Yz250 top end kit.

[Chris555]

Hey just bought a clean tidy older yz 250 2003 and am starting to rebuild it to a standard where I can ride it when ever and not have to worry to much if I ride it hard it’s going to break down on me . I’m going for advice on what’s the best  top end kit to get ? Cheers 

[EmpireofDerp]

Oh geeze, here we go again. 1 vote for ProX cast piston kit.

[Smoking 2's]

I highly recommend taking a forged piston and sawing in half, then a cast and weld together and you'll have a piston that is so good that there's zero chance of ever losing a race or breaking down or just put in either(Wiseco, vertex, pro-x) and replace it on a reasonable schedule

[ss-racing66]

I use the Wiseco like this :    make sure you get a small end bearing as well  (not incl in the kit) 

If you want to go all out, get a VHM Machined-from Billet piston ....I have one in my YZ125,  i'm pretty sure they make them for the YZ250 

[Matthias V.]

VHM doesn't make pistons for the yz250. I use vertex and change the piston every 20 hours like they say in their manual.

I only ride mx, almost never low rpm's..

[Motox367]

Prox cast #1 ??? and cheaper than the rest 

Edited April 20, 2019 by Motox367

[snowfever]

My son races MX, started on yz85, yz125 now on his second yz250, always used Yamaha rebuild kits and pistons, never had a problem. Buddy of his keeps using after market pistons and keeps blowing them up.

[eXc]

To save you searching:

 

Oem gaskets - there is a genuine kit.

 

Piston either oem or prox for cast or wiseco for forged. Prox was $50 cheaper for me over oem.

 

I just did mine with prox as most in here prefer cast...had I not been on here, I would have gone wiseco... I don't think it matters if you build it with correct tolerances and warm up properly...main reason I went cast is my brother is half owner and I wasn't sure if he'd follow warm up process, so one less risk.

 

[eXc]

And have a read through my thread, and also "spencerr" (with two r's) thread as a few on here helped us two numpties through the builds :-)

[Curtisy]

I bought a 2001 yz250 super clean with a blown top end. After making several calls I went with www.lukesraceing.com I decided to go with a 293 big bore kit. 750$ shipped to my front door in 3 days. It came with everything you need. Excellent cs if you get a chance check them out.

[YZDOC]

58 minutes ago, Curtisy said:

I bought a 2001 yz250 super clean with a blown top end. After making several calls I went with www.lukesraceing.com I decided to go with a 293 big bore kit. 750$ shipped to my front door in 3 days. It came with everything you need. Excellent cs if you get a chance check them out.

Something ESR has no clue how to be. I would be interested in who their R&D is. That search doesn't work.

On 4/19/2019 at 10:39 PM, Chris555 said:

Hey just bought a clean tidy older yz 250 2003 and am starting to rebuild it to a standard where I can ride it when ever and not have to worry to much if I ride it hard it’s going to break down on me . I’m going for advice on what’s the best  top end kit to get ? Cheers 

OEM (kits are only in B size)/Vertex/ProX/Wiseco/Wossner, heck even a MSR or Moose as long as they are ART you'll be fine. Just never a Namura as they are junk. 

Edited April 22, 2019 by 2 STROKE YZ DOC

[Curtisy]

Hey just bought a clean tidy older yz 250 2003 and am starting to rebuild it to a standard where I can ride it when ever and not have to worry to much if I ride it hard it’s going to break down on me . I’m going for advice on what’s the best  top end kit to get ? Cheers 

Keep us updated on the top end. Something I didn't do was check the squish so after I spent another 300$ to make sure I did the install, come to find out my top end psi is 213 so I can either send my head in so they can machine it down so I can run pump gas or leave it alone and run straight vp and in Las Vegas it's 90$ for five gallons so that's what I've been doing. I was also told I could stack my head gaskets to drop the psi but I'm not sure if that's a good idea so I just run the VP for now

[markmc2]

@2 STROKE YZ DOC

working link: http://lukesracing.com/luksr/yz300.htm

[Motox367]

3 minutes ago, markmc2 said:

@2 STROKE YZ DOC

working link: http://lukesracing.com/luksr/yz300.htm

Oh no Chinese made lol let us know how it works ??

[Curtisy]

Oh no Chinese made lol let us know how it works [emoji1417]

Omg ya I see what you mean. That is not what mine is. I still have the OG box and paper work I will look later when I get home. What I thought I was getting is a stock cylinder bored out to a 293. I do no that it dose not have that Chinese brand on it. It is identical to my stock cylinder but like I said I will inspect later when I get home.

[YZDOC]

Namura? Oh crap!!!

[Curtisy]

Namura? Oh crap!!!

Ok well I sent doc a few pic of my cylinder in his msg. It has no stamps on it what so ever. I'm guessing that's bad news. Sry for changing your topic. I guess if this big bore is a Chinese atleast I learned something.

[YZDOC]

IMO not going to be top quality. A couple extra huntit, and you would have a Athena GYTR approved, or even an EG kit.

Edited April 24, 2019 by 2 STROKE YZ DOC

[8675309]

Just rebuilt my 17 X,

Vertex kit

Needle bearing

Tusk gasket kit (crap)

$148.00

 

[Motox367]

8 minutes ago, Leftdagrid said:

Just rebuilt my 17 X,

Vertex kit

Needle bearing

Tusk gasket kit (crap)

$148.00

 

Best gasket set to oem is Comedic. They are same metal type gaskets as oem