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I got a question. I own a 2016 KX 85. It ran amazing after it first bought it used. I was riding one day with a bogging issue and about 35 minutes of riding I shut it off to take a break. Came back 20 minutes later and it would not start.I changed the spark plug, cleaned out the carb,checked the reeds,and tried hill starting it but nothing .When ever I try to hill start it I can hear it trying to crank and It starts for like half a second but then dies.There is spark coming from the plug though.I took the cylinder off and the piston and cylinder are &%$#@!ed.The piston rings were stuck in the grooves and I had to use pliers and a screwdriver to get it out.There was a ton of blow-by and the cylinder was scored.I bought a new piston already but how can I fix my cylinder.Im thinking of getting it repaired and replayed by either millennium,PowerSeal USA, or usnicom.This is my first time owning a 2 stroke.Any answers or tips.

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Did you run straight gas or pre-mix in the tank? That sucker ran REALLY HOT! I would be also looking at the rod's big and small end for a gray color over the middle brownish color of the rod. The cylinder will need to be replated and a piston sent with it. 

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5 minutes ago, FPMXer said:

Did you run straight gas or pre-mix in the tank? That sucker ran REALLY HOT! I would be also looking at the rod's big and small end for a gray color over the middle brownish color of the rod. The cylinder will need to be replated and a piston sent with it. 

I run it at 32:1 if I’m on the pipe and then 50:1 if am just trail riding and on low rpms.

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The cylinder definitely needs replating. I did mine with usnicom and I'm really satisfied.

You mentioned you already order the piston, remember that you need to send the piston when repairing the cylinder as they will match the bore to the piston.

Many times, people replace the piston without properly checking the clearances of the piston and rings in relation to the cylinder. The clearances are measured in 1/1000 of an inch. So, if the piston requires a .0035 clearance and you have .0015 (which is impossible to visually observe) you will have premature wear and failure among other things.

When you you buy a used bike with "brand new top end" you may just be buying a bike that had the piston replaced but clearances not checked.

It will run fine and strong, but will cost you later.

Good luck.

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38 minutes ago, Motox367 said:

Head gasket was leaking and burning coolent making stream why piston is black 

I don’t think it was that.My coolant was always full after every ride. I’m pretty sure pistons are supposed to be black from carbon deposits but not on the sides.

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4 minutes ago, Monsour Saleh said:

I don’t think it was that.My coolant was always full after every ride. I’m pretty sure pistons are supposed to be black from carbon deposits but not on the sides.

Um not like that 

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17 minutes ago, Monsour Saleh said:

What you mean?

Looks like was burning coolent to me. Here's a 85 that come in while back. Muddy harescramble race no shaker screen on rad. Got hot melted head oring and was burning coolent. Bike still ran 

20170504_095331.jpg

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Just now, Motox367 said:

Looks like was burning coolent to me. Here's a 85 that come in while back. Muddy harescramble race no shaker screen on rad. Got hot melted head oring and was burning coolent. Bike still ran 

20170504_095331.jpg

But after every ride I would check it and I never had to fill it up.It was always at the brim of the radiator.

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2 minutes ago, Monsour Saleh said:

But after every ride I would check it and I never had to fill it up.It was always at the brim of the radiator.

Ok 

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42 minutes ago, KDXGarage said:

How many hours has it ran since the last ring or piston and ring change?

The previous owner said he put 20 hours on it and I just got an hour meter but I’d say that I put on another 20-30

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1 hour ago, Motox367 said:

Looks like was burning coolent to me. Here's a 85 that come in while back. Muddy harescramble race no shaker screen on rad. Got hot melted head oring and was burning coolent. Bike still ran 

20170504_095331.jpg

And also there was no black gunk on the top of the cylinder where the coolant goes through.

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2 hours ago, viga said:

The cylinder definitely needs replating. I did mine with usnicom and I'm really satisfied.

You mentioned you already order the piston, remember that you need to send the piston when repairing the cylinder as they will match the bore to the piston.

Many times, people replace the piston without properly checking the clearances of the piston and rings in relation to the cylinder. The clearances are measured in 1/1000 of an inch. So, if the piston requires a .0035 clearance and you have .0015 (which is impossible to visually observe) you will have premature wear and failure among other things.

When you you buy a used bike with "brand new top end" you may just be buying a bike that had the piston replaced but clearances not checked.

It will run fine and strong, but will cost you later.

Good luck.

I asked millennium tech if the cylinder scores get fixed during the plating process or I had to add the repair package on to it and they said you had to add the repair package.I know millennium is the best of the best but 295 Dollars is a lot.But I’d rather get it done at millennium than buy a brand new oem cylinder.

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That cylinder doesn't look too bad to me.  Can you catch a fingernail on those vertical marks? 

I would put a fresh top end in and I bet it would run great.

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17 hours ago, Monsour Saleh said:

I don’t think it was that.My coolant was always full after every ride. I’m pretty sure pistons are supposed to be black from carbon deposits but not on the sides.

Don't doubt the experts .....   burning coolant ...    why change fuel mixtures ?   Just looking for trouble  ?    

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1 hour ago, bweighmaster said:

Don't doubt the experts .....   burning coolant ...    why change fuel mixtures ?   Just looking for trouble  ?    

But my radiators were always full and I never had to add any coolant.I change the fuel mixtures because at low RPMs too much oil will result in splooge and insufficient burn.

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