Harley Carburetor Jets

Question Hello and I love all the info from this site as I have learned a lot from it. I have a question about my carb. I have a 1999 wide glide twin cam 88. At low speed, in first and second gear, going slow I get a hesitation and popping back through the carb and it seems as it’s gotten colder it happens at around 55mph also. I’ve followed your video and took the carb apart and cleaned it but it makes no difference. The bike has a big sucker air cleaner and screaming eagle open exhaust and I noticed the pilot jet was a 42 and the main is 165. My clymer manual states that I should have 65 pilot and 190 main. I feel like it is too lean with the factory but I am unsure of such a big jump in size from what the clymer manual says. Should I rejet or try to find a stock air cleaner setup and see if that fixes the problem. What Harley carburetor jets should I use? Thanks for your time.
CHris

Answer Not exactly sure why your m/c was ever jetted so lean. 42 & 165 are small for most evolution motors. Anyway, assuming your intake is sealed and your carbs accelerator pump is functioning correctly; we would suggest moving up to a 46 or 48 pilot jet and a stock 190 main jet. Play with your mixture screw and pay attention to the coloring of your spark plugs. You really can’t get into any trouble. Good luck

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31 Responses to “Harley Carburetor Jets”
  1. Lance Van Winkle

    I always suggest this to any motorcycle owner. Form a relationship with a technician. I was a PHD Harley Tech and Honda Pro and most of the others for years. I still take donuts to service departments just to say hi. A quick text or call to a friendly tech with your combination in your area (Altitude and other factors) will yield the correct info. Assuming no intake air leaks or other issues this should do it.
    Thanks,

    Reply
    • Nick Williams

      I also have a1999 twin cam that is doin the same thing at slow speeds and worse when it’s colder. I have a big sucker air filter and boneshaker open exhaust I just put new seals in my intake and it is all sealed tight. I have a 45 jet and a 174 jet in the carb but I’m sure it is still running lean where should I be with jets here in the north east?

      Reply
      • Mike

        45 and 180 drill out the mix screw adjust 2 1/2 turns out read plugs put easy screw new o ring

        Reply
  2. STEVE

    Q: I’m trying to figure out why my 1990 FLSTC- CV carb. has a cough now at low RPM’s? Leaving the choke out a little helps unless it’s very cold out.

    Reply
    • Dennis Santopietro

      HI Steve, Have you had a chance to watch the Carburetor Video Class? Bob goes over several issues like the one you are having.

      Reply
      • Douglas

        Dennis, what “class” video is that? I switched from a Hyper Charger to a Kurykayn Mach 2 and I’m getting backfire during decell and “choking” when I blip the throttle. I’ve messed a little with turning the mixture screw counter clockwise, but the bike idles pretty well, and at speed it’s performance is better than ever….I know “some” popping is ok, but just unsure?

        Reply
  3. Gene

    I’m sure you know to re-jet when you deviate from stock to a “hot” air cleaner and straight pipes. Since the pipes and air cleaner are the variable your choice of jet sizes will be by trial and error but increasing the sizes one size at a time. 42 & 165 sound like stock jets which (comply to harsh EPA standards but you didn’t hear that from me) cause a lean mixture. 65 & 190 sound large, too big a jump from stock. Too rich which will create a sluggish feeling at throttle. Also importantly, 90% of poor carburetor performance is due poor vacuum. You should definitely go to CVPerformance.com for parts and theory. I am a 1994 Heritage Softail Classic. I went to straight pipes and a S&S Stealth air cleaner. It ran terribly. I went from 45 & 180 to 46 &185 and repaired vacuum leaks at the manifold with a new rubber manifold seal ring also new accelerator pump kit and vacuum diaphragm and replaced a cracked piston slide diaphragm. It runs like a beast ! VACUUM VACUUM. Good luck.

    Reply
  4. Joe K.

