THIRD TIME

[YZGreg]

Nikisil lasts longer and over all performs better against wear. I reccomend using all OEM parts since Weisco pistons are usually junk.

WTF are you talking about, Wiseco pistons are far superior to stock cast pistons and they're cheaper. I've never seen a racer that runs a oem piston, they're junk and a rip off. I prefer cast liners too, even though they wear faster they can be bored out many times for cheap so the cylinder actually lasts longer.

[02mncr250]

yzgreg,

Weisco pistons are throw aways, that is why theay are "cheap" as you said.

Have ran both in sleds and bikes,,,,,OEM has always lasted longer. steel sleeved cylinder walls offer a whole bunch of problems that most people do not account for. Nikasil is by far the best coating for cylinders. It doesnt wear,,,,,or very slowly at best, and is extremely hard. With your steel liner wearing out and boring all the time,,,,,i am able to slap in a piston and run,,,,then i run a diamond hone thru it after 3 pistons.

I also race,,,,,,and race the living crap out of my bike,,,,I get almost a full season out of an OEM,,,,,weisco,,,,,i will go thru 2-3 pistons.

jeff

[steiner]

i agree with with oem is better, seems to me like they would know what works the best in there engines, if it was me doing the bike i wouldnt just slap new piston rings in it and run it, you gotta find the problem or it wont quit. the nikasil is a way better cylinder, sounds like its a four corner seize. piston expanding faster than the cylinder, if it was just on the exhuast side it would be lean, sounds like it could be a cooling problem, check your jetting again might be missing something check your reeds too, you have to tear it down again might as well check it twice i wouldnt just throw parts at it until it cures it self though, do you have pictures of the pieces.what does the plug look like after you let it idle for a minute, and when you ride it, a good plug idea isnt the color but of where the burn is at on the plug you want it about on the corner of the bend. and when you get it back to gether start it run it tell its operating temp, not riding it in your shop drive way shut it off let it cool check it after it is completly cool, check your plug. see if it is good start it warm ride ita bit not wide open. come back let it cool check your plug and maybe your cylinder if you can. then when you know its fine and everything is working good, then ride it, if you dont find the problem and fix it, it will not go away.

[Dirt Surfer]

I think the cast/ forged (Stock/Wiseco) piston debate is similiar to the 2/4 stroke debate. Everyone has a different opinion and preference. My experience with a Wiseco piston is that as long as you bring the bike to operating temp before running hard, the piston will last a long time. If not, the forged piston expands to fast and will cold sieze on the cylinder wall. $$$$ I has also been my experience that a plated jug tends to dissipate heat much better then sleeved jug. Just my $.02

[Woodsie]

So, you guys are all under the impression, that, if I put on a new nikosil jug, toss a coin to see what piston to put in,(yamaha or aftermarket) use hi-test to mix pre-mix, fresh oil on my air filter. use BR9EG plug like the book says, I can break the bike in, let it warm up, then, LET IT RIP.........!!!!
Man this is scary.

[02mncr250]

Dont just get a jug,,,get a whole new cylinder. By the time you get a jug, have it put in, etc, you might as well buy a new cylinder that is all STOCK.

i checked the price at Troy,,,,,they are about 229.00

If you lived close to me I would be there to help ya out,,,,,but i assume you dont live in MN.

How high octane gas are you using???? If you put a new cylinder and piston in,,,,start with 92 octane from a gas station,,,some VP fuels require re-jetting so be careful on how high of octane you go with.

I think if you do those thongs you should be ok. With all new parts you are eliminating most of the variables that would affect what has been happening.

Jeff

[Woodsie]

Yeah Jeff, thats what I meant, a new stock cylinder.
I'll use 92 octane.
Thanks for the offer to help me out.
Sure you can't run over here to western Pa. and give me a hand.
Think I should go to a bigger main jet, just in case? I think the stock one in there is #350.

[02mncr250]

As long as all the jetting is stock,,,main, needle position and pilot, you should be fine.

Do this when you are start it.

Let it idle for a minute or so,,,,shut down and check plug.

1/4 throttle, shut down and pull plug.

you want that plug to look dark brown to a tanish color.

Anything lighter than that is lean.

Let us know how it goes.

Jeff

[Dirt Surfer]

Jug is the slang term for cylinder.

[Shifting]

Ever check your float level? Also, your CDI could be faulty and it's not pulling the timing out in the upper RPMs like it's suppose to. . .

[Woodsie]

Float level is good.
OK how do you check the CDI? Doubt if anybody around here does that.

[Woodsie]

Hey Jeff
You said you checked the price of a new cylinder at Troy...$229??
I see $357. Whats up with that?
2000 YZ125
I hope you're right.

[02mncr250]

woodsie,,,

ooops,,,it says From 229.00.

Sorry.

Man,

that is spendy!!!! My cr 250 cylinder was 240.00.

[cr2504life]

You could try ebay, ive seen brand new ones on there at a pretty good price. cylinder, head, and complete pv system for 250 i thinkg that was for a CR tho.

[dirtdemon4life]

I wanna TRY to clear some things up.

1)Running 1 hotter a plug wont melt a piston. It doesnt burn the mix any hotter. A "hotter" plug is just a plug that doesnt get rid of heat as fast, thus making it less prone to fouling. BUT, this shouldnt be used to "jet" your bike.

2)Running a lowgrade gas will not mean you WILL have DETONATION problems. You may, but you can also run 88 grade if you dont have detonation problems. I beleive low grade can cause detonation, which is differant then preignition.

3)Check your intake. My friend fried his 04 yz in no time, and almost did it during break in, but we caught it. The boot was barley on the carb...

Btw, Im no eric gorr, so if you have your opinion, please post!

[Woodsie]

I don't have any simple air leaks like a carb boot. I checked all this by spraying the critical areas with starting fluid, with the bike running.