Took a trip to Dumont, and I finally got a chance to ride my 03 Viper with all of the carb mods suggested by Oldman Racing. I was very pleased with how the bike ran. The difference is not "night and day" like when you put on a pipe or end cap, but it now pulls a little harder throughout the powerband and it never once sputtered or hesitated. I always seemed to have that problem before. All in all, it seems very crisp. Anyone that plans to stick with the stock carb, read his thread and do these mods to the spring, needle, snorkels, slide and balance tube. You won't be disappointed. On a down note, I crashed about three hours into riding on the first day and separated my shoulder. Had to then sit back at camp and stare at my bike the rest of the trip. Won $100 playing roulette in Pahrump, though.

 

Did you buy a DJ or Moose jet kit?

If you are running the stock needle:
5th groove
45 or 50 pilot jet
Pilot screw 5 turns out.
170 main to start

Sorry you hurt yourself, but like owning a horse, you just get back in the saddle
and life will be good again.

Let me know where you are at and maybe we can find alittle more power.

Thanks for the positve remarks.

 

I am running the stock needle, C Clip at fifth position (closest to sharp end).
Washers are reconfigured on the needle as per your specs.
170 main jet.
Stock pilot jet.
Is the "pilot screw" the same as the "air/fuel screw"?
I am 3.25 turns out on what I know to be "air/fuel screw?"


Thanks, Mr. Oldman, it is mostly due to your advice that I now have the bike running how it should.

 

http://www.predatorowners.com/index....40&thrid=15549

Here is a picture of where the pilot screw and pilot jet are located.

Yes it is the same as air/fuel screw. Different name,but same principle.
Because the pilot is located between the venturi and the motor, it is a fuel screw,
that is, the more you turn it out, the richer the mixture. It controls fuel.

I would do a run with your quad, then turn screw out to 4 turns, do another run,
then turn out to 5 turns and do a final run. You should notice more bottom/mid power.
For Christmas buy the DG or Moose jet kit. They really work well with the Stock Carb Mods.

Hope each day you are feeling better.

 

I agree with OMR, the DJ needle made a huge difference in the midrange of my DS. I haven't had a chance to try the slide and balance tube mods yet, just got my vent filter on Sunday. Will have results on this by the end of the week.

I have to give you a pat on the back as well OMR, the jetting specs you give for the stock carb gave my DS enough power for trail riding that I don't think I need much more.

 

Here's my test results. I used a set distance timed with a Victory laptimer mounted to the quad. I did four runs for each setting and then took the average time.

190 DJ mainjet
DJ needle in the 3rd position from top
45 pilot
4 turns out on mixture screw
Airbox lid off, 9" cut off of the intake tubing.
Temperature of 0 degrees C (32F)

Balance tube still in place - 14.34 seconds
Balance tube removed from carb w/filter on carb - 14.27 seconds. Felt more of a hit, but very subtle
Drilled out vacuum holes on slide to 1/8", balance tube in place - 14.51 seconds. Quad felt lean.
Drilled out vacuum holes on slide to 1/8", balance tube removed, filter on carb - 14.45 seconds. Still felt lean, but filter helped.
Changed mainjet to 200 DJ - 13.99 seconds. Quad felt very smooth, didn't feel faster because powerband was smoothed out.

I'm not sure about drilling the 1/8" holes in the slide at this point. The filter on the carb both felt faster and timed faster. I'm not sure if the times would have been better if I would have changed the mainjet first and then drilled out the holes. I think the slide opened so much quicker that it leaned out the mixture and slowed the quad down. I ran out of time otherwise I would have drilled two more holes in the slide as per OMR and timed again. This will probably be my next step, then I'll be looking to port the intake. As I have already completed the mods as per OMR, I will probably try timed runs with the airbox lid on and jetted down as well

 

Thanks for taking the time to test.
To do all this testing in 32 degree weather is great of you.
Looking forward to your next test session.
OMR

 

iceracer, what was the distance at which you ran these test in the 14's?
Thanks

 

Good question. I just marked out a distance that allowed my quad to reach top speed for a couple of seconds, I wasn't as concerned about the distance as I was the comparison of times to get there. As I do not have access to a dyno, this method gives me the ability to change settings and see if I am improving. I see where you are going here, comparing my times to the times guys are running the 300 foot drags. I wouldn't want to compare as my quad is almost completely stock. I was looking for a longer distance so as to be able to see larger changes in times.

Just for kicks, I'll see if I can measure it out, my guess is about 550 yards, 1650 feet.

Well, I was way off, measured it off at 360 yards, 1080 feet.

 

I also followed Oldman's mods, and am very pleased. However, I did the mods before checking the carb's float. I felt no difference after the mods, but it was because the float was "overfilling" the carb, making it apparently rich. That fixed, and the DS felt a LOT better.
So I strongly suggest to FIRST check your float (pain!!) and after that, begin the mods.

I am feeling no difference with or without the balance tube. I have no access to dyno, so cant "prove" it, but I feel the quad accelerates exaclty the same.... Might have something wrong?
Here are the mods:

4 - 1/8 holes on slide.
Stock needle in 5th.
170 main
Stock pilot, 4 turns out
D shape bottom washer