Prairie started missing at high rpm's
 

We went to Ocotillo Wells this weekend, and my Prairie was running fantastic. I raced my brother's DS, and a friends TRX 450, and smoked them both in a short drag. Everyone out there was shocked that I could keep up. The next day, she started missing at high rpm's. My first thought was a dirty air filter, because it was dusty out there, so I checked it and it was fine. The next thought was that the Dyna was going bad so I put the stock one in and it did the same thing. I did shim the needles .060 before I left, but I don't see how that could affect it, since it ran so well the day before. Can a 4 stroke foul a plug? Very curious what this might be.[img]i/expressions/face-icon-small-confused.gif[/img]

Prairie started missing at high rpm's
 

Since Ocotillo Wells is anywhere between sea level and 400 feet, I would think she would've been running a little lean. And don't you have to run the main jets quite lean to get the dial-a-jet to work right? You said you shimmed the needle, but what about the main? Maybe it's too lean.

Was there any water out there from the recent rains? Splashing some water up onto the carb vent line can cause it to miss, but usually it's pretty bad. My KLR-650 will caugh and sputter.

Or what about bad gas?

Just some thoughts.

Prairie started missing at high rpm's
 

I had a similar problem soon after I installed my DAJs earlier this year...my quad would run perfect in the early morning when I did timed runs...but as it got to be lunch time and the temps rose from mid 50s to about 70 degrees or so, it would start cutting out and running poorly at high speeds only (45mph or more)...the weird thing was it still ran great from 0 to about 40mph or so. I eventually figured out that my carbs were jetted too rich for the DAJs to work properly and after selecting the correct main jets (a trial and error process), I finally got rid of my problems at high speed. FYI: With DAJs installed, I ended up using main jets that are 3 sizes below the stock size for it to run good.

Happy trails...[img]i/expressions/face-icon-small-smile.gif[/img]

Prairie started missing at high rpm's
 

Can a 4 stroke foul a plug? Yes. If your jetting is not correct you can. Plugs are a simple device but they can mess with you, I have had plugs that would fire outside of the cylinder and not fire under compression and plugs that fire only at low rpm and miss at high rpm.

Prairie started missing at high rpm's
 

Maybe I should just remove the shims, and try it again. The part that puzzles me is that it ran fine the day before. I did change 1 thing though, I took out about 4 of my supertrapp discs, but it seemed to run fine for a couple of hours like that. Maybe it's running too rich. I noticed that when I turned the choke on slightly when the throttle was wide open, it missed more.

Prairie started missing at high rpm's
 

Customfab,
Jetting is a funny thing b/c so many variable come into play. With that said, I recommend that you remove the shims on your needles...remember that DAJs require the carbs to be in a lean condition in order for the DAJs to work properly. Of course, I could be wrong in my recommendation...but I dont' have any shims on my needles and my carbs run just fine with the DAJs.

Happy trails...[img]i/expressions/face-icon-small-smile.gif[/img]

Prairie started missing at high rpm's
 

I will do, but it was a little bit of a chore to do that, I think that I'll have to get those allen head bolts as was recommended on this forum.

Prairie started missing at high rpm's
 

Customfab,
Good idea...I replaced the 8 carb bowl screws with allen head bolts the very first time I re-jetted my carbs (I had problems getting 4 of the 8 screws out cleanly)...the allen head bolts have saved me lots of aggrivation each time that I rejetted thereafter b/c I no longer had to mess with the fragile stock screws. I found my allen head bolts at the local Lowes or Home Depot (can't recall which one it was).

Good luck and happy trails...[img]i/expressions/face-icon-small-smile.gif[/img]

Prairie started missing at high rpm's
 

4mm x 14mm or 12mm

Prairie started missing at high rpm's
 

I had the same thing happen to me with the DAJ. The inlet snorkel hose was kinked and it caused it to do what you were describing. I had it happen a few times and I just decided to remove the DAJ and install the correct jetting and haven't had any problems since. Anyone want a DAJ system cheap??