Another "Jetting with Mods" Question
 

OK, my plans to leave my bike stock until my riding skills exceeded its capability went out the window when I bought a slip-on, filter and jet kit from another member this week. I know that jetting is voodoo science and every bike is different, but I would like to get some opinions on where to start so hopefully I get close the first time. Setup:

- FMF PowerCore 4 slip-on, stock header
- Uni Foam Filter
- DynoJet 2182 jet kit
- KDX 200 snorkel
- Riding mainly between sealevel and 2' below sealevel depending on rainfall :)

A couple of questions:

- What combination of main and pilot jets would you suggest I start with?
- What clip position on the DynaJet needle?
- I want to pull the carb and clean it when installing the jets and needle, but if I need to rejet will I have the pull the carb again, or can I rotate it and access the jets?
- Any other words of wisdom would be appreciated!!

Follow the Dynojet instructions, I believe that is the clip on the 3rd notch from the top, 124 main jet, leave the Pilot alone...I forget where the air-fuel screw is...I think it is 1.5 turns out from lightly seated. You CAN use the 120 jet, probably, as long as you make sure you keep the KDX snorkle in.
You CAN rotate the carb to get to these items, but, you have the float to worry about, as well as dropping dirt into the bowl, etc. I always just grit my teeth and take the darn thing out. I think it's best to do it that way.

+1 on following DynoJet's instructions.

If things aren't running perfect after you do that, then email DynoJet (via their website) and let them know what your exact setup is, what altitude you live at, and what the problem is. Be specific! In my experience, they are VERY GOOD at getting back to you quickly with a recommendation customized to your exact situation.

I have a similar setup and used the Stage 1 & 2 Dynojet kit. I stuck to the instructions and it worked fine for me. I'm on the 3rd clip and I think the 124 main. I think those should be a good starting point for you. Afterwards you can tweak it via the mixture screw.

Oh ya, you might want to pull your smog crap while you're at it.

Really, your riding 2' below sealevel. I would try and stay away from sea water & sand, it has a tendancy to get into everything, then it wears out.

Thanks guys, appreciate the real world input.

I was kidding. I'm in flatlander country in N. Florida and the woods get very wet with the seasonal rain at times. The water and mud is unavoidable but I keep the bike off the beach. Now the jeep is another story....

Or you can just buy a Dial-A-Jet kit, install it and pretty much forget it, since the OEM jetting is lean already. It is a proven fuel adder with reviews from DirtBike!, MXA, Motorcyclist, and others. Highly accepted in the ATV and snowmobile markets but snubbed in the old school motorcycle world. Although Dick's Racing uses them on his tricked out MX racing carbs.

As a fuel adder it simply uses the vacuum draw of a lean engine to siphon a gas/air mix as needed. When the vacuum is high, the fuel/air mix added is high, when low the fuel/air mix added is low or even stops. That doesn't happen with hard jetting. You get what the jets allow past. And by the way, the jetting circuits in the carb work under the same principles of fluid dynamics in a vacuum. The Dial-A-Jet is simply another circuit to add fuel and is externally adjustable.

Just saying, you can tear your carb apart several times for jetting, or you can do it once with an adjustable system that has proven to work quite well. I've got a bit over 20 years experience with the regular Dial-A-Jet and will tell you I put it in, then opened up my airbox, then went big bore with a full reverse cone megaphone exhaust and have yet to change the adjustment. The plug is virtually perfect tan, exhaust end has consistent color and the performance doesn't change from temperature or altitude extremes that I encounter. Friends and some KLX650 riders on the Yahoo KLX650 group have had the same experience. No one I've known has found anything less than an improvement in performance.

But if you enjoy tearing carbs apart - have at it. This was simply a suggestion to consider as an alternative to the same old/same old from the invention of the carburetor. See what the media says, and I guarantee you neither DirtBike! nor MXA are afraid to call a spade a spade, there is no big buck advertising at risk and I doubt that would matter either.

