powervalved z questions

[3wheelBandit]

hey guys, what piston is better in an 83 powervalved tri-z engine, non-window yz or windowed tri-z? i would assume the non windowed since they de-tuned trikes. or did yamaha not know about the windows till 85? anyway anyone have some experience with this? also what pipes are you powervalved guys using? i know i am gonna need to modify a pipe because of the flange, but whats a good bottom end pipe to start with? thinking of a 83-87 yz pipe because they are designed with the powervalve, but dont even know if that would have anything to do with it. thanks-gary btw- this is my engine so far

[ATC-Eric]

OMG thats beautiful. Have no clue on your piston, just wanted to say that engine is soooo cherry looking.

[Bryan Raffa]

I got everything to build one of thoe's... and your making me want too!!!... Window for shure!!

[badass350x]

Beautiful, Nice choice on the color!!

[3wheelBandit]

thanks guys for the praise, ive been working hard on this for a long time, im pretty anal :) . 83 cyliner, undamaged 85 cases, 6-speed tranny, all moving parts are new, lots are VERY hard to find new. high-temp paint, gold n black, and wire-wheel finished high-temp clear coated aluminum parts, stainless hardware. fresh sleeve, piston, rod, bearings, the works. now i gotta buy a new tri-z windowed piston, lol.

[TimSr]

thanks guys for the praise, ive been working hard on this for a long time, im pretty anal :) . 83 cyliner, undamaged 85 cases, 6-speed tranny, all moving parts are new, lots are VERY hard to find new. high-temp paint, gold n black, and wire-wheel finished high-temp clear coated aluminum parts, stainless hardware. fresh sleeve, piston, rod, bearings, the works. now i gotta buy a new tri-z windowed piston, lol.

Are you running the YZ crank and magneto system, or the TriZ one?

[3wheelBandit]

im running yz system, dont need lights to go fast!

[barrett8]

even if you wanted a light you need to use the yz crank and electrical or your bike wont make the power you want because the yz electrical is meant for a power valve the tri z's is not

[tecat-z]

The cranks have nothing to do with power output. The Tri-z crank and electrics will work fine, as long as you have done your research and have all of the correct items to facilitate proper P/V operation. If you desire to have lights, Tri-z ignition will be fine. My particular machine "in avatar" utilizes 84 yz250 Trans as it's a closer ratio than the 85 Tri-z's, and much more beefy than the smalish 86. "fear of breaking" I run a 84 inner rotor fly/stator ignition w/ crankworks crank. But, the 85-86 yz is a better set up imo..My bike runs fairly strong as a mild port design. But nothing that will blow any minds if you are familiar with strong Tri-z performance. Uniqueness is what i was after. My engine has been very reliable thus far for 2+ years.

[TimSr]

The cranks have nothing to do with power output. The Tri-z crank and electrics will work fine, as long as you have done your research and have all of the correct items to facilitate proper P/V operation.


I strongly disagree. The purpose of the powervalve is to restrict exhaust to improve the low end powerband at low RPMs. The entire reason they never included it on the TriZ is because the TriZ flywheel is much heavier than the little YZ flywheel and produces similar low end results. If you simply add a powervalve cylinder setup to a stock TriZ motor, it won't accomplish much. Its the light flywheel that makes the YZ so much more of a top end high rever, but its at the expense of low end for which the powervalve helps.

[3wheelBandit]

" Window for shure!! "

now that i think about it good, the piston windows would allow the air/fuel mixture to be drawn in under the piston a bit sooner. so a tri-z piston in a yz would be kinda like a port job, right?? any help on the exhaust?

[tecat-z]

The reason the YZ had a powervalve, "or any engine that has one" was an attempt at capturing some of the lost torque due to the YZ's higher exhaust port. Flywheels don't create torque, and they don't make horsepower. Engines do. Heavier flys only smooth out the delivery of power on any engine. But has absolutely zero effect on max horsepower output. It meerely slows down the hit of aggressive engines. " Which is why they sell FW weights for MX bikes" Tri-z engines were designed to accomplish a completely different task than that of a YZ. Very conservative port layout, extremely small and restrictive intake bell, dinky carb, and the need to have lights and tractable power, allowed the engineers a convenient place to stick the large lighting coil inside the fly too. The ignition system and the powervalve assembly have absolutely no interaction at all. The powervalve begins to open when the governor weights are centrifically forced over, which is driven mechanically based on the speed of the crank.

[badass350x]

Very well said Tecat-z....