Stumble and carb backfire
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Cruiser
Joined: Oct 2010
Posts: 205
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From: Houston Texas
Stumble and carb backfire
New to this forum and new to HD's. Just bought my dad an 03 heritage softail with 4,500 miles. Original owner said it's been sitting for a while and the tags expired back in August so it's been sitting for at least 2 months.
Here's the problem. I get a backfire out of the carb and a stumble. It only does this when I level off the throttle and am cruising, in any gear. It doesn't do this under acceleration.
Far as I know and can see, it has a screaming eagle intake and pipes. It has a 190 main jet and I can't read the pilot due to the previous owner scarring it up, pms set at 3 turns out. Not sure about the needle. It's different than the metric's I mess with.
Any help would be appreciated.
Here's the problem. I get a backfire out of the carb and a stumble. It only does this when I level off the throttle and am cruising, in any gear. It doesn't do this under acceleration.
Far as I know and can see, it has a screaming eagle intake and pipes. It has a 190 main jet and I can't read the pilot due to the previous owner scarring it up, pms set at 3 turns out. Not sure about the needle. It's different than the metric's I mess with.
Any help would be appreciated.
Road Captain
Joined: Nov 2007
Posts: 731
Likes: 2
From: Montreal Quebec Canada
sounds like its too rich, remove the spark plugs and take a look. than try the mixture screw, im sure you will get lots of members helping out, i would check the plugs, if they are black rich, throw some plugs in and close the screw till it stumbles a bit and back it out 1.5- 2 full turns, not more with the 190 main, wonder what the pilot is, you can put a 44 and see how that works, or a 45. trial and error, took me 3 tries to get the right jets and mixture setting. good luck
If you can believe that. Dyno is expensive and hard on an engine, IMO. I bought mine with the same mileage on it and had lean idle problems, finally went all the way to a #50 pilot, but then my mileage dropped...but we may be on winter blend fuel now, so I'm not sure.
Anyway, the '88 sportster needle makes it run great with the stock jet. Yours does sound rich or has the wrong float level.
Anyway, the '88 sportster needle makes it run great with the stock jet. Yours does sound rich or has the wrong float level.
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
go to biketech at nightrider.com.
you can read up on the CV carb ( which was also used on some Triumph and Kawa models)
For comparison, my 1995 FLH ( 80") runs a 165 main, n65C needle and a 42 pilot.
stock spring, drilled and chamfered slide.
Screaming Eagle hi flow air cleaner, supertrapp pipes.
I get 44 MPG @ 65 and it pulls great up to my limiter @6000.
MK
you can read up on the CV carb ( which was also used on some Triumph and Kawa models)
For comparison, my 1995 FLH ( 80") runs a 165 main, n65C needle and a 42 pilot.
stock spring, drilled and chamfered slide.
Screaming Eagle hi flow air cleaner, supertrapp pipes.
I get 44 MPG @ 65 and it pulls great up to my limiter @6000.
MK
Last edited by mkguitar; Oct 25, 2010 at 10:06 AM.
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Scott
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WOW! Just got off the phone with these guys and they'd had a customer with similar problems like mine...and like the hog mechanic said, I probably shouldn't have to run a #50 pilot on a stock motor...but the problem for me is probably the PETCOCK not operating properly with the vacuum. So, it's on to cleaning it if it needs it and if not, removing and plugging the vacuum line and see if I can go back to leaner jetting, thus hopefully getting my fuel mileage back.
I'd have never caught that one, I tell ya. Oh, these guys were super nice about it too. I'd do business with them come rebuild time.
I'd have never caught that one, I tell ya. Oh, these guys were super nice about it too. I'd do business with them come rebuild time.
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Tourer
Joined: Feb 2009
Posts: 404
Likes: 0
From: L.A. (Lower Alabama)
Might have gunk in it from sitting. Here are 2 hd specific tuning guides.
http://www.harley-performance.com/ha...arburetor.html
http://www.nightrider.com/biketech/hd_cv_mods.htm
They jet them quite lean from the factory, and even with recommended settings from the dynojet kit, I had to move the clip down 1 slot on an 02 Sporty. They are good carbs when you get them right though. They do not come with an in-line filter, just a screen in the tank, and I recommend installing one as part of your repair. It will pay off later.
http://www.harley-performance.com/ha...arburetor.html
http://www.nightrider.com/biketech/hd_cv_mods.htm
They jet them quite lean from the factory, and even with recommended settings from the dynojet kit, I had to move the clip down 1 slot on an 02 Sporty. They are good carbs when you get them right though. They do not come with an in-line filter, just a screen in the tank, and I recommend installing one as part of your repair. It will pay off later.
HDF Community Team
Joined: Jun 2006
Posts: 12,773
Likes: 2,603
From: san antonio
The dyno jet kits are notorious for poor mileage. I know you are getting a lot of advice and I don't mean to add to the confusion but if I were you, I would pull the carb off, toss the dynojet stuff, return to stock jetting, check float adjustment, clean the carb and reasssemble. It will probably be a bit on the lean side, I think the stock main was 175, so 190 might be a tad rich. 45 slow should work with A/F 2-3 turns out. Shim the stock needle with a couple of brass washers, or use the Sporty needle.
The advice to check out the Nightrider site was spot on; very good and detailed info on the stock CV carb.
The advice to check out the Nightrider site was spot on; very good and detailed info on the stock CV carb.