Tri-Z Engines

[El Camexican]

Went to install the cylinder studs last night only to realize that with the decking and eliminating of the head gasket I going to have to shorten the brand new OEM (and freshly plated) studs about 3mm if I want to use acorn nuts. While mulling that over and realizing that even extra tall acorn nuts wouldn’t cut it, I remembered that the YZ engine uses dowel collars. Given that the Tri-Z is famous for head leaks and that the YZ was getting the newest upgrade I decided to drill the Selvy head to suit. Kind of a scary process knowing what it would take to replace it.



After finishing, and realizing that the collars don’t fit the factory holes in the cylinder very tight it occurred to me that they are more so to hold the gasket in place. No matter, it’s done and the head has way less movement on the cylinder than it did.

[ironchop]

Looks fantastic sir

I'll bet you're glad you didn't polish this motor

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[El Camexican]

Looks fantastic sir

I'll bet you're glad you didn't polish this motor

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Yeah, that’s never happening again

[this old rz]

Good God! I never realized the Tri Z had so many problems until reading through your posts...lol
Never was able to get my project going.....So glad I didn't jump in head 1st with mine as my bike has been Micky moused 6 ways to next Sunday.
I never would have figured all these shortcomings out.
Rob Selvy built all my friends ATCs 250Rs and Tecates.... I was recently thinking of pulling my for sale ad; and having him do my TriZ, as he had a few custom cool parts for one at his shop.
But now with his passing away....Think I'll leave my TriZ advertised on Craigslist.
Hoping a dedicated individual will seek her out and give her some long overdue justice.

[6spdls1z28]

What did you mill the yz head to?

[ATC King]

Yeah, that’s never happening again

WOW!

A Steampunk edition Tri-Z engine. Did you follow through with the design for the rest of the trike?




Looks nice, but I couldn't resist havig some fun in pointing out the coincidence.

[El Camexican]

What did you mill the yz head to?

I did not use a YZ head as the spigot locations are different.

I sent a stock Tri-Z head to Yaeger performance who had Rob Selvy weld up the combustion chamber and machine a completely different chamber.

[El Camexican]

WOW!

A Steampunk edition Tri-Z engine. Did you follow through with the design for the rest of the trike?




Looks nice, but I couldn't resist havig some fun in pointing out the coincidence.

Hopefully they don’t sue me for plagiarism.

http://www.3wheelerworld.com/showthr...Z-Engine/page4

[El Camexican]

I had planned on checking the squish and timing one last time before I get ready to bolt this thing together when it dawned on me that I had not installed the vacuum port, or elbow if you will for the pressurized fuel system.

The Tri-Z cylinder has a machined flat spot on the cylinder for the elbow, but the YZ does not, so I had to drill the hole at an angle to the curved cylinder. Drilled .004” smaller than the elbow and ed it in with green Loctite on it.









With that in place, I checked the bore one last time and then both of the cylinder down and Chechen the timing one last time and measured the squish.

Exhaust opens at 83 ATDC and the transfers open at 115 for 32 degrees of blowdown. Squish is .042”

[6spdls1z28]

You get this thing together yet?


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[El Camexican]

You get this thing together yet?


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No sir. Had a few issues come up including a week in bed. Will post when time permits.

[6spdls1z28]

No sir. Had a few issues come up including a week in bed. Will post when time permits.

Feel better looking forward to seeing it together! I have to take my crank to get a new rod put in before I assemble mine.


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[El Camexican]

Re-wired some stators today including one with all new parts from Ricky Stator and eBay. All of them got Shep’s super awesome grommets. Every Tri-Z deserves these. Thank for the consult ps2fixer!

[El Camexican]

I thought I was just about ready to button this thing up the other day. I started by removing the cast ribs on the stock clutch cover that are known to rub on the aftermarket clutch baskets.






Then I went to setup the power valve only to find out I’d installed the wrong bearing in my finest Tri-Z clutch cover. I tried to remove it, but ended up breaking the puller. At that point it occurred to me that the clutch cover is probably the most expensive and unobtainable part on the engine, so I carefully ground the end of the governor shaft down to 7mm in order to get it to fit the incorrect bearing. By far the most halfassed mod. I’ve made since turning 18, but in my defense, it came out almost perfectly round and fit the bearing nicely.



With that cringe worthy southern engineering event behind me I installed the Sprock impeller and installed the cover. With all the bolts in place I attempted to turn the engine and it wouldn’t budge. For some reason the NOS Yamaha washer that’s supposed to prevent the backside of the water pump impeller from rubbing on the clutch cover was too thick, or maybe the bushing in the case wasn’t pressed in far enough causing the pump gear to bind. Whatever the reason, a thinner washer fixed it.



With the cover secured I went to hook up the PV linkage only to discover once again I was the victim of an ill informed eBay seller. Note the slightly different bends on the arm on the top. Fortunately I had another that came with another 85 cylinder and it fit. As far as the adjustment goes I only have a Clymer manual and it either has a horrible translation, or they copy pasted Info from another manual. If anyone happens to have an honest to God 85 YZ250 manual, or knows what the base line setting is, please let me know. For now I just raised the PV to the open position and scratched a witness line into the bushing. When I rev it up with the cover off I can adjust to match. Given all the adjustments to the cylinder height it’s probably the best way to check it.





Then a nut and wrench had to be modified in order to accommodate the weld that was placed on the rear left corner of the cylinder in order to add a nice big boost port.



So with everything but the head installed I thought I’d check the squish one last time.



Good thing I did because the gaskets compressed enough under full torque that I ended up a little below the safe mark for something that isn’t being rebuilt every week. No combination of my many stock, Sprock, or Auto Zone gasket paper combines to what I need without triple stacking, so I decided to call Cometic. Ended up ordering four .075” rubber coated aluminum gaskets and two .250” aluminum spacers that can be used for future projects. The tech’s name name was Evan and he was a pleasure to deal with.

[knappyfeet]

Aw....the modified wrench.

I have many of those laying around.

Nice modification on the governor shaft....save that clutch cover!