Beta rx300 jetting

Racer142
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Racer142
Edited Date/Time 8/5/2022 6:50pm
I got a 22 rx300. Stock jetting and its a little fat. Anybody running one and got some jetting suggestions? Mostly seems a little rich in the bottom so I'm between a smaller pilot or lowering the needle. Pic of the plug for reference. Maybe 2-3 hours on the bike.


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Racer142
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Racer142 8/4/2022 10:35am
8/4/2022 10:35am Edited Date/Time 8/4/2022 10:35am
Running moto at 1000' elevation, 90 plus degrees right now.
motoracer58
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motoracer58 8/4/2022 10:52am
8/4/2022 10:52am
I have a 2020 300RE so not sure if jetting is the same but I moved the clip one notch leaner and corrected the float level and that's it. I'm not moto'ing it but it runs pretty good now
digger
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digger 8/4/2022 11:20am
8/4/2022 11:20am
Beta blew it by spec'ing that N2Zx duel taper needle series, but the slide, pilot, and main are close. On that bike, as a nice flexible all around needle, I would recommend an NEDW in #2 clip or NECW in #3 along with a 38 pilot and 165 main. The D is 1/2 clip position richer than the C.
Racer142
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Racer142 8/4/2022 10:12pm
8/4/2022 10:12pm
digger wrote:
Beta blew it by spec'ing that N2Zx duel taper needle series, but the slide, pilot, and main are close. On that bike, as a nice flexible...
Beta blew it by spec'ing that N2Zx duel taper needle series, but the slide, pilot, and main are close. On that bike, as a nice flexible all around needle, I would recommend an NEDW in #2 clip or NECW in #3 along with a 38 pilot and 165 main. The D is 1/2 clip position richer than the C.
Good info. What's a bigger step: dropping the needle a clip or going 1 letter leaner on the needle?

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digger
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digger 8/5/2022 3:13am
8/5/2022 3:13am
Racer142 wrote:
Good info. What's a bigger step: dropping the needle a clip or going 1 letter leaner on the needle?
Where in the throttle range do you think the bike is running rich ? Diameter effects up to about 1/4 throttle and the clip position effects from about 1/4 to 3/4 throttle range. There is some over lap though.
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Racer142
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Racer142 8/5/2022 8:05am
8/5/2022 8:05am Edited Date/Time 8/5/2022 8:08am
digger wrote:
Where in the throttle range do you think the bike is running rich ? Diameter effects up to about 1/4 throttle and the clip position effects...
Where in the throttle range do you think the bike is running rich ? Diameter effects up to about 1/4 throttle and the clip position effects from about 1/4 to 3/4 throttle range. There is some over lap though.
Right off bottom. I have a ktm xc300 and the beta doesn't have then grunt off the bottom I would expect out of a 300. Feels fat from bottom to mid. Mid to top feels crisp. The jetting chart suggests 1 step down on main (172-170) half turn leaner on the air screw and 1 needle leaner. Just curious what others may be running
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digger 8/5/2022 2:06pm
8/5/2022 2:06pm
Racer142 wrote:
Right off bottom. I have a ktm xc300 and the beta doesn't have then grunt off the bottom I would expect out of a 300. Feels...
Right off bottom. I have a ktm xc300 and the beta doesn't have then grunt off the bottom I would expect out of a 300. Feels fat from bottom to mid. Mid to top feels crisp. The jetting chart suggests 1 step down on main (172-170) half turn leaner on the air screw and 1 needle leaner. Just curious what others may be running
It sounds like you need a leaner needle.

The problem you are going to run into, is that oem series needle is to short on the L-1, clip position. Even in the 1st clip position, you won’t get what you need. Those Beta’s respond really to the Suzuki NExx triple taper series needles. Take this for what it’s worth. The last Beta 300 that in jetted , It was the MX version, it was 30 degs F at sea level I used the stock 40 or 42 pilot and the stock main, 170, and just swapped the stock needle for a Suzuki NECH that I put in the #3 clip and set the air screw 1 3/4 out.
The bike work really well in those temp, so I don’t honk it could easily handle a little leaner setup in summer temps. The bike was, what I considered awful prior to the needle swap. I can’t imagine how bad it would be in summer temps.
Racer142
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Racer142 8/5/2022 6:50pm
8/5/2022 6:50pm
digger wrote:
It sounds like you need a leaner needle. The problem you are going to run into, is that oem series needle is to short on the...
It sounds like you need a leaner needle.

The problem you are going to run into, is that oem series needle is to short on the L-1, clip position. Even in the 1st clip position, you won’t get what you need. Those Beta’s respond really to the Suzuki NExx triple taper series needles. Take this for what it’s worth. The last Beta 300 that in jetted , It was the MX version, it was 30 degs F at sea level I used the stock 40 or 42 pilot and the stock main, 170, and just swapped the stock needle for a Suzuki NECH that I put in the #3 clip and set the air screw 1 3/4 out.
The bike work really well in those temp, so I don’t honk it could easily handle a little leaner setup in summer temps. The bike was, what I considered awful prior to the needle swap. I can’t imagine how bad it would be in summer temps.
Good information. I'm sure gonna look into the needle change. It needs some help off the bottom for sure but I wouldn't call it terrible is just but crisp like it should be

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