crank seal, again....seriously?

2000 cr250. 45pilot, needle 2nd clip, 175main, runs like a raped ape usually. as of my last check it has 25hrs on the top end and 18hrs on the bottem end. both wiseco kits.

ran for a good bit then i started noticing the spooge. i thought it was just my jetting due to the weather change. changed my jetting, spooge continues. went home, rode again next weekend, went home and changed my tranny fluid. noticed it looked earlily low. we drained my friends 01 cr250 and he had easily double what i had and his top and bottem end were done at the same time as mine (18 hrs). but whatever, leaking crank seal.

replaced it this time with an oem honda one, lubed up the lip a bit more than last time and slipped it on. 1 trip, no spooge. second trip it started again. drained and again, low but not as much as last time. how am i blowing crank seals back to back? i replaced the crank seal collar with a brand new oem honda one during the rebuild and i inspected it again when i installed the second seal. so now im lead to believe i have another seal leak since it went away after the new one then started again.

how is this happening? i did a leak down test after the rebuild and held 6psi perfectly for 5 mins.

ya missing a knick/wear mark on the crank thats cutting the seal after running it ??

Unsuspected endplay?

How are the crankbearings doing?

ya missing a knick/wear mark on the crank thats cutting the seal after running it ??

the 2000 cr250 uses a collar around the crank shaft. the seal makes contact with the collar and the collar sits around the ride side of the crank. the collar was replaced with a new one 18hrs ago and then when i installed the new honda seal i rechecked it, and sure enough it was smooth all around, not a single knick.

Unsuspected endplay?

How are the crankbearings doing?

you know, i didnt even bother to check because i didnt think 18hrs was enough to cause the bearings to have play. the stock bearings had play, but that was the stock bottom end on a 10 year old bike that was used in the sand with its previous owner.

i think when i do the pressure test again (just to verify its not a center case gasket), ill also make sure there is no play. id hope the bearings hold up a little better than that though.

kind of aggravating to see my buddies bike (we both worked on each others bikes for the complete rebuilds) running around while im spewing black crap everywhere.

Well, I hope I'm wrong, but most cases of seal failure that I've seen were actually a result of bearing failure (mostly in chevy v-8's and other machines)

Same theory rears it's ugly head everywhere.

Well, I hope I'm wrong, but most cases of seal failure that I've seen were actually a result of bearing failure (mostly in chevy v-8's and other machines)

ok, i will check it out the next time im in. looks like i may have to split this thing again then

Are the replacement main bearings Chinese. Chinese bearings are always hit-or-miss.

Are the replacement main bearings Chinese. Chinese bearings are always hit-or-miss.

nope. i made sure the wiseco bearings were not chinese. i was actually going to use oem honda ones until i saw "made in japan" on the bearings.

Are you sure it is the crank seal? Did you pressurize the crankcase and then spray soapy water around the seal? The reason I ask is I get the same spooge and air leak coming through the exhaust valve shaft that runs from the crankcase up to the exhaust valve. Have tried several things like adding small orings and gobbing grease. It always holds pressure right after I get it back together but after a few rides starts leaking and spooging again. An air leak into the crankcase can come from either the crank seal or the exhaust valve linkage. The first thing to do is check the crank seal with soapy water while doing the pressure test. If that is not leaking, put the clutch cover back on, pressure test again. If still leaking then it is the linkage. I am going to try replacing the bushings that go around the linkage shaft and the shafts themselves. I'm not convinced this will do any good and think it is just not a good design. I've also thought about machining the cylinder to allow for an oil seal around the shaft but there does not seam to be enough material around the shaft to accomadate the hole for the seal.

