Trailmaster tm31x carb

Kart74 · 10-27-2023, 10:24 PM

I recently purchased a trailmaster tm31x with the 223 engine. I am working on getting the carb better but still have a bog when snapping throttle. It removed the bowl screws and mixture screw plug. It came with a 40 pilot and 116 main. It seemed lean so went to 42/125. Didn't help much. Went to 45/130 and it seems worse. I am going to try 40/120 and see if I just missed the sweet spot but wondering what others have done. The needle is not adjustable. I would also buy a different carb if needed. Any help would be great. Thanks

severely · 10-28-2023, 07:52 AM

Quote:

Originally Posted by Kart74

I recently purchased a trailmaster tm31x with the 223 engine. I am working on getting the carb better but still have a bog when snapping throttle. It removed the bowl screws and mixture screw plug. It came with a 40 pilot and 116 main. It seemed lean so went to 42/125. Didn't help much. Went to 45/130 and it seems worse. I am going to try 40/120 and see if I just missed the sweet spot but wondering what others have done. The needle is not adjustable. I would also buy a different carb if needed. Any help would be great. Thanks

Welcome Kart74. With a search you'll find a lot of folks trying to fix the same problem you have. It appears you are experienced enough to know carb jetting and engines and have a leg up on most new buyers. I'm also going to guess you come from a two-stroke engine background and have come to expect immediate throttle response when snapping the throttle at low engine speeds. Well Kart, these engines/carbs are tuned differently in that there is a certain response time required when "snapping" the throttle. You can improve the situation with an accelerator pump equipped carb but IMO you're chasing a ghost trying to totally eliminating this "bog". You might be better served by tuning the carb for real world response when actually riding the bike rather than in neutral. That plan worked for me at least. Good luck, maybe others have different information or tuning tips than I.

Thumper · 10-28-2023, 08:51 AM

Hello kart, I have a 249.9cc OHC engine (the FMM172-3) with OEM intake, carb and exhaust system. It came with 40 pilot, 120 main. I tried 45 pilot and it was too much. 42.5 pilot jet was perfect. I bumped the main jet from 120 to 125. The needle in this OEM carb has only one position, so technically, it isn't adjustable...

But actually, it turns out that it is in fact adjustable.

I learned how to do this many years ago on my Suzuki GS bikes. You can shim the needle with tiny washers and in fact, it is more adjustable doing this since you can shim to any position with combinations of thick or thin washers.

I describe this for my Templar in the Templar resource (a sticky in the top of the dual sport section). It is post #5

https://www.chinariders.net/showpost...79&postcount=5

Mine didn't need much of a shim. One ~1mm thick washer was perfect. The process is described in that post. The washer does have a clip with only one position, so you remove the needle from the slide and place the washer uder the clip and put it back in. It is just as easy as repositioning the clip on an "adjustable" needle, but you can stack as few or as many washers there that you want.

The retainer may not seem to fit right over the installed needle since the clip and washer are thicker than the clip alone. But the large slide spring holds that retainer down anyway, so it doesn't matter.

Kart74 · 10-28-2023, 09:18 AM

Thanks for the responses. Yea this process isn't new to me, but have found this one more difficult. I also have a tao 140 that I put a vm26 on which virtually eliminated the bog. I understand that it won't be 2 stroke snappy but right now falls on it's face. I was going to run an get some washers for the needle today. I also adjusted the valves right away which needed it. I know some carbs just work better than others and thinking the stock carb just isn't one of them. I will try a few more things today and report back. Thanks again

severely · 10-28-2023, 10:07 AM

Quote:

Originally Posted by Kart74

Thanks for the responses. Yea this process isn't new to me, but have found this one more difficult. I also have a tao 140 that I put a vm26 on which virtually eliminated the bog. I understand that it won't be 2 stroke snappy but right now falls on it's face. I was going to run an get some washers for the needle today. I also adjusted the valves right away which needed it. I know some carbs just work better than others and thinking the stock carb just isn't one of them. I will try a few more things today and report back. Thanks again

An accelerator pump equipped carb will help reducing the bog. Should have been with my first response.

Kart74 · 10-28-2023, 03:07 PM

Well no luck. Tried 40/120 and 42/120. It is much better but still sucks. Tried air screw from 1.5 to 2.5 in 1/4 increments. If you roll on the throttle slowly it is fine. But coming out of a corner or trying to get on power to wheelie over a jump it basically dies. Everyone seems to like nibbi carbs but I have tried 2 and had terrible luck. Anyone using one or have a carb suggestion?

Fast_Freddy · 10-29-2023, 08:56 PM

Shim the needle with two M3 washers and check the float adjustment.

Kart74 · 10-30-2023, 04:49 PM

I did try the 2 washers under the needle as well. It maybe helped a little but the issue remains. I ordered a pe28 nibbi and will try that. It is frustrating because it is a fun bike to ride, but this is really annoying.

Fast_Freddy · 10-30-2023, 09:00 PM

Quote:

Originally Posted by Kart74

I did try the 2 washers under the needle as well. It maybe helped a little but the issue remains. I ordered a pe28 nibbi and will try that. It is frustrating because it is a fun bike to ride, but this is really annoying.

Yeah, I've had that problem before and it sucks. My Youall PE28 works well after re-jetting as do most of the members here but over on Facebook almost everyone swaps in a Nibbi immediately. The Nibbi looks like a better made part to me and hopefully it will solve the hesitation issue.

