube it. :bonk:

I was holding the trans just like the picture in the manual thinking YA RIGHT I'm going to get all six shafts into their holes without something slipping out.:bonk:

Its a joke! The only reason it must be done this way is Yamaha decided to pin the forks to the shift shafts. If they went the much better route that Honda (and im sure others, I just dont have personal experience) does you wouldnt have to be an octopus to install the trans! I sure hope the only reason they do this is patent restriction based and not because they think its a better design, as its way worse! :lol:

BTW Im also in Vegas, so if you need some help (or 5 extra hands) let me know, id be glad to help... :ride:

I sure hope the only reason they do this is patent restriction based and not because they think its a better design, as its way worse! :ride:
In theory, the YZ design is potentially better from the standpoint of reducing binding of the fork as it slides because of the wider load bearing base presented by sliding the entire shaft compared with the much shorter length of bearing area provide by the fork on the shaft. Makes it less prone to bind due to a rocking load.

I actually don't install the whole mess at once, either. I start the trans shafts part way in, add the forks, and slide it together. It's just not that tough.

In theory, the YZ design is potentially better from the standpoint of reducing binding of the fork as it slides because of the wider load bearing base presented by sliding the entire shaft compared with the much shorter length of bearing area provide by the fork on the shaft. Makes it less prone to bind due to a rocking load.

I disagree based on the fact that aluminum wears much faster and therefore will have more slop develop faster, plus the shafts dont go very deep into each case anyways.

The other problem is that once this wear occurs, you have to replace BOTH cases to correct it. Where as on the Honda design you simply replace the fork and shaft (waaaaay cheaper/less hassle).

Secondly, the "moment of inertia" is much greater now that your foot has to move the weight of the shift fork and a big steel shaft. This added force required also transfers to greater wear on the shift fork cam and your foot! :ride:

I disagree based on the fact that aluminum wears much faster and therefore will have more slop develop faster, plus the shafts dont go very deep into each case anyways.
You can, but I haven't seen any significant wear at that point, and that is the rationale for why it's done that way.

Dragging up an old thread again, but I'm putting my engine back together after replacing water pump seals and want confirmation which direction the crankshaft seal goes. This is on a 426, but I would think the seal direction would be the same between bikes.

From the previous thread replies - it looks like it was determined that there were two different orientations discovered. Grayracer said his was installed the conventional way, and Justin and another said this seal goes in backwards from conventional seals in that Yamaha installed it with the open side of the seal facing the crankshaft and not the bore in the engine case (red side of the seal driven down into the bore) - is that correct?

Who is right? Which way does this seal go?

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