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Oil Migrating from Transmission to Engine

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Hi guys,

After two weeks of research and failed fixes, I've decided to post this.  I just put a new bottom and top end in my 2014 CRF250R.

The bike runs great but it's dumping the transmission oil into the engine, then blowing it out of the cam chain vent breather.

I know this has been discussed a lot, but I still haven't figured it out.

I've not overserviced it.  I've measured the oil from both sides after draining and it's definitely migrating.

I've changed the RH main crankshaft seal 3 times and it's still doing it.  I have balance shaft seals on order.

Is there anything I'm missing or need to look at?

Thanks

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I removed the balancer shaft last night after posting this, and found the D shaped o-ring torn when I pulled the drive gear off.

Hopefully this will fix my problem.

Thanks for the info!

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Ok, now I'm really stumped.

I replaced both bearings in balancer shaft along with a new balancer seal and a new D shaped o-ring (which was torn).

The bike is still pumping oil from the transmission into the engine???

I've replaced the crank shaft main seal 3 times with a new seal in the last month.

It seems to do this worse when the engine is hot.

I'm wondering if I've put the crankshaft seal in backwards (metal is facing outboard).

I've read it's possible to install the crankshaft bearing not square with the case and it will cause the seal not to seal properly.

The engine is running great, with lots of power.

This is extremely frustrating though, and I'm totally at a loss on what to do next.

I appreciate and advice or recommendations

 

Thanks

 

 

 

 

 

 

 

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are you checked bleeding tube that ins't cloged?

I've checked both the transmission vent and the valve cover vent tube several times during this issue.
Neither tubes are clogged.

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I had the same on 06. Changed everything and anyway there was migration from tranny to engine. But in my case it was around half level on oil stick per one oil change. I left it and fill 1/3 of oil stick in engine side and +100ccm in tranny.

I had stroker crank. Little bit more vibration maybe somewhere some seal couldn't handle. And one snapped crankcase bolt and some scratches around it on surface after unsuccessful unscrew attempt. Therefore my guess was that there is problem. This bike now have 100 hours with this problem and total 350

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I had the same on 06. Changed everything and anyway there was migration from tranny to engine. But in my case it was around half level on oil stick per one oil change. I left it and fill 1/3 of oil stick in engine side and +100ccm in tranny.
I had stroker crank. Little bit more vibration maybe somewhere some seal couldn't handle. And one snapped crankcase bolt and some scratches around it on surface after unsuccessful unscrew attempt. Therefore my guess was that there is problem. This bike now have 100 hours with this problem and total 350

I talked to a local mechanic that specializes in Honda's yesterday and he told me that I might have a hairline crack in my crankcase bore.
He said he's seen it a couple times. Could have happened during the bottom end rebuild.
When the engine gets hot, the crack expands, allowing the oil to migrate.
I'll keep you posted.

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On 09/09/2017 at 9:42 PM, spokeking said:

Ok, now I'm really stumped.

I replaced both bearings in balancer shaft along with a new balancer seal and a new D shaped o-ring (which was torn).

The bike is still pumping oil from the transmission into the engine???

I've replaced the crank shaft main seal 3 times with a new seal in the last month.

It seems to do this worse when the engine is hot.

I'm wondering if I've put the crankshaft seal in backwards (metal is facing outboard).

I've read it's possible to install the crankshaft bearing not square with the case and it will cause the seal not to seal properly.

The engine is running great, with lots of power.

This is extremely frustrating though, and I'm totally at a loss on what to do next.

I appreciate and advice or recommendations

 

Thanks

 

 

 

 

 

 

 

I've been through this on my 05 (which is a common issue for those years of bikes) and I fully admit I'm not familiar with the new year bikes so the following is just a suggestion and MIGHT help narrowing it down BUT .....

For the 05's its the right side crank seal OR the left side balancer seal so I did the right side crank seal first since IMO you only have to pull the right side

Then I reassemble the right side and with no engine oil and the engine oil drain bolt out, I filled the tranny and it quickly started pouring tranny oil out the engine drain so obviously the left side balancer seal.

Then pulled the right side, then the left side and did the left side balancer seal.

Again not sure how applicable this is for the 2014 OR if its going to help since you say its worse when its hot but its away to check when the engine is cold.

 

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I've been through this on my 05 (which is a common issue for those years of bikes) and I fully admit I'm not familiar with the new year bikes so the following is just a suggestion and MIGHT help narrowing it down BUT .....

For the 05's its the right side crank seal OR the left side balancer seal so I did the right side crank seal first since IMO you only have to pull the right side

Then I reassemble the right side and with no engine oil and the engine oil drain bolt out, I filled the tranny and it quickly started pouring tranny oil out the engine drain so obviously the left side balancer seal.

Then pulled the right side, then the left side and did the left side balancer seal.

Again not sure how applicable this is for the 2014 OR if its going to help since you say its worse when its hot but its away to check when the engine is cold.

 

The 2014 doesn't have a balancer shaft seal on the left (engine) side.

It has a balancer seal on the right side, a d-ring under the counter balance gear that drives the water pump (right side), and seals on the left and right sides of the crankshaft.

 

I appreciate the input though.

How did the oil get to the engine drain? Not sure if I'm following you

I'll have to pull up the 05 engine diagram

 

Thanks

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14 hours ago, spokeking said:

The 2014 doesn't have a balancer shaft seal on the left (engine) side.

It has a balancer seal on the right side, a d-ring under the counter balance gear that drives the water pump (right side), and seals on the left and right sides of the crankshaft.

 

I appreciate the input though.

How did the oil get to the engine drain? Not sure if I'm following you

I'll have to pull up the 05 engine diagram

 

Thanks

Balancer shaft goes from the left side (engine oil) into the right side (tranny oil) but the seal is in the left inner case #22 which is the engine oil side, hence when the seal was gone the tranny oil migrated into the the left side and firstly overflowing the engine oil up the vent into the air box.

Then first 2 things I did was drain both oils, then one I did the right side crank seal and started filling with tranny fluid migrated into the engine oil side and out the engine oil drain hole.

At least on the 05 I did most of the seals there were easy on both sides for about $200 in parts BUT it is slightly complicated and I had you use multiple micro fiche to get all the OEM #'s, then a clymer and service manual for the work and even then the work was easy and I did it in my back yard in a couple of hours.

Sorry this isn't helping you specifically with the 2014 and may someone else will comment.

Otherwise from the O5 if anyone cares.Clipboard01_zpslhkzcxdc.JPG.760941cd9437157e0c6a1e701d9f1645.JPG

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