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Does this cylinder need replated?

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Hello everyone,

I'm going through my '00 YZ 250 as the weather has turned and I have been casually riding it for a year and a half after purchasing used. I planned on a fresh top end but don't know if I need to get the cylinder replated. Pics of the cylinder and piston are attached... the cylinder is smooth, but there is a large whitish patch around the exhaust port. I dunno if it is the plating coming off or what. Any advice would be appreciated. Oh, and any reads on the piston top... to rich or something else?

Thanks!

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Looks to me like the plating is wearing off.. Piston looks a bit rich to me.. And I see some blowby.. Me? I'd buy a new piston and replate..

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From what I can see it needs re plating...

The piston skirts look like they have some wear, so a new piston and rings would be the go..

As zilla said, it may be a little rich....2 stroke jet requirements can change on a daily basis with changing climatic conditions...

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I Agree, the plating is gone around the exhaust port and it's time for a re-plate.

You should use a new piston kit with the fresh cylinder. It will be as good as new when you're done.

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Don't know what everyone else is looking at but that piston is a touch lean, not too bad but could be an issue in colder weather or riding in the sand.

The cylinder looks worn around the port, see the dull grey?

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Thanks all.

I'll send the cylinder out for replating and order a new piston. I"ll check into my carb settings and may be back with more questions for you all :lol:

-chris

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Thanks all.

I'll send the cylinder out for replating and order a new piston. I"ll check into my carb settings and may be back with more questions for you all :lol:

-chris

Send the cylinder with the new piston, they will match the bore to the piston for you.

As far as lean or rich, it can be hard to diagnose on a piston that could very well be the original.

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Post up a pic of the underside of the piston

Also, list your current jetting specs, other mods, your climate, and riding style.

If your jetting is way off, that info will tell the story.

It's hard to judge jetting from just the top of an old piston.

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Post up a pic of the underside of the piston

Here is a pic of the piston interior. I'm sure it is an OEM part based on the number but that is all I can say. I did ride it a couple times in cooler weather this fall. I'm rarely WOT on this thing too as I'm just learning the ropes and it has way more power than I need. I just want to keep my machine running good.

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thanks!

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I Agree...

That's an OEM piston and it was hot/lean.

You don't want to see any black/charcoal down there. It should be about a dime size (or slightly smaller) light brown stain.

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Also, list your current jetting specs, other mods, your climate, and riding style.

If your jetting is way off, that info will tell the story.

It's hard to judge jetting from just the top of an old piston.

Pilot jet has 52 stamped on it.

Main jet has 175S stamped on it.

Only mods (installed when before I owned it) are FMF Gnarly pipe and an FMF silencer that is about a foot long.

I'm basically trail riding and have a heavy flywheel weight on the bike. I do occasionally wander onto an MX track, but for now that is not my primary target.

Temps range from 80's to 50's in Central Illinois.

-chris

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This time of year, that 175 may be lean if you're running pump gas.

Race gas will work with a 175 most of the time, but the cold weather and pipe may require a 178.

Stock needles are N3EJ (N3EW for 2007 - later)

The stock clip position is the 2nd groove from the top.

Stock is a good starting/reference point for the YZ. The N3EW is a touch richer and works best for pump fuel.

The standard airscrew setting is around 1 turn out. You have to set that per your bike/conditions.

That 52 pilot actually may be a little rich. I think most guys are running the stock #50 or as lean as a #45. With 100 octane fuel, I run #48 in the winter and I need to switch over to #45 in the summer.

I haven't run the FMF Gnarly exhaust. Hopefully someone with experience on that pipe can offer a little help too.

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