99 yz 125 - 134 or 144?

[robwbright]

Hi guys:

Tomorrow I am purchasing a '99 YZ 125 that needs a cylinder and piston makeover. ($475 for the bike in otherwise good condition).

I've talked to Eric a couple times so far, but I'm torn
between the 134cc and 144cc?

My riding will be on local tracks and trails with maybe 5-7 outlaw races per season. I prefer mx/sx to trails but there's so many trails near SE Ohio . . .

Ultimately, I would like to know the difference between stock, 134 and 144 as far as hp and torque. Are we talking about something like 28 hp stock, 32 in the 133 and 35 in the 144? Approximate #s would be fine and seat of the pants testimony would be great as well.

Thanks

Rob Bright

 

[Eric Gorr]

Forget peak power, think powerband. The 134 is a great all around powerband and doesn't require case mods like the 144. Thats your best bet. That bike had no low end, so making the porting choice for low/mid is a good choice too.

 

[robwbright]

Thanks Eric:

I was planning on calling you today to discuss, but you've answered my question here.

Rob

 

[trailrider12]

well, i think the yz125 would make over 30 hp, right? stock its 33 for 05....

 

[marcusgunby]

Some dynos will read as low as 28hp for a std 125 and some read as high as 34hp.

 

[SpDyKen]

Thanks, Eric, for the info.! Just bought a used '03 cyl.& head (damaged; needs repair.) Will be sending to you when I receive. Missed the "no case mods. required for 134cc kit" info. in my casual research. That makes the decision obvious for me. Had been considering low/mid porting only to eliminate the need to split the cases. (Yes, I know, some people don't.) I don't need more power, just some low end for when the tight woods up-hills get slippery.

 

[moore_716]

i had eric do the 144 on my 99 yz125. He did the bottom/mid porting for me also. At that time he told me the bike should be around 37hp. I had a vforce2 reed cage, doma pipe and silencer(Istill have the silencer if someones interested), and started up 2 teeth on the rear sprocket. The bike made so much bottom end that it would do 3rd gear starts and spin all the way thru 5th gear. I changed the gearing back to stock and left the jetting stock too. The bike was awesome I only sold it because it was ready for a lot of other things. I now have a ktm 200sx and the powers not that much different, the YZ had a vicious hit though.