Out with the old - in with the new

As soon as we heard about the new pumper-series carburetor from Edelbrock, we knew it was a "must have" for our 400EX. The QwikSilver carb features an adjustable accelerator pump that provides instant throttle response, internal fuel cell and an anti-slosh plate to ensure consistent fuel delivery. The easy tuneability will be much appreciated when we make the next trip to the mountains, i.e. no more jet changes!

Let's get started

Strip it down!

Make sure your fuel is off and then disconnect your battery. Now remove your seat, front fender assembly and fuel tank. Remove the throttle cables, airbox intake tube, and stock carburetor. *Pay attention to the cable routing as you will want to route the new cables the same as the stock ones. Next we installed a new twist throttle and cable. The QwikSilver carburetor uses two cables - a pull cable and a push cable. If you use a thumb throttle, it will be necessary to grind away some of the throttle housing to obtain full throttle.

New twist throttle

Old twist throttle

Remove the rubber aligment tabs from the manifold. Trim the air intake tube you will be re-installing. If you are running without an airbox lid, you may want to plug the airbox and leave this off.

Remove the rubber alignment tabs from the manifold with a razor blade.	Cut approx 1 1/2" off the air intake tube for cable clearance.

Remove the pipe plug from the top of the carburetor.	QwikSilver with metering adjustment tool installed.

View of metering adjustment tool from inside.	A view of the top of the slide and the needle adjuster.

Original carb -  The butterfly causes airflow turbulence, giving poor low-end.	QwikSilver - At wide open, throttle airflow is only restricted by a .125" needle.

Install the QwikSilver carb into the manifold. Install the pull cable and the idle cable on the cable wheel and adjust the cables for 1/8" free-play in the throttle. Now align the carb vertically and tighten the manifold clamp. Install your fuel tank and cut new fuel line to the proper length. Re-install your plastic and any other items that you removed and you are ready for a test ride.

How about some results?

Our 400EX fired up immediately with no initial adjustments. We warmed her up and headed for the QwikSilver chassis dyno. With the QwickSilver carb installed, the dyno showed much more consistent power delivery through-out the RPM range. The dyno showed that our HP had increased from 29.3HP to 31.7HP. This was almost 2 1/2 HP over stock but the expert R&D team felt the 400EX was running a little lean at full throttle. A quick needle change to the 17e would help this. With the 17 needle and the metering adjustment at 12 clicks from full rich, the R&D team was much happier with the dyno reading, even though we showed a slight HP drop. We were now showing the 400EX at 31HP. This is still a gain of 1 3/4 HP and almost double the 1 HP gain from the exhaust system, K&N filter, and removal of the airbox lid.  Dollar for dollar, you get more for your money with the QwikSilver carb than you do with the typical exhaust kit.

Enough is enough, get it out on the trail!

Throttle response is incredible. The 400EX starts easier and it pulls through the complete RPM range. Since the QwikSilver carb is less affected by altitude changes, it means no more jet changes next time we head to the mountains. 

If you own a 400EX, 300EX, Warrior, or Bombardier DS650, you should put the QwikSilver at the top of your list for performance modifications.

Special thanks to the R&D crew at Edelbrock QwikSilver!
http://www.edelbrock.com/motorcycle QwikSilver
1320 Buena Vista Street
San Jacinto, CA 92583
Phone: 909-654-667
Tech line: 877-888-7504