Oil on top of piston

kx450sr
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kx450sr
My recently rebuilt kx450f blows a lot of white/gray smoke. I removed the spark plug and i see oil on top of the piston.

I do know that timing was set wrong on it and the exhaust valves hit the piston for about 45 seconds.

Also noteworthy when i spun the piston thru the crankshaft i noticed the piston was leaving a lot of oil on the cylinder walls when being moved either up or down. Rings and piston are new. Cylinder is not.

Is it more likely that the valves got bent when the contact happened and bent? therefore they prematurely let oil into combustion chamber?

Or is my cylinder shot out and letting the oil come up thru the rings.

Any help is appreciated guys thanks in advance!

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kb228
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kb228 12/31/2020 8:45am
12/31/2020 8:45am
Bent valves allow an excessive amount of oil to leak past the valve guides. All the oil from your cam area is leaking into the cylinder. You should be able to confirm this with a leak down test.

Did you check the cylinder diameters and ring gap or did you slap the top end together without inspecting it?
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hypermoto
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hypermoto 12/31/2020 12:39pm
12/31/2020 12:39pm Edited Date/Time 12/31/2020 12:40pm
The valves are probably bent.

Similar thing happened to a buddies yzf250, except they put the piston in backwards. Valves hit the piston for a few seconds, they tore it back down and turned the piston around. Bike ran great for 2 entire months of riding every weekend, then it seized right up. The valves had actually broken in half and dropped into the cylinder.

It was a 18 yzf and the reverse engine had confused them. They had no idea the valves bent after the initial run
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kx450sr
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kx450sr 12/31/2020 6:24pm
12/31/2020 6:24pm
kb228 wrote:
Bent valves allow an excessive amount of oil to leak past the valve guides. All the oil from your cam area is leaking into the cylinder...
Bent valves allow an excessive amount of oil to leak past the valve guides. All the oil from your cam area is leaking into the cylinder. You should be able to confirm this with a leak down test.

Did you check the cylinder diameters and ring gap or did you slap the top end together without inspecting it?
Yes that's what I imagined. I did not check the cylinder diameters or ring gaps. I built this bike back together without doing the shit I always normally do. SMH. I also suspect and hope its the valves because when I first fired her up I don't remember seeing smoke like I do now I only remember hearing metal on metal smacking. The piston had light scratches on it from this. Should I also replace that? Its a pro x stock compression which WAS new. Im affraid it might crack down the road

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kx450sr
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kx450sr 12/31/2020 6:28pm
12/31/2020 6:28pm
hypermoto wrote:
The valves are probably bent. Similar thing happened to a buddies yzf250, except they put the piston in backwards. Valves hit the piston for a few...
The valves are probably bent.

Similar thing happened to a buddies yzf250, except they put the piston in backwards. Valves hit the piston for a few seconds, they tore it back down and turned the piston around. Bike ran great for 2 entire months of riding every weekend, then it seized right up. The valves had actually broken in half and dropped into the cylinder.

It was a 18 yzf and the reverse engine had confused them. They had no idea the valves bent after the initial run
Yikes I guess ill have to do a measurement on everything that could've seen damage.
kx450sr
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kx450sr 12/31/2020 6:30pm
12/31/2020 6:30pm
Factor E wrote:
Did you stagger ring gaps?
Yes I did, according to my kawasaki manual. I think the problem here would be the valves being bent from hitting the piston or maybe even the valve guides from the impact the piston and valve made..I got some work ahead of me
kb228
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kb228 1/3/2021 4:35pm
1/3/2021 4:35pm
kb228 wrote:
Bent valves allow an excessive amount of oil to leak past the valve guides. All the oil from your cam area is leaking into the cylinder...
Bent valves allow an excessive amount of oil to leak past the valve guides. All the oil from your cam area is leaking into the cylinder. You should be able to confirm this with a leak down test.

Did you check the cylinder diameters and ring gap or did you slap the top end together without inspecting it?
kx450sr wrote:
Yes that's what I imagined. I did not check the cylinder diameters or ring gaps. I built this bike back together without doing the shit I...
Yes that's what I imagined. I did not check the cylinder diameters or ring gaps. I built this bike back together without doing the shit I always normally do. SMH. I also suspect and hope its the valves because when I first fired her up I don't remember seeing smoke like I do now I only remember hearing metal on metal smacking. The piston had light scratches on it from this. Should I also replace that? Its a pro x stock compression which WAS new. Im affraid it might crack down the road
Id replace it if it were mine. If you remove the piston and look underneath it might be perfectly fine. Never know.
kx450sr
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kx450sr 1/9/2021 11:17am
1/9/2021 11:17am
Thanks guys I replaced all 4 valves along with springs and it eliminated the smoke. Problem fixed
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