CR250R Oil leak

I have a Honda 2001 CR250R. I have oil leaking out of a small (factory built) hole in the bottom of the engine. The oil leaks all the time, while running and not. My piston recently shattered and I replaced piston, rings, gaskets, wrist barring. I rode it for less than eight hours and the piston shattered again. I have recently been having problems with power and power band. I would like to know why the oil is leaking, I feel like it's a signal that something is wrong in the crankcase. Any suggestions would be great. Thank you.

Time to replace all of the seals in the case. You can get away without splitting it but you might as well replace the crank bearings too. This way you can inspect the case halves for cracks and such.

Is the oil coming from under the water pump area? That may explain the bike blowing up twice in a short period of time. The water pump shaft has two seals that ride on it. One is for the trans oil and one for the coolant. If these seals are bad oil and coolant will come out the weep hole. Are you losing coolant? The trans oil is separate from the crank area on a 2 stroke. The only other ways to lose trans oil is from either the shifter shaft seal on the left side of the engine or the kick starter seal on the right side.

Is the oil coming from under the water pump area? That may explain the bike blowing up twice in a short period of time. The water pump shaft has two seals that ride on it. One is for the trans oil and one for the coolant. If these seals are bad oil and coolant will come out the weep hole. Are you losing coolant? The trans oil is separate from the crank area on a 2 stroke. The only other ways to lose trans oil is from either the shifter shaft seal on the left side of the engine or the kick starter seal on the right side.

The weep hole is not under the water pump, it is in the center of the engine.

First off there should not be any weep holes on the bottom of the crankcases. Loosing g trans oil would not cause a piston to shatter. If your shattering pistons you probably have bad crank bearings or some sort of lean condition. My advice, tear the whole engine down and rebuild it its probably way over due.

First off there should not be any weep holes on the bottom of the crankcases. Loosing g trans oil would not cause a piston to shatter. If your shattering pistons you probably have bad crank bearings or some sort of lean condition. My advice, tear the whole engine down and rebuild it its probably way over due.

Well, there is a hole there. What can I do about, one person suggested to just plug it with JB weld.

Plugging that hole is not going to fix your piston issue. But for the hell of it upload a picture of it...

Time to sell it...

Do u have a frame guard or did u get the bike that way with the hole?

lol, yes there is suppose to be a hole there. DO NOT plug it.

 

i have not had my 00 cr250 cases apart in some time (5 years???), but im 99% sure this indicates a failed center case gasket. the honda manual says to inspect for leaks there after the case splitting section, so this would agree with it being an issue with the case gasket. these engines have 1 inspection hole for the water pump seal and 1 for the cases.

 

heres a nice close up from dogger315, we ARE talking about this hole correct?

 

00CR250Engine021.jpg

Edited by mynewcr250

Yes that hole is supposed to be there. Do not plug it. Ok, on to the leak. As long as you had the right sized piston, cylinder was good, and you assembled it properly, I'm still going to say seals (without being there to see anything this is an educated guess). Magneto side seal leaks, causes a lean condition and melts the piston. Clutch side seal leaks and causes oil to get into places it's not supposed to be.

Someone above said case gasket. That's a good possibility as well. Any way you can get a pic of the two shattered pistons up here? I want to see pics of the top, sides, and the underside of the dome.

lol, yes there is suppose to be a hole there. DO NOT plug it.

 

i have not had my 00 cr250 cases apart in some time (5 years???), but im 99% sure this indicates a failed center case gasket. the honda manual says to inspect for leaks there after the case splitting section, so this would agree with it being an issue with the case gasket. these engines have 1 inspection hole for the water pump seal and 1 for the cases.

 

heres a nice close up from dogger315, we ARE talking about this hole correct?

 

 

Yes that is the hole. So it is the case gasket that is broken. I guess I will have to split the case to get to all that?

honestly, and im sure you dont want to hear it especially after spending the money on 2 top ends already, but on a 12+ year old bike, i would be looking at a bottom end. there is no reason to split the cases to replace just the gasket and seals on a bike that old.

 

i know on my 2000 when i did the bottom end, the main bearings really didnt have any play you could feel at flywheel, until you split the cases then it was obvious i was due for them for some time.

