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2-stroke pistons, im off the forged band wagon

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so after being on the fence and running both, i am switching back to cast pistons for my 2001 Honda cr250

What are you guys running for cast pistons?

How often do you change them ?

my cylinder is out at US chrome getting plated and matched to a Pro-x 66.35 piston

i ran wiseco's for a while and i just have not had good luck with them, they eat rings and the excessive clearance needed to run them has always made me feel uncomfortable

before anyone says warm you bike up ... i do every-time

this is not a cast vs forged debate ... i have done my research and i think cast is the way to go

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cast are way to go for me coz I get 'em MUCH cheaper than forged. change 'em out prolly around 75 trail riding hours or so. I suppose I could go forged and stretch it to 100 hours but I'm cheap.

The proverbial argument is that forged won't shatter which is true. They no doubt noiser however. IMO, the best one is the cheap one for me. :bonk:

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i usually run wiseco in my bikes just because they seem to have a good rep with pretty much everyone, but recently i did the top end on my brothers 03 rm 85 and my mom was the one who payed for the piston for him, so obviously it was going to be as cheap as she can get a piston which isnt COMPLETE crap... she got an namura... not sure about namura, have heard alot of different things cast pistons like them grenadeing and the like, so i warned her not to go cheap, and what do you kow, i get home one day and theres the namura sitting on the counter... :bonk:

but now the bikes got about 40+ hours on it and still going

would never buy a cast piston myself though, forged are just alot sturdier

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I have had a namura piston grenade in a well jetted bike with less than 25 hours. I went cheap and ended up paying a lot.... lesson learned. In my ktm I use vertex, which makes the oem piston.

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they eat rings

Please explain to us how a piston can "eat rings"?
and the excessive clearance needed to run them has always made me feel uncomfortable

You need to move forward into the 21st century.

The OEM spec (OEM pistons are hypereutectic cast) for piston-to-cylinder clearance for my bike is .002" or .051mm. the Wiseco Racers choice is .0015" or .038mm. How is a tighter clearance than OEM "excessive clearance"?

Gone are the days when forged pistons use low-silicon-content alloys like 2618. Most are made from 4032, which has approximately 11% silicon alloy. The added silicon of modern alloys, combined with better CAD analysis and design, and more accurate CNC machining, allows forged pistons to often run as tight or tighter than cast pistons.

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Please explain to us how a piston can "eat rings"?

You need to move forward into the 21st century.

The OEM spec (OEM pistons are hypereutectic cast) for piston-to-cylinder clearance for my bike is .002" or .051mm. the Wiseco Racers choice is .0015" or .038mm. How is a tighter clearance than OEM "excessive clearance"?

Gone are the days when forged pistons use low-silicon-content alloys like 2618. Most are made from 4032, which has approximately 11% silicon alloy. The added silicon of modern alloys, combined with better CAD analysis and design, and more accurate CNC machining, allows forged pistons to often run as tight or tighter than cast pistons.

to be honest i can't explain the rings being eaten so fast i instal them the right way proper end gap, not upside down and for the past 3 top-ends the rings are warn enough to get blow by after only 30 hours, not to mention they don't have the same tension as the oem one did when they came out at the same interval

i had good luck with wiseco's in my 99kx125 my girls kx 100 , an 04 yz125 and an 03 rm 250 , all came out looking much better than mine did, the oem piston came out looking the best i run motul 800 @ 32:1 in pump 93 ( lately 50/50 c12) and i jet always a little rich,

the fact that the OEM piston was so much quieter than the wiseco made me feel allot better

i maintain my bikes very religiously they are spotless

again this has just been my experience but i have talked to allot of people and it seems cast is a little easier on the cylinder wall/coating so like i said im off the forged band wagon for a while at least in my 01 cr250

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Sheeesh… not another piston debate. You guys and pistons are like the oil debaters. Change oil way too often and change pistons way too often.

