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Thunder Products’ Dial-A-Jet – Dirt Bike Magazine

It makes jetting so easy you’ll do it.

Dirt bikers are more mechanically inclined than normal people.  Most of us know what carburetor jetting is and what it can do for performance.  While most dirt bikers are performance-hungry, the possibility of better performance isn’t enough to motivate a surprising number of riders to jet their bikes properly.  Maybe it’s the time-consuming nature of jetting tests.  An afternoon of trail riding beats an afternoon of jetting any day.  Some riders won’t rejet unless their bikes foul two plugs per ride.  Some have to seize an engine before they will tear into the carb to set things right.

What if you could change your overall fuel/air mixture as easily as you adjust your idle?  No tearing the carb off.  No box full of four-dollar jets.  No lost circlips or float bowl screws (did it land in the sand or-gasp-the intake?).  Just turn a screw for a richer or leaner mixture.  Sounds heavenly, doesn’t it?  It is.  That’s why Dial-A-Jets are so common on racing snowmobiles.  When the snowmobile guys rejet it’s often so cold that fingers barely move.  Then there’s the joy of removing bodywork just to get to the carbs.  That’s right, carbs.  As many as four on some machines.  No wonder they found an easy way to rejet.

Convenience has a price.  In the case of the Dial-A-Jet, the price is $74.95 and a little more than an hour of installation time.  First, you have to do a little old-fashioned jet changing.  If your bike is running acceptably well, the Dial-A-Jet people suggest you install a main jet one or two sizes smaller and move the needle one position leaner before installing the Dial-A-Jet.  The extra-lean jetting lets you use part of the Dial-A-Jet’s adjustment range to provide leaner-than-stock jetting and part for richer jetting.  On most dirt bike carburetors you have to drill and tap the float bowl or float bowl drain plug for the Dial-A-Jet’s fuel supply line fitting.

No matter where the Dial-A-Jet draws fuel from, it is mixed with air at the chamber near the carburetor mouth and delivered in atomized form into the intake airstream.  Dial-A-Jet claims the atomized fuel mist fills in lean areas in the poorly atomized fuel charge from the carburetor for improved throttle response and less detonation, even with crisp, lean jetting.  There was some evidence of this on our KDX.  The bike detonated lightly even with the fat stock jetting in high-load, part-throttle situations.  With the Dial-A-Jet we used leaner jetting and could roll the throttle on in deep sand and get strong acceleration with no pinging.

Improved response is just a side benefit of the Dial-A-Jet.  The real beauty of the device is the ease it brings to the traditionally unpleasant task of rejetting.  Once the Dial-A-Jet is installed, all you do to change jetting is turn the adjustment screw on the Dial-A-Jet mixing chamber.  What you are actually doing is altering the amount of air mixed with the fuel delivered by the Dial-A-Jet.  since air is being fed through the Dial-A-Jet mixing chamber, a filter is available to keep dirt out of the Dial-A-Jet ports and the engine.

Finally, there’s a practical way to jet a bit richer run for strong performance in the cold morning air without dooming your bike to being a plug-fouling, blubbering beast in the afternoon.  Leaner jetting that makes sense in high temperatures or in tight, technical conditions where crisp throttle response is important and periods of sustained full-throttle running are rare is easily available.  You can also set your carburetor jetting so that the Dial-A-Jet provides five leaner jetting steps for rides into extremely high elevations.  No matter where you ride, it’s likely that the Dial-A-Jet would come in handy.  If your riding takes you to a variety of temperatures and elevations, it almost seems foolish not to have it.  The Dial-A-Jet is available from Thunder Products, Inc. 320-597-2700.