how's my piston vital?

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8/25/2017 1:19 AM
Edited Date/Time: 8/25/2017 1:41 AM

original oem
60-80 hours more or less
most recent jetting 6.5-13hrs hours since
What are your thoughts on condition, wear patterns, current tune?
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8/25/2017 3:54 AM

Very clean and also rich. The lack of carbon on top and lack of a dark spot underneath indicate cool running temps due to being rich. Same for the plug color. Also, running a cast piston over 40 hrs in a YZ250 is a bad idea as they are well known for cracking at the window on the intake side.

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Powerband in every gear !

8/25/2017 4:47 AM

FGR01 wrote:

Very clean and also rich. The lack of carbon on top and lack of a dark spot underneath indicate cool running temps due to being rich. Same for the plug color. Also, running a cast piston over 40 hrs in a YZ250 is a bad idea as they are well known for cracking at the window on the intake side.

I think it looks pretty good, but I'd still install a new one with those hours. Plus, you do have it apart. Might as well, right?

What altitude do you typically ride at there in Colorado? Has to be at least 5000 feet because you're in Denver.

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8/25/2017 8:23 AM
Edited Date/Time: 8/25/2017 8:58 AM

FGR01 wrote:

Very clean and also rich. The lack of carbon on top and lack of a dark spot underneath indicate cool running temps due to being rich. Same for the plug color. Also, running a cast piston over 40 hrs in a YZ250 is a bad idea as they are well known for cracking at the window on the intake side.

I agree this is exactly what I was suspecting the current tune to be. I know its a little rich overall fuel wise. I am wondering also about the oil ratio. It seems to be all right. It might be a little oil rich but probably ok.

With the plug should I go up a notch to bring a little more heat? I got a BR8EG in right now. Maybe I will try a 7.

Yep. Definitely a high hour piston. Half the time I estimate from previous owners was fairly easy running and since I have had it the bike stayed in the lower rpms on technical trails so its had a pretty easy life. Probably how it was able to go so far and stay in good shape. I rode as far as I dared to see how the piston fared at high hours. It was definitely time for a new piston. It may have been starting to slap the past few rides but not much and it may have just been the tune causing the rattle to some extent. Either way that piston was long in the tooth with the high hours. laughing

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8/25/2017 8:44 AM
Edited Date/Time: 8/25/2017 8:49 AM

FGR01 wrote:

Very clean and also rich. The lack of carbon on top and lack of a dark spot underneath indicate cool running temps due to being rich. Same for the plug color. Also, running a cast piston over 40 hrs in a YZ250 is a bad idea as they are well known for cracking at the window on the intake side.

Harry Backmon wrote:

I think it looks pretty good, but I'd still install a new one with those hours. Plus, you do have it apart. Might as well, right?

What altitude do you typically ride at there in Colorado? Has to be at least 5000 feet because you're in Denver.

The old piston does look surprisingly good but I definitely installed a new piston and rings. It was time. I am thinking to pull this new piston around 30 hours to reinspect and compare.

I am riding primarily between 8000 at 10000 feet with this bike. All slow and go technical trail. That is leading to some of the rich conditions I think as the bike spends a lot of time rolling just above idle or coasting with a closed throttle. Last time I was out the last hour of the ride was in the rain with cooler temps which probably pushed the tune a little cool too as the engine temp was so low which may have effected the look of the piston.

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8/25/2017 8:54 AM

Thanks for the input guys

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8/25/2017 11:20 AM

Looks good but i cannot fathom running a piston for more than 10 hours

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2009 Kawasaki KX450F
2009 Kawasaki KX250F
2002 Suzuki GSXR 600

8/25/2017 12:31 PM

10 hours? He said he was trail riding the thing at low rpm. It will go 100+ hours doing that kinda riding with a forged piston in.

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8/25/2017 1:04 PM

You keep your air filter very well maintained. I'm impressed.

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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

8/25/2017 3:37 PM

FGR01 wrote:

Very clean and also rich. The lack of carbon on top and lack of a dark spot underneath indicate cool running temps due to being rich. Same for the plug color. Also, running a cast piston over 40 hrs in a YZ250 is a bad idea as they are well known for cracking at the window on the intake side.

Underneath, as you noted, no carbon. Almost looks new.

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8/25/2017 4:10 PM

Get an hour meter so u know exactly what the hrs are

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8/26/2017 6:10 AM

Acidreamer wrote:

Looks good but i cannot fathom running a piston for more than 10 hours

lol what? Are your pistons made of glass or something?

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8/26/2017 8:03 AM
Edited Date/Time: 8/26/2017 8:04 AM

ktm-5 wrote:

Get an hour meter so u know exactly what the hrs are

I do keep track of hours on my bikes. I got this bike with unknown hours. It was probably 30-40 give or take when I picked it up hence the estimate.

I would also state, hours are a good indicator but they are by no means a standardized measurement. Engine wear is more based on revolutions spun, how hard the engine is pushed and the conditions of the environment being ridden in. If an engine is pushed hard and revved high a piston kit could easily be needed in 10-12 hours. The same engine though could see an easy life at mostly at low rpms and go for 50 to 100 hours no problem regardless of whether the piston is cast or forged. The pics above prove this. That piston looks near new as some have noted yet definitely has over 60 hours.

The guy up thread that replaces pistons every ten hours probably rides pretty hard and isn't wrong. In a perfect world ten hours is a good time to replace a piston pushed hard. I have seen both sides of the spectrum with my bikes as to piston replacement. This piston here is the longest I have ever gone but its also my lightest used bike as its for slow trail riding and occasional bursts of speed. I have also replaced pistons in ten hour increments with a 125 I rode hard almost exclusively at a hillside track. The throttle was either pinned accelerating and climbing or closed decelerating. The bike was well maintained and in tune. The hard use and high rpms though would just wear the pistons and rings out quick.

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8/26/2017 8:08 AM

FGR01 wrote:

Very clean and also rich. The lack of carbon on top and lack of a dark spot underneath indicate cool running temps due to being rich. Same for the plug color. Also, running a cast piston over 40 hrs in a YZ250 is a bad idea as they are well known for cracking at the window on the intake side.

Harry Backmon wrote:

Underneath, as you noted, no carbon. Almost looks new.

I know right? I have never seen a piston look so good. I took a look at it when I first got the bike and was surprised how clean it was. After putting all the hours on it since I am surprised at how good of shape it is. I think the easy use combined with keeping the mix slightly rich and possibly a little rich with oil is the ticket to longevity of a piston.

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8/26/2017 8:11 AM

c0ncEpT wrote:

You keep your air filter very well maintained. I'm impressed.

I do clean the filter religiously. I have three filters in constant rotation. Also the slower speed use helps probably. With slow and go trail conditions the engine doesn't pull as air hard or in as much volume as a bike that sees harder use.

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8/27/2017 7:14 AM

That is a lot of piston wash. Looks a little rich IMO.

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8/27/2017 9:23 AM

piston smiston........quit flipping us the birdsilly

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If I'm healthy enough to complain. I shouldn't be complaining.

8/27/2017 7:27 PM

Rich, but ok. You have some room to make a bit more power by going leaner.

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Tomac and/or Anderson for 2020.....

8/29/2017 5:58 AM

Your bike loves you bro. It's quite obvious.
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8/29/2017 6:19 AM

Acidreamer wrote:

Looks good but i cannot fathom running a piston for more than 10 hours

rmoto003 wrote:

lol what? Are your pistons made of glass or something?

most service intervals for pistons are 10-15 hours.

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2009 Kawasaki KX450F
2009 Kawasaki KX250F
2002 Suzuki GSXR 600