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. For your bike, it could also be an elevation issue with your current jetting. For me I bought a 28mm SC3 Smartcarb and sold my Keihin. I haven’t had any issues with it since. You may want to consider a Smartcarb. Smartcarbs don’t have jets and 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/

Edited Saturday at 10:55 PM5 days by RonH

Thanks, for the tip on the SC. I am at 600 feet elevation and about 70 degrees F right now.

I have a 2024 TXT and have been chasing the starting/jetting issue since purchase about 3 months ago. I had a 2020 version and never had any issues with it. I have run stock jetting, leaner main, leaner pilot, up and down on the needle clip position. It has never run bad, always clean just not as crisp as I feel it should be. I have red where guys are running a richer slide. So with that in mind I have a 52 pilot (which I have tried briefly before), JJH in the #2 clip position, 125 main, stock 3.5 slide. Haven't ridden it yet but went out to start it and it was a pain. Actually started with the choke off but cleaned out really quick. The air screw actually made a difference turning it both ways. I'll ride it tomorrow and hope for the best.

On a side note....anyone get a lot of metal shaving on both the drain and fill bolts?

Are you talking about the transmission oil drain/fill? Yes, I did see some on both. Some fine stuff is normal I think for wet clutches that wear on friction disk/metal plate interface.

I got the S3 low-compression head installed. Easier to kick and start, even in gear. I don't have to hunt for the just-past-TDC point anymore. Just get the pedal to the top at the hardest point and kick hard back and down. Before I would hurt my knee sometimes when it hung up at TDC.

Another thing that helped with starting is new plug and especially a new iridium version.

For jetting, I haven't changed anything, but I don't kick too many times with the choke on. Two max then turn it off. Usually fires up on the next kick or two. When hot I find that opening the throttle a bit during the kick helps a lot.

I still have a bit of popping noise at low RPM that I think is normal. Also, the idle seems to hang and take a bit to come down after revving, but I am also thinking that is also normal for these bikes as compared to an enduro 2-stroke.