XRAY - Model racing cars

Hi,

I just bought a new NT18MT last week. Struggled to set up the HUDY starter because the chassis wouldn't go down far enough to make contact with the starter wheel because of the protruding clutch bell cover hitting against the press-down switch. I switched that around, so I got more clearance, and removed the middle adjustment block, and kept the front stop, so now the car goes down on the starter wheel nicely.

It was really difficult to start the engine, because it was very tight at TDC, and I still stuggle to turn it over TDC with the starter. Using a 3300MAh 7.2V battery pack. The starter just stalls and overheats the 540 motor.

Finally I got the engine started (didn't touch the carb settings) and ran in the engine according to the manual. However, with a full tank of nitro, I only get around 5mins of engine run time. Is this normal? I seem to be going through fuel like crazy! IS there something wrong with my settings? I also noticed after about the 3rd or 4th run on grass, the muffler is covered with oil as well as the plastic body. I adjusted the main needle valve CW by 1/4 turn to make it run leaner at 3/4 throttle so I use less fuel, and I also tried to increase the low speed by turning the low needle valve CW by 1/4 turn to also use less fuel. But when I ran the car at this setting, the top speed seemed slower, and I keep rolling the truck when I turn, even at low speed. And therun lasts for about 6 minutes before the engine cuts out because of no fuel.

Can someone tell me why I get such short run times, and how to increase the performance of the engine?

From what I understand, 5 minutes is about right. You can probably get more from adjustments and breaking in as you have. Don't forget you can refuel the tank while its on. The nitro micro owners here should speak up eventually, but they don't visit everyday.


The NT18MT does have a higher center of gravity since it is monster. You can try using no ride height clips so it droops lower in its suspension travel.

Just got back from racing my truck this morning. First run on tarmac was good. Truck starts to move on a little trigger movement on the radio. Got 7mins run time, running it for about half the time on 3/4 throttle in circles. Tires were getting chewed, So moved onto the grass for second run.
This time I turned the main needle valve 1/2 turn CW. Engine started easily on starter. I put the truck on the grass, applied some throttle fast, and the engine just cut out. Set the MNV back to factory, restarted and bashed about on the grass. Found that aout 5 meters away failsafe kicked in and front wheels started moving from side to side very quickly and erratically. Is that what is called glitching? I had coiled the antenna wire around a small piece of cardboard and tucked it away by the steering servo. Receiver responded well when I was on tarmac but not on grass. I thought transmitter batteries were going flat (using dry cells, wasn't sure about voltage given by rechargable cells used in cameras etc.)
Anyway, uncoiled the antenna, and did a range test with engine switched off, and I got good range this time.
While I was trying to figure out what was causing the range and glitching/ failsafe issues, I messed about with the carb settings.
1/2 turn CCW from factory setting gave slow top speed and slow throttle response.
1/4 fCW rom factory and engine cut out while running. I still feel factory setting was best.

Then, with the engine switched off, and taking a break, I completely lost my settings on the carb because I I wanted to see how far out I could turn the MNV. I also removed the air filter so I could seen the valve shaped like a > which gets adjusted by the throttle servo. I tried to turn the LNV CCW to see how far I could get the valve to open. I didn't see the opening get any bigger after a couple of turns, and by then I completely lost the factory setting. So now both MNV and LNV have lost their factory setting. I turned the LNV in, until the top of the head is flush with the tube, and the same for the MNV.

Didn't run the engine yet. The reason why I made such drastic changes is because the engine was getting harder to start after the 3rd run on grass. It just wouldn't start for about 4 to 5 seconds, even though it was being turned over by the starter. How many runs does a glowplug lasts for? I noticed once while starting the engine that if I took off the glow starter, the engine cut out. Happened only once though.

Also just remembered that the truck makes a loud grating or knocking noise when turning hard right on almost full throttle on the grass. It started this morning during the second run on the grass.

Could it be a diff problem or the servo? How can I check for this noise without running the truck?

Did you break in the ball diffs while you where breaking in the motor? Factory, they are set a little loose and you run and tighten them over 5 minutes or so to break in the rings with ball grooves.

You can see if your diffs are ok by holding the spur and spinning one of the front tires to see if the other side reacts without nay real feeling of grittiness.

You could also have a bad bearing though in your outdrives from running in the grass.