Running in a new 4 stroke piston

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11/21/2020 1:57 PM

Just had a new piston on my 2020 KX450, what's the best method for running it in? I usually just warm it up fully and then ride it steady for 20 mins, then let it cool right down, then warm up again fully and let it rip. Am I doing it right?

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UK Vet rider - 2020 KX450

11/21/2020 2:08 PM

Probably should do multiple heat cycles at moderate but varied rpm, not lugging. Cool and check head and cylinder bolts. Check a service manual for the bike. After a few heat cycles you should run it hard to seat the rings.

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11/21/2020 2:25 PM

You sound like you already know what to do. Or go by your owners manual to break in. I swear guys over think this break in. Don't let it sit in your garage idling. Stupid. These thing aren't made of glass. The bike needs air moving over through the radiators.

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The older I get, the faster I was.

11/21/2020 2:30 PM

3 heat cycles and then ride it.

Paw Paw

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11/21/2020 2:35 PM

What is a heat cycle?

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The older I get, the faster I was.

11/21/2020 2:35 PM

The heat cycles are just a few minutes at idle until radiators hot, then allow to cool completely. After 3 cycles and checking bolt torque, run a few minutes at various throttle settings and gears up to half throttle on a gentle grade. Then a few minutes up to three quarters. Then run it hard. Change oil after first hour.

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11/21/2020 3:48 PM

Put some Rotella in it

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11/21/2020 5:41 PM

Do not “ heat cycle “ it in the garage on the stand. The rings need to be seated immediately after starting it for the first time by putting a load on them. Be ready to ride it down the street / dirt, whatever you have outside your garage or wherever you may be. Go thru the gears at a decent pace then allow the engine braking to pull the motor down putting a decent load on the rings. Definitely no wide open fire roads but varying rpms and slowing down numerous times. Ride it like that for 5-10 mins or so. Let it cool. Check for leaks etc then ride it exactly how it’s going to be ridden .

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11/21/2020 6:25 PM
Edited Date/Time: 11/23/2020 4:20 PM

Get the engine up to operating temp. Ride the bike to the gate. The bike is now broken in.

For real though. Ride the bike as you normally would. The only break in is seating the rings. Which needs to be done with a load on the engine.

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Race Bike: 2018 KTM 350SXF

Other Bikes: 1985 CR80R, 1990 CR250R, 1998 PW80, Specialized Fuse Comp 29.

Sold: 2016 YZ250F, 2012 CRF250R

11/21/2020 8:30 PM

I have rebuilt a lot of engine I let the warmup on the stand for few minutes through it in the truck. Head to track and rode it how I plan on riding never had a issue at all . To me best method it’s so over rated and mixed emotions on the break in method.

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11/22/2020 7:40 AM

Ride it for 30 mins easy and then let it rip.

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11/23/2020 2:47 PM

c0ncEpT wrote:

Get the engine up to operating temp. Ride the bike to the gate. The bike is now broken in.

For real though. Ride the bike as you normally would. The only break in is seating the rings. Which needs to be done with a load on the engine.

^^^This. Warm it up well, check it over & ride...........

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11/25/2020 8:39 AM

I always used to ride my bikes easy for the first hour or so, then let 'er rip. My mechanic friend says to ride it like you stole it from the first minute, though. I just can't bring myself to do that.

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Braaapin' aint easy.

11/25/2020 9:21 AM

Here's what Yamaha recommends on the 2020 Yamaha YZ450F:

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11/27/2020 9:17 AM

Rider 5280 wrote:

Here's what Yamaha recommends on the 2020 Yamaha YZ450F:

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How often does yamaha suggest you replace the piston on the 450?

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11/27/2020 11:55 AM
Edited Date/Time: 11/27/2020 12:56 PM

See below for the 2020 YZ450F.

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