New to trials and setting up a low-hours used 2022 gas gas txt 300. It has factory jetting, JJH clip 4, 125 main, 48 idle, float parallel with base. Carb cleaned and checked out. Sometimes hard to start and can foul the plug if choke used too many times/kicks. Also, sometimes it will try to start cold without the choke. This makes me think it is too rich on the idle jet. I tried adjusting the air screw to maximize idle speed after setting the idle a bit high. This was not very conclusive honestly, but it seemed like the air screw wanted to be at least 2 turns out, so also pointing to a smaller idle jet. What are people usually running on these engines? Are they usually run a bit rich to maintain low end power?

Additionally, I ordered and am going to install S3 lower compression head to help with starting and tame the power for learning a bit. Will this affect jetting? Any other recommendations appreciated!

5 hours ago, bw123 said:

New to trials and setting up a low-hours used 2022 gas gas txt 300. It has factory jetting, JJH clip 4, 125 main, 48 idle, float parallel with base. Carb cleaned and checked out. Sometimes hard to start and can foul the plug if choke used too many times/kicks. Also, sometimes it will try to start cold without the choke. This makes me think it is too rich on the idle jet. I tried adjusting the air screw to maximize idle speed after setting the idle a bit high. This was not very conclusive honestly, but it seemed like the air screw wanted to be at least 2 turns out, so also pointing to a smaller idle jet. What are people usually running on these engines? Are they usually run a bit rich to maintain low end power?

Additionally, I ordered and am going to install S3 lower compression head to help with starting and tame the power for learning a bit. Will this affect jetting? Any other recommendations appreciated!

BW123,

I had the same issues with my ‘23 Gasgas. I was always having trouble with jetting and it was a total pain to start. In the end I bought a 28mm SC3 Smartcarb and sold my Keihin. I haven’t had any issues with it since. Because Smartcarbs don’t have jets I haven’t had to tear down my bike since to get the old carb out and cleaned up. I also never have to worry about jets again no matter what elevation I’m riding at. I get much better MPG too and my bike doesn’t smoke anymore.

If your interested in a Smartcarb they always have a Christmas sale when they take $100 off the price.

https://smartcarb.com/product/smartcarb-for-gasgas-txt-250-280-300-trials/