I have a 2004 HD Sportster 883 custom. I recently put a set of Vance & Hines pipes on it. After I did this, my bike started to miss after it warmed up from 800-1800 rpms only. I was told by two different harley dealerships that the slo jet was the problem. The slo jet was a 42. I replaced it with a 45. Also, the main jet was 175. I replaced it with a 185. I drilled out the plug to get to the mixture screw. Everything adjusted correctly but the problem is still there. I would like to know if I am possibly going in the wrong direction and need to check the electrical system instead. Does anyone have any ideas?

 

I would not think it an Elec. problem if it is limited to the rpm band you quote. You say all is adjusted correctly, how do you make that judgement? What procedure did you follow in the adj?

 

I also say that it's most likely carb related. Did you clean the carb when you changed the jets. Anytime that i've rejet carbs on all my bikes, I'll also do a thorough carb cleaning, basically dissassemble all parts of the carb, soak in a bucket of carb cleaner for an hour or two, then spray out all jets and passages with Gumout, followed by blowing compresses air through all passages. Also check for vacuum leaks, as this can cause rough idle-1/4 throttle, simplest method is to spray wd-40 around the joints of the intake manifold while the engine is running and listen for changes in rpms.

Have you checked your plugs yet, make sure you didn't accidentally foul them up while tuning.

I wouldn't suspect anything electrically related, because it most likely would have been noticeable before the rejet as well if it was electrical.

BTW, personally I think the 185 is too rich for the main, general rule with exhaust and a/c is ussually 2 sizes up, so a 180 from a 175 is ussually the best choice, although it shouldn't have any affect on your idle unless you revved the hell out of the engine and fouled the plugs up from it. But the 45 pilot is right on.

 

Factory setting was out 2 1/2 turns on the mixture screw. Turned screw out to 3 turns. This smoothed the idle, still had extremely quick throttle response, no smell of fuel or burning of my eyes behind the exhaust. No black soot around the end of the exhaust.I have always built old hot rods and this is the way I havealways worked on them.I just figured that they would be the same. Thats why I was leaning toward the electrical system.

 

While I don't think it has anything to do with your current problem, I also think a 185 jet is to rich. A 180 is probably the better choice. I don't know if you got the jet kit from Sorgys on Ebay but they often ship a 185 and it's to big for most situations.

 

Three turns out sounds like a lot. Most bikes I've done wind up at 2 - 2.5 turns out. Maybe try closing it down a 1/4 turn at a time and see if it helps.

Edited: you may need to increase the idle a little.

 

I was having the same problem before the rejet. When you first start the bike it runs great at low and high idle. When it warms up is when the busting up from 800-1800 rpms begins. If I get it out on the highway, riding above 1800 rpms, you would never know there is a problem. Plugs are new, and gapped correctly. While I had the carb off I cleaned it thoroughly and blew it out. My apology, it was an 180 main jet I went with. I also checked for vacuum leaks. No change in idle.

 

first I would ask if you have the stock a/c or an after market free flowing one. if you have only added pipes I would think you are running way to rich. with stock a/c and after market pipes I would suggest a 45 pilot and a shim maybe .03 under the needle isall you need I wouldnt even worry about the main until you add a high flow a/c. the main dont even come into play until you get 2/3-3/4 to wide open throttle. I learned this lesson the hard way but hope I can help somebody else save time money and head ache.

 

I took the a/c off to see if that would help, but the problem stayed the same. The reason I changed the main jet was that I was already in the carb and have plans on going with a high flow a/c in the very near future.

 

Pinned at the top of the Front Page here in the Sporty Forum, is acomplete detailed description of how to adjust yer Carb Correctly. What you are seeing is improper adjustment. Follow the directions on the Thread Pinned at the top and see if yer problem doesn't get 95% better, and if yer lucky, solved completely. Without setting the idle before adjusting the main, you are pissin in the wind. Words of experience here, you iwll be mighty lucky to get it tuned correctly "by ear". The minimum way of tuning is with a tach, so you can see the rpm changes as you adjust the idle and mixture screws. You can buy a Multi-Meter type automotive diagnostic device at most Better tool supply stores, it should have an Inductive tach feature (clips on a sparkplug wire). They run around $120. After my Stage 1 upgrades I was not impressed with my Scoots performance, after buying the Tach and readjusting my Carb, I WAS AMAZED at the difference. You will be surprised how much effect a 1/4 turn has when dealing with the mixture Screw. As stated here, most mixture screws are 2-2.5 turns OUT.