Most PE28 ZS172 owners run 42/125 and the Nibbi guys recommend position #3 on the needle. I recommend starting at 1.5 turns out on the idle air screw. GL

Kart74 · 10-30-2023, 09:20 PM

I got the nibbi on. Similar issues. Could tell by the plug it was lean. Went to 45/130 and it is almost perfect. It was also 38 degrees here today so that doesn't help. I think a 135 main is next. It is already soo much better. Actually has power to wheelie! I will post what I end up with so others can use it.

Fast_Freddy · 10-31-2023, 02:42 PM

Quote:

Originally Posted by Kart74

I got the nibbi on. Similar issues. Could tell by the plug it was lean. Went to 45/130 and it is almost perfect. It was also 38 degrees here today so that doesn't help. I think a 135 main is next. It is already soo much better. Actually has power to wheelie! I will post what I end up with so others can use it.

Good news. FWIW I conducted a few polls on several forums where the ZS172FMM engine is common and although the most common jetting is 42/125, there are many folks running 45/130 a few running 135 and at least one guy running a 140 MJ. When I finally get around to it I plan to swap out my 125 for a 130.

What's your elevation? I'm at ~400 ASL.

Kart74 · 11-03-2023, 10:47 PM

Ran the 42/135 today at 55f and was great! It might be a little rich on the low level end. Warmer weather might. Need 40/130. But huge difference in performance!

10-27-2023, 10:24 PM	#1
Kart74 Join Date: Oct 2023 Posts: 6	Trailmaster tm31x carb I recently purchased a trailmaster tm31x with the 223 engine. I am working on getting the carb better but still have a bog when snapping throttle. It removed the bowl screws and mixture screw plug. It came with a 40 pilot and 116 main. It seemed lean so went to 42/125. Didn't help much. Went to 45/130 and it seems worse. I am going to try 40/120 and see if I just missed the sweet spot but wondering what others have done. The needle is not adjustable. I would also buy a different carb if needed. Any help would be great. Thanks
	0

10-29-2023, 08:56 PM	#7
Fast_Freddy Join Date: Nov 2022 Location: Pennsyltuckey Posts: 291	Shim the needle with two M3 washers and check the float adjustment. __________________ 22 Templar 250
	0

10-28-2023, 08:51 AM	#3
Thumper Join Date: Feb 2021 Location: Kansas City Posts: 2,237	Hello kart, I have a 249.9cc OHC engine (the FMM172-3) with OEM intake, carb and exhaust system. It came with 40 pilot, 120 main. I tried 45 pilot and it was too much. 42.5 pilot jet was perfect. I bumped the main jet from 120 to 125. The needle in this OEM carb has only one position, so technically, it isn't adjustable... But actually, it turns out that it is in fact adjustable. I learned how to do this many years ago on my Suzuki GS bikes. You can shim the needle with tiny washers and in fact, it is more adjustable doing this since you can shim to any position with combinations of thick or thin washers. I describe this for my Templar in the Templar resource (a sticky in the top of the dual sport section). It is post #5 https://www.chinariders.net/showpost...79&postcount=5 Mine didn't need much of a shim. One ~1mm thick washer was perfect. The process is described in that post. The washer does have a clip with only one position, so you remove the needle from the slide and place the washer uder the clip and put it back in. It is just as easy as repositioning the clip on an "adjustable" needle, but you can stack as few or as many washers there that you want. The retainer may not seem to fit right over the installed needle since the clip and washer are thicker than the clip alone. But the large slide spring holds that retainer down anyway, so it doesn't matter. __________________ -2022 5 speed Templar X Orange, OEM 51T rear sprocket, 14T front sprocket -NOS 2020 KTM 250SX (2-stroke motocross), less than 10 hours on it
	1

10-28-2023, 09:18 AM	#4
Kart74 Join Date: Oct 2023 Posts: 6	Thanks for the responses. Yea this process isn't new to me, but have found this one more difficult. I also have a tao 140 that I put a vm26 on which virtually eliminated the bog. I understand that it won't be 2 stroke snappy but right now falls on it's face. I was going to run an get some washers for the needle today. I also adjusted the valves right away which needed it. I know some carbs just work better than others and thinking the stock carb just isn't one of them. I will try a few more things today and report back. Thanks again
	1

10-28-2023, 03:07 PM	#6
Kart74 Join Date: Oct 2023 Posts: 6	Well no luck. Tried 40/120 and 42/120. It is much better but still sucks. Tried air screw from 1.5 to 2.5 in 1/4 increments. If you roll on the throttle slowly it is fine. But coming out of a corner or trying to get on power to wheelie over a jump it basically dies. Everyone seems to like nibbi carbs but I have tried 2 and had terrible luck. Anyone using one or have a carb suggestion?
	0

10-30-2023, 04:49 PM	#8
Kart74 Join Date: Oct 2023 Posts: 6	I did try the 2 washers under the needle as well. It maybe helped a little but the issue remains. I ordered a pe28 nibbi and will try that. It is frustrating because it is a fun bike to ride, but this is really annoying.
	0

10-30-2023, 09:20 PM	#10
Kart74 Join Date: Oct 2023 Posts: 6	I got the nibbi on. Similar issues. Could tell by the plug it was lean. Went to 45/130 and it is almost perfect. It was also 38 degrees here today so that doesn't help. I think a 135 main is next. It is already soo much better. Actually has power to wheelie! I will post what I end up with so others can use it.
	0

11-03-2023, 10:47 PM	#12
Kart74 Join Date: Oct 2023 Posts: 6	Ran the 42/135 today at 55f and was great! It might be a little rich on the low level end. Warmer weather might. Need 40/130. But huge difference in performance!
	2