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Old 01-31-2013, 10:54 AM   #163
FJ_Kevin OP
Gnarly Adventurer
 
Joined: Dec 2010
Location: Maryland ==> originally from Long Island
Oddometer: 345
Carburetor

With the motor back together and back in the bike, attention was turned to the carburetor. The YZ/IT 465's and early 490's sported a 38mm Mikuni carburetor with left side idle adjustment screw. Later 490's came with a 40mm carb so be careful when comparing jetting across the model range.

It is important to note the side of the adjustment screw because replacement slides are available in left and right hand versions. If you choose to buy a replacement slide, say with different cut away,you will want to make sure you get the correct one for your carburetor.

It's alway good to get things cleaned up before starting a carb rebuild. Like others, I have been moving away from using harsh carburetors cleaners (when possible!) in favor of something safer.

I had good luck with Pine-Sol on some Goldwing carbs I rebuilt a couple of months ago and so that's what I chose to use here.

The following photo shows several carbs going into a tub I picked up from home depot. These tubs come with a handy top that helps keep unwanted items from falling into the solution while the carbs are soaking.

Using the top also keeps the smell from being over powering.

I used pine-sol at full strength and soaked 4 (added one more after photo) disassembled carbs for about 12-14 hours.



And here they are after soaking,



The carb in front had a bit of corrosion in the top of the float bowl area but it should still work OK.




Here is one that's easy to miss.

The bell of the Mikuni accepts an air correction jet (see hole at 12 o'clock position) for some applications. The IT490 uses a jet here but it is completely left out for the YZ465. Aways a good idea to check this if you dont know the bikes history.



I already has some baseline jetting combinations in mind from experiments on the IT490. Before going forward I had to see what parts I already had on hand.

The main jets are along the top with values of 350 through 460. The needle jets are in the center Q2, Q4, Q8. It looks like I had 2.0 and 3.0 slides on hand. Pilot jets are mostly in the 35 to 50 range with one flyer at 80.



More to come...



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My '81 YZ465 Factory Race Replica
http://www.advrider.com/forums/showthread.php?t=772033

My Vintage Husqvarna/Motocross Restoration Extravaganza Thread
http://www.advrider.com/forums/showthread.php?t=964670

FJ_Kevin screwed with this post 01-31-2013 at 12:20 PM
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