1982 YZ250

Okay everyone about a week or so ago I aquired a YZ250 she is from 1982!!  Well dirt cheap and I do not mind dumping money into her that will not be the issue.  I know everyone has mixed feelings about this particular bike but from my persepective it's solid will need TLC like most things from the 80's and overall someone to love her like she needs it. 


So original owner stated they were unsure if it still ran, no gas when I got it bone dry.  Everything was intact nothing missing and all plastics solid with good tires.  I got it home, put in some fresh mixed 2 cycle oil with high end grade gas at a 32/1 and she fired over after a few kicks.  Needless to say everything wasn't all that bad but she smoked a lot.  Was thinking maybe too rich IDK?? 


My problem I have now is this bike is a bitch to start.  First off I have watch numerous videos displaying you should rock it back and forth while in gear to allow a prime, then kick it a couple times but not full kick to also prime, then you should be able to kick it hard and fire up.  Well not so much!  I have had some sucess until I decided to tear down carburetor and rebuild it.  Not my first carburetor and recently just rebuilt a LTZ400 no issues.  Started it back up after rebuild and it was fine.  This bike however my luck is not good. 


So again hard starts or kicks to get it running didn't try to pop start only kick so I'm not sure if that is any better.  Then two the carburetor was torn down and soaked overnight, washed the metal parts of carb in hot water to get solution off and then additional passeges cleaned out.  I have some parts on order the needle and seat set and gasket.  I got antsy and decided to put carburetor back together with all original parts.  Figured worse case the gasket wouldn't seal and gas would come out of bowl.  Well that was not it.  It took forever and a day to get it to start but only after some starting fluid.  Once I did it fired up but ran so high of a idle I thought it was going to blow so I shut it down.  Mind you I did not touch the idle screw during tear down and only did I have to remove air screw I measured the turns which was 1 1/2 turns out with it set all the way in before you back it out. 


I'm out of ideas, I know the jets were fine so I do not understand why once it started up it ran at such a high idle, I even tried to adjust the idle screw and then backed it all the way out and it still wouldn't shut off until I killed it on kill switch. 


#2 day I decided to tear carb down again only this time I couldn't even try to start it once I put it back together, because it spit gas all out the over flow under bowl and out the vent holes on the side.  &%$#@! is going on?


I decided at this point I would just order a brand new carburetor on Ebay for $99 figured what the hell and since yamaha has new parts coming for old one once I get those I could rebuild it the right way next time and have a spare.  But for the love of god could someone help with my high idle, hard starts, and assist with rebuild on this carburetor?  It's a 38mm round carburetor from my knowledge.  Before anything was messed with it did start like I said but wouldn't run with the choke off and smoked a shit ton and hard kick over.


Hope you get the idea with my long ranting.  Sorry about that.


Edited by irishhawk81

When dealing with bikes that old, you really need to start with the basics.


Hard starting could be any number of things that you need to check and eliminate:  Worn top-end, bad reeds, dirty air filter, mis-adjusted carb, weak ignition, old spark plug, crap gas, etc, etc, etc.  The list can be pretty long, but I would start with the very basics and check your top-end and reeds.


The high idle is indicative of an air leak.  Since it didn't have the high idle until after you cleaned the carb, I would double and triple check your intake boot for cracks and tears.  I would also make sure that the base gasket and the intake boot/reed cage gaskets are good and sealing properly.


From the pic you posted, it doesn't look like you have an '82 as I cannot see the radiator which was mounted behind the front number plate in '82.  The water cooling design in '82 was a complete bastard setup and prone to leaking in the steering stem.  It was so bad, that the Yamaha factory team actually ran air cooled engines in many races.

Old bike sitting for so long your main seals have hardened up causing air leaks and compression loss And the hard starting and the high idle issue. it was stored with no gas in it so nothing to keep the seal lubed with any kind of premix.

Somehow had a double post.

Edited by USED YZ426F

I agree with all the above,if you can run the VIN number you will know exactly what you have,actually if it's an 80/81 you have a very desired bike in the vintage world of mx.Cool bike,I would like to see more pic's if you don't mind.

Is the topend in good condition?  Have you checked the compression?  I didn't crack the top end open to look is that how I would check for topend condition or is a compression test sufficent?  What should my compression be?


Are the reeds in good condition?  If they are not sealing properly it makes starting a real pain in the rear.  How would I know if my reeds are in good condition?  If I remove the intake boot those are attached or do I remove those after the intake boot?


Is the carburetor jetted correctly?  Many times the old bikes are jetted way off base.  I would start with the stock jetting and work from there.  The carburetor has stock jets, I have checked this over and over and referenced to a yamaha OEM parts catelog that stated the exact numbers mine has.  As for what I do know its no after market exhaust and still running all original internals meaning no need for jets.  I live in Orange County California so not much of a need for elevations either some yes but not really considering my quad runs fine with stock jets.


