Jetting question
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Stage II
Joined: Jan 2012
Posts: 2
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From: louisville ky
Jetting question
I have just installed a 1250cc kit (10.5 to 1 reverse dome pistons) from Hammer Performanceon my 2003 883 sporster, and would like your input on the proper jet sizes. It is a stock with the exceptions of a K & N filter, and tone flex exhaust from American Custom. I don't want to take a chance of running this too lean before it is broken in.
Thanks for your advice
Rick in Louisville
Thanks for your advice
Rick in Louisville
HDF Community Team
Joined: Jun 2006
Posts: 12,776
Likes: 2,607
From: san antonio
Never rejetted a carb for a Sporty build but it doesn't appear anyone else has either. I can't say for sure but I would suggest raising the needle with a .025" washer and going up two sizes on the pilot, say if OEM pilot is a 44, try a 46. Same with the main; if the OEM main is a 170, try a 190. Remove the cap over the A/F adjustor (if you haven't done that already) and try about 2.5 turns out. Once the bike as warmed up, play with the A/F screw and give the engine want it likes for the smoothes idle. Run the A/F screw all the way in and if the engine stumble and dies, go up one size on the pilot.
Once you think you have the idle worked out and the transition from the pilot to the main is smooth, get out on the highway and while accelerating in fifth, say from 60 to 70, when you hit 70 back of the throttle just a hair. If the engine surges, the main is too lean; if no surge, main shoud be OK.
Watch the plugs for color. It's a process and can be frustrating. Don't worry about mileaage until you think you have the jettng right. If there is a dyno tuner in the area familiar with carbureted builds, have a few pulls done; check AFR at idle, cruise and WOT.
A carb is easy to work on but also a compromise; just gotta be tenacious and stick with it. What you are looking for is easy starts, no coughing, spitting or stumbling through the carb and no popping on decel.
An adjustable ignition like the Daytona Twin Tec may be necessary to really tune the build.
Once you think you have the idle worked out and the transition from the pilot to the main is smooth, get out on the highway and while accelerating in fifth, say from 60 to 70, when you hit 70 back of the throttle just a hair. If the engine surges, the main is too lean; if no surge, main shoud be OK.
Watch the plugs for color. It's a process and can be frustrating. Don't worry about mileaage until you think you have the jettng right. If there is a dyno tuner in the area familiar with carbureted builds, have a few pulls done; check AFR at idle, cruise and WOT.
A carb is easy to work on but also a compromise; just gotta be tenacious and stick with it. What you are looking for is easy starts, no coughing, spitting or stumbling through the carb and no popping on decel.
An adjustable ignition like the Daytona Twin Tec may be necessary to really tune the build.
Thread Starter
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Stage II
Joined: Jan 2012
Posts: 2
Likes: 0
From: louisville ky
Thanks djl, exactly the advice I was looking for. My first Harley, and it has been completely different from the rice burners I have ridden over the years. Should not have waited until I was 56 years old to move up. BTW, if anyone else is trying this build, it was fairly easy and took me about 10 hours from start to finish.
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