Why not preform a leak down test. That will help confirm that seals are bad or not. The other issue to remember is that if there are any pieces of metal that you may have not been able to remove that will ruin seals bearings and so on. There are instructions on how to build a cheap reliable leak down test. I did it and spent like 20 dollars total and maybe an hour and a half of my time. If you need pictures or sizes of material just ask. I have a 2000 cr250 so it should be the same size! Good luck but before spending big bucks on a rebuild determine where it is coming from if you get bubbles from there from the air then you know it is crank related! If you do not get bubbles from there you know it's transmission related! A gasket or seal. You might even get lucky and be able to fix it without splitting the cases or removing the engine from the bike.

Why not preform a leak down test. That will help confirm that seals are bad or not. The other issue to remember is that if there are any pieces of metal that you may have not been able to remove that will ruin seals bearings and so on. There are instructions on how to build a cheap reliable leak down test. I did it and spent like 20 dollars total and maybe an hour and a half of my time. If you need pictures or sizes of material just ask. I have a 2000 cr250 so it should be the same size! Good luck but before spending big bucks on a rebuild determine where it is coming from if you get bubbles from there from the air then you know it is crank related! If you do not get bubbles from there you know it's transmission related! A gasket or seal. You might even get lucky and be able to fix it without splitting the cases or removing the engine from the bike.

i agree with a leak down test being beneficial, but the problem with these hpp motors is that they will leak air passed the exhaust valve and into the cases allowing it to vent. you can pinch off the crankcase vent but that wont guarantee you'll see enough pressure for the leak to show up. IMO, there is a correlation to the oil leak starting after the shattered top ends, cant be 100% sure, but i think the odds of there being some crankcase damage is pretty likely.

 

i agree that having a leak down tester is essential (i built one for ~$20 just like you and have used it multiple times) and if you did end up doing a complete rebuild you should be doing a leak down test anyways, so might as well spend the extra few bucks and verify your repairs when youre finished.

 

edit: did some research and a few guys have had this issue before. here are a couple quotes from allthingsmoto

 

 

 

I split the cases yesterday because it failed a leakdown test. It turned out to be damaged in the  wall that separates the crank from the tranny so if anybody has oil coming out that  small hole at the bottom it is not a good sign

 

 

 

Hello, if it is leaking tranny oil thru that weep hole the center case gasket is leaking. you will have to split the case's and replace the gasket. Has it had a piston failure lately? That is what damaged my center gasket
Edited by mynewcr250

I missed that this is the second piston you went through. I would just rebuild the bottom end. Servicehonda.com has the best prices. Took a little while for the parts to show up though. I'm in the process of rebuilding my bottom end currently. It's not to bad. I took a million and one pictures while tearing it down. The most time consuming part is all the cleaning and inspection of parts! Keep everything labeled nicely and in plastic bags. Read the manual a couple of times and while putting back look at the parts diagrams.

Good luck,

Chris

I took apart the top end today. The piston is in tact but the engine is still seised. Any oil put into the engine imediatly comes out the hole in the bottom. I just wanted to get it running so i could sell it as a "needs work" bike but it seems like ill have to rebuild the bottom end if I ever want it to run again.

I took apart the top end today. The piston is in tact but the engine is still seised. Any oil put into the engine imediatly comes out the hole in the bottom. I just wanted to get it running so i could sell it as a "needs work" bike but it seems like ill have to rebuild the bottom end if I ever want it to run again.

im gonna bet on the crank stuffers coming apart and cracking the case.

Edited by mynewcr250

im gonna bet on the crank stuffers coming apart and cracking the case.

What are crank stuffers? Ive never heard that term.

before 05, honda used what most guys call "tin cans" to take up space in the crankwell. yamaha does the same thing but they use (or used to) plastic stuffers and not in the same manner. these metal tin covers aren't the toughest things out there. they do get pretty easily damaged when you have a piston failure and sometimes just fail due to fatigue.

 

im taking a 100% guess here as you haven't split the cases yet, but i would not be surprised if when your last top end shattered it nicked or damaged the tins like this

 

crankshaft0017nv.jpg

crankshaft0036xi.jpg

 

 

once they are damaged, it can lead to this which considering the amount of space in the crank well, could quite easily damage the cases.

 

998575983_fQEj9-L-2.jpg

 

it doesnt take much to damage the crank when you shatter a piston and sometimes a tiny crack isnt super obvious if youre not looking for them. i assume you didnt split the cases to clean the engine out after the first failure? have you tried turning the crankshaft in the reverse direction or is it completely locked up?

Edited by mynewcr250

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