Need help IDing a bike...

Its a yamaha YZ dirt bike that that is all I know. I need to know the year and engine size. Please help.
Thanks here are some pics.

 

you can look somewhere around the bottom of the cylinder and find out what displacement it is. It could be a late 70's (somewhere around 79) 125 or 250, or a late 70's, early 80's 490. Sometime around 1980 or so, I know the 125's became watercooled and I think the 250's did as well.

 

I had a 79' IT250 the mono shock was different(inside the back bone) than on this model but the YZ's where usually more on the cutting edge if you will than the IT's so late 70's or possibly early 80's (81-82?). Looks to be a 250 just from external cylinder size.

 

Further research has found that 1982 was the first year for that style swing arm & shock for the YZ's. So it is 82' or newer, I'm not sure when yellow went totally away for the Red & white but both colors where available in 82'.

Update: 81' was the last year for the air cooled 250, so that would leave the 490 which stayed air cooled. 85' was the First year for disc brakes on the 490 so it is between a 82' & 84'.

 

I looked at the bottom of the head and it says Y1 on it. Does that mean anything? I can't figure it out either but you guys came with some sound advice thanks. I thought it would have been newer though. Buy the way it looks its pretty sweet looking. It might be just what I needed since I sold my 74 honda XL 250. This is way different than that one. I think its a 125cc because the engine is really small looking. I can't tell if it turns over since the kick starter is gone, so is the chain and I think its in neutral. I didn't feel like messing with it right now. But it was free so if I can get it to work great, if not I will part it out on ebay. I need to know for sure what it is before I start messing with though.

Any more info that you might have would be great. Thanks in advance.

 

If its a 125 it has a pre 82' engine in a 82'-84' chassis no air cooled 125 or 250's in that chassis only air cooled motor was the 490. After looking @ the pic's though it does appear to have an awfully narrow rear tire for a 490

 

Here is a better picture of the front left side...

Here is a picture of the back side with the extra tire.

Here is a close-up of the left side of the engine. As you may have already noticed. Its air cooled with very small engine/trans.

The right side of the engine.

The rear shock area...

Under the right side...

And the VIN number too in case that helps. I don't have a way to decode the VIN right now. If you could help with that in any way that would be great.
Here are some more pics if you need them. I don't know if it helps but the second tire is one that I got with the bike. The other one that is on it came seperate but fit so I used it to roll the bike around.

 

Do you think that it is worth fixing? Or should I part it out?

 

??? dirt bikes are fairly easy to restore to good usable condition & its a two stroke so rebuilding is as simple as it gets. Go for it

 

You have had one of these haven't you? Are they nice bikes? I am 6' 210 lbs. Is this bike right for me? Also what year is it, and what size engine? I need to know this stuff before I start buying from ebay. (They have a lot of stuff for these bikes but the years very a bit.)

 

Based on the info I found the year range for parts will be 1982 to 1984, & I have to assume the engine size is a 490 as that was the only air cooler motor in a YZ from 1982 on. In which case being a 490 this bike will be able kill you just as fast as you can twist the throttle. My IT250 had a 6 speed trans yz's where only 5 I beleive & I had no problem staying verticle in all 6 gears it also liked to rear up & go over 90 deg. going up hills I got good enough @ anticapting it I could catch the bike 80% of the time & throw it away from me the other 20%. ( IT's had shorter wheel bases, set up for enduro racing)
To verify the displacement there should be a flat area machined into the cylinder jug in close proximity to the base gasket w/ the displacement stamped into it. To get a better veiw take the motor out I should only take a matter of 15 mins there are only a couple of thru bolts that hold in the frame. Then either take the thottle assm off the bar if you want to leave the carb on or disconnected the carb from the reed valve block.( take a look @ the reeds to if they are chipped & cracked they will need to be replaced, boyseen used to offer pretty good performance reeds for the YZ had a set in my IT.)

As far as height/weight I'm the same height & @ the time I had the bike probably the same weight or more( We won't discuss now) The bike had plenty of performance & if this is a 490 be more concerned w/ controlling an excessing amount of power & an insane power band. Suspension is adequate top shelf for the year, I used to cliff jump my IT @ times being 30-40 in the air & don't recall ever bottoming out when I landed right. If you landed wrong the bike would generally pile drive your ass into the ground.

 

Wow, a 490 two-stroke. Watch that powerband!

 

ound: ound:
Love your avatar.

 

That seems like a big motor. I don't know for sure. I will have to look to be sure. I don't have a phone right now or else I would have called a Yamaha dealer to decode the vin. I think that if its that big though I will have a lot of fun with and will restore it.

 

Bad disk brake info apparently

Apparently the info I had on years for disk brakes was wrong, found this pic of a 1986 YZ490. It should look very familiar to you, same tank decal & everything.

http://bikepics.com/pictures/301891/