Is the air filter clean?  This may need cleaning and I will just order a new one but first attempt ot clean the old one first



What does the spark plug look like?  Have you tried a brand new one?  Spark Plug is brand new and its a BR8EG, factory said B8EG but Yamaha had only the one with the BR8EG guy said thats not a big deal IDK?


Have you thoroughly inspected the electrical system.  If the coils are weak and not developing a good strong spark, starting can be tough.  I do get a spark but only tested during day time so how would I know if it is strong enough?  I mean if I can see spark in day time would think its pretty good at night?


I agree with all the above,if you can run the VIN number you will know exactly what you have,actually if it's an 80/81 you have a very desired bike in the vintage world of mx.Cool bike,I would like to see more pic's if you don't mind.




If I posted the VIN could someone here run it?  I don't have a title for it but I do have the VIN which matches the frame as well as the stamp on the engine.  Also no radiator and I checked where the water pump would be on a 82 model so your right it doesn't have a radiator or for that matter never meant to have one so it's obvious its not a 1982 damn was I wrong?!?!?  :)  So what year could it be?

Edited by irishhawk81

 What pics of the bike would you like to see?  I don't have the luxury to do it tonight as I'm at work and its dark but I could post the pictures tomorrow once I wake up and snap some.

I agree with all the above,if you can run the VIN number you will know exactly what you have,actually if it's an 80/81 you have a very desired bike in the vintage world of mx.Cool bike,I would like to see more pic's if you don't mind.

No hurry on the pic's and as far as checking the vin# I just type in Yamaha vin and it will guide you through.I would post a link but my computer is having a breakdown.

Thanks I will get more information:


So far the bike has brand new plugs, brand new fresh gas at a ratio of 40/1, tore down carburetor and cleaned it out soaking overnight in solution.  The next day I pulled all parts out and washed off the only metal parts in hot water to remove all solution.  The rest of the parts including after I washed down the metal parts I sprayed with Carburetor cleaner as well as all passeges and blew out with air.  I ordered new needle and seat kit, and gasket for bowl.  I was told those parts would take a couple days to come in so I jumped the gun and decided to install all parts into carburetor and attempt to start with fresh gas and brand new spark plug.  After about 20 kicks and a squirt or two of starting fluid it fired up and then ran very very high idle.  I shut it down and that is where I am at now. 


Before that like I said it ran find but would not run with choke off.  So that is why I tore down carb to investigate, it wasn't a one kick startup at that time either but didn't seem near as bad as now.  Now I can't get it to start at all and gas pours out of air passeges on carburetor and below the bowl when gas is on before startup.  So bad it is not worth even trying to kick over or I might die! Gas near electrics = dead!


Anyways I wanted to make sure you know all of what I have done so far.  I have a brand new carburetor coming by next week, I think though my intake rubber grommet that attaches to the small round hole on carburetor is slightly dry rotted meaning a potential leak of air.  With that being said though if it was taking in air to cause a high idle then why did it not do that before the carburetor removal?  Did it have a good seal and now it does not being so old?


I will check compression tomorrow as well as post more photos.  I will investigate the top end and see if I can locate the condition of the rings as well as pull the reeds and see the condition.  I know now what to look for I think when it comes to both so I will check.  Then that compression test will help too.  I will also clean that air filter and when that new carburetor comes if everything checks out I will install and attempt to start it. 

So here is my VIN 3R4-005345 and from what I gather it means its a 1980 YZ250 so moderators please change my title!? Reason it not having a radiator cooling system.  Thanks for that catch guys.  Also seems like it is made in Ontario, Canada? 


So is this a rare bike of this year?  Worth more then most?



I agree with all the above,if you can run the VIN number you will know exactly what you have,actually if it's an 80/81 you have a very desired bike in the vintage world of mx.Cool bike,I would like to see more pic's if you don't mind.

can you post some more pics please?

Nice bike....good find!   Much better than a '82.  

More pics to follow soon sorry for the delay but I work night shift and when I started this thread, I was supposed to be working ha ha! 


Now that I am awake I will get out to the garage and take photos.

Edited by irishhawk81

Congrat's,I see a lot of people get ripped off but in your case,you win for sure.That's just flat out COOOOOOLLLLLLLLL !!!

Here are some photos of my 1980 YZ250.  Also I did a compression test today and hoping I got a good seal my reading was 126psi.  Is that okay or signs of a top end needing replaced?


photo 1.JPGphoto 2.JPGphoto 3.JPGphoto 4.JPG

And here is a engine shot as well as the intake carburetor boot that is in need of repair?


photo 2(1).JPGphoto 1(1).JPG

Definitely not an '82 as you already found out.  Looks like an '80 or '81.  Very rare to find one in such good condition and complete.  You got a pretty good score there.  The vintage racers would love to get one that nice to start with.


When new, that was probably the best all around 250 class bike made.

with the cracked intake boot that could be a serious air leak causing all your issue..  very cool find.  Looks clean!

So is the 126psi compression good? Also what plug type is better NGK or Champion? Plus anyone know the specific number plug to get and gap?

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