1980s IT490 vs 1989 YZ250

[Svizzera]

Hi guys,

An older friend of mine used to have an IT490 Yamaha from the 80s and used to swear by the power/torque and just overall madness of the bike. I was too young to ride it when he have it but I remember it being pretty nasty but never rode or drove it.

I recently bought a 1989 YZ250WR which needs it top end redone (Just compression tested last night at 140 lbs) and had a backfire which pretty much did it for me and a new Wiseco kit is being ordered.

So, he has rode my broken down YZ250 and come to the conclusion is it "fast" but nothing like the "IT490" which I told him is actually correct. When the YZ250 is running properly it is faster AND quicker than a IT490 which he sternly denies. (yz250 = approx 46 hp IT490 = 36)

So with very little details even online about the Yamaha IT490 I figured I would put this argument to you guys. On top of it, my newly purchased used YZ250 is running with serious compression issues and even myself has no idea because of I haven't driven a properly running YZ250 yet.

How would you rate the two bikes in a head-to-head comparison?

1980s Yamaha IT490 vs 1989 YZ250WR?

If you wouldn't mind, could you maybe give your marks on categories?

Handling

Acceleration

Top End

low/mid/high

This has been a burning question amongst two nobodies! I hope you can help!

Thanks

[shagger]

The thing about the old air cooled bikes is the way they made power. They were party animals. They weren't as powerful as people remember them. But what they did have. They served up in big satisfying manly doses. If someone tells you that an IT490 has earth de-orbiting power. It's because that is what they felt like when you rode them. You'll not be able to tell them any different. And it doesn't hurt for them to remember it that way. That's just part of the game.

[Svizzera]

The thing about the old air cooled bikes is the way they made power. They were party animals. They weren't as powerful as people remember them. But what they did have. They served up in big satisfying manly doses. If someone tells you that an IT490 has earth de-orbiting power. It's because that is what they felt like when you rode them. You'll not be able to tell them any different. And it doesn't hurt for them to remember it that way. That's just part of the game.

I don't doubt it had power and of course I haven't rode it so it is out of line for me to judge beyond pure statistics, but I guess I like to distill it down to pure numbers and someone has to 'win' when all things are equal.

I get the feeling you think the 1989 YZ250WR is indeed faster/quicker than the IT490 or did I misinterpret your post?

[RCannon]

A good friend had a 1977 IT 400. They were very cool bikes. They made great power down low. LOTS of torque. As far as it running with a 89 yz 250, LOL Things are exactly as shagger said. Down low, they were very powerful, but at anything above 6000 rpm's, your 250 would have an advantage

Yamaha created the "IT" bikes to rid themselves of old yz parts. Back then dirt bikes changed dramatically from year to year. They would add a kick-stand, large tank, and maybe a wide ratio transmission. Instant offroad bike. The big ones though, 400. 425, 465 and 490 ended being heavy.

I'd love to have one of the old 400's engines in a modern chassis.

You'll never be able to beat a memory.

[Svizzera]

A good friend had a 1977 IT 400. They were very cool bikes. They made great power down low. LOTS of torque. As far as it running with a 89 yz 250, LOL Things are exactly as shagger said. Down low, they were very powerful, but at anything above 6000 rpm's, your 250 would have an advantage

Yamaha created the "IT" bikes to rid themselves of old yz parts. Back then dirt bikes changed dramatically from year to year. They would add a kick-stand, large tank, and maybe a wide ratio transmission. Instant offroad bike. The big ones though, 400. 425, 465 and 490 ended being heavy.

I'd love to have one of the old 400's engines in a modern chassis.

You'll never be able to beat a memory.

Haha very true. Thank you for the response.

So you would give the low end advantage to a IT490 and mid/high to YZ250? Or everything to the YZ250 regardless once you get up high in revs?

I have to settle this tonight! I'm ready to brag!! Sorry for the silly comparison that 99% of you probably think is a stupid, old comparison.

Edited May 1, 2013 by Svizzera

[ickfinger]

140lb compression is not bad at all.

[Svizzera]

140lb compression is not bad at all.

Really? I was told it should be in the 190-220 lbs range? I was planning on picking up a Wiseco rebuild kit, it isn't putting down power at all. I can barely get the wheel off the ground in 1st gear absolutely hammering it, and it seems to blowing a lot of smoke.

I honestly wouldn't be surprised if it is even possible if this is the original piston/rings in this 1989.

So 140 lbs on 1989 YZ250WR is tolerable/acceptable? I feel like this is the main reason the bike acts like a 125 4t.

[ickfinger]

A bike will run all the way down into the 70-80lb range. It will be hard to start, may even need to bump start it. 120 is a well broken in motor, 160 would be considered tight and nearly new. I'm not sure you would be able to kick a 200psi motor

[Svizzera]

A bike will run all the way down into the 70-80lb range. It will be hard to start, may even need to bump start it. 120 is a well broken in motor, 160 would be considered tight and nearly new. I'm not sure you would be able to kick a 200psi motor

Interesting...I've seen on many of threads well over 200+ psi and multiple people claiming 'new' YZ250's come around 225psi off the lot.

