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KX250F 2014 Engine Head Compatibility and Lubrication Issue

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Hi All, 

First time poster but long time reader. I have had some dramas with the head on my 2014 KX250F. 

Pulled it apart for the first time and saw that the camshaft bearing surface was wearing on the exhaust side. I sent it off to an engine shop who said they thought it was salvageable but I would have to replace valves. I did so and put it back together, rode it for 2 hours and then it stopped again (insufficient lubrication to the cams again). 

I pulled it apart again only to find a worn out cam bearing surface on both exhaust and intake side(See attached) . A new head will be required (cams as well). 

I am hoping someone can help me out with the following questions. 

1. Do you know if there has been major engine architecture changes since the first year the bike went injected. Ie could I bolt a 2011 head on a 2014 motor?

2. There is obviously some sort of lubrication problem with the motor. The gasket is the right way round, I can check the oil galleries in the top end fairly easily but I can't tell on the bottom end. Does anyone have any suggestions to what it might be? 

Cheers. 

 

 

 

IMG_6879.JPG

Edited by ltr1991
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Cylinder base gasket collapse or oil filter maybe? Perhaps the one you are using is too restrictive?  Oil pump weak, suction lines not as clear as they should be.  Cylinder base gasket extruded into oil groove, restricting flow, upper oil galleries and grooves in the journals partially blocked from prior head damage ...  a few ideas.  Aftermarket gaskets, use of rtv.   Have a look over this diagram, it may trigger some thoughts for you.  

I think I would be pulling the cylinder and checking that base gasket isn't blocking things off.  The oil comes up through a hole in the case between the head bolts on the right side.  There is a groove from this hole to the head bolt holes, this groove is in the top of the case where the cylinder seats.  If memory is correct ... the oil flows up the hole, passes along this groove to the bolts, goes up the bolt holes of the cylinder in the gap along the bolts and then into the head and up through holes under the cam journal.  If that cylinder base gasket is in poor condition or say some rtv gasket maker was used, it may be extruded into that oil groove or may be too tight around the bolts; causing restrictions to the oil flow.

So here my suggestion.   1) Verify the filter. 2) Pull the cylinder and put a new proper oem gasket on the base (NO rtv or anything like that), 3) chase drill the oil ports in the cam journals, use Dremel or similar to ensure there is a good groove in the journal from the hole to the cam cap joint so oil coming up has a place to go and isn't blocked off by a super tight precise journal fit.

 

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Definitely make sure bolts are not to tight, check o ring between head and cams cap around spark plug hole, check oil pump and surface mating areas, have had a few kx 250fs, pretty good bike all around, also on ignition side of engine take cover off after you drain oil and remove oil screen and clean it, good luck

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Check both oil pumps, located in the lower case behind the clutch.

also check to see if the oil filter cavity is full of oil.  a good amount of oil should drain out when you remove the cover

If not, the oil pump isn't working and a good chance the gear pin is missing or broken Part #92043 below.

Its also possible the oil pickup screens inside the center cases are blocked with sludge, rtv sealer, or other stuff.

Whats the history of this bike? I assume its new to you?

 

Here's a motor one of my customers brought to me with the same problem.

one of the screens was bent when the cases were assembled, and both were completely clogged with RTV before I cleaned them.

The oil pump in this motor sucked a piece of metal past the displaced screen, which jammed the gear and broke the oil pump gear pin shown as part number 92043 in the fiche picturer. 

IMG_0088.jpg

IMG_0089.jpg

IMG_0093.jpg

oil pump.gif

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On 4/23/2017 at 6:41 AM, nesc103y said:

Check both oil pumps, located in the lower case behind the clutch.

also check to see if the oil filter cavity is full of oil.  a good amount of oil should drain out when you remove the cover

If not, the oil pump isn't working and a good chance the gear pin is missing or broken Part #92043 below.

Its also possible the oil pickup screens inside the center cases are blocked with sludge, rtv sealer, or other stuff.

Whats the history of this bike? I assume its new to you?

History of the bike:

Bought at 20hours, it is now at 52 hours.

Oil and oil filter done ever 5 hours. 

 

Thanks for that advice, I will pull the bottom end apart next week and see if it is any of the problems you mentioned. 

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4 hours ago, ltr1991 said:

History of the bike:

Bought at 20hours, it is now at 52 hours.

Oil and oil filter done ever 5 hours. 

 

Thanks for that advice, I will pull the bottom end apart next week and see if it is any of the problems you mentioned. 

Before you pull the bottom end apart look at the oil pump.

Remove the right side engine cover, remove the clutch, and you'll have access to the pump. There's 2. One is behind the other

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On 4/27/2017 at 8:29 PM, nesc103y said:

Before you pull the bottom end apart look at the oil pump.

Remove the right side engine cover, remove the clutch, and you'll have access to the pump. There's 2. One is behind the other

The oil screen looked fine, a few minute oil shavings. 

What exactly should I be looking for in the oil pumps?

 

IMG_7039.JPG

IMG_7054.JPG

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On 5/5/2017 at 6:42 AM, ltr1991 said:

The oil screen looked fine, a few minute oil shavings. 

What exactly should I be looking for in the oil pumps?

 

IMG_7039.JPG

IMG_7054.JPG

look at the diagram above.  To check the oil pumps you will have to remove the right side engine cover, remove the clip holding the gear near where the case is marked OK, thats the oil pump drive gear, then remove the 2 screws holding on the oil pump. look at the fiche picture above to verify no broken pins.

The oil screens I was referring to are inside the cases - part number 49065.

However since you have the motor on the bench you can also verify the oil pump - spin the crank by hand. After a number of crank revolutions you should see oil start to flow up the the hole from the case at the base of the cylinder stud. this is the path to the head. If theres no flow there theres no oil getting to the head

 

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