Jet size for straight pipe?
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Stage III
Joined: Mar 2020
Posts: 3
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From: WI
Jet size for straight pipe?
so I picked up a 03 883 sporty and the previous owner put on some straight pipes but did nothing else. Now I'm getting a pretty wicked back fire and I've been told to either put stock back on or change the jets. Don't really wanna put stock back on. Any ideas?
HDF Community Team
Joined: Dec 2011
Posts: 8,512
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From: San Diego, CA
Straight pipes are horrible performers, unless you ride around at wide open throttle wherever you go. Stock pipes with some good slipons are proven on a dyno to provide better performance. I don't think you can solve the reversion problem of straight pipes with jets. Those old "H" type pipes with some slip ons do as well as you're going to get, actually very good. I have a 1991 with the same setup, H pipes and SE1 slip ons.
Good luck.
John
Good luck.
John
Last edited by John Harper; Aug 7, 2020 at 05:11 PM.
Seasoned HDF Member
Joined: Jul 2011
Posts: 27,096
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From: Frozelandia, Minnysota
You can get rid of most of the backfiring by going up a size on the low speed jet, but as John said, the only performance increase for normal riding you'll get is in noise. Throttle response probably won't be as smooth, either, and your mid range will suffer. Unless you're prone to high rpm drag racing, no need to change the high speed jet. You can do other more complicated tweaks to the carb to smooth it out a bit, but I doubt you'd notice much for the effort. My used 1200 had drag pipes on it, way too loud for me anyway, put stock take offs on it and was very pleased with the performance increase. Harleys have been so lean for many years that even with a size up low speed/idle jet they'll run fine, maybe even a little better with just a tweak on the mixture screw. Sounds like the previous owner did not do a jet change, so if you want to re-jet it to keep those pipes, the anti tamper plug is probably still in the carb, but those are easy to remove, just drill in it just big enough to put a screw in, best to use a fine thread sheet metal screw, and then just yank it out with pliers. I didn't even take the carb off one I did, just loosened the carb enough to roll it enough to position the carb bottom away from the bike, easy access then. Another backfire culprit to look into, especially if that plug is out of the carb indicating a possible jet change already, is the intake seals. You can spray a little WD 40 around the intake joint at the motor while it's running and if the idle picks up, there's probably a leak. I've changed those on a sportster, too.
Road Master
Joined: Sep 2010
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Stock jetting will be way too lean (if that's what's in there now) so changing to the 'one size fits most' jetting recommended for an 883 (45 pilot and 175(?) main, can't recall exactly off hand) will get it at least in a decent ballpark. Also, lookup the 'lolipop' mod. It seems like 'snake oil' but it really does help with the sag in the midrange. I have drag pipes on mine (for the moment) and it made an undeniable difference in the middle.
As far as people telling you drag pipes are worthless at anything below WOT, don't listen. Drag pipes are pretty much the worst choice in exhaust (aside from stock), but that doesn't mean you can't get them to run acceptably and if that's what you got or you can't afford to change them, or if *gasp* you actually like them, there's no reason why you have to live with a crappy running bike. My bike runs smooth, pulls cleanly top to bottom and has no running or starting issues. Granted, the pull from 3000-4000rpm is softer than it could be but it's hardly a giant cavernous hole that the bike barely pulls itself through.
As far as people telling you drag pipes are worthless at anything below WOT, don't listen. Drag pipes are pretty much the worst choice in exhaust (aside from stock), but that doesn't mean you can't get them to run acceptably and if that's what you got or you can't afford to change them, or if *gasp* you actually like them, there's no reason why you have to live with a crappy running bike. My bike runs smooth, pulls cleanly top to bottom and has no running or starting issues. Granted, the pull from 3000-4000rpm is softer than it could be but it's hardly a giant cavernous hole that the bike barely pulls itself through.
Cruiser
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From: 40.2444° N, 75.6419° W
Yes, I believe CV performance sells a jet kit, nice if you want to "play around" to get it dialed in .
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Road Master
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Using the 'tried and true' suggestions will get you close, normally very close. If you REALLY want to dial it in then yes, you need a few sizes and you REALLY need to know what to 'feel' for. Or else you need a dragstrip and lots of time or a dyno. Lots of individual factors will play into getting it right, not the least of which is altitude (a guy at sea level is gonna be jetted very differently than a guy at 10000ft), as well as specific combination of air cleaner/exhaust/engine mods.