Tri-Z 490 project

**Tri-Z 490** · 01-20-2003, 02:42 PM

Has anyone ever heard of or seen a YZ 490 motor on a YTZ. It has always been a dream of mine to do it. any suggestions?

**Jeroboam7** · 01-20-2003, 04:04 PM

I think I would use a different engine, maybe CR500, or KX500, or maybe a big four stroke before I tried to use the YZ490 they are very tuff to get to run right, and you will end up chasing jetting and cooling issues everytime you have it running.

**OldSchoolin86** · 01-20-2003, 07:39 PM

I think it would be cool. If your going to build a Tri-Z you might as well use a Yam motor.

**Dynofox** · 01-20-2003, 09:32 PM

The big thing back in the day was turing yz 490's into trikes.

**Rod** · 01-20-2003, 10:32 PM

There was one for sale quite a while back close to me. I didn't see it in person but the pics look pretty cool though. Seems that it would be a little easier then the kx or cr conversion because of the air cooling. Keep us informed if you go through with it.

**TimSr** · 01-21-2003, 12:14 PM

Im not sure about year to year models on the 490 motor, but I had a YZ465 motor, and the cases were the exact dimensions of the TriZ motor, except for where the cylinder mounted. Id guess that a least some of the 490's would be the same way. If it werent for the coolant pump, even the side covers would have been the same. Looks like it will bolt right in. The one issue though would be the backward kickstarter on the YZ's. I havent explored this theory, but Im thinking maybe the TriZ guts inside the YZ cases, while keeping the YZ crank and top end, and the problem would be solved. I guess I should have kept that 465 bottom end to test this theory!
Ive never owned a 490 before, but I dont think Id be so quick to accept that it will automatically give you problems with cooling and carburetion. They seemed to have a reputation for reliability. Jeroboam, what experiences led you to this opinion?

**Jeroboam7** · 01-21-2003, 01:13 PM

Tim I had this great idea at one time as well but after some research and watching the few that exist around here I dismissed it as more of a headache than it was worth!

For some reason Yamaha had a head design that was completly inadequate for this engine, after warming up and doing some hard riding these engines would start to detonate and ping, there were a couple fixes for the problem. One was to have the head completely redone! The other was to install two base gaskets and a 2 mm smaller carb, and then retard the timing, these worked but as you might well know when these engines are retarded to the point were the pinging quit, the engine on occasion would run backwards!!

If you were just going to do some drag racing then let the bike cool down, this would be a great engine for that, but if you were planning on any sort of extended rides such as dunning for example, I would think you would be sorely disapointed.

There fore I suggested one of the other big bore engines, by the time you got the YZ490 to run right, the extra cost would have paid for a engine that was much better designed in my opinion the CR or KX!

Just my thoughts on the subject you can do with them as you like.

**Jeb** · 01-21-2003, 01:59 PM

Rod, was it a 490 3-wheeler conversion or just a YZ490 bike? Would you mind posting those pics if its a 3 wheeler? I and I'm sure many others would love to see them!!

Thanks!

**TimSr** · 01-21-2003, 03:58 PM

Thanks for the info. Im comtemplating a similar project but had some concerns about an air cooled motor on an ATV. I was thinking of a TriZ motor, but then when I realized how that YZ465 motor fit right in, it got me thinking. One problem with air cooled bike motors on ATV's is that there tends to be less air flow, on the average. I figured this out when trying to ride a bike with fellow ATV riders, who generally cruised trails slower, and stopped a lot more often. The big advatnge to sticking with a Yamaha solution is that so many will fit right in without having to weld and fabricate special mounts. I figure if your gonna start trying to adapt Honda or Kaw motors, you may as well work with a better chassis, because the Blaster chassis isnt my first choice for a sport quad.

**Tri-Z_Jim** · 01-21-2003, 08:19 PM

Hey Tim Sr,I hope I wasnt 1 of the slower trail cruisers

I also would love to have a Tri-Z 490.Not to ride of coarse,just to have up on the shelf to say "I have one" I never rode or worked on a 490 so I dont know much about it.If I was to put the 490 in a tri-z I would just get it running right and looking like new,then pick a color and paint the frame and everything and slap it all together.Then coat everything with armorall. I have 2 parts tri-z's waiting for motors,someone find me a YZ490 or motor for a reasonable price.I would take a stab at building one.

**OldSchoolin86** · 01-21-2003, 08:26 PM

Originally Posted by Jeroboam7

after warming up and doing some hard riding these engines would start to detonate and ping, there were a couple fixes for the problem. One was to have the head completely redone! The other was to install two base gaskets and a 2 mm smaller carb, and then retard the timing

Sounds like a little more octain is needed.

**Rod** · 01-21-2003, 08:52 PM

It was a tri-z with the 490 motor in it. I don't thionk that I have the book around anymore but I will look.

**Jeroboam7** · 01-21-2003, 10:34 PM

Oldschoolin Race Gas didn't cure the problem either!!

**Jeb** · 01-22-2003, 02:43 PM

Thanks Rod!

It's been about 10 or 11 years since I've ridden a YZ490. A buddy of mine had an '86 model for several years. It was brutal. I've heard the same about all those old air-cooled open class motors like the CR480R, Maico 490, YZ400,465,&490, RM 500, KX 420 and such. I don't remember him ever having much trouble with it except for the fact it would hurt your @$$ if you weren't careful. I trail rode on it quite a bit and even rode some MX tracks. I kept it a gear high and lugged it and I was not fast on it, but I had fun with it. The only time I ever got on it was out in an open, flat area. :-D

I'd think vibration in a 4 wheeler frame would be pretty bad. I've always thought it'd make an awesome Tri-Z motor.

**Big Darn Mike C** · 01-22-2003, 03:31 PM

Didnt yamaha have a WR500 for a few years that was a liquid cooled 2 stroke? This is more of a question. If so why not use that motor?

Thread: Tri-Z 490 project

Thread Tools

Tri-Z 490 project

..