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04 Sportster 1200 conversion jetting

MrPepper

Veteran Member
Joined
Jun 1, 2020
Total Posts
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Location
LA, CA
This is for an 04 sportster 1200 conversion with hi flow intake and exhaust
getting pinging under load

i am on the highway a lot and thought installing a cooler plug wouldn't hurt. Was surprised to see this

Am going to start tackling jetting. Timing is fixed so may need to shell out for an aftermarket module
 

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When you upen up the intake and exhaust on a Sportster, you just about HAVE TO bump the jets up a little, because they are so choked down in stock form to meet the noise regulations and already lean to meet emissions standards. Add a significant displacement increase, and that aggravates the lean condition even more.
 
Original carb from the 883? If so then I think the engine is under carbed so regardless of jet changes it can't breath enough to fill the cylinders completely.
 
Yep, stock 883 CA model carb. I put a steel washer under the jet needle and fattened the pilot screw but looks leaner than before. I also noticed the top motor mount cracked so just finished welding that up.
 

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Stock CA carb, you know it was lean to begin with LOL. And what a shock that the top motor mount was cracked :lol: can't count how many I replaced on the big twins while working for the City garage
 
Carb model, and jetting looks pretty fat at 48/180

Those jets sound large enough. I’m pretty sure the 883 and 1200 used the same basic carb with no increase in venturi size for the larger engine. Have you changed out the main jet needle for the one that comes in the carbs used on the 1200 models?
 
hey guys, thanks for all the replies!
im going to try another shim under the jet needle since its easiest to access.
took for a short test run and no improvements with 1 shim.
will also look into picking up a non-CA 1200 carb
 
Mods, can you rename this thread 04 Sportster 1200 conversion jetting

Threw a bunch of gas at the bike til the plugs fouled and it struggled to idle... in hindsight should've done updates in increments.

Ended up drilling the jets to about 190 main and 50 pilot with fuel screw about 3.5 turns out. Needle shims didn't produce any notable results so kept 2 of the 4 i installed.

Pinging seemed reduced and plugs have color. Will swap in a cleaner set to get a better read but we can probably call this done. If I still have issues then will look into a different ignition module setup.
 
Update on this project

Picked up a ignition module and retarded the initial timing by 5 degrees and advance by 5 degrees. Still had pinging issue.

Doubled up on the MLS head gasket and had light pinging at hi rpm.

Yesterday pulled the 1200 kit and installed 883 jugs and pistons. Raining here so haven't had a chance to put it on the highway, but reset timing and advance to factory settings and took for a short spin around the block and seemed ok.
 
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