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09 yz290f - engine rattle


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Ive recently put a je 290 kit in my 09 yz250f.

For the first 2 hours it was fine, but it has started to produce an engine rattle. It sounds like a rattly bucket of bolts. Its definately not normal, as ive had three 250f yamahas and never heard this rattle before.

It sounds like its coming from the cylinder area. At first i thought it was my mega bomb header, but ive put the original header back on and its no better.

It gets worse with revs. Its also not there at idle.

Ive also checked my valves and they are in spec.

Any help is appreciated!

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Ok so ive pulled it all down and there is nothing seriously wrong with it.

It appears that it is simply piston slap.

Ive measured the bore and piston. Bore measures at 83.0mm

Piston measures at 82.3mm. I believe that this is a little too much clearance? Does anyone agree?

I also noticed from the plug that my jetting is extremely rich, however bike ran well.

I was running a 172 main, middle clip and 45 pilot 1.5 turns out.

So ive gone down to a 170 second clip from top and see how that goes.

Is it worth speaking to JE about the piston size?

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Ok now ive measured the std bore and piston.

Bore: 77.0mm

Piston: 76.6mm

So the JE piston has a lot more clearance, nearly double!

No wonder its so noisy

Should i worry or just suck it up?

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After looking into this a bit more, ive read the manual and they always measure across the skirts. I was measuring across the top of the piston. Anywho this is what ive found.

The manual says for stock piston cylinder arrangement:

Normal piston / bore clearance 0.03mm to 0.055mm. Maximum of 0.1mm.

My stock piston with 50 hours on it measures at 76.92mm. Bore measures in at 76.95mm. Clearance is 0.03mm.

The JE piston measures in at 82.85mm. Bore measures in at 82.96mm. Clearance is 0.11mm.

Although its way out of spec according to the manual, it is a forged piston, and im not convinced the piston itself is just the cause.

Does anyone think the jetting would have something to do with it?

Im just thinking back, and it didnt rattle when i first put it together. I did change the pilot jet from a 42 to a 45 as it would pop on decel, and this is about the time it started to rattle.

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But wait theres more........

Someone has seriously f%ked something up here....

Now that ive got it all apart and can see properly, THE PISTON HAS BEEN HITTING THE F'ING HEAD!

After measuring cylinders and gaskets:

Stock:

Cylinder Height: 66.48mm

Head Gasket Thickness: 0.8mm

Base Gasket Thickness: 0.62mm

Total: 67.9mm

Magnum/JE:

Cylinder Height: 66.37mm

Head Gasket Thickness: 0.73mm (Athena)

Base Gasket Thickness: 0.60mm (Athena)

Total: 67.7mm

Difference of 0.2mm

This is the second BB kit that I have purchased that has been farked. The first was a Wiseco kit from atvunlimited on ebay. The cylinder was a magnum cylinder, and had to be sent back because the water dowell hole on the bottom was too small and out of position. Could not get the cylinder onto the cases. So i sent the whole kit back and got a refund (i had to pay return shipping too).

This second kit has come from vipracing. It is listed as a JE kit. When it arrived i was concerned to see that the cylinder was also a magnum cylinder. It also had the same problem as the first cylinder, but i was able to get it to fit on. At least the hole was the correct size!

Now this JE kit is only a 12.5:1 compression and shouldnt be anywhere near the head, so it could still be a dodgy piston rather than dodgy cylinder given the slop in the skirts, but there is no doubt in my mind that the cylinders are rubbish. Il be sending this kit back and not buying another heap of crap magnum cylinder!

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If the cylinder has been hitting the head you may have more issues than just returning those parts. It has obviously been putting stress on the crank and other components, so those need to be checked as well since was running like this for a considerable amount of time.

What took so long to see that the piston was hitting the head?

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If the cylinder has been hitting the head you may have more issues than just returning those parts. It has obviously been putting stress on the crank and other components, so those need to be checked as well since was running like this for a considerable amount of time.

What took so long to see that the piston was hitting the head?

Its only just hitting. I only noticed because there is a patch of carbon missing from a section of the piston, and also the same section on the head. Its on the exhaust side. There is minimal deformation to the piston and head thankfully.

Crank and small end seem ok. No play in crank, and small end not egg shaped. As i mentioned in my first post i think, the rattle was only evident once revved. Not there at idle, so must have only been just tapping.

The guys from Lukes racing have just told me they use the Magnum cylinders, and use two base gaskets to solve the "clearance problem". First ive heard of it. These magnum jugs are crap. The head surface and dowell holes should be machined at least. As is they are just straight out of the casting!

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  • 4 months later...

i know this is and old post and i dont mean to hijack it, but i just got a 290 bb from lukes and it has a copper ring machined into thr cylinder on the head gasket surface, the copper ring is not flush with the surface and when i put it together it leak antifreeze into the engine, anyone else have this issue

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