Jump to content
Sign in to follow this  

yz 490 motor

Recommended Posts

im looking at putting this motor into something newer. how was this motor power wise? did it have good power? were was did it have the best power? was it controllable power? just kinda the good and the bad of the motor

Share this post


Link to post
Share on other sites

im looking at putting this motor into something newer. how was this motor power wise? did it have good power? were was did it have the best power? was it controllable power? just kinda the good and the bad of the motor

one of my friends had a 490. It was a tank. He never did any maintenance and it always ran. He said it had a lot of torque. But it could barely pull away from my 125 out in the open desert...

Share this post


Link to post
Share on other sites

I would say there would be NO WAY a 125 could beat a healthy 490.  They are beasts.

Check out this important link too for squish info.  I see they deleted the images on this site, probably because it's so old.  If it's no help, RB designs would be.  Squish is super-important on the 490.

http://www.allthingsmoto.com/forums/f-30/yz-490-tips-tricks-head-mod-diagram-43867/#post566515

Share this post


Link to post
Share on other sites

The YZ490 motors were absolute BEASTS!

 

The later years had considerably more power than was available in the first couple years.  I think they finally topped out around 60-65HP in '89-90.

Tons of torque, and a rip snarling mid-range hit that will lift the front wheel in just about any gear.

 

The single biggest downfall was the vibration issues that can be lessened with a lot custom machine work and balancing.

 

They can be a real bear to jet properly so they don't ping themselves to death.  The link about setting the proper squish clearance will greatly improve the jetting and general engine performance.

 

Just a side note about the guy who posted he could run with one on a 125......Five years ago I still had my '89 YZ490 and took it to the local track.  I am an older guy and all of the younger kids on their new shiny 450s were pointing and giggling at that old air cooled motor.  Fired it up after a couple kicks and took it out for some slow, pacing laps on the track.  Those same kids spent a few laps roosting me and generally being pains in the butt IMO.  After six or seven laps, they were coming around me again on the back straight and we all made a sharp turn to the left where they all passed me, and headed up a long hill.  Enough, I dropped into 3rd and hammered the beast.  She instantly sprang to life and lifted the front end up.  I was shifting into 5th with the front wheel off the ground as I blew past them at the top of the hill.  They had a very different appreciation for the old air cooled motor when we all got back to the pits.

 

The YZ490 motor will outdrag any modern 450, and would hang with any of the other open class smokers of its day.  They are just finicky when it comes to jetting and they can vibrate your hands until they are numb.  But power????  They have more than 99% of riders can use.

Edited by USED YZ426F

Share this post


Link to post
Share on other sites

When I think of YZ490 I instantly think of how many more titles Broc Glover would have won if he was not so loyal to (or well paid by) Yamaha.

 

Air cooled. 60HP and nice power at the beginning of his motos, then by mid-moto, degrading to about half that HP and pinging it's self to death once it heated up.

 

As already mentioned the vibration would turn me off. I rode one in the late 80s. Hated it. Like a bumble-bee.

 

BTW: If you want the ultimate 500 motor, you'd be considering the KX500 motor tuned by Tom Morgan. Jeff Ward's mechanic.  Poor Broc on the YZ490 trying to beat Jeff.  I got a lot of respect for Broc Glover's riding skills and tenacity.

Edited by numroe

Share this post


Link to post
Share on other sites

I loved the power but it was a bitch to start cold because of the piss poor head design

you better ask super hunky about yz490s before you buy

Share this post


Link to post
Share on other sites

Regarding balancing, I don't know about cycle rebuilders but race car engine builders are masters at balancing.  I have one near me that will balance anything from car engines to cycle engines to high speed printing press rollers.  Basically, anything that spins fast enough to need balancing.  If I had a 490 apart, I'd definitely send it to someone for balancing.

Drilling a crank counterweight and plugging with either heavy or lightweight metal I would hardly call "custom" machine work.  It's quite routine for them.

Share this post


Link to post
Share on other sites

Wow this takes me back. Last time I rode a 490 was when I was 15. Cripes that beast had so much damn compression and was so high I had to lean it against the barn just to start it. Talk about power. Wow is all I can say. The most amazing thing was the guy that owned it was a Korean guy that weighed like 130 lbs. Still don't know how he handled that bike like he did. Thing was a hill climb monster.Let me tell you at the time I had a yz 125 and on a short track I beat him all the time but on a longer straight he blew my doors off.

  • Like 1

Share this post


Link to post
Share on other sites

So how do i fix the head design. This is a project i will be doing in a few years when i get the money and the two bikes.

Edited by dmonster

Share this post


Link to post
Share on other sites

So how do i fix the head design. This is a project i will be doing in a few years when i get the money and the two bikes.

Either look at that link I posted above but if the info is gone, ....RB Designs.

Share this post


Link to post
Share on other sites

Depending on what year, the early 4 speed models sucked. Impossible to jet right unless motor work done, and a powerband that would kick in + or - 1500 rpm. Truly unnerving!

Share this post


Link to post
Share on other sites

I think I could go for pink slips 125 against 490. I think I can come with a 490. Wheres the 125 lmaco

Share this post


Link to post
Share on other sites

They rattle and vibrate badly and are a mother to jet without head work and race gas. On a side note, I'll never forget Damon Bradshaw out there on a factory 490 at the Glen Helen 500 gp back in the late 80s/early 90s. It was a dinosaur then. Cheers

Share this post


Link to post
Share on other sites

Impossible to jet right unless motor work done, and a powerband that would kick in + or - 1500 rpm. Truly unnerving!

Yeah, that's right. I forgot about that. It had a mind of it's own. Roll open the throttle and you never know what to expect. 30 years ago, to help Brock try to win, I guess Yamaha threw about a million bucks at it, on wages and parts, then gave up.

Share this post


Link to post
Share on other sites

And the head work pretty much cures all of that.  Easier to jet, easier to start, runs cooler and if you desire, you can specify you will be using pump gas.  It's just squish band work, not something really expensive.

Share this post


Link to post
Share on other sites

I had an 87 YZ490 about eight years ago....went through the engine and ported it and had the local machine shop do some head work with it. That bike was a beast for sure, but I still don't think it had the power the CR5 does stock......wish I would have kept that old YZ

Share this post


Link to post
Share on other sites

004.JPG008.JPGThe 490 is pretty strong it had its bad spots. But with a few simple mods it works really well. And most of the vibration is in the pipe and jetting. And putting the motor in a updated chassis is a kick but ride.

Share this post


Link to post
Share on other sites

attachicon.gif004.JPGattachicon.gif008.JPGThe 490 is pretty strong it had its bad spots. But with a few simple mods it works really well. And most of the vibration is in the pipe and jetting. And putting the motor in a updated chassis is a kick but ride.

does that blue one have an extended swing arm on it? it looks like it.

Share this post


Link to post
Share on other sites

Yes it does. it is used in what they call altered stock class. In most races you can run a max wheelbase of 66". The motor is 515cc with a 5spd

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×