Rough running at low RPM
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Intermediate
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Seeing the photos you posted, I may have been unclear about the 1/8 hole. It's on the end opposite the diaphram and near the edge of the outboard side, not the actual side of the slide (no holes there). If that's the one you measured as over 1/8" definitely pick up a diaphram (comes with slide) but don't throw that one away just yet.
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Joined: Sep 2007
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From: Bluffton, South Carolina
Congratulations, you are the proud parent os a stock slide that someone drilled out, I am sure his intentions were pure though!! Sometimes when these "wizards" get drilling there is no stopping them and they start modifying peices that cant be fixed.
Just my two cents worth, I would try to get an unadulterated CV off of E-Bay, swap meet or Craigs List. Just ensure that the lead plug is still in place, that ususlly means that the carb is stock. Try to get one with the least time on it, the last two numbers indicate the oldest it could be. Then just replace the needle, check the jetting and you should be fine for your application.
Just my two cents worth, I would try to get an unadulterated CV off of E-Bay, swap meet or Craigs List. Just ensure that the lead plug is still in place, that ususlly means that the carb is stock. Try to get one with the least time on it, the last two numbers indicate the oldest it could be. Then just replace the needle, check the jetting and you should be fine for your application.
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Well, God Bless my local indy shop, Rick's Custom Cycles, he had a new slide on the shelf. Take a look at the difference:
and Rick included enough jets, main and pilot, along with a stock needle for me to spend some time dialing it in without destroying my bank account (and you just know an old drum roadie's account is pretty shallow).
and Rick included enough jets, main and pilot, along with a stock needle for me to spend some time dialing it in without destroying my bank account (and you just know an old drum roadie's account is pretty shallow).
Last edited by oldroadie; Jul 22, 2009 at 03:10 PM. Reason: left out a word
HDF Community Team
Joined: Dec 2005
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From: NC USA
Yes, someone got carried away with that slide and went way too far.
The pictured spring IS the super shorty 5" from the SE 44mm performance kit which has a tension rate 130/210 grams. The stock spring has a tension rating of 200/290 grams and is 5 5/8" long.
The "lighter" spring in the Thunderslide kits are about 5 3/8" if memory serves me - don't want to take my carb down for a measurement if I can get out of it
With a stock needle and stock slide, you may do very well with the SE short spring. If it were me, I'd put the new slide and needle in and not touch the jets before riding it for testing. Like I said, with it "hunting" only around 1800-2200, you were close anyway. But I am still baffled about the 48 wetting your plugs. With the screw anywhere under 3, they generally won't do that - another reason I'd suggest checking the float level with the method I mentioned, before changing any jets. That way if you do re-jet, you can save (or eliminate) at least one bowl removal in the check/adjustment process.
If you care to, look at the needle, on the side and at the top. There may be 2 letters seperated by 2 numbers that will identify the stock needle, usually N86* or N72* and if there are no markings, it could be one of 3 California needles which go from lean to rich - no way to tell on them. (* = "R" "S" "E" or "F") And I don't have a clue how the Sportster needle would be marked.
The pictured spring IS the super shorty 5" from the SE 44mm performance kit which has a tension rate 130/210 grams. The stock spring has a tension rating of 200/290 grams and is 5 5/8" long.
The "lighter" spring in the Thunderslide kits are about 5 3/8" if memory serves me - don't want to take my carb down for a measurement if I can get out of it
With a stock needle and stock slide, you may do very well with the SE short spring. If it were me, I'd put the new slide and needle in and not touch the jets before riding it for testing. Like I said, with it "hunting" only around 1800-2200, you were close anyway. But I am still baffled about the 48 wetting your plugs. With the screw anywhere under 3, they generally won't do that - another reason I'd suggest checking the float level with the method I mentioned, before changing any jets. That way if you do re-jet, you can save (or eliminate) at least one bowl removal in the check/adjustment process.
If you care to, look at the needle, on the side and at the top. There may be 2 letters seperated by 2 numbers that will identify the stock needle, usually N86* or N72* and if there are no markings, it could be one of 3 California needles which go from lean to rich - no way to tell on them. (* = "R" "S" "E" or "F") And I don't have a clue how the Sportster needle would be marked.
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I went against my usual "change one thing at a time" practice and threw in the kitchen sink: 48 pilot, 180 main, new slide Dynojet D146 needle with the clip in the third groove (from the top) but I only got a static check at idle as rain kept me in the garage. Big difference just idling it up in the garage.
Whatever was going on with the old slide had the idle adjustment way, way off and it took a minute to get the bike to idle smoothly; for the first time the mix screw actually had an effect on the RPMs and now I should have a range of adjustments to pursue.
