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Discussion Starter · #1 · (Edited)
All right guys bare with me im new and im sure this has been posted before.
I have an 03 LTZ400. I just had some performance work done and I cant for the life of me get the jetting dialed in. This thing should rip way more than it is. I ran 4 plug checks and rejetted each time this weekend and the plug was white as can be which im assuming its running lean? Any leads in the right direction would be most appreciated.
Here is a run down of the new upgrades and my setup:
Cylinder works 440 bigbore
Stage 2 hotcams
Kibblewhite valves
Port and polish
Uni air filter/ Air box lid off
Stock carb
Dj165 main
30 pilot
Dj needle in the 4th position
2 turns out on the fuel/air screw
Elevation roughly 5000 ft @ Little Sahara, Utah
Do Dyno jets read the same as the regular jets? Or is the a chart I can go off of?

3 Posts
Discussion Starter · #3 ·
That picture was after upping the jetting to a dj165 and 4th clip position on the needle.

Super Moderator
3,700 Posts
I think you will go mad, trying to jet by the color of the plug. What exhaust do you have? If it is a full exhaust you should be close. Maybe a tad rich at 5000 ft. Not sure why you have a 30 pilot, but if it idles clean at 2 turns, ok. If it is stock exhaust, you need to jet it down by 5 at least, probably 10.
Does it pull clean to full throttle? Try it with a 155 DJ, see how it pulls, compared to the 165.
There is a chart under maintenance of the difference between jets, but stick with what you have and work from there.
From Dynajet...
1. Remove the airbox lid.
2. Remove vacuum slide from carb. Remove stock needle & spacers,
noting order of assembly (Fig.A).
3. Install Dynojet needle on groove #3 for applications below 5000 feet,
groove #2 for above 5000 feet, using all stock spacers (Fig.A). NOTE:
The DSP77 spring does not have to be used, it is supplied in case the
stock spring is misplaced. The Dynojet washer (DW0001) does not
need to be installed at this time, it is for half step adjustments. After
installing the slide in the carb be sure to check slide movement
manually before airbox installation.
4. Remove stock main jet and replace with Dynojet main jet provided.
Use the DJ155 below 3000 feet, DJ150 from 3000 to 6000 feet and
DJ146 above 6000 feet. When using an aftermarket exhaust with a
high flow baffle, use the DJ160 below 3000 feet, DJ155 from 3000 to
6000 feet and the DJ150 above 6000 feet.
5. Locate the Fuel Mixture Screw (Fig.B). If you see a screw head at
Fig.B then proceed to the adjusting procedure. With the 5/32 drill bit
provided carefully drill through the plug. NOTE:The mixture screw is
directly underneath this plug, be ready to pull back on the drill the
instant you break through. Use the screw provided to secure and
remove this plug. Carefully turn the mixture screw clockwise until lightly
seated, then turn out 3.5 turns, 3 turns above 5000 feet
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