Big Gun SDS

1 reply to this topic
  • Rfaster

Posted May 03, 2000 - 01:18 PM


First I'd like to say how much I already like my WR - Drove all the way to Fresno to pick it up last Saturday - rode Hollister on Sunday. I only wish there was a group like this for my '00 380 - I could use some hints on tuning it-

Just ordered a Big Gun SDS system (after reading everything on this list about pipes)for my '00WR from White Bro's of all places, and was wondering what jetting I should start with. I spoke with someone at Big Gun and they recommend 1 up on the pilot and a 180 or 185 main. They did not mention anything about changing the needle - do I need to worry about this? I should probably mention that I have never touched the carb on a bike - should I have the dealer perform this job they quoted $26 which seemed cheap. I was thinking about asking if I could watch them - and learn... but not sure if shops allow such a thing.

Btw, according to Big Gun the Spark Arrestor won't be available for a couple of weeks.

I'm in Northern CA - riding 1/2 moto and the rest trails, Air box lid and pipe insert are off - has run fine for all of the 30 miles the bike has on it.

'00 WR400
'00 380EXC
'01 -Waiting for 520MX

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  • mcarp

Posted May 03, 2000 - 02:42 PM


I can't help w/ exact specs, but the 1 step up pilot (45) is probably good advice. 185 is probably too rich for warm temps. Post the mods you have done.

The carb is complicated, yet rather easy to work on. The hard part is deciding which jets to use, not actually doing the work.

To change the jets--turn off fuel and drain gas from carb (left side bottom-small allen screw. There is a lot of gas to drain, so trace the host and hold a container under it.

Now remove the coil (right side black cylinder in front of carb. Pay attention to where the wires go.

Now back to the left side--loosen the boots on the carb-one is a large phillips, the other the same size allen wrench as above.

Some folks remove the throttle or loosen it and move it inwards to allow for more cable slack. I haven't found this to be necessary.

One the two screws are loose, grab the carb and turn it with the bottom turning towards you. Now remove the 17mm plug on the bottom-there will be some gas there too, not much. The first 6-sided hex "bolt" you see is the main jet. Use 1/4" socket to remove. Just in front of this (towards the engine) but farther up in the carb body (recessed) is the pilot. Use a small flat screwdriver and loosen this.

Now just put the jets back it, DO NOT tighten these jets very hard.

To get at the needle, move the carb back the other way so the top is sort of facing you. Remove the 2 allen screws. Remove the screw that holds the needle. Use a long, thin pair of plyers to gently pry the needle up. Maybe a magnetic object will help.

I'm not saying to mess w/ the needle, but that's how you get to it.

Doublecheck your work before you put it back together-remember the coil and wiring. To align the carb, there is a flange that fits into a recess in the boot. Force the carb in this recess and tighten the boots.

May as well cut down that throttle stop while your working on it. It is on the right side of the carb-remove the black cover, and the screw is near the rear-bottom area. It has loctite, be careful.

Good luck. Post your riding conditions and bike setup, maybe someone can help w/ exact jetting specs.


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