Tri-Z PowerValve Project

[NeverLift]

I am in the process of installing a 1985 YZ250 cylinder/power valve, flywheel, stator and wire harness on my 85 tri-z.

For starters I love my Z the way it is but this is something I've always wanted to do.

My Z is currently ported the Yamaha wrench report specs for pump gas. With the extra boost port drilled all the casting imperfections cleaned up, 39mm Keihin D slide carb, K&N pod filter, DG silencer and a pipe I've never seen one like it before(I will post pictures of that later to see if anyone can help me ID it). 6 speed 86 transmission, Progressive fork springs, Works Quadcross Banshee shock, 2in swingarm extension, Lonestar axel.

I have started porting the new PV cylinder, I added the extra boost port to this one also, cleaned up the casting marks and polishing the exhaust. I started taking apart my z for to gather a parts list of everything I'm going to need.

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[oeduardo67]

I think if you can get it perfected that tri z will be sure to scare a couple of 250r's off. The addition of the powervalve is a night and day difference. While both have negatives and their positives i like both models of the cylinders. On my tecate 4, i love the way the powervalve opens and unveils a whole different machine. You can really tell the difference in port change when you are hill climbing. Half throttle hitting a big hill in second gear, just when it seems youre not going to make it, the powervalve opens and you better hold on cause you might just land on the moon lol.

But yea loos like a really nice project. Make sure to take a ton of pics and post your progress on.

[NeverLift]

Thanks, last night I installed the cylinder to see fitment. The angle of the intake puts my carb boot very close to the exhaust. I will have to find or make some kind of adapter to angle it straight back. I knew this would be an issue. Does anyone have any suggestions? I will take pictures of this and post them tomorrow.

[Mosh]

Dont waist your money on the dirtbike electrics. The YZ flywheel will not fit the Z crank.

[NeverLift]

Thanks for the heads up but I have a complete YZ motor and electronics. So I will swap the crank if I have to.

[Mosh]

K thats cool then. Just and FYI to save you some headache.

This has been done before and you can swap your YZ crank into your 86 case to keep the 6 speed. They do directly interchange. Here is a thread for reference and if I recall it may help you with an adapter plate idea for the intake. I think in the end, the owner really found that the PV steup was not much of an improvement over the regular Z engine.
http://www.3wheelerworld.com/showthread.php/30686-How-to-power-valve-your-Tri-Z?highlight=how+to+powervalve

[NeverLift]

I took some pictures of my how my carb now touches the exhaust. I think if I just make a new elbow for the filter it should be ok. Then here are some pics of the difference in the 2 flywheels and crankshafts. the tri-z is the bigger of the 2. I will have to install the YZ crank in the tri-z cases.

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[JasonB]

someone murder that spam bot above.


awesome looking tri z man, looks good and good luck with the PV project!

[wildacres00]

Cool build. A friend of mine installed a power valve on his worked banshee and the difference was amazing. The bike was always in the power band. It acted like a 4stroke but had the boost of a 2stroke. Alot of fun. Good Luck

[NeverLift]

Waiting on the funds to buy all the crank bearings and piston. I've been polishing in the mean time. I plan on doing the entire motor this time.

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[NeverLift]

I finally have the time and money to order my parts. I'm dropping off the piston, cylinder, crank and connecting rod to Bill Bune in Anoka, MN this week.
To solve the angled YZ intake I ordered some turbo intake parts. the silicone boots are rated to 400 degrees so even though it's close to the exhaust I think it will work fine.

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[Bird76Mojo]

Wow, I'll be watching this one..

[NeverLift]

Thanks, I'm dropping the crank and cylinder off at the machine shop tonight.