Now this is one of the few times that I might be OK with trying Seafoam!

The bike has sat a few months with pump gas in it, in an unheated garage......might just get by with a battery charge and a slug of fuel system cleaner.

What in the world are you still doing with the stock vacuum petcock on that bike?  With the Raptor petcock you would have turned it to "OFF" on the way up your drive the last time you rode it, and run the float bowl out of fuel before putting the bike away for an extended stay.....well maybe you would have.

Go to the Yamaha Dealer and ask for this part number:

Yamaha 5LP-24500-01-00

Or go to Ron Ayers or a similar online store and get the same number.  Great deal at the moment for some reason.....just $ 19.05.

http://www.ronayers.com/Search.aspx?k=5LP-24500-01

When you install your new jets, start the bike and get it warmed up.  Then adjust the idle speed just a tad lower than normal.  Then adjust the idle fuel screw...turn it in until you hear the speed start to drop a bit...then turn it out until you hear the the engine smooth out and the rpm's increase just a bit.  If you have to turn the screw out more than 2.5 turns....or if you can turn the screw all the way out and the engine idle doesn't change - they put the #50 back in and try again.  Mikuni claims that the correct pilot jet size is the one that will result in the smoothest running at 1.5  turns out on the idle mixture screw.  Because of the tendency of the big single to pop and bang when you close the throttle, it is best to have the pilot jet a bit too rich rather than a bit too lean.  If you can turn the idle mixture screw all the way in and the engine still runs....then the pilot jet is too big.  (There is a bypass circuit around the idle fuel screw that will still allow fuel flow even when the screw is all the way in.....the idle mixture screw is the "fine adjustment".  Too big of a pilot jet and the bypass circuit allows enough fuel for the engine to run even with the idle fuel screw turned all the way in).  Then set the idle speed back up to the recommended 1,000-1,100 rpm.

Once you have the pilot jet sized correctly, take the bike out for a full throttle run.  In a high gear with the throttle wide open....pay attention to the way the bike feels.  If the bike pulls strong - but feels like it speeds up a bit as you roll off the throttle, then the pilot jet is too big (that won't happen with a #145).  If the engine feels like it is surging and accelerating a bit unevenly...the jet is too small.  Another good way to test is to find a straight section of road, and uphill is good as it takes longer to accelerate....and find a telephone pole or sign as a landmark.  In high gear at 40 mph roll on full throttle as you pass the sign and accelerate to another landmark down the road and note your speed.  Then put in the next larger size main jet and repeat the test...continue going to larger main jets until the bike actually gets slower, accelerates more when you roll off the throttle, or you hear the bike blubbering as if the choke was on.  When you find the jet that provides the fastest speed...that is the best jet for performance, and for best mileage you may be able to back off one jet size and still be OK.  Maximum efficiency is obtained at 14.7 pounds of air for each pound of fuel - while maximum power is obtained at around 12.5 pounds of air for each pound of fuel...once you get beyond 13 pounds of fuel per pound of air the engine is too rich and the power begins to drop off.  That explains why you can jet for power...then drop a jet size for economy and still not be too lean.

Finally the adjustment of the slide needle.  When you first start to open the throttle beyond an idle, the slide begins to raise the tapered needle and provide fuel flow.  With the stock white spacer on top of the needle the engine can run too lean at low throttle settings.  My bike had a very noticeable surge when you would roll on the throttle and ride away gently.  I had done the 3 washer replacement for the white spacer, and I tried removing a washer and I ended up with only 2 washers and the surge was gone.  I was then able to drop the main jet size one size and the bike ran great.

My bike had the best performance and mileage with a #50 pilot, #150 main, and 2 washers on top of the slide needle.

Here is a video of how to adjust the idle mixture screw.  Once you have backed the screw out 3 turns - it no longer provides any additional flow as the needle is no longer restricting the flow and the hole in the carb is completely open.  The screw ideally should be out 1.5 - 2.0 turns at the best idle - if the screw is in farther the pilot jet is too big, and if the screw is out farther than 2 turns the pilot jet is too small.  I have attached an image that shows the idle circuit....and you can see the screw only controls the fuel flow out the second hole - the other hole that bypasses the mixture screw is only adjustable by changing the size of the pilot jet.

This is a long - but very good video.
https://www.youtube.com/watch?v=zm5mB3R8Ucw

MM,

There is a very flimsy fine mesh tube that filters the rust flakes out of the gas on each of the two legs on a Raptor.

There is a piece of clear shipping protector tubing over the longer leg's flimsy mesh to keep it from getting crushed in shipment.  

You remove the clear shipping protector tubing before installing the thing.   (or you did when mine was new)

Does that point you straight?   Do you see the mesh on the long leg as a separate thing from the clear shipping cover tube?

There is a chance they have changed it all up into something different, but you'll need to tell us that.

I could have answered that for you a couple weeks ago, as I ran mine to reserve, then refueled about 20 miles later
I remember thinking I might get 40-50 miles on reserve after fueling, based on how much gas it took, but I don't remember how many gallons it was, sorry

it's a rough guesstimate, based on how much gas it took, but I may be off there, I'll try to find the gas receipt but I probably lost it already

Don't leave that clear tube on there....I am not sure the plastic is fuel proof.

If you want to make your "MAIN" fuel stem longer....cut the brass tube and either solder on an extension - or get some real fuel tubing like TYGON that fits the brass tube tightly and use it to extend the tube.

When I mounted my Raptor, I checked the volumes of each petcock and found:

The reserve provided by the Factory Petcock is larger than the reserve provided by the Raptor.  The difference is caused by the height of the tube that provides flow to the ON position.  This could be corrected by removing the filter and extending the height of the tube on the Raptor - which may be a subject of a future tech article.  I turned each petcock to ON and let the fuel run out - then switched the petcock to RES and let the fuel run out and measured what was in the bottle.  The stock petcock provides 78 oz of fuel, while the Raptor provides 60 oz of fuel on RESERVE - this is whithout shaking the bike to get any remaining fuel out of the right side of the tank and you may get more when actually riding.  If you got 55 MPG on your bike the stock petcock provides 33.5 miles of reserve and the Raptor provides 25.7 miles of reserve.