Please Help!!!

[bpope]

Hey guys,

I have tried all of my resources...internet search, calling the dealership...but, I can't figure out what year my Yamaha is.

It is a YZ250, with the serial # reading: 5X6-001575

I am pretty sure it is a 250 (motor says 246), but from the pictures I have looked at, it appears to be at least a 1982. But, someone has put the early tank and seat on it so I thought it might be 80-81, but it has the mono shock suspension with the linkage and the box aluminum swingarm. Not the one with the braces that run up to the top. It has the 1982 up swing arm.

If anyone could please help I would appreciate it...I'm just trying to figure out the year so I know what piston to put in and plastics to buy so I can start riding! Thanks in advance :cool:

 

[Moose]

If you put a picture of it on, then that'd be tons of help.

Elliot

 

[bpope]

Thanks for the fast reply...unfortunately, I have it tore down to bare frame...does that matter? Also, it is super confusing because the bike is not liquid cooled and the research I have done reads like 1982 is the first year to be liquid cooled...this bike is prolly some frankenstein job. :bang:

 

[bpope]

OK, I'm 99% sure it is an '82 frame as it has the swing arm as I described and the shock is on the backbone of the frame...it looks like '83 up has the shock in the location where you see all of them on newer bikes.

The engine I have yet to identify...it looks like they put an '80-'81 250cc engine on it as it is NOT water cooled like the '82's came out with. Can anyone confirm this? The serial number on the engine is 4V6-00972

Thanks,

bpope

 

[chicoman]

4V6 doesn't show up in my manual, the 81 yz 250 starts with 4V3. All the 1981's started with a 4, all the 1980'a started with a 3 and all the 1982's started with a 5 so it's a good chance that your engine is an 81. Are u sure about the number? Also, it could be an IT engine but I don't have a manual for those.

 

[VintageDirt]

I checked over at Jeffscycles.com and they claim the 5X6 is a YZ490 and 5X5 is YZ250

Model: YZ490J Year: 1982 Start Engine#: 5X6-000101
ENGINE TYPE: 2 STROKE, REED VALVE, SINGLE
DISPLACEMENT (CC's): 487
IGNITION: CAPACITOR DISCHARGE
STARTING: PRIMARY KICK
TRANSMISSION: 4 SPEED
WHEEL BASE: 59.1" (950 MM)
COLORING: COMP. YELLOW
FRONT SUSPENSION: TELESCOPIC FORK W/PROPORTIONAL VALVE
REAR SUSPENSION: SWING ARM WITH MONOSHOCK

Here's what the 490 looked like:

 

[bpope]

Guys, thanks for the responses. So, from VintageDirt's relply, I guess it is a 490 chassis. Wish it would have still had the 490 engine!!!! But here is what is wierd...pretty sure the tranny is only a 4 speed. I was thinking that 80 and 81 were 5 speed and 6 speed respectively. But my engine only has a 70mm bore.

Chicoman...was the IT a 4 speed tranny?

Also...anyone got a 490cc engine I can put back in this thing. ;)

 

[bpope]

Ok guys, verified the numbers on the block. Chicoman was right...it is an IT250 motor. So, it is an IT250 motor in a 1982 yz490 frame, LOL. Thank you guys so much for the links and good info.

Now I'm deciding whether to tear down the whole 250 motor (needs lower rod bearings) or just trying to find a 490 or 465 engine. The 250 would be fun, but I think 400 something would be more fun. :)

Thanks again.

 

[VintageDirt]

4V6 is an IT465

 

[cr250mMxer]

all these people are giving different answers just check the jug and it will tell you how many cc it is

 

[bpope]

I already knew it was a 250cc, was just trying to figure out what year it was. :cool: And Chicoman, I verified the numbers on the block and it was 4v5 instead of 4v6 which says it is an IT250. Thanks again.

 

[IndyMX]

http://www.quickinet.net/gallery/main.php?g2_itemId=13514&g2_imageViewsIndex=1

Here's a pic of a friend of mine rippin it up on his early 80's 490..

It's a rather sweet bike. I suggest you find a 490 for that beast, and show a few kids on new toys what it's all about!

 

[chicoman]

Before you spend any time hunting down a 490 motor, check out this article: http://www.superhunky.com/worstbikes.html
Also do a search of Rick sieman's "Don't Ask" colum: http://dirtbike.off-road.com/Don't+Ask
and see what he has to say about the 490. Apparently there was a flaw with that engines combustion chamber.

 

[chicoman]

Oh, by the way the IT had a 6 speed. The previous owner may have sapped trannies with the 490, which had a 4 speed. From what I've heard the 465 engine would be the one to get it you want open class power.

 

[bpope]

Thanks again Chicoman! :cool: