OK, I have a 883c with newly installed V&H Shortshots. I plan on also installing a Scream’n Eagle A/C Kit.

After talking to you folks and seeing what it will cost otherwise, I’m figuring on doing the carb work myself, but I’m a little confused???


For the rejet, should I just get a new slow jet and a new fast jet, each going up one step or should I mess with a “kit” and fool with needles, shims, and springs?
will I have to drill the mixture cap??? I see some things say yes, some say no. [/ol]

As always, any other help is always appreciated. Also, thanks to those who have already provided the links to the great reading material.

- Jerm

 

well i have a 06 883L and i bought the rejet kit from sorgys off of ebay for $15.00 you get the 45 slow and a 180 main jet and 4 stainless hex head screws. i drilled my a/f screw cap my self installed the jets and turned a/f mixture out 2 full turns from closed positions. and the bike runs great. i'm also running cycle shack slash cut slip ons and a SE air cleaner kit.

 

There's a lot of debate on this. Generally speaking the rejet process is very simple. Get the air-to-fuel ratio adjusted to provide desired results. The ideal air-to-fuel ratio for proper emission is about 14.7:1 (14.7 parts air to 1 part fuel by weight). When a Harley runs with this mixture, the engine usually hesitates, staggers and spits back through the carburetor. When the air-to-fuel mixture reaches a ratio of about 13.8:1 or so (less air, more fuel), the rider can begin to feel an improvement in throttle response.

The best mixture for throttle response and drivability is about 13.0:1. In other words, the richer the mixture (to a point), the better the bike runs. Unfortunately, at this kind of mixture ratio, mileage suffers. That's the important thing to remember about rejetting.

Stage I upgrades are intended to improve the bike's performance and drivability but do so at the expense of fuel mileage. The OE carb delivers good mileage and low emissions. With stage I jetting, it will deliver good power and poor mileage (relative to stock mileage numbers). Take your pick.

Jets alone:
The reality is you can spend a few dollars on the jets and possibly a couple tiny washers to shim the needle and get the bike tuned in pretty good. Some also drill a larger hole in the slide to get it to move quicker (a.k.a. more responsive). The positive of just getting a 45/180/and a few shims is that you are only spending money on what you need right now. One of the drawbacks to this option is the lack of additional jets/parts to use in future upgrades like cams, big bore, etc. In that case, you'll have to guess what you need and go get new jets again. For the Stage I, the 45/180 setup is pretty much guaranteed to work. But when you start with other engine mods the jets required are not always as much of a sure thing. When you get to that point, you run the risk of not getting the right jets first time and having to go back and forth to the store a few times to get the right ones. This could get frustrating and expensive over time. That is where some jet kits could prove to be a better investment.

Simple jet kit:
First you have some simple parts kits like the one Diehard purchased. You get the specific parts you need (Allen hex screws are a nice to have but not required). These are convenient and in cases can be had for the same price the pieces would be separately. The positives are that they are inexpensive and you get everything you need (for a Stage I rejet) in one box. The potential drawback with these kits is the same as with individual parts described above. You have limited future upgrade capability.

Complete kits:
An example of this type of kit is the Dynojet Kit or Dynojet Thunderslide Kit. There are other brands available but these are the main ones used by most, including many dealers. These are more expensive than the previous options. They contain multiple jet sizes, a new needle with adjustable shims, as well as a new return spring, drill bit, etc. They also have very easy to understand and detailed instructions that help you pick the right jets for your setup. The positive to this is you have everything you need to tune your carb for any modifications you’ll do on your bike short of changing the carb. The downside to a kit comes down to cost alone. It applies if you only plan on a Stage I upgrade and may never do more. In that case, the expense of the kit might be harder to justify.

There is tons of info on the topic. Google some combination of ‘Harley’, ‘Stage I’, and ‘Jet kit’. I deliberately tried to not suggest one method over another and instead only provide information. This topic usually results in some very emotional posts about which methods are better and what you

 

My jetting for a good all around tune is as follows:

1. One size larger slow jet
2. Needle for a 1988 1200 Sportster
3. Cut two coils off of the slide return spring for faster response.
4. Pop out the idle screw cap and set the idle screw at two turns out from the bottom.

The high jet will probably be okayif you are just doinga stage 1 and no other modifications.

I have used Dynojet kits before and they work no better than this method, and cost a lot more.

As far as drilling the slide, I have never heard of that.There is a port in the carb bodythat can be drilled to improve slide response however.

I don't know the size of the drill, but I think it is 5/32. I have one that came with a dynojet kit that I bought, so if you decide you want to drill the port let me know and I'll mic the drill and give you a size for sure.