Turns out the needle Rick gave is a N4NN and from what I can tell that's for 2004 and later Sportsters so it's probably useless. Still, I got a complete set of mains all the way up to 205 and a variety of pilots so there's plenty to try. Too bad I have to work this weekend but it'll be waiting for me when I get back from Texas.
Looks like I'll have to source a stock spring. I did get a spring with the jets but it's the same size as the one I already have and now I'm left to wonder with the Sporty needle is it also a stock Sporty spring?
Thanks for all of your help, the continuing education is excellent.
Whatever was going on with the old slide had the idle adjustment way, way off and it took a minute to get the bike to idle smoothly; for the first time the mix screw actually had an effect on the RPMs and now I should have a range of adjustments to pursue.
Turns out the needle Rick gave is a N4NN and from what I can tell that's for 2004 and later Sportsters so it's probably useless. Still, I got a complete set of mains all the way up to 205 and a variety of pilots so there's plenty to try. Too bad I have to work this weekend but it'll be waiting for me when I get back from Texas.
Looks like I'll have to source a stock spring. I did get a spring with the jets but it's the same size as the one I already have and now I'm left to wonder with the Sporty needle is it also a stock Sporty spring?
Thanks for all of your help, the continuing education is excellent.
HDF Community Team
Joined: Dec 2005
Posts: 5,430
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From: NC USA
Been doing a bit of looking and only learned that I only thought I knew a little about needles, springs. I had NO idea there were so many variations for the Sportys and Buells...
Yeah, the butchered slide had you playing against a stacked deck for sure. And now you have a good, tunable base from which to tune. Try the spring you have. It may prove to be the trick for increased response without ruining driveability. I know you'll be looking forward to tinkering
PS, 2 on the screw worked well for mine when I ran a 48
Yeah, the butchered slide had you playing against a stacked deck for sure. And now you have a good, tunable base from which to tune. Try the spring you have. It may prove to be the trick for increased response without ruining driveability. I know you'll be looking forward to tinkering
PS, 2 on the screw worked well for mine when I ran a 48
Tourer
Joined: May 2006
Posts: 256
Likes: 7
From: Western NC
I just wanted to thank you guys for sharing all of this excellent info on carbs. As I have stated earlier my gas mileage never got any better than 38mpg. I was running stock head pipes with max performance slip-ons, the baffles started coming loose inside the slip-ons so I hollowed the pipes and created my own internals out of 1 7/8" exhaust pipe (money is tight right now..lol). I used the thumbscrew method for back pressure. Bike ran like crap!!! So I started playing with the jetting and needle settings...didn't realize how much that needle position affects response. My carb has the drilled slide and a dyno jet kit..i guess. Gonna change back to a stock slide and emulsion tube as soon as possible, anyway got it to running good and pulling strong all through the rpm range. Ended up with the clip on the needle on the last notch and a stock spring, rode this weekend and got a steady 44mpg. Once again thanks guys!
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Well sometimes you just have to be patient with the mail and life. I finally got a stock spring from Dave63 and check it out:
That's the stock spring on top, a J&P "Performance" spring in the middle and the one that was in the carb on the bottom. I got the stocker in tonight and I could tell immediately that the majority of the rough running was cured. The air mix screw actually has an effect now. All that's left is to run a few miles and see how I'm doing jetting-wise.
So, right now here's the set up: stock slide, stock spring, DynoJet 146 needle with clip in the third from the top groove. 48 pilot, 180 main, mix 2 1/2 turns out (the big jets are to accommodate the Andrews EV-27 cam). I'll bet if I need any more pep I'll be able to move that needle clip down one groove and that do 'er. I'll still have that J&P spring and a box of jets to futz around with once I get a good base tuning accomplished.
That's the stock spring on top, a J&P "Performance" spring in the middle and the one that was in the carb on the bottom. I got the stocker in tonight and I could tell immediately that the majority of the rough running was cured. The air mix screw actually has an effect now. All that's left is to run a few miles and see how I'm doing jetting-wise.
So, right now here's the set up: stock slide, stock spring, DynoJet 146 needle with clip in the third from the top groove. 48 pilot, 180 main, mix 2 1/2 turns out (the big jets are to accommodate the Andrews EV-27 cam). I'll bet if I need any more pep I'll be able to move that needle clip down one groove and that do 'er. I'll still have that J&P spring and a box of jets to futz around with once I get a good base tuning accomplished.
Last edited by oldroadie; Aug 4, 2009 at 09:36 AM. Reason: spelling...you'd think I'd learn
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So the home remodeling project has had me sidelined and it was yesterday before I got a decent ride in. My thoughts: the pilot is too fat so I think I'll try a 46; and, I need to adjust the clip on the needle down one groove due to the fact that I've narrowed the rough spot down to a 300 RPM range centered around 2K. All the same, she pulls so much stronger it's amazing and despite the longer spring it seems like the throttle response is dramatically better.