Are you sure it is the crank seal? Did you pressurize the crankcase and then spray soapy water around the seal? The reason I ask is I get the same spooge and air leak coming through the exhaust valve shaft that runs from the crankcase up to the exhaust valve. Have tried several things like adding small orings and gobbing grease. It always holds pressure right after I get it back together but after a few rides starts leaking and spooging again. An air leak into the crankcase can come from either the crank seal or the exhaust valve linkage. The first thing to do is check the crank seal with soapy water while doing the pressure test. If that is not leaking, put the clutch cover back on, pressure test again. If still leaking then it is the linkage. I am going to try replacing the bushings that go around the linkage shaft and the shafts themselves. I'm not convinced this will do any good and think it is just not a good design. I've also thought about machining the cylinder to allow for an oil seal around the shaft but there does not seam to be enough material around the shaft to accomadate the hole for the seal.

i have not pressure tested the bike since the rebuild. i will try to do one this weekend, i still have my tester laying around. im basing my crank seal leak on this, im loosing transmission fluid and the only places it can leak internally are the crank seal or the center case gasket.

hey, also about the power valve linkage have you tried the moly paste from honda? it worked for sealing my engine really good, then again, you might be right, i didnt repressure test after, so maybe the moly paste doesnt last any longer than regular grease/paste

anyways, honestly though, if the bike spooged due to jetting id be ok with it, but loosing transfluid?

Maybe the crank or collar is not straight? Put a dial indicator on the primary side collar and turn the crank. Should not have more that .003" run out.

Edited by seehogs
i have not pressure tested the bike since the rebuild. i will try to do one this weekend, i still have my tester laying around. im basing my crank seal leak on this, im loosing transmission fluid and the only places it can leak internally are the crank seal or the center case gasket.

hey, also about the power valve linkage have you tried the moly paste from honda? it worked for sealing my engine really good, then again, you might be right, i didnt repressure test after, so maybe the moly paste doesnt last any longer than regular grease/paste

anyways, honestly though, if the bike spooged due to jetting id be ok with it, but loosing transfluid?

I do use the moly paste on the powervalve linkage and it works for a while. I know right away when it starts leaking again as the spooge comes back. I do lose some tranny fluid as well. Bike loses some crispness when leaking. It is just a pain to always be pulling the cylinder and relubing the pv linkage. I know from pressure testing that both my crank seals are good.

Maybe the crank or collar is not straight? Put a dial indicator on the primary side collar and turn the crank. Should not have more that .003" run out.

Good idea! I didnt even think of that. Will do that after the pressure test.

Yep, the crank should be measured for run-out. You want under .001" of run-out. A good percentage of aftermarket cranks exceed that.

Firstly, there is nothing wrong with Japanese bearings, they are far different to Chinese bearings.

If you are having repeated trouble with crank seals, maybe you should try and find a 'viton' material seal of the same dimensions from your local bearing suppliers and try one of them, they have a different material make up, generally stronger, and more heat resistant than nitrile seals.

Firstly, there is nothing wrong with Japanese bearings, they are far different to Chinese bearings.

If you are having repeated trouble with crank seals, maybe you should try and find a 'viton' material seal of the same dimensions from your local bearing suppliers and try one of them, they have a different material make up, generally stronger, and more heat resistant than nitrile seals.

you must have misunderstood me. i said i was going to use honda oem bearings, until i saw that the wiseco bearings said "made in japan", that was good enough for me and i never bought the honda bearings. i didnt avoid honda bearings because they said made in japan on them :thumbsup:

Is the spooge coming from the ignition side seal or the exhaust? The right side seal would allow antifreeze in the combustion chamber and would result in a very sweet smelling exhaust along with white smoke.

If you don't see the oil coming from the left side seal and the exhaust is spooging, I would guess that you didn't get the R/L case gasket to seal properly when you assembled the bottem end and you are pulling tranny oil into the combustion chamber. The only other place you could loose tranny oil is though the countershaft, shifter, clutch rod, or kickstarter seals. And you haven't mentioned that those are leaking.

Time for a leakdown test and if needed split the cases again and make sure your center case gasket is not the source.

Honda OEM bearing are identical to Wiseco main bearnings. Same MFG and part numbers.

Repeated seal failures are caused by failed main bearings. Also, is the collar grooved? You may want to replace that with your next seal.

And, FYI, Moose, Wiseco, OEM bearings are all made by Koyo. 63/28 is the size if I remember correctly. And, that's why you pay the same for OEM and aftermarket bearings. I think the aftermarketers realized quickly that using the Chinese main bearings would be very damaging to their reputation as well as your engine.

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