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KX250F -09 Issues with cam bearing, please help.

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Last week when I was out driving, the bike started to sound strange and lost power. I went back and turned off, then I could not kick-start it again. Tried to push start it but then it came a strange rattling / clanking sound, but it never started.

Yesterday I tore apart the engine and found that the piston seize up in a terms I had never seen before. It is only on one side of the piston where the scratches are

When I looked at the bearing seat to the camshaft, I saw that it started eating into the estate, but think it looks strange to oil supply on the inlet side. You look at one oil passage (intake side) so there is no passage to bearing race on the bearing cap, should it be so? You can also see the damage to the bearing seat.

Does anyone have an idea what could have happened?

Can you do something about it, or have to buy a new Cylinderhead and bearing caps?

The camshaft seems to have fared well

The bike has approximately 55h and piston change was made about 15 hours ago ..

I enclose some pictures of how the piston and bearing cap looks.

I'm from Sweden and using Google translate so please excuse the language.

Thanks in advance!

The piston


Bearing cap


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What does the top of cylinder head look like ?

Looks like a oil problem there is a spray nozzle that sprays into the cylinder chanel and lubricates the cylinder wall and keeps crank cool and lubed as well.

How does the crank look any play- if crank is going it can wear on piston like the pic you showed but i never seen it that bad.

There is no oil passage to the bearing as the bearing is clamped between the head and cap and stays still. However if you look at the cam journal on the head there will be a oil grove cut into it. The cut goes to a hole on one side this is where I believe oil is pump up through and follows this grove around the cam. There is also a grove on the cam cap where this journal is. If the head was starved for oil then at these cam journal the grove would be worn into.

to your knowledge has someone ever used form a gasket on the bike. The problem with this is when the form a gasket is squeezed down it will expand inside the engine and outside the engine. The outside of engine can just be wiped up but on the inside, the form a gasket will fall and get into the oil passage and can clog it.

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Thank you for you're answer!

Oh, my bad, i don't mean the bearings.. I think the correct name is journal bearing or sliding surface? :)

Yes i saw it was i cut into the journal(?) on the "head side", but because it was a cut on one side here I noticed it.

On the head side it looks better, there are some small scratches in it, but not much.

The crank feels good, i haven't removed it just feel it and there are no gap or noise..

Someone has using "gasket on cans" on it, probably the mechanic who changed the piston, and i saw some residues between the head and the valve cover.

What you say makes sense, because it has both warm in the cylinder bore and camshaft bearing.

Something I reacted to was a pretty quiet ticking from the valves when I started the bike, and this happened about 1 kilometer later. Most likely it was the lifters(?) who ticked by poor oil supply?!

It remains well to examine the oil pump and look through the oil passages, and probably a new cylinderhead :(

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I now see what you were trying to say with the cam cap.... on the exhaust side you can see the oil grove goes into where the cam journal is and on the intake side it is not. I am not sure if it is also supose to flow into where the intake side is. I would try to find pictures of someones elses cap and see if it is like yours or not. May be a defectice cap.

Can you get better close up pictures of the cam journal damge on the head and cam cover ?

also cylinder wall and bottom of head. - the head might be savable

however the engine would have to be taken apart and oil passages blown out. Then on the first start up I would start it up and let it run for 30 sec to a min and then pull the valve cover off to see if oil is getting back up to the head then put the piston at bottom dead center and see if u can see oil resadu on the cylinder wall with a flash light looking through spark plug hole.

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Yes exactly, I was calling a Kawa mechanic today and ask him if it should be like that, and he has no clue either, But he said its enough if its a cut in the direction of the cam rotation. And i can't find any pictures on other cam caps.. Think it's okey then.. Or?! Hmm..

I bought a new cylinder and piston, they was not savable :p

Is it no way to check the oil passages without split the engine? I had hoped to avoid it :)

I attach some pictures to look at the cam cap and the cylinderhead..

Thanks for answering!





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I think your head is savable. cam cap is questionable though I sould start with 300 grit and work your way up to 2500 grit then finish with a felt pad and polish

you can go to my post from my profile and find one on 2011 mod engine / polished trans/ cam journal and read i had to bore my cam journal out a little bit

also I looked at pics I had of a PR2 head I sold from a 2011 and the cam cap is the sam as what you have so your cam cap in terms of the oil groove cut is good.

as far as cleaning the oil passage out I am not sure I imageing you can blow air through the passages but if I were you I would split motor and for 300 bucks put a new crank in only real tool you need is a flywheel puller its not as hard as people think to split cases

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There is supposed to be a port where you can check while the engine is running the oil pump pressure.

if the pump pressure is no good then this will happen.

Piston has A lot of damage on exhaust side. could be a overheating issue , possibly a detonation issue which causes lots of heat.

look at the top of the piston after cleaning it and see if there is any small pin marks on the dome. If so this is a problem with detonation.

Also spark plug porcelain should have small specks of black if detonation is present.

Detonation is caused by:

Too high compression :

Octane is too low : ( fuel prob )

High heat :

Ignition timing too advanced:


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