questions / leaking crank seals?

[BigAirStyle]

Newby here looking for some help.
I have a 02 CR250R. The problem i am having is this... bike starts no problem but when i go beyond 1/4 throttle it bogs real bad and sounds like it has a rev limiter or as if were jetted to rich. I have just replaced the top end, cleaned the Pvalve, new reeds, 100% went through the carb, drained and replaced gas, cleaned air filter, replaced plug, and within last year i put on JD racing ignition and had bike dyno'd and have made no changes or mods since the dyno. I noticed when doing the top end that i have some oil on the crank as it rotates around. The oil is only on half of the crank as it rotates around. I am assuming this is from oil sitting in the bottom of the crank area which i think would be caused from a leaking crank seal (clutch side). Can anyone help with some input if this assumption could be correct and if so can i replace the seals (clutch and alternator sides) without splitting the case? Any suggestions are greatly appreciated.

 

[zaneyzrex]

if its clutch side seal it will smoke like crazy and if its stator side it will be lean and eventually burn up. now if both seals are good and your trans oil is low then it could be a bad seal between the trans and crank. (it will suck trans oil into the crank area when riding. make sure your trans oil is staying full.

 

[BigAirStyle]

It smokes like crazy for sure and i can't ride it due to the bog so tranny fluid level probably won't change a whole lot. Is there any way to know for sure whether it is the clutch side seal or the crank/tranny leaking without accually being able to ride it. Would a leak down test tell me which is leaking?

Thanks for your reply :bang: :bang: :bang:

 

[IndyMX]

A leakdown test will certainly show a bad seal..

What did the oil look like that you saw on the crank?

I've seen premix oil coat the crank, which should look nothing like the gray nasty crap floating around in your clutch.

Once you determine for sure that you have a seal issue, it really doesn't matter which side it is. Replace both of them. Problem solved.

 

[whenfoxforks-ruled]

If the leak down test is good. That could be residual oil from being not properly jetted, or a damaged needle. Clogged air filter or silencer packing? Ignition? A dyno yesterday may not do any good today. Other than give you a good baseline. No jets laying in the bowl?

 

[TWRT]

I had oil show up like that on my 93wr250. It was a puddle of oil from the clutch side. I replaced the clutch side seal. It was not overly difficult. I did remove the engine from the frame and followed the manual's instructions.

 

[kx125412]

Do what indy said take your bowl off and check for a pilot jet. It happened on my friends bike one day riding. Would start up and run at 1/2 throttle plus but wouldnt idle and smoked like crazy if the rpms went down. Similar thing happened with the really rich sound beh beh beh. Might as well take a look it makes sense.

 

[Red Pinger]

There should be residual oil in the crankcase. Some of it seperates from the fuel charge and the crank lobes sling it around. That's how the bottom end gets lubrication.
I would be worried if there wasn't residual premix oil in the crankcase.

 

[armyvet2]

Exactly,there should always be some oil in the bottom of the crankcase.

 

[steve.emma]

premix oil in the bottom of the crankcase is NORMAL, like its been said before the gas evaporates and leaves the oil behind. when the engine is turned over the bottom of the crank flyweights pick the oil up as they rotate.

 

[BigAirStyle]

Well i have finally got the factory service manual and the seals in so i can can fix this problem but first to respond to a few of the reply's that posted...

The puddle of oil that is sitting in the bottom around the crank is definatly not premix. It is very dark and very obviously gear oil. So i am almost positive that either my clutch side seal is the issue or the seal/gasket between the tranny and crank is leaking. As far as the carb goes... I have not only went through the entire carb once but i doubted myself so i went through a second time totally dissasembling and cleaned everything just to make curtain i did not miss anything. I checked the float height, seat, needle, jets, A/S, etc... The only thing i have yet to do is repack the scilencer but when i pulled it apart it was still in pretty decent shape. I did go and get the parts needed in order to put together a make shift leak down tester and as soon as i am finished writing this i am going out to the garage and going to do a leak down test and hopfully this will help me with my direction. I am still looking for some direction because i have never split the case before and i just want to make sure that this is the direction that i must go into. I was really hoping that i would not have to do so but it appears that i have no choice if the leak down test does not hold. Can anyone tell me if it is possible to replace the seals without splitting the case? I understand the correct way to do this here is to split the case, replace all bearings and seal, as well as the crank if necc. but i am sure looking for a quick fix that will by me some time. I only say this because the bearings are all good, i have no play or movement at the crank or even the rod. I think that my last ride i simply got it way too hot running wide open a bit further then i should have pushed it and this damaged the seal.

Well i will say that i do appreciate everyones replys and help. From the short time that i have been around here on DRN Forum, one thing is certain. Everyone on here seams to have a true desire to help others with the knowledge that they hold or the experiences that they have had. Thats Awesome!!! :cool:

Hopefully everyone is getting to go out and get some seat-time tomorrow as i know i would be if i could. It is going on four+ weeks now since i have got to rip it up and it is killing me.

Be Safe but Ride Hard.

GWS

 

[whenfoxforks-ruled]

If I had to do it(Its kinda like kissing your sister), I would get a shop vac handy, drill 2- 3/32" pilot holes 180 degrees apart, in the middle of each seal. Get some long #10 or 12 sheet metal screws. Screw them in carefully, just till it gets full thread. Put a pair of vice grips on the screws and yank. Vacuum, clean and Vacuum some more. Leaving metal debris, damaging the bearing or ducking out of another issue is why I do not like this maneuver. How are the rest of the seals?

 

[BigAirStyle]

From what i can tell it is just the seal (clutch side). When doing a leak down test, when i have a bit of air coming out the trans vent hose. So is this a safe assumption?

GWS

 

[whenfoxforks-ruled]

A leak down test is a specific volume of air, and its timed release. The numbers come with the kit. Motion Pro has a nice one. For the air to vent out the trans, either the seal or the case center seal. Put about 5 psi and spray a soapy solution over the seal, no more assumptions?

 

[AV8R]

The puddle of oil that is sitting in the bottom around the crank is definatly not premix. It is very dark and very obviously gear oil.

The premix oil in the bottom of your crank case is going to be dark due to combustion particles and some heat coloring it dark.
I think your chasing your tail. If you have a leaky seal on the clutch side, oil in your crank case is not a reliable indicator of that.
Lots of grey smoke black oily residue on your plug and a loss of tranny fluid is. Or a significant volume of air leaking by your seal through the tranny vent tube is.
Like these guys said it is ideal to have residual oil in the bottom of the crank case.
If your pressurizing it past 6 psi, your using too much pressure.
It is not neccesary to split the case to replace the crank seal on either side.
If the bearings are tight then don't change them until it is needed.