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View Full Version : Thinking about powervalving my tri-z....


VenomRS4
10-09-2007, 09:17 PM
I was thinking about powervalving my tri-z. I have looked through all of the powervalve threads and it doesn't seem to hard. I am probably going to pick up an 85' or so YZ250 Engine if I decide to go ahead with this project.

But I do have a few questions about it though. In one of the tri-z PV threads, it was said that the power gains were not worth the work/effort. But I looked at the specs for the YZ250 motor and they have almost 10 more hp! You'd think a gain like that would be pretty noticeable. The person that said it wasn't any better only swapped the top end and a few other parts related to it. Would swapping the entire engine and just switching the kick start make the difference in power? I always thought the tri-z and yz250 motors were the same except for the powervalve and forward kick though.

Also, what is involved with switching a YZ motor to forward kick? If you have directions on how to do it, that would be great. Also, if I have a complete tri-z motor and a complete YZ250 motor, can the kick start swap be done without buying any extra parts?


Thanks
VenomRS4
10-10-2007, 10:32 AM
Someone must have some answers for me!!!!
VenomRS4
10-11-2007, 04:44 PM
Please!!??!?!!!!!!!
tecat-z
10-11-2007, 07:46 PM
There are many things you will need for this conversion. All of which are bolt on, but have to be matched to work properly and reliably. I have been gathering parts for this conversion for a little over a year and finally have everything. I will be using a tri-z bottom end and utilizing the rest of the components from a 83 yz 250k. This way you can use the tri-z head. 84 up yz cyls have a slightly different bolt pattern so you would have to use the yz head. Coolant hoses and head stay location wont work with tri z. You'll need from the bearings that support the governor all the way up. Some of the 85 components will work in the conversion, but using a 83 cyl will save a lot of grief since it has a straight intake bell. I would imagine you could drop in the yz engine and possibly use tri-z kick gears and covers??? But don't quote me on that. Lots of the parts required to complete this are discontinued, so depending on which way you go with this, it will take time. Unless of course you happen to buy a basketcase yz doner for parts.
VenomRS4
10-11-2007, 09:10 PM
Yeah, im starting to lean toward just picking up a yz250 engine and seeing if I can convert it to reverse kick. And if its possible, I'll just go that route.
VenomRS4
07-29-2008, 01:59 AM
I am finally ready to get into this project. I am planning on purchasing a whole YZ250 for this...cant seem to find a reasonably priced motor alone. Im going to try to take the YZ motor and just convert it to forward kick. But before I start looking around for a donor bike, can anyone else chime in here? Maybe give me a few more tips before I jump into this...

Has this even been done before?



Thanks
Swamp trike
07-29-2008, 06:19 AM
Iīve done the conversion and it work like a charm!
I used the bottom end from the Tri-z and used governer and top end from a yz.
The only "problem" was that the carb. is mounted slightly to the right on the yz, and the stock is going straight back, but it worked just by forcing the inlet rubber in place..
The bigger cylinder from the yz makes it really tight with the coolers but it can be done, and I had to use the top from the tri-z to make the hoses work
I donīt think it would be to much problem using the yz motor and swap the clutchside-cover, to get the forward kick, since the cranckcases are the same..
Another thing I did, was to build a cath-tank on the right side of the carb, to make sure that thereīs always a constant supply with gas (noticed that it had a tendency to loose fuel when I was doing wheelies or climbing steep hills)

Good luck!!