I recently bought a new OS 18TZ, but prior to putting it on the car, I took the carb off and ran it on a different motor. Unfortunately, I changed the factory settings to tune-in the motor I put the carb on. Now that I am trying to "run-in" the new motor with the carb it came with, it takes forever to start. I have to trim the throttle so that the carb is open quite a bit before it will start (after 3 minutes on the starter box!!!). Once it starts I trim the throttle back down and it idles fine and runs without stalling. I have set the carb back to factory settings but I have to go through the above process every time I try to start the damn thing. Can someone, anybody please help me with this!!???

Anybody? I changed out the crank, piston and sleeve, and it's the same. I thought maybe it was the modified port and crank timing, but obviously it's not, because with the stock sleeve and crank back in the block it still takes forever to start. I checked for an air leak but there isn't one. Is it the carb? But the carb ran fine on my other highly modified motor.

I've become a firm believer in 'preheat' for new motors through breakin.

The little monsters need some help to get combustion started and friction
from grinding that long on the starter is the hard way.

Is your glow starter at proper voltage (charged).

Yeah, the glow starter was fully charged and the plug is new. Also, I heated the motor with a hair dryer to 150 degrees before I attempted to start it. Its just taking forever for it to hit, and once it does all is well until I try to start it again after it has cooled down.

What i do before i start the engine is take the exhaust tubing wich goes to the tank en blow on it to let the fuel fill the tube wich goes to the carb.
Open the carb by hand and blow some more to let fuel in the carb.
Then start the engine on the startbox. If it doesn`t start right up something is wrong and extended time starting the engine on the startbox can damage your engine rod. I run 10th scale national racing by the way. The engine`s always fire right up. Almost imediatly. Some racers don`t like the taste of nitrofuel (toxic) so they close the exhaust with their finger and let the engine do some turns on the starterbox wich gives pressure on the fuelline also. I feel that it still does a few turns with no oil though.

you should take your glow plug out, and see if it is wet ? and while its out, bump it ont eh box and see if a rush of fuel comes out ? if so it could have too much fuel in it. but generally if you turn your top end needle to flush wiht the top of the housing, then its just your bottom end then that could be too lean or rich.

blowing fuel into a new engine is not reccomended unless yu know what you are doing. if you blow too much in, then the engine could hydraulic which is worse then running a few turns wiht out oil. if you blow it, then just watch the line till fuel just reaches the carb, not actually blowing fuel into the engine.

lean the needles some dude ! probably got it too rich at factory settings......

That's sound advice, and I have tried that and the other method. Unfortunately, nothing seems to work. I have never had this problem. Amazing!! Even more unfortunate, I may have damaged the engine trying to start the thing!

Pattojnr:

One of the things that I find strange is the fact that the glow plug is never wet, and with the plug out there is no fuel coming out of the head while turning the motor over on the starter box. I have opened the carb up quite a bite and still no mist of fuel coming out of the head. I think the carb is bad and it new!

Thanks guys! I fixed the problem by removing the OS Slide Carb and replaced it with a Traxxas 3.3 carb. Set it to factory settings (same as I did with the OS carb) and it fired right up! I guess the OS carb is faulty.

Glad you got it to run...

Sounds like you have a booooooger in the needle valve.
Should be able to blow that back out of the hose spigot.

OS shouldn't have a 'bad' carb. You might have got a particle
in there during the remount of that carb when you switched
from that other vehicle.

I agree with you because it was working fine. I live in Denver (corrected altitude between 6,500 and 8,700) and at times these little engines can be very touchy. Thanks for the advice.

Correction; it was not the carb (OS or otherwise). It was the flywheel. So if anyone else ever have this issue, insure that the flywheel is not hanging beneath the chassis and sticking to the starter box wheel.