    I am a PHD tech and have found that in almost ALL cases that using the stock carb that Twin Cams respond very well to a 205 or 210 main jet and deliver better mileage that the factory jetting. I agree with the 48 slow jet or even a 50 if you live in a cooler climate. Also install a HD P/N 27094-88 needle and drill the air bleed hole{the offset one on the top of your power piston} to 1/8″ for much better response and mileage.

    Reply
  5. Paul

    I had the same problem with my 2003 Wide Glide. It had 33,000 on it and started to hesitate, even worse in cold weather. Turned out to be my intake manifold gaskets. I would definitely check that.

    Reply
  6. john raymond

    you can rejet your carb if you want but ,it sound like a simple vacuum leak to me ,you can test this with wd40 spray it around your intake,all tree spots it can leak,if it revs up then settles down,you gotta leak .if not rejet.

    Reply
  7. William

    I want to thank the site and contributors for the great help provided here. I wound up rebuilding the lower half of my carb on my 99 FXD Glide. New accelerator pump – rejetted both the pilot and main using a 48/190 jet package – replaced all the screws with allen caps & added a lock washer. Supreme change. Low end power restored – smooth top end response with a little extra on top. No decel popping & no idle fluttering. But the most significant change was restoring the heartbeat. She thumps on time every time – very impressive steady idle state and very smooth acceleration. Thanks again folks.

    Reply
    • Aaron

      Hi, I’m thinking of the same combo except 195 main as I’m in the Uk and it never gets hot here. May I ask what mixture setting worked for you? How many turns out? Many thanks, Aaron

      Reply
  8. Perry Williamson

    I got a 2000 stock wide glide and I got the same trouble re; the popping and the hesitation , and a got of trouble getting it to keep running I got a sneaking suspicion it running too lean. Other than this little problem everything is bang on. Spark plugs are looking good, anything else I should be looking at ? Beside the the obvious

    Reply
  9. poppy

    my polit jet is a 46 and my main is a 190 and it has great power but it is flooding and my plugs are black and at slow speed it jumps like its all cam up but it is stock can someone help me with it please thinkyou poppy

    Reply
    • Customer Service

      Hi Poppy, please send us the model and year of your bike so we can further assist you. Thank you!

      Reply
  10. Tom Perry

    what is the actual size of the pilot jets? mine has a 42 and after sitting for 3 years is completely clogged..I opened it up with a .020 bit but afraid to go larger without knowing the actual size. I am 60 miles from a dealer and would rather get it going now and pick up a new one later…Tom

    Reply
  11. Jeff Chambliss

    Here in Southern Illinois a #48 pilot and #170 main works great. Have been to below sea level in New Orleans to above 12000 feet in west. No fouled plugs, no “coughs”.

    Reply
  12. Michael

    I have a 1990 FLSTF with a ‘92 CV (non-California). Also running V&H pipes and Crane Cam. I recently added the pipes and rebuilt the card, leaving the existing Main Jet @ 180, but dropped the Slow Jet to 44 where I was able to get some response adjusting the fuel mixture resting now at two turns. A quarter turn in and she’s missing. She’s running good at two, but blows too much black – sooting up my fender. When I checked the plugs after the last jetting, they were grey with black at the tips. Dropping to 42 seems too low. Is this just an old Evo issue?
    Mike

    Reply
  13. Giuseppe

    Hello, i have a question about the carb of my 2004 Sportster Custom 1200….What are the stock sizes of original jets? Thanks, greetings from Italy, Giuseppe

    Reply
    • Dwayne Correa

      Giuseppe, In most of the USA Stock 2004 XL1200 jets are 42 pilot and 170 main. See what you have for sure by removing the float bowl at the bottom of your carb. The numbers will be visible on the jets.

      Reply
  14. Ron

    2005 TC88 Pipes, aftermarket air cleaner. Just jetted to 48 slow and 190 main great throttle response but loading up and backfiring after hard run. Should I lower my 190 o a 180?

    Reply
  15. Michael J Riddle

    Just bought 2005 Electra glide has stage 1 and now I live at 6000 elevation what size jets do I need for this elevation ?

    Reply