I recently purchased a 1997 John Deere 425 with the Kawasaki OHV engine. Hour meter shows 900+ hours. I have noticed what appears to be engine oil blowing by thru a plastic tube coming from up by the carburator. There isn't any smoke from the exhaust so I'm wondering if there is some valve in the upper engine that might be causing the engine oil to escape. I also would like to find a link to print out the JD425 electrical schematic. Thank you.
Engine John Deere 425 oil Blow By
- Thread starter jd322
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BBO
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I worked hours on a 445 with this problem. It was so bad the air filter was saturated in no time.
I once rerouted the hose to go underneath the mower.
Finally I had the rings replaced to fix the problem.
The engine may have a small reed switch that can cause this. It has something to do with the engine venting somehow.
But IIFC you almost have to remove the engine to even find this.
Thanks BBO for your input. I noticed the plastic hose from carburetor that is dripping engine oil is already routed to below engine. I would like to know where originally it is suppose to be routed. And this reed switch you mentioned sounds like a automotive PCV valve. As I stated earlier there isn't any engine exhaust smoke so it sounds like this reed valve might be defective. Is it located under the carb and can it be replaced without much trouble? Thanks.
BBO
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I am more familiar with the 445 so I may be misleading you.
See if this diagram helps any.
View attachment x.pdf
The reed valve is not like a PCB valve at all, and it's really hard to find.
The 445 has a crankcase vent that goes from the top of the engine almost straight up into the air box assy.
Then the crooked pipe inside diverts the crankcase vented air back down into the throttle.
It sounds like you are talking about another hose...
Below is the black crankcase vent hose on the 445 with the injector body removed. I am sure yours looks different.
Click to enlarge
Thanks again BBO as you were a great help. After looking more closely I discovered that the former owner had disconnected the Black tube coming out of the top of the engine that connects to the bottom of air box and had spliced in a clear plastic tube and routed it to under the engine to drip the bypassed oil. I now have taken the Black tubing and connected it back to the bottom of the air box as it was originally to see how it reacts. And I've also added a good dose of SEAFOAM to the 91 octane non-oxygenated gasoline to see if this might help the blow by. If this doesn't work I imagine I'll have to pull the engine out of the frame to do a ring job. Thank again for your help. 
Retiredcarguy
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With almost 1000 hours on it oil control can be an issue. The proof is the oil contaminated air filter. Run it in proper configuration and see how it is.
7394
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I've used Seafoam* also with great results on engines that had lot of blow-by.. Rings get gummed up & the Seafoam 'can help' clean them up.. Won't work over night tho..
& can't expect it to work on every situation..
& can't expect it to work on every situation..