Re-Jetting 06 FXST

Greetings, I am new to this site and recognize it as a great learning opportunity. I have a question, I hope someone can give me advice.

I recently bought a used 06 Harley Softail Standard, it already had the 1550cc upgrade, I think that is called a Stage II upgrade. I am having problems with the carburetor and from what I have read on this website, I think I will need a new Main Jet. I tried to follow the Harley-performance web page instructions on adjusting the carborator mixture settings but with not much results.

The bike idles well and runs well in mid range but when I give it max throttle, it boggs down and will sometimes spray a bit of gas out of the carburetor, which leaks out of the air cleaner and splatters onto the oil tank, while riding. I have a high-flow K&N air cleaner, with the cover off, but I may put the cover back on. The bike is not performing well when I give it max throttle at freeway speeds.

The bike ran pretty well when I first got it. It came with slash-cut mufflers with no baffles, it was super loud. I don't like super loud pipes, neither do my neighbors. I put some stock tapered mufflers on, with baffles, then it was too quiet and the bike became very sluggish. So I drilled a 1/2" hole thru the baffles and it sounded just right, it also ran better. But now I have this carburetor problem. I live in an area around Santa Fe, NM, with an altitude of almost 7000 ft, the bike came from Kansas City, where the altitude might be around 2000 ft, so the air is much thinner here. From reading this site, I think my carb is running "rich"? Does rich mean too much gas and not enough air? From reading some of the carburetor articles, I am deducing that I will need a new Main Jet, to fix the performance at high speed. After that, the fuel mixture will have to be adjusted. I am asking y'all so I can learn about what is going on with the carburetor, before I take it into an expensive shop, where they will charge me a huge amount but won't take the time to explain it to me. Should I pay a little extra to take it to a Harley shop, with a dyno, rather than a local, private Harley mechanic? Is the real high tech diagnostic equiment necesary to do a good job at carburator/performance tuning? Thanks.

Hey, Welcome, Yeah rich is too much fuel not enuf air.With a 5000' gain in altitude yer prolly rich. If its only the last quarter throttle where your having problems it would be the main jet. To dial in the carb tho first you have to get the idle mixture right, then the slow jet ,off idle to about 1/4 throttle then the needle jet, like it's been said on here many times the best Indys do looks after 1/4 to 3/4 throttle then the main jet does last 1/4 from 3/4 to Wide Open Throttle(WOT).
You should be able to find a good Indy(private shop) in your area, rather than go to the dealer(stealer) Just ask a few other riders and they can tell you where one is,like it's been said on here many times before the best Indys don't advertise there work does it for them. Hope this helps you.:devil:

A good independent shop will always charge less than a dealer & it's not rocket science to get a CV carb dialed in. The needle is a key issue 'cause that's what you're on most of the time - you're not all the way on the main until full throttle @ higher rpms. Also, a properly tuned CV adjusts itself to altitude changes.

The key factors are slow jet, needle & main & any good indy shop can get the right ones for your bike dialed in without a dyno. Going to the dyno is always good, but really not necessary for a great running street/road bike. One of these days I'm going to try the "Stage I Tuner's Kit" because I like the needle design & I'm interested in the emulsion tube, but with $15 worth of carb parts & a little tuning, both my street bikes run fine.

As Lucifer mentioned, many of the best indy shops don't advertise because they don't need to, so ask other area riders where they go & you'll find @ least one good indy. I live outside a one stoplight town & there are 3 in this area. Also, the best wrenches will tell you what they're doing & explain why they're doing it - if the guy working on your bike doesn't want you watching, he's probably not very good.

Re-jetting 06 FXST, With 1550 Upgrade, Stage II

Thanks for that info. If my FXST has the 1550cc upgrade, is that automatically called Stage II? I guess that means it has the bigger cylinders and pistons, upgraded cams, a high-flow K&N air filter, but what would they have done to the stock carburetor? Would they have automatically added bigger jets as part of that upgrade? I think the carb and manifold are stock.

The mixture screw seems to be set at a little over 1 turn out from seating. I have read here that the mixture screw should be around 2 1/2 turns out. My bike is apparently running way too rich now, if I open it another turn, it might make the bike run even richer, and cause more gas to spray out of the carb, at WOT, right? The bike came from an elevation of maybe 2000 ft and I am at almost 7000 ft. I recently looked at the plugs, they seem to be in average condition, maybe a bit darker, since it is running rich.

Here is some current performance info. I have a stock five speed. At 72mph, my tach shows 3000 rpm. My gas mileage seems to be in the low 30s, when I get the carb mapped, I hope I will be getting at least 40mpg. My current top speed is around 85 mph but I try to stay away from WOT, so gas doesn't spray out of the carb. If I stay away from WOT, just keep it at 65-75mph, it seems to run well and I can take long day trips, with no real problems.

I have put about 1500 miles on it since I got the bike. I haven't taken it into a shop to map the carb yet, because I wanted to try a couple of different used exhausts, to get the sound right. I just got a used 2into1 exhaust that I am about to put on and see how it sounds/performs. I can't see a brand on the 2into1 but it looks to be good quality. The large, tapered muffler has a fairly open flow design with high-tech looking, perforated tube lining. Does anyone have any strong opinions about 2into1 exhausts, versus my tapered stock, drilled-out, semi-quiet mufflers?

You can bet they did 'cause the engine wouldn't run worth a flip with the stock jetting & it'd be so lean it'd overheat quick.

Baseline is 2.5 turns out & with the engine fully warmed up, you can adjust a little bit either way from there until you hit the "sweet spot" 1/2 way between too rich & too lean.

As mentioned, a CV adjusts itself to altitude changes pretty well, but it has to be set right 1st. And it's harder to read plugs with today's unleaded gasolines & additives - what would have been considered lean years ago isn't today. See:
How to read Plugs and other links @ the end of that article.

