Tri-z to newer YZ conversion

[Shawn72]

Other than mount mods and fabrication, would there be any showstopper reasons why this couldn't be done? The drivetrain is on the correct side so it seems possible.

[Yamaha_Rules69]

Your talking about the motor I assume? What year and size YZ motor were you thinking about using? From what I have heard the 83-87 YZ 250 is a direct bolt in. The YZ suposedly has more radical ports, a little higher compression, and of course the power valve system. In my opinion the power valve system dosnt add more power, just gives you a little better control of where the power comes from, and when you want it to hit. It takes that "light switch" feeling away when you crack the throttle, and you know where it is. The kicker can be set up to kick forward, just like the tri z motor, you just have to swap some internals between the two. Good luck, and let us know a little more info!

[this guy]

If you are up for some cutting and welding try the yz400F or the 426 they are reliable and pull like crazy through the whole RPM range.

[Mosh]

I thought about doing this a few years ago.

I was looking at doing a 93-98 YZ motor.
Lots of parts for them.

Just never got around to it.
Looking at those years of engines, they looked likt they were close as far as dropping right in.
I am sure there would be issues though..LOL
Pipe fitting,at the newer jug, carb clearence issues,and intake set-ups, not to mention,adding a fuel pump port on the newer jug, or going with a top mount tank.
Also, the newer engine would require a cut fender to kick it backwards.

[atc sam]

what about banshee low pro fenders for the kicker problem?

[mike from long island]

MAke sure you install new power bands if you put a YZ motor in.Dont want them failing when you need them!!! :naughty:

[AutoXer]

MAke sure you install new power bands if you put a YZ motor in.Dont want them failing when you need them!!! :naughty:

Yes Mike I am glad you mentioned this it was in another thread but I will mention it again .... DON'T use the power band from the yz250 put the power bands out of a four stroke in the 250 motor it will pull right of of the bottom end that way it is a great mod i can't see why more ppl don't do this shens shens shens

[Yamaha_Rules69]

Ohhhhhh here we go again..............:lol:

[mike from long island]

Ohhhhhh here we go again..............:lol:

I know what was I thiking???? Its been awhile since we had this descussion.So wont agree and say they will never fit!! But what do they know?? :beer

[code200k]

MAke sure you install new power bands if you put a YZ motor in.Dont want them failing when you need them!!! :naughty:

make sure they are yellow too the green ones always break and cost you more money

[this guy]

I love these. Blue ones work good too. make sure you get the tapered end muffler bearings too.

[Shawn72]

I broke the powerband on my tri-z recently. Lucky I had a spare one for my 250R. And it will drop right into the Z.

[Shawn72]

I thought about doing this a few years ago.

I was looking at doing a 93-98 YZ motor.
Lots of parts for them.

Just never got around to it.
Looking at those years of engines, they looked likt they were close as far as dropping right in.
I am sure there would be issues though..LOL
Pipe fitting,at the newer jug, carb clearence issues,and intake set-ups, not to mention,adding a fuel pump port on the newer jug, or going with a top mount tank.
Also, the newer engine would require a cut fender to kick it backwards.

Seem to be pretty minor issues for such gains. Also there are Bigbore kits available for those years.:naughty:

[Micahdogg]

Your talking about the motor I assume? What year and size YZ motor were you thinking about using? From what I have heard the 83-87 YZ 250 is a direct bolt in. The YZ suposedly has more radical ports, a little higher compression, and of course the power valve system. In my opinion the power valve system dosnt add more power, just gives you a little better control of where the power comes from, and when you want it to hit. It takes that "light switch" feeling away when you crack the throttle, and you know where it is. The kicker can be set up to kick forward, just like the tri z motor, you just have to swap some internals between the two. Good luck, and let us know a little more info!

I just wanted to comment on the power valves. They were never designed to increase the top end output. Rather they were just a devise to add low end without sacrificing top end. Early PV's consisted largely of a bufferfly, flap or some other obstruction in the exhaust port to restrict the flow of exhaust at low lower rpm.

I'm not very familiar with the YZ design, but looking at pics from 85 it appears to be a similar "basic" drum that limits the exhaust flow. At some point through 1998 it looks like it evolved to actually change the compression ratio and port timing. In 1999 it definitely changed to the Honda design (like most others use) which essentially gives you two engines in one. Below 6000 rpm is about 11:1 compression, above 6000 rpm is around 9:1 compression. The torque increase is the real advantage with PV's.