Last note, Mikuni uses a similar set up, but pumps raw fuel with their PowerJet set up, no air mix for atomization. Those are the people who KNOW carburetors and they use the same fluid dynamics process to compensate on fuel mix.

I don't recall anyone that actually uses a Dial-a-Jet that complains about it. It's something to seriously consider!

The more I read on the dial-a-jet the more I like it. Does seem to bridge the gap between a purely mechanical carburetor and and EFI. I suspect it may actually help to optimize both mileage and power by adapting itself towards to a known A/F ratio.

This jetting discussion brings up some interesting perspectives. I have no issue with Mark's Dial-a-Jet, as they seem to work. I've never used one, but the reason I've never used one is that once I get my jetting right...and that usually only takes a short experimentation ride or two...I never have to mess with it again. On the many race bikes I've had over the years and the dual sport bikes I've used on my big trips out west, I've never rejetted or found the need to putz with the jetting after initial setup. Now, I'll also add that I almost always took the given bike and did all the mods I was going to perform on the bike and do them upon getting the bike and do them all at once. Whether riding in Death Valley or going over Imogene Pass in Colorado at over 13,000 feet, my bikes were very rideable, had good response, and yielded good fuel mileage. I will add, however, that the bikes I rode in those different extremes were nearly all DS bikes with CV carbs. CV carbs have better latitude at dealing with different altitudes. My race bikes didn't have CV carbs, but I didn't take them to riding venues like CO and other western locations with wildly varying altitudes.

From a sledder, dial a jets were a pita, everyone I know that used them gave up.

IMO,one of those products that's been around forever and resurfaces about the time everyone forgets about them..

My complaint is they were very finicky and didn't add or subtract fuel like a main jet swap did. It fueled into the needles range. Tuning with egts, you'd dial them up to cover a hot wfo but end up up rich in the middle, or visa versa, They work but are not the same tuning effect as changing the main jet,

I can no longer say I haven't heard a complaint!

You sure knew what you were advising when you helped me with my jetting...thanks again!

I wonder if people were trying to get close on the jetting and then use the DAJ? The instructions are clear about starting with a MJ 2-3 sizes lower than you expect for perfect jetting to allow a useable range of flow and not be forever in the over/under syndrome.

They have for me. Both in a 700 four and in my KLX650 as well as my friend's XT225 and the guys on the Yahoo group who bought them. As I said, Mikuni uses a similar set up in their PowerJet, used to keep engines from leaning out at high rpm.

Now, of course I did start with a fully lean carb set up in the first place, so I didn't have any risk of being fat in the mid range or top end.

If it didn't work I would think that would have shown in the media testing as well as the work that Dick's Racing did when setting up their high performance MX carbs. How is it that so many others in the ATV and snowmobile media field had such good experience? Seems only some individuals have had negative issues, not the media. People have trouble with jetting as well, does that make jetting bad? I've seen people remove carburetors and go back to stock, because they can't get the jetting to work. I did the same when I put pods on my S3 Kaw triple. Jetting was a pain... but then I found it was my ignition setting on the points. Problems happen with change. Jetting or with Dial-A-Jet. Some people will have problems, that's life.

In doing research on-line about the Dial-A-Jet, one of the oddest exchanges in a thread I've read was one where a rider told another that some other rider he heard of didn't have good experience with the part. The rider asking the question said "nice to hear of some real experience"... real experience! Heck if that was the case and people did that no one would own anything. I've heard how bad the Dyno Jet kits were to use and jet in. I've heard how bad the KLX650s were, the KLX250s, the XR650Ls, and about any bike you can find. Back in the 80s I also had some guy come in the bike shop, look at the bikes and procede to tell us about some rider who had his head lopped off when the chain flew off his BMW... think about it...

