here is a similar product installed by dicks racing
http://www.dicksracing.com/motorcycl...ance/intelajet

I know this company installs them most of their race prepped bikes.

 

KLX678, can you explain one little thing?
The theory of how this "Dial-a-jet" works, as you explained it, depends on "a lean vacuum".

How does a too lean mixture create stronger vacuum than correct mixture or a too rich mixture?

--
Mikko

 

I see how the system woks and I think mixed gas and air is better than just raw fuel.

I also think to tune a carb or whole engine is an art. This product is trying t bypass fine tuning a carb with jets.

My first job out of tech school was rebuilding automobile carbs, alternators, and starters on 70s cars. I have a thing for getting them right.
The "new" unleaded gas makes reading a spark plug more difficult and catalytic converters make reading the exhaust more difficult. Just a couple more years and we will be seeing fuel injected lawnmowers.

We raced Polaris snowmobiles in the 70s and if it was well below zero F they would run lean and burn up. We would have to jet them richer. These were free air 2 cylinder 2 cycle engines. With direct pull round slide Mikuni carbs.

David

 

Hey David -
Can you explain the "reading a spark plug more difficult" thing and why it's different with the gas we have now? Is it because its unleaded, or ethanol, or other additives, or what?

I can still get ethanol free unleaded gas around here and try to run it in my play toys. Was planning on "reading" plugs in the KLX (ok, just one plug here) come spring and a '96 Polaris Ultra triple liquid cooled and a couple mid '90s Arctic Cat 440 air cooled this winter. What's different now compared to the good 'ol days?

 

IDRDR It used to be I wanted a spark plug porcelain (the white part around the + electrode) to be the same color as coffee with cream, a light tan up to brown. Now the spark plug can be white or a little grey and everything is fine. Its not as difficult with a 2 stroke because oil is burning too.

I also think we are getting a far better spark than came from points so it helps keep the spark plug cleaner.

There are also no ash deposits from the lead.

Right now my KLX has a little black if I stick my finger in the exhaust, so its getting plenty of fuel. The last time I pulled the spark plug it was still white with a little grey. I replaced it with a new one because it was the original. Look in any old MOTORS repair manual and it will have one or two pages of pictures of spark plugs and descriptions.



David

 

I was also wondering this.

 

I quite honestly can't explain the science to the nth degree. I just know a lean condition does pull stronger vacuum effect. If you've ever done jetting or even just taken the air filter off and reved an engine (when you rev it it is lean and the gas will start flowing from the jets) you will hear it draw a vacuum. If it's lean the vacuum will be strong and continuous. As it gets adquate fuel the vacuum will lessen. This is also visual if you've ever done/seen carb balancing with vacuum gages or tubes. You can actually see what the vacuum draw is on a given cylinder.

If you want, pull off your air box cover and air filter, then start blipping the throttle. You will hear the vacuum sound in the intake. If you open the throttle and hold it you will hear the vacuum sound decrease as the engine gets adequate fuel. If you've ever had an extremely lean condition it is possible the engine will not get adequate fuel and will either hold rpm with huge vacuum or it will stall due to lack of fuel. There are only two things that will cure a lean condition - add fuel or restrict intake. I had a bike that was way off on the slide cutaway - talk about sucking air. I'm wondering what need be done and my buddy standing there sticks three fingers into the carb and it starts smoothing out and taking throttle. He says the slide cutaway is too big, too much air and not enough fuel from the main circuit.

I just now thought of the other proof. Start your bike cold and try to take off the choke (fuel adder circuit through the carb bypassing the slide) and try to keep the engine running - listen to that lean vacuum sound. The cure - add fuel through the choke circuit. By the way, the choke circuit is tiny and will only really affect mixture at idle. And it is similar to the DAJ and PJ in that it lets the vacuum behind the slide nearer the intake to suck air and fuel through a tiny set of passages to the intake. Same with the pilot or idle circuit when the slide is closed. Vacuum behind the slide adds air and gas as needed. So you see your carb already has three circuits that operate on the same principle, two are minimal in size to affect very low rpm running and the other is fixed and must be changed out to deal with conditions.

The fact is that vacuum through the throat of the carb is exactly why and how the fuel is drawn from the float bowl through the fixed mainjet/needle jet/jet needle. The problem is when that fixed jetting is exceeded in fuel demand the engine runs lean. The Dial-A-Jet and the Mikuni Power Jet are simply fuel adders that take some stronger vacuum to activate than the main circuit. The vacuum has to be strong enough draw fuel from the bowl up to the top of the carb throat to get flow. If the main circuit is maxed out at full flow of fuel for the throttle opening and the vacuum is still strong, the DAJ or PJ will start adding fuel/air or fuel respectively.

I wish I could tell you the specifics, basically all carburation is a siphoning effect, with the exception of accelerator pumps on the carbs which quite literally squirt or inject fuel. When the vacuum of the air rushing over a tube that is in fluid, pulls hard enough the fluid will draw into the air flow - can you say paint gun (not the gravity feed, the ones with the can under the nozzle) and carburetor? Carbs work on the vacuum draw to pull fuel from the float bowl. Both the Dial-A-Jet and the PowerJet use that variable vacuum to add fuel, allowing slightly leaner jetting that will work better at partial throttle settings and to compensate for atmospheric and mechanical conditions that cause variation in the rate of air coming into the carb; aka less/more dense air due to temperature or altitude and increased air flow due to intake/exhaust modifications.

Fuel injection uses a pump and either mechanical or electromechanical injection of fuel into the intake throat. A totally different method.

 

These questions are not to insult or insinuate anything about your knowledge, but rather to use it to back up what I've said. Did you ever notice the vacuum draw of lean carburation when learning about and working on them? In addition, did you learn about vacuum leaks - what conditions do they cause?

I think your knowledge would back up my statement that stronger vacuum indicates a leaner condition? As the throttles open, creatig a lean condition, a stronger vacuum will occur and as the fuel system works to catch up on the fuel mixture that there will be a stronger draw or vacuum on carburetors until the mixture catches up, vacuum decreasing as the mix gets closer to optimum. If the mixture does not get up to near an optimum that stronger vacuum will remain.

I will say yes the DAJ and the PJ are both methods to circumvent having to do jetting changes on carburetors and there certainly isn't anything wrong with that for most riders. Racers might be another story, trying to fine tune things to perfection. Automobiles have complex circuits to alter fuel mix to compensate for lean mixture, that do not exist in motorcycle carburetors. Both automobile and motorcycle carburetors have used one trick to alter fuel mixture when throttles open fast - accelerator pumps, which squirt raw fuel into the intake when throttle plates or slides open rapidly, but it's a one shot deal. If the vacuum remains strong the DAJ and PJ will suppliment. That simple.

Could you hard jet to solve the issue? Sure you could. But really, would you want to stop at the base of some mountains and tear your carbs apart to maintain reasonable performance when you go up 3000-5000 feet in elevation, then have to do the same again when you come down? And what if this is going to occur several times a day? Now you see the value of a fuel adder for the average rider. On a single and as displacement decreases keeping power up is more important than ever. And I can tell you I've not experienced any sluggishness, heasitation, or drop off when riding from sea level to about 5000 feet nor have I seen it happen from 18-95 degrees.

You are right, eventually fuel injection will be on most everything except vintage stuff. It would be nice to be able to bolt on an FI set up that would work, but with all the electronics involved, I just don't see it happening as an add on for carbed bikes.


Until then as long as carburetors are around jetting is an issue. Four strokes are tolerant of lean and rich jetting to an extent that two strokes are not tolerant. Both the Dial-A-Jet and PowerJet systems work to add fuel when needed based on vacuum draw. Both have some tunability, one with a click dial for five settings and the other using brass jets. Both require stronger vacuum than the standard jet circuit in the bottom of the carb throat due to the requirement to draw fuel up above the throat before it can flow into the throat. DAJ requires the jet needle be positioned between 90 degrees of the top (from 9 o'clock to 3 o'clock to use the standard reference) the PJ is top center per Mikuni's application.

I guess I have just found something that works and am enthusiastic about it. My bet is 99% of single cylinder four stroke riders would find this sort of thing great. From the riders of KLX650s who installed Dial-A-Jets I have yet to read one who didn't find it to work or one who had any problem - other than maybe trying to fit things into a compact space on the carb. I used the air boot band to mount the body of the DAJ on mine, a bit of creativity to suffice for needs and space. Most of the negative on Dial-A-Jet comes from riders who've never used one, the "I heard" or "It won't work" without hands on. I have hands on, as do my friends and fellow riders who tried the DAJ at my recommendation.

The question was asked and I answered - Yes I use a Dial-A-Jet and yes it works. It works over a range of temperatures, elevation changes, and engine modifications with no adjustment in my case with my bored out, modified air box, full reverse cone tapered head pipe exhaust system without a click of the adjustment..

 

Our KLXs have these goofy CV vacuum carbs so the fuel is only added when the airflow demands it. Does the DAJ work with the CV carbs? I don't really need to hear about experiences with slide carbs if they don't apply to our CV carbs. I read through the site and it doesn't address the CV carbs at all. All the pictures show old fashioned slide carbs.

I've got stock jetting and plan to either buy a DJ kit or?

 

You have to take the carb out for either install, the dial a jet has been around for a long time as I remember it from my sport bike days years ago, but I would just install the Dynojet kit per instructions as I have close to perfect jetting on the first try just by doing what the instructions said. From what I understand from some of these guys who ride at some elevation that these CV carbs do ok on their own to compensate for most changes you are likely to experience.