Most of the above information I got from Joe Minton who was a tech writer for one of the major bike mags.

Regards,

Bill

 

The thing to watch is getting the correct A/F ratio for your specific bike, and remember that what is best for one bike might not be the best choice for another..

Most tuners like to run the air/fuel mixture "slightly rich", with the ratio being approximately 13 to 1. But if you go below that figure you risk running too rich, which is not good.

Besides the additional horsepower you will gain running the correct A/F ratio will also allow your engine to run cooler than if you are running a lean mixture.

My FatBoy had the exhaust/intake opened up (what most now days calls Stage 1), and it also had the factory computer download completed. True, it's EFI, but your engine doesn't care if you are running a Carb or EFI, it just cares about the end A/F ratio it receives.

The bike also had a SERT (Screamin' Eagle Race Tuner) loaded, and was placed on a dyno to have everything dialed in.

Best rear wheel power figures (79 horsepower at 5,500 RPM and 84 pounds of torque at 3,750 RPM) came when the air fuel mixture was right at 13 to 1. This was with the stock 88" engine. We plan on upgrading to a Stage 2 95" setup within a couple weeks, and my tuner said we should see rear wheel figures of 88+ horsepower and 96+ pounds of torque.

Bottom line, jetting your carb'd bikes, or using a tuner on your EFI bikes to get the ideal A/F ratio is important for both the life of your engine, and the additional performance it will provide.

Every bike reacts differently to carb modifications, and what works best for one might not be best for another. The elevation of where you live, different fuel blends in various parts of the country, and other factors will determine how your bike needs to be tuned.

The old "seat of the pants dyno" might not be as accurate as you might think. Running your bike under power, cutting the engine and reading the plugs might get you fairly close, but the only way to make sure your bike is dialed in is to hook up some gauges to check the A/F ratio, or put it on a dyno.

 

Here is a good link for both carb tuning and rejetting.

http://www.harley-performance.com/ha...arburetor.html

http://www.harley-performance.com/ha...r-jetting.html

I purchased a rejet kit no ebay for $16. It included a 45 jet and a 180 jet, for my 883. It also came with the stainless steel hex head screws to replace the stock screws on the carb bowl. Plus very good instructions. I had never worked on a carb before at all, but I was able to just follow the directions, and had no problems.

That was one of the easiest things I've done to my bike. I was at a Christmas party at a local Indy shop. They were all standing around looking at the dyno machine, and the owner wanted to show off his dyno, so I volunteered for a complimentary dyno test. He said, I had pretty much nailed the carb setup and idle mixture screw.

Since I didn't pay for this testing, he didn't give me the print out.....

 

All you ever need to know about rejetting. Read the Note about 04 and later Sporties
http://www.sportster.org/tech/carb/rejetting.shtml
I just rejetted my 05 883 and all i replaced was the Slow jet with the #45. I am waiting the K & N filter to get here. Before I do any more jetting
As a side note, I DID NOT remove the carb to rejet. I simply removed the float bowl.

 

I am far from an expert, but I have been doing some research on this. And I had my bike on the dyno for my re-jet, because I wanted a baseline to work with.

I would just be careful on what you¨do and exactly how you do it if you want it to turn out right.

This is what I have learned talking to a lot of Harley mechanices in the last couple of months:

The 04-06 Sportsters tend to be tuned lean from idle to mid throttle. BUT for Wide Open THrottle (WOT) they tend to run a little richer.

So just blindly throwing in a larger main jet will only make that even richer. Chances are you'll never run WOT for too long and never notice it, But it could make a difference.

The slow jet controls the flow for idle to partial throttle/pull away.

The needle affects the mid throttle ranges -- the driving ranges when you're rolling.

And the main jet affects the WOT range.

For the most part, one size larger slow jet and some shims on your needle are all you really need. Your main will probably be fine as is, and in some cases can even come DOWN one size if you truly want to tune it to perfection (depending on your area).

So anyways -- point is, you'll get 100 different recommendations on what jets to use etc. The only one that seems consistently true is going up on size on the slow jet. Past that it really depends on your bike and where you live. It's worth a couple Benjamins to put it on the dyno and have it fine-tuned, in my opinion. And in my opinion, I think shimming the needle is key as well to really fine tune in the carb. If you're just changing the jets -- all you are doing is the extremes, you are missing part of the most important, driveable range of the throttle range. JMHO fart fart backfire backfire

Oh, and yes, drill out the mixture screw. You'll want that out so you can make fine-tuning yourself if the weather changes or you change altitude etc.

I am no expert, so someone please chime in and correct me if I have misstated something.