I only know what experience I know of first hand and personally and have said such. It seems most people who detail what they have done will have success if the bike is stock (usually stock is lean jetting all the way through) and those who have problems have usually jetted everything beforehand and tend to fiddle a lot. I had one variable, the Dial-A-Jet. It went in and worked fine. One forum had a guy with a DAJ working fine, until he had to mess with it some more, then had problems. Odd thing is I catch a similar thing from some about a part I make. Start overthinking it or involve too many variables and problems occur. Go figure.

No amount of claims or examples will alter things and opinions (key word here) for some, so I will leave it at this:

The Dial-A-Jet works well installed on a stock jetted carb, the idle mix will need adjusted since it is a separate circuit from that where the Dial-A-Jet works. I had smoother power delivery eliminating a flat spot in the mid range. The bike felt better and pulled top speed of about 105 or so mph easier and quicker.

The Dial-A-Jet only can add fuel, not subtract, so if there is a rich range in the carburetion it will not deal with that. Fortunately all of my bike's carburetion was EPA lean, as many stock carburetor set ups are and as increasing air/exhaust flow will do as well.

It took me all of an hour or so to install on my stock 650. I had to rotate the carb sideways to remove the float bowl, because I wanted to keep the bowl drain, my bike never has started if the gas in the bowl is over 5 days old since I got it with 1710 miles on it. I left the setting on the center setting since it felt fine. Although I should have, I didn't adjust the idle mix until nearly 12 years later, living with the bit of popping and backfiring under decel that was there when stock. I finally adjusted it this year, far less popping on decel. I have 30,000 miles ranging from rain to dusty dirt with the standard set up, but put a small piece of filter foam over it. Far easier than any jetting I ever had to do on the flat tracker or motocrosser. Didn't even mess with the needle.

It has never needed adjustment from the center position based on plug reading and exhaust tip color, even after cutting the air box lid a bit, installing a 2mm larger piston (Vulcan big bore), and an old unobtanium BajaDesigns full reverse cone megaphone exhaust. Actually experienced an increase of 10 mpg after letting the engine breathe (stuffy stock muffler). It has been run from 18-95 degrees and from sea level to about 5000 feet above sea level again no change and no noticable power loss.

The company is totally cooperative in helping with information, with a simple phone call.

I've used the system in a stock Honda Nighthawk S and a friend used them in a 700S with a Kerker, back in 86. No one who picked up on it by my suggestion has come back with any complaint. I once got flack from the administrator on one web site, Thumper Talk I think, when I offered to buy one off of a rider who didn't like it. I need one for my SR. I was told I wasn't allowed to do that, offer to buy a part from another rider. Just saying I have had good enough experience I am going to do one in the SR. Don't have them in the Zephyr because I don't really want to spend the couple hundred it would take right now. Other projects to do first.

So take it how anyone wants... I'm just one of the people who have had success. It is a legitimate alternative using sound science. Like anything, some will have good experience others will not. All I can tell you is exactly what my experience has been... and I have.

This makes a LOT of sense to me! Thanks for going to the trouble to post it!

Got all of my mods installed today: fmf slip-on (actually it was installed a few days ago), Uni filter, kx200 snorkel, dynojet needle and 128 main jet w/ clip in 3rd slot from top, kouba screw 3 turns out, iridium plug. Wow, what a difference. Jetting seems right based on seat of the pants but I will pull the plug and see what it looks like. One minor issue: got everthing back together except the plastics, fired it up sounded great, then noticed gas just pouring out of the carb around the bowl. Had to pull it all back apart and use some sealant at the bowl to carb seal. I'm already better than I ever wants to be pulling and reinstalling the carb.

you didn't lose the o-ring that goes between the bowl and carb body did you ?

No, but my bike is an '07 and I really should have replaced the gasket on the bowl but i didn't have one. So I just used a very small amount of sealant on both surfaces along with the old gasket.

I suggest ordering the gasket now so when it does leak again you can fix it on the spot. One of those parts you don't want to wait a week to get.