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Just bought a YZ490 1989

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Hello,my name is Maks,i have a 1989 YZ490.

I have a questiong about carb settings and the hoses on the carb.

I am new to the 2 stroke world and any suggestions would be great,thanks.

Does eveything look good on the picture when it comes to hoses on the carb

 

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Edited by Gogolsev

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Everything looks alright from what I see.  Those hoses are vent and over flow hoses from the carb/float area.  They are just fine where they area.

 

this forum is a great palce to get your questions answered.  Might have to post pictures for us old fogies, but we all can get you going.  

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Everything looks alright from what I see.  Those hoses are vent and over flow hoses from the carb/float area.  They are just fine where they area.

 

this forum is a great palce to get your questions answered.  Might have to post pictures for us old fogies, but we all can get you going.  

thank you for your reply,this forum has proven it self in the last 2 days ;)

 

The main picture i posted (1st one) the hose that is connected from the buttom to the top is wrong right?it suppose to be 2 went hose coming out right?

 

When i try to start the bike the fuel POURS out of the lower "hose" or "the buttom of the carb"

 

And one more question,is lean to the RIGHT or to the LEFT on the needel?How many turns is the OEM specs?

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Yz490 are cool as he'll I got a 82 I'm restoring. Good luck with yours !!

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Yz490 are cool as he'll I got a 82 I'm restoring. Good luck with yours !!

6baa6f8eca9611e399880002c9d07a7c_8.jpg

Thanks

Your floats are stuck, or need adjusting. It's a simple fix.

Took the carb apart today,you were right.It was "moldy" looking,lots of green corosion and yellow gue(what ever it is)

Also the reed valves on one side were chipped.

 

Floats are stuck or most likely needs a needle and seat assembly to stop the gas from overflowing.

 

Also, the vent hoses should be longer length and routed behind\under the engine

So the carb had 3 vent hoses?Is that correct?

 

 

Thank you EVERYONE for your help.

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the last pic shows a engine serial number as 1LV.............which is the number for a 1986 engine..............weird

 

and those hoses go behind the engine in front of the swingarm and hang about a inch below the engine........or as comfortable as you are with their hang length 

 

fuel pouring from a vent is a bad fuel needle valve......you can get them from any carb part supplier......but i have found them to be cheaper from yamaha

Edited by sjsingle1

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the last pic shows a engine serial number as 1LV.............which is the number for a 1986 engine..............weird

 

and those hoses go behind the engine in front of the swingarm and hang about a inch below the engine........or as comfortable as you are with their hang length 

 

fuel pouring from a vent is a bad fuel needle valve......you can get them from any carb part supplier......but i have found them to be cheaper from yamaha

Took the carb apart yesterday and cleaned it,i will see if that makes any difference.

 

How can i check what year it is exactly?

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there are websites that will tell you the serial numbers and corresponding yrs......dont know them off hand......google is your friend here :)

 

the 490 you see in my profile pic had a really messy dirty carb when i got it.............would not even start

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Tenth digit in the VIN is the year. That is on US models at least. An '89 would have the letter "K', a 1990 would have the letter "L" and so forth until you get to the year 2000.

As in the Wiki: http://en.wikipedia.org/wiki/Vehicle_Identification_Number

As a general rule, all the hoses from the carb are vent hoses with the obvious exception of the fuel inlet. They should run down between the engine and the swingarm to atmosphere as has been suggested. Sometimes these hoses are linked together with a tee, but that is not necessary.

The photo from the right side shows the idle mixture screw toward the rear of the carb on the right side. As it is toward the rear of the carb, this is an air screw. Therefore turning the screw clockwise reduces air though the circuit and enrichens the mixture.

If your carb has turned green, this circuit is almost certainly plugged. Clean with an ultrasonic carb cleaner, or try to use aerosol carb cleaner, whatever you have to do but when you are done, you should be able to unscrew that screw all the way out and blow air into the hole, that air should exit in three places. Out the rear of the carb, out the pilot jet, and out of a tiny circuit that runs ahead of the slide and dumps out into the bore of the carb toward the very front.

Before I got my ultrasonic, I would remove all of the brass jets and heat them with a propane torch until they glowed. Careful! Don't melt them!! Once cool, the remains of the crusties would easily blow out with compressed air. This is particularly true of the idle jet, which is a small diameter. Once cooked and blown out, I would gently thread a wire from a stainless wire brush through the hole and spin it a couple times then blowing it out again. Almost certainly oversizing the jet a bit in the process, but you have to get those passages open.

Oh, and that air filter boot looks to be in danger of popping off.

Have fun, be meticulous and please let us know how you fare!

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New here myself. Just got a Yz490 as well. Can't help much on the carb hose routing issue but as far as model years go, '82 to '90. Yamaha skipped a few letters in the alphabet. 82 was an L, but by the time you get to 86, it's an S. I'm trying to figure out the year of my bike as well and the 1LV engine code says it's an 86. But there's a few variations with frame colors and tank decals that help pinpoint the year a bit better.

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My apologies for the late reply,been enjoying the bike a lot.

 

I would like to thank everyone that helped me with questions i had.

 

p.s still dont know which way to turn the air/fuel screw to lean it out :D

Edited by Gogolsev

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My apologies for the late reply,been enjoying the bike a lot.

 

I would like to thank everyone that helped me with questions i had.

 

p.s still dont know which way to turn the air/fuel screw to lean it out :D

If the air/fuel screw is located near the front of the carb, then it's passing both fuel and air, so turning it in will lean the mixture out.

If the air/fuel screw is located near the rear of the carb, then it's only passing air, so turning it out will lean the mixture out.

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The photo from the right side shows the idle mixture screw toward the rear of the carb on the right side. As it is toward the rear of the carb, this is an air screw. Therefore turning the screw clockwise reduces air though the circuit and enriches the mixture.

 

     

 

        Quoting myself .  .  .  .  .

Edited by Jon K.
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Just wanted to thank everyone again for great help! :thumbsup:

Summer wouldnt be as fun if it wasnt for the help of this forum! :rolleyes:

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