Can't say exactly what the mileage ought to be for your big engine, but low 30's definitely says too rich.

Gas spraying out of the carb is primarily a "reversion" problem & running too rich makes it show up even more. If I knew the cam specs I could tell you more, but basically, what goes back up the exhaust pipes is more important than what goes down. With lots of overlap in the cams (time period when the intake valve is opening before the exhaust valve has closed), reversion waves can go in thru the exhaust port, all the way thru the cylinder, out the intake port & into the intake manifold. And since we're dealing with an "odd-fire" engine (firing order = 315-405), what comes up the front & rear pipes arrives @ the intake manifold @ uneven intervals.

I've seen what's called "standoff" on the dyno time & time again - with the air-cleaner off, there's a fog of air/fuel mixture standing just outside the carb throat - reversion is literally blowing mixture out. It gets drawn back in & blown back out over & over again so fast all you see is the fog. That normally only happens in a fairly narrow rpm band though.

I don't like 2-1's on a Harley engine 'cause they only work in a limited rpm range, but on a big engine like yours, it really isn't a big deal like it is on a bike like a Sportster. I've got drilled-out stock mufflers on one bike & they work great for normal riding, but the bike will "nose over" on the top end. And your big engine needs more flow than drilled stockers will allow.

You could go with quality slip-ons on the stock pipes & that'd work well without being real loud, but one thing about 2-1 pipes is the sound comes out behind you instead of under your right ear. So even if the pipe is fairly loud you won't notice it as much. I know some folks who got a 2-1 for just that reason & also because some use saddlebags & carry a passenger often - the 2-1 is just more practical for them.

mapping the carb, reversion, 2-into-1 exhaust

Thanks for that info Art-NJr. If reversion is out of kilter and may be causing the fuel to spray out of the carb at WOT, might that it mean I need more back pressure? Would 2-into-1 exhaust help prevent reversion problens, since the back pressure is all going through one exhaust pipe, rather than two separate pipes? I will try to get my used 2-into-1 system on the bike this weekend and see if it isn't too loud and how it affects performance, etc. They seem to be a high flow design, so they may be just right for this engine. But if they are way too loud, I may go to some slip-ons, as you suggest. I live in a very quiet, rural neighborhood, with lots of horses, some horses get spooked by loud bikes. Actually, I live on the highway where they filmed several scenes of the "Wild Hogs" movie, this area has become a biker Mecca, after that movie came out.

NO !! I don't know where the idea came from that you need back pressure in a street exhaust system & it's been for around as long as I can remember, but back pressure is always bad. Especially when you have a lot of overlap in the cams & anything other than stock is going to have a substantial amount of overlap - you don't want more going back up the pipes, you want less. Reversion is is accentuated by cam timing & certain exhaust setups & you can't get rid of it, you just have to manage it (in racing you use it to your advantage).

What a 2-1 is designed to do is to make the engine act like an "even-fire" engine, with a firing order of 360-360 instead of 315-405. The idea being that the exhaust coming out of one cylinder helps pull exhaust from the other on the next cycle, fresh mixture into the cyl. that needs it @ the same time & the sound & pressure waves from both cylinders hit the collector @ even intervals. But you can only make that happen in a range about 1500 rpm wide - typically 3000 to 4500. However, a well-designed baffle & collector will break up a lot of the reversion & it'll split off on the way back up so it has less effect on each cylinder.

Think of it this way - the atmospheric air pressure outside the pipe is like a wall the exhaust coming out of the collector hits. The exhaust pressure is higher than atmospheric, but it slows down & dissipates as it comes out. Then after the exhaust pulse has come out, the pressure inside the collector drops below atmospheric & air rushes back in to fill the void. If there's enough time, it'll go all the way up the pipes, thru the cylinders & into the intake manifold. That's bad. And if there's back pressure in the system, that's worse. So a baffle(s) in the exhaust not only tones the noise level down, it restricts what can go back up & that's why straight drag pipes are so awful - there's nothing to break up reversion waves or slow them down.

Most stock exhaust systems have a crossover pipe & there's a reason for that - the mufflers (or slip-ons) break up the sound & positive/negative pressure waves going both directions & the crossover equalizes what's left over on the way back up. A well designed 2-1 collector will do the same thing, although not as effectively.

You will need to adjust the carb to work with that pipe. Baseline jetting will be the same, but the idle mixture will need to be adjusted & you will probably need a different needle - if so, the venerable N65C was about $8 last I saw. H-D part no. 27094-88. One of the problems with a 2-1 is there's a big dip in torque in the 2500 rpm range & that's also where the "carb farts" usually occur - that range is a bear to tune. But that needle helps smooth it out, as it goes thru the transition phase sooner & faster. Looks like the one in the Stage I Tuner's Kit does too but I haven't tried that (yet).

If you can figure out the manufacturer of that pipe, you may be able to get a quieter baffle if the pipe is too loud the way it is. If not & the pipe's too loud for your liking (& your neighbors'), then the SuperTrapp 2-1 would be a good choice, as it has discs @ the end of the collector which dissipate the sound waves. The fewer you use, the quieter the exhaust will be - but - the less exhaust flow you'll have, so that's a double-edged sword. But even adding discs for more flow, that exhaust isn't nearly as loud as a lot of other 2-1 setups. Bad part is the SuperTrapp is expensive & you're not likely to find a used one.

mapping the carb, reversion, 2-into-1 exhaust

Art_NJr, Thanks for taking the time to explain that whole concept, I will study this whole thread until it all gets put together in my brain, I will show a print-out to the local Indy tech and hope he takes heed, too. Reading Bike-talk is like taking a class called Harley 101.