Has anyone heard of a YZ 265 Stroker Kit??

L

lastoman

Member

Aug 19, 2006

11

0

• Aug 25, 2006

• #1

I've been doing some searching, and cannot find anyone who makes or made a 265 stroker kit for a 1995 yz 250. When I bought my bike I was told that It had a stroker kit, and it does indeed have a 4mm spacer plate under the jug, when you do the math it comes out to right around 264cc. I have no idea wheather or not the bore has been increased. the only stroker's I've commonly found have been accompanied by big bores to bring the total to 315cc. I'd just kinda like to know exactly how big the motor is.

 

Rich Rohrich

Moderator / BioHazard

LIFETIME SPONSOR

Jul 27, 1999

22,839

16,904

Chicago

• Aug 26, 2006

• #2

lastoman said:

I'd just kinda like to know exactly how big the motor is.

Click to expand...

Then pull the top end and measure it.

 

L

lastoman

Member

Aug 19, 2006

11

0

• Aug 26, 2006

• Thread starter
• #3

Rich Rohrich said:

Then pull the top end and measure it.

Click to expand...

I was hoping to avoid that, until a rebuild is necessary.

 

Rich Rohrich

Moderator / BioHazard

LIFETIME SPONSOR

Jul 27, 1999

22,839

16,904

Chicago

• Aug 26, 2006

• #4

Then I'll guess it will be a mystery till then, ;)

 

C

Chokey

Uhhh...

Oct 12, 2003

70

0

• Aug 26, 2006

• #5

That 4mm spacer is probably for a long-rod kit, and would have nothing to do with a displacement increase.

 

9

91kx

Member

Mar 6, 2004

87

0

• Aug 27, 2006

• #6

I'd agree with chokey .It's probably a long rod kit.

 

G

gurt

Member

Feb 25, 2006

111

0

• Aug 27, 2006

• #7

how does having a longer rod not affect displacement? I guess my question is what's the point of having a longer rod?

 

C

Chokey

Uhhh...

Oct 12, 2003

70

0

• Aug 27, 2006

• #8

The rod length has nothing to do with displacement. The stroke and bore size are still the same as stock, the longer rod simply moves the piston farther away from the crank centerline.

The purpose of the long rod kit on that generation YZ250 was to reduce primary compression, increase crankcase volume, and increase piston dwell time at TDC and BDC. It did a good job of waking those engines up.

The rod is 5mm longer than stock. The spacer is 4mm, and the gaskets (2 of them) are .5mm each after being torqued down. The kit did not change the displacement, or the compression ratio.

 

L

lastoman

Member

Aug 19, 2006

11

0

• Aug 29, 2006

• Thread starter
• #9

that makes perfect sense. a longer rod would also likely increase durability, because it would cause less strain on the cylinder wall.

if there had been no actual displacement increase, just a long rod kit, that would explain why it still had the stock jets in it when i got it. on question though, if a long rod kit doesn't change the compression ratio; why does a compression test read 170+ psi, when stock is somewhere around 125?

 

C

Chokey

Uhhh...

Oct 12, 2003

70

0

• Sep 10, 2006

• #10

lastoman said:

why does a compression test read 170+ psi, when stock is somewhere around 125?

Click to expand...

Where did you get that figure from? At 125 psi, the engine would run very poorly, and be very dificult to start. Even 175 is marginal for a healthy 250 two-stroke. My stock KX250 runs about 205 after rebuild/break-in.