Can anyone else add to any of this? Again, this is a 1989 YZ250, but it seems to me that this model/year is pretty much a clone of every YZ250 I've seen since then with marginal gains and additions.

I've been under the impression my 140 lbs compression test is a completely failing grade and scream to have top end rebuild.

If it is indeed Ok at 140 lbs, what else would you suggest for my terrible lack of power? The carb?

I got a new jet, yamalube + 89 octane (32:1)

Calipers don't seem to be sticking or locking either.

[adam728]

A bike will run all the way down into the 70-80lb range. It will be hard to start, may even need to bump start it. 120 is a well broken in motor, 160 would be considered tight and nearly new. I'm not sure you would be able to kick a 200psi motor

Far too many factors here. Those might be good numbers for a 125, or even something like a KDX, but way low for a YZ250.

A buddy had a YZ250 that did 190 psi on my gauge. New piston and rings put it at 230-ish, it was easier to start and gained a lot of low end that had been missing. My modded 250 does 245-255 psi on my gauge.

Now, my 125's have been 140-160ish, and my KDX was typically around 150 psi. String trimmers and the such are around 100 psi on my gauge.

Some of it has to do with the volume of the hose vs engine size. The volume in the hose acts as a reservoir of sorts. Say it is 2 cc, and the engine you are testing has 10 cc of head volume at TDC. That means that 2cc in the hose will reduce your compression number by 20% of what it actually is with a spark plug in. Now, say you test a big engine with 30 cc of volume at TDC, that 2cc in the hose is only reduces the number 6.7%.

As for what's faster? I don't think there's ever a winner in bench racing. 490's are brutes and feel very, very fast. Older 250's are the same way, a modern one might have 5+ hp more, but make power in a smoother fashion and don't feel as quick. I have my doubts that a 1989 YZ250 is a 46 hp bike, and that it's any faster than a 490 in a drag race.

Edited May 1, 2013 by adam728

[Svizzera]

Far too many factors here. Those might be good numbers for a 125, or even something like a KDX, but way low for a YZ250.

A buddy had a YZ250 that did 190 psi on my gauge. New piston and rings put it at 230-ish, it was easier to start and gained a lot of low end that had been missing. My modded 250 does 245-255 psi on my gauge.

Now, my 125's have been 140-160ish, and my KDX was typically around 150 psi. String trimmers and the such are around 100 psi on my gauge.

Some of it has to do with the volume of the hose vs engine size. The volume in the hose acts as a reservoir of sorts. Say it is 2 cc, and the engine you are testing has 10 cc of head volume at TDC. That means that 2cc in the hose will reduce your compression number by 20% of what it actually is with a spark plug in. Now, say you test a big engine with 30 cc of volume at TDC, that 2cc in the hose is only reduces the number 6.7%.

As for what's faster? I don't think there's ever a winner in bench racing. 490's are brutes and fell very, very fast. Older 250's are the same way, a modern one might have 5+ hp more, but make power in a smoother fashion and don't feel as quick. I have my doubts that a 1989 YZ250 is a 46 hp bike, and that it's any faster than a 490 in a drag race.

.

I read that about the compressor gauges. The one I used probably only had about a 3-4 stem on it, so it was pretty short/marginal reservoir. I will try it again today by pushing it off with WOT and make sure I can reproduce the results.

[USED YZ426F]

Speaking as one who has owned/currently owns both:

1980s Yamaha IT490 vs 1989 YZ250WR?

Handling <--------YZ. Duh, they are designed and built for motocross action. Tight twisty tracks with lots of jumps. The ITs on the other hand were far superior for straight-line stability.

Acceleration <---------YZ, after about 5-6K RPM as Roland said. Down low, the IT490 will eat a modern YZ250 for lunch and spit out the bones. They were just plain and simple tractors with gobs of power down low.

Top End <--------YZ. The IT490s (or even the YZ490s) quit at around 6K RPMs or so. The YZ250s rev higher and that is were a lot of their peak power HP number comes from. HP = Torque x RPM

low/mid <-------- IT490, hands down. All of their power is right off idle, but it is all over by around 6K RPM.

In all honesty, you are comparing an apple to an orange. Each bike was designed and built for different core purposes. I love my YZ250 and WR250. I loved my '84 IT490L back in the day and will love my '83 IT490K when I get her done. But I won't be taking the IT to the track because that is not what it is all about. I also won't be taking the YZ250 back to the woods when the IT is back in running form as the IT is just SOOOOOOOOOO darn much fun in the woods.

[bobbyward]

Rolland,i can hook u up with a yz 490....... those big motors had torque.