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Discussion Starter #1
I rebuilt my 2009 TK carb with a moose racing rebuild kit and used the suggested (from pro cycle) jet setup #125 Main Jet and #34 Pilot with the kits needle and one shim/washer. My intention was to make the bike run a bit cooler as suggested on here. Question is if I am using more gas does this mean I am now running with a "cooler" setup? MPG used to be 75-78 MPG first full tank MPG now 62 MPG. Bike runs fine. Thank you for your time. M
 

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I tuned both Harleys with a combination of plug reads, throttle response and an oil tank temperature gauge.
Going richer than factory brought the oil temp down ~ 20 F on sustained grades.
It also dropped MPG ~ 14 %.
I would look up posts on Sportster.org, to check my memory, but it ceased in 2012.

From memory, going up interstate 5 from Los Angeles with the 1200 Sport, stock was almost 60 MPG (1200 cc, dual plug heads, W grind cams).
Again, from memory, the same trip, after rejetting, dropped from 60 MPG to 52 MPH.

This was on a Keihin CV40 carb, with mixture at 2 3/4, pilot from 42 to 45 (0.45 mm), needle N65C (stock for 1988, with no accelerator pump) and 195 main reamed to 203 (2.03 mm). So it was made richer every which way.

BTW, both Sportsters were California models, the leanest of the three produced by Harley at that time (CA, 49 state and international), so base was very lean.

However, if too rich, the mixture can "wash down" the cylinder walls to dilute crankcase oil, darken plugs and send unburned fuel (black smoke) out the exhaust.

Riding to over 8,000 feet elevation, my TW performed very well with only a mixture screw adjustment (from 1 1/4 turns out from factory to 2 3/4 turns out from gentle seat)

Bottom line, how do your plugs look?
Does it seem to run any cooler?
Instead of hesitating, if it was lean, does it now blubber from too rich?

If any rich symptoms are present, I would first remove the needle shim.
 

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Here is what I posted for TW mileage:

Initial around Red Rock Canyon Loop for break-in was 78 MPG.

Once I started working it, it dropped...

I am not a big fan of shims and most riding is mid range (using the needle).

After I dialed in the 1200 Sport with what I posted in post #2, I shimmed the needle and performance dropped.

http://tw200forum.com/forum/general-discussion/33354-114-miles-today-2.html

http://tw200forum.com/forum/trails-off-road-adventure-riding/33697-north-shore-drive-along-lake-mead-overton-return.html
 

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You will take a hit on gas mileage and it would run cooler.
 

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Were there signs of overheating?

I run my TW's lean and tend to ride them hard, albeit asphalt riding. I have had zero problems with overheating or burned pistons or valves. You must be riding it easy to get 75 to 78 mpg. If it ran well I would have left it alone.
 

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I have not done any mileage testing on mine but it seems odd to me that the Moose kit comes with a 125 jet when stock is 126 and mileage dropped. Would this be because their jets are non oem and the #'ing system does not correlate or are they making up for it with needle shape and height. The only known here is that it uses more fuel and the mileage dropped which means it will likely run a bit cooler.
 

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i put the same kit in mine and it turned it into a brand new bike. i was so impressed on how much better it ran. yes i lost about the same mileage as you, but it was worth it. also if you hold the 125 jet up to the light, you will see it is actually bigger than the stock 126. i'm guessing it ran cooler as i never had an overheating problem
 

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Discussion Starter #10
I have not done any mileage testing on mine but it seems odd to me that the Moose kit comes with a 125 jet when stock is 126 and mileage dropped. Would this be because their jets are non oem and the #'ing system does not correlate or are they making up for it with needle shape and height. The only known here is that it uses more fuel and the mileage dropped which means it will likely run a bit cooler.

Exactly the #'s on my rebuild kit are not the same as stock but thankful procycle stick a note in the package with their suggested setup. I used that and the bike started first try. Been riding everyday for a week (to work nothing fun) bike performs like it used too just getting less MPG. M
 

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This is why I like and recommend OEM parts over an aftermarket kit, you never know if the jet number correlate. FYI, certain years, like my 2004, came stock with a Yamaha 125 main jet, so they weren't all 126s.

OP, run the numbers over more tanks to get a better avg., although high 50s-60s is about normal for us that have richened things up. Lean it back up if MPG is your primary goal.
 

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Discussion Starter #12
Were there signs of overheating?

I run my TW's lean and tend to ride them hard, albeit asphalt riding. I have had zero problems with overheating or burned pistons or valves. You must be riding it easy to get 75 to 78 mpg. If it ran well I would have left it alone.
This carb was on my original engine which burned up at 50,000 miles. Engine was stock and carb was stock. PPL here had suggested I adjust the jets because I was running at highway speeds and its hot hot so hot down here in asphalt land (Central Florida). Would like my used replacement to last forever or the rest of my life.
 

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Discussion Starter #13
This is why I like and recommend OEM parts over an aftermarket kit, you never know if the jet number correlate. FYI, certain years, like my 2004, came stock with a Yamaha 125 main jet, so they weren't all 126s.

OP, run the numbers over more tanks to get a better avg., although high 50s-60s is about normal for us that have richened things up. Lean it back up if MPG is your primary goal.
"MPG is your primary goal" sure I like getting more mpg but if it helps keep the bike running longer I can live with lower mpg. It's the first of march today and its 90 outside.... probable over 100 at the road surface.
 

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I would generate a baseline of head temps during the cooler evening, then during the day. What feels HOT is often not, in my experience.

Like most of my friends that have Harleys. They ALWAYS think they are overheating. Not so.
 

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.... Would like my used replacement to last forever or the rest of my life.
It sounds as though you have achieved exactly what you set out to do: make the engine run cooler in very hot temps at highway speeds. The mpg hit is the price of admission. It would be nice to know the exact diameter of that 125 so as to compare apples to apples. My guess from the mileage hit is that it is pretty close to an OEM 130, precisely the size most southern desert guys at sea level like to run. Or you could just buy an OEM 130 and compare it.....:p
 

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Just as a comparison I have rejetted for DG pipes at seal level. 130 main jet, 34 pilot two .020 washers. M P G is @ 59-65. In our case the washers really made a big difference. With a stock pipe maybe not so much. Pilot screw is @ 2 1/2 turns. Before the bikes were pinging and running very hot, even after adjusting the pilot screw.
 

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Discussion Starter #20
elime that is one of my fathers favorites and mine as well. Here is one "When in doubt DO'NT"

Bike has been running fine sense the motor swap. Have over 500 miles on it (to and from work running around town all asphalt) Grateful for this forum not sure I would have even attempted the carb rebuild with out this place.


There is an old hot rodding adage that goes something like : "If it ain't broke then don't fix it."

I have fallen into this trap many times. I spend minutes thinking I will make things better and then hours trying to get it back to where it was before I started.
 
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