I just recived my RB Concepts TM523 carb. You have to cut off this plastic sleeve around the base of it. Becareful not to cut your self it's very tuff to get off. You need to be carefull not cuting into the carb when trying to remove the plastic cover. It could possible create air leak and make it hard to slide into engine case. Once you do this the carb aclty fits nice and snug as it should be. Then you need to grind a little bit off the front of the carb to alow for it to sit flush on the base of the engine case and also to clear the fly wheel. It just fits with the stock fly wheel after you do a little grinding. Theres no way a 40mm fly wheel will fit. Now You have to remove the stock throttle lever thats on the carb and replace it with the stock traxxas unit. Next you need to move the throttle horn thats on the engine motor mount and move it out to the next hole. Next to get wide open throttle you need to remove the throttle and brake horn off the servo and turn it one spline towards the front of the truck and re-adjust your set screw coller. With a little tinkering you will get it to go wide open.
I added a Motor Save Air filter Part# RT80
Running Traxxas 33% fuel
Traxxas Glow plug
Engine temp 245
Stock gear ratio 15/36
Wide ratio trans
My opinion there needs to be a heaver gauge wire for the throttle, it's to thin and flexible. I watch it flex when it's going wide open.
The Test: it's too fat out of the box but that's a good thing. I leaned it out a little bit and all I can say is WOW Mission control we are ready for take off. It has silly power now. That little hesitaion bog or bobble off the line is gone. When I got it dialed in and cracked the throttle it would just rev to the moon, I thought I broke something or the clutch was bad or even the slipper was bad. None of the above It was just spinning the tires out of control. I never laughed so hard in my life. It was like electric truck or like hitting nitrous button.
Caution: slide the carb down as far as it goes and see were it needs to be clearanced, it just needs to be grinded a tiny bit. If you grind to much you will cut into the base of it were the O-ring goes and it might not seal and creat a air leak and ruinon the carb.
I have more testing to do but it was alot of fun and nite and day difference in throttle response and performance.