YZ motor in Tri Z...whats the deal??????

[Darius1502]

Would a 1999 YZ 250 motor (or similar 1996 to 2004) YZ motor fit into the Tri Z frame?

Do the motor mounts line up? Is there anyway to find out?

Thanks!

Darius

Here is a pic of a YZ frame and the Tri Z frame...can anyone figure it out?

[TRI-Zbrian]

im sure chain saw will know but i am pretty sure that it is not a direct bolt in but it can be done and has been done chain saw has a tri z right now with an i think 87 YZ 250 engine in it dont quote me on the year but he does have a Z with a YZ engine in it... doing this would be a good deal because you will be able to have a powervalved engine. :D

[Darius1502]

looking at the Tri Z frame the mounts are close.

Also you can get a big bore kit for the YZ....but if its a modern YZ engine you probably won't need it!!

20 years of development means alot more power!!

I am going to create a cut out of my motor mounts and then see how it would line up on a YZ 250

This could get interesting!!


Another issue will be the fuel pump but I think I can drill a hole in the YZ cylnder to get pressure...this is Yamaha did for the Tri Z anyway.

[TimSr]

I dont know about the 99, but if you go back just a few more years, a whole lot of Yamaha motors, not just the 250, had exactly the same geometry, and would fit right in. Only problem was the backwards kickstarter.

The vacuum tap for the fuel pump is nothing more than a hole with a nipple theaded in at the cylinder base.

[Darius1502]

Great point Tim.

I read that in 99 the Yamaha changed the motor quite a bit and started with a fresh slate.

Interestingly the Tri Z motor is basically the 1983 YZ motor. From the sound of it there were only minor changes to the motor for the next 15 years (mostly powervalve mods and other changes). If this is true then the geometry should be the same.

There is an easy way to deal with the kick starter issue....just bolt the fenders to the seat pan (like the ATC 250R) and take off the whole seat / fender assembly when you kick it over.

[Darius1502]

My next question is whether its actually worth the effort?

Has any one ridden a 1990 to 1998 YZ and compared the power to the Tri Z?

[TRI-Zbrian]

talk to chainsaw he will be able to answer all your questions.... also by using the tri z right side cover and kick start gear assembly you can make the earlyer YZ engines kick backwords like the tri-z .... do a search and you will find a crap load of info about this on here..

[84250r]

Chainsaw has an 87 YZ 250 motor in his 85 Tri-Z. He said it was way better. He should be able to give you some advice. Is this your 86 tri-z? You swapping out the 86 Z motor for a YZ motor?

[Darius1502]

I found a 1999 YZ 250 motor for sale and I am considering doing the swap.

I want a modern (i.e., 1996 to 1999) motor in the Tri Z. Yes it is my 86 Tri Z that I am considering doing this too.

I also like the fact that I can modify the newer YZ motor to a big bore (300 + cc's).

Once I get this done the Tri Z can run forever and will be way fast.

I will keep researching.

Thanks for the input!

Darius

[TRI-Zbrian]

how much are you paying for the engine?

[Darius1502]

I suspect around $500

[CHAINSAW]

My 85 does have an 87 YZ motor in it. It does bolt right in, no mods to the frame or anything.
Some differences to consider are as follows.
The kickstarter as stated above. Mine just uses a Tri Z side cover, and kick assembly.. it bolts right up! So mine kicks forward like the Tri Z.
The intake is not straight like the Z is. It points to the right (looking head on at the machine) to clear the rear shock on the YZ. I have an aluminum gas tank, and did the ole swaperoo with the air filter, so this does not affect me either. It would be a problem if you were to keep the stock gas tank, and airbox assembly on a Tri Z though.
Mine does not have a head stay on it. Im not sure if it wil bolt right up,., never tried it, and it doesnt bother me to not run one.
YZ doesnt have lights, but companies do make aftermarket stators that have the ablility to add lights to them.
Also as stated above, the fuel pump. again, Im running the normal style tank, so I dont have a fuel pump.. gravity does the work.

A Tri Z pipe will also bolt right up to the YZ motor.

One thing I have noticed, the YZ doesnt seem to vibrate as much as the Z motor. My dragster is actually pretty smooth riding compared to any other Tri Z.

Im no expert on YZ motors, so I can't answer all questions. From parts listings, and what Ive gathered, 85-87 were pretty much the same. 88-90 something were different, mid 90s there was a change, and so on.
If you guys got any more questions for the older motors, I can try to help. As for the late model YZ motors, I dont know much about them. My 87 motor rips!! there is no comparison between it, and the Tri Z motor. So if you have any doubts about them performing about the same, forget it. It was totally stock (besides 20 over bore) when I first tested it. My coil went bad, redoing the plastic, and thought what the hell, and sent the jug off for an all out port n polish for drags (because its no sleeper.. its pretty obvious what this machine is for.. lol)