I hate to be a big cry baby, but we have had my sons new matrix for about three weeks. So far, the throttle servo has shorted out and smacked us into a fence, I have not been able to get this thing tuned so that it is crisp, and now I cant even get it to start and run. It dies as soon as you give it throttle. It is spitting fuel everywhere. I have pulled on that darn pullstart so many times that the one-way is starting to slip and the pullstart itself is about worn out not to mention that my forearm and fingers are about to fall off! I have tried every carb setting, including the one posted by Cen, and I am getting no results. I know you are thinking that it is too rich,which is exactly what it sounds like, but I have tried leaning it out until it was less than two turns out on the hsn and all that will do is prevent it from starting at all. Please dont think that I am just inexperienced. I have tuned a bunch of motors in the past couple of years but I have never seen anything like this. Also, I have tried replacing the fuel lines and tightened the seal on the fuel cap because I was seeing bubbles in the fuel lines but no help. Please help me, I am just about to give up on Cen motors.

hmmm... not good. One thing i know that happened to me with my old Tmaxx is that the LSN was kinda bent/crushed at the end and would basically eitehr be wide open of totally closed. Maybe check your needle tips? Sounds like you know what you are doing so maybe just give CEN a call. It's easily the quickest way to get a response.

sound like the same problem that I had with my original motor... you mentioned air bubbles in the fuel line.. there should be none.. try checking the fuel tank for leaking.. the cap is not usually an issue... its pretty tight.. If you have the plunger(priming) tank.. get one without.. I had more problems with that..
some other things to consider are glow plugs.. I know you are experienced but it never hurts to check... finally.. take off the carb and check the gasket seal around the base.. it might be damaged or missing.... I highly doubt its the engine, but you never know.. call cen racing in california if you can't resolve the problem, they are very good...

One time I could not get my CEN engine to run AT ALL...it would "kick" the piston up and down a few times but would not start. I took the glow plug out and checked it...was glowing dark red...

SO I proceded to take the entire engine apart and clean it.

Put everything back together...put a new air filter sponge on it....adjusted the carb to the factory setting...still would not start.

Put a new battery in my glow igniter so the plug would glow BRIGHT red...started on about the 4th pull!

I find the engine starts on about the 4th pull with the glow plug BRIGHT red.

Also I have the trim adjusted to so the throttle is at about 1/4 open when I'm trying to start...Just make sure your ready when it fires or put your foot in the way so the car wont take off down the street with your glow ignitor sticking out.

I had the same not with Cen engine but with Nova Rossi, I spent too much time checking every thing with no success, finally I found that the carburetor was not tighten down to the engine body, I took the carburetor out, clean the down surface of the carburetor and checked the Rubber O-ring, I placed it insuring that the carburetor pushed well down to the engine body, after the engine started

Thanks for the the support, but I already tried all those. I did however call Cen and talked to Andrew. Come to find out, my motor is shot. I guess when the servo went crazy my motor overreved and caused substantial wear. My piston/sleeve is too loose to build the compression needed to burn the oil out of the fuel causing it to load up. I have sent it back to cen to be replaced along with the servo that caused all this trouble. Im going to tell you guys something, if you havent talked to Andrew yet, dont hesitate when you have a major problem. This guy is knowledgable and very helpful. I WAS IMPRESSED! Although I am not happy with the fact that my son is not going to be racing this weekend, I could not be happier with Cen support. Its nice to see a company stand behind thier products like Cen!!!!!

I got the same impression from emails I had with him. I do wish CEN would have had a real .21 in there but the rules out here allow RTR motors if its the one that comes with the vehicle. Once mine dies, I may just get an OS RG .

OK, I talked to Cen and told them my problems. they told me to send them the motor back, which I did. I got the motor back 8 days later, pretty quick turn around fromn texas to calif. and back to texas. The only problem is they did not fix the problem. The motor still does the exact same thing. The tech. that I talked to wed. said that they ran and tuned the motor on the bench and that it was ready to drop in and finish break in. The peice of junk wont even run!!!!!!!!!!!! I have tried to eliminate every possibility other than the motor but I cant find anything else wrong with anything. I checked all fuel, tank, glow, and exhaust possibilities. Tomorrow I will put a proven .26 on my matrix and see if it works.