I suppose you forged guys change the pistons in your truck engines? You don’t? Why not? How the heck can a piston in your truck go 200k miles, yet only 20 hrs in your bike? Ehhh…. Well, lets not go on about your lawnmower or boat motor…..(just funnin’ ya’ll here. Don’t get all hissed up)

I use cast pistons. They wear out just about same time the cylinder plating does. Replate the cylinder, install a new piston. About four sets of rings in between. If, and I say if, an engine is lubricated properly and parts are within tolerances, the piston should not break. A forged piston is a poor substitute for improper lubrication and shoddy maintenance. About all a forged piston will do for a bike is provide a bit of forgiveness in the tolerance area.

This statements apply to a 2t bike. get about 175hrs of recreational riding from a top end/w ring changes.

My DRZ400 has 13k miles and seems to be running just fine. All stock. How many hours is that? Good question. Probably around 400 or so. Stock OEM piston and rings, Still going and going and going….

Happy trails everyone

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everyone talks about narmura( or w/e it is) idk about chinese pistons whats their deal ?

Namura is a japanese company who built a factory in taiwan (outsourced). Probably one of the more modern piston factory in the world. They can make junk or they can make good stuff depending on the spec. I built 925 and 1000cc twostroke prostock and land speed motors with them and they held up fine. No higher failure than any other brand. Didn't know they made them for bikes until a friend mentioned it recently.

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How the heck can a piston in your truck go 200k miles, yet only 20 hrs in your bike?

My truck doesn't spend 35 out of every 40 hours spinning at 9000 rpm at full throttle. It also doesn't make nearly 200 hp per liter.

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Please explain to us how a piston can "eat rings"?

You need to move forward into the 21st century.

The OEM spec (OEM pistons are hypereutectic cast) for piston-to-cylinder clearance for my bike is .002" or .051mm. the Wiseco Racers choice is .0015" or .038mm. How is a tighter clearance than OEM "excessive clearance"?

Gone are the days when forged pistons use low-silicon-content alloys like 2618. Most are made from 4032, which has approximately 11% silicon alloy. The added silicon of modern alloys, combined with better CAD analysis and design, and more accurate CNC machining, allows forged pistons to often run as tight or tighter than cast pistons.

I always thought that oil threads were the dumbest type of thread on TT...

Not anymore lol

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To the OP, MXA lists fragile stock cast pistons as a major weakness of the 00-01 generation cr 250, and they recommend replacement with forged. Even if you don't agree with their assessment, it's worth looking up what they have to say about that iteration of the CR 250. I found a lot of their tuning tips worthwhile when I had my 01 CR 250 (in which I always used forged pistons). Also, MXA has some recent articles (last year or so) about one of their regular test riders having considerable success against modern bikes on an 01 CR. Whatever you do, keep that bike going. It's a great bike and I wish I had not sold mine. My brother just picked up an 00, and seeing some of his helmet cam video is really making me want another one!

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to be honest i can't explain the rings being eaten so fast i instal them the right way proper end gap, not upside down and for the past 3 top-ends the rings are warn enough to get blow by after only 30 hours, not to mention they don't have the same tension as the oem one did when they came out at the same interval

the fact that the OEM piston was so much quieter than the wiseco made me feel allot better

i

My guess would be that you're running too much clearance.

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To the OP, MXA lists fragile stock cast pistons as a major weakness of the 00-01 generation cr 250, and they recommend replacement with forged. Even if you don't agree with their assessment, it's worth looking up what they have to say about that iteration of the CR 250. I found a lot of their tuning tips worthwhile when I had my 01 CR 250 (in which I always used forged pistons). Also, MXA has some recent articles (last year or so) about one of their regular test riders having considerable success against modern bikes on an 01 CR. Whatever you do, keep that bike going. It's a great bike and I wish I had not sold mine. My brother just picked up an 00, and seeing some of his helmet cam video is really making me want another one!

i will never sell this thing :bonk:

like i said i like forged pistons but i have to read what my bike is telling me you know , i didn't want to admit it was the piston that was causing issues but the oem came out looking so much better i think im going to stick with them and just change it regularly , the larger intake port puts alot of stress on the skirt , i knew this i won't let one go longer than 20hours with out looking at it, i ride tight trail with the occasional WFO fire road in-between

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