Help with apparent fuel delivery problem?

[johnsland8]

I have a XXX-NT RTR version w/ a Mach 15. When I pull on the starter, fuel does not get sucked into the carb. I can drop a couple of drops into the carb and get it started and as long as it is set rich enough it will keep running. If I lean it out or it dies, it will not restart unless I drop fuel into the carb. I have replaced the fuel lines and the tank "appears" to be sealing although I have not pressure tested it and I see no obvious leaks. Again, it will only run if set very rich otherwise it will die when I hit full throttle and release quickly. It will also die when I hit the brakes although I cannot see the carb opening actually change, I have it set open correctly w/ the idle adjust screw...

Any ideas?

Thanks,
John

 

[Maxx Trooper]

do u prime ur engine before u start it? that could be the problem. or the engine is just worn out. my TRX .15 got to the point where it was so worn out, i had to flood the engine to start it, so it had compression to start. lol. but then it would die after awhile. how many gallons of fuel have been through it?


later

 

[Skyline Racer]

prime da engine bro

 

[johnsland8]

Sorry, I guess I should have given you more info to work with. I just rebuilt the motor yesterday. During the break in period I was running it very rich so it would run through a tank of gas no problem but I still had to put fuel in the carb to get it started the first time. As soon as I began to start leaning the motor out, it really doesn't want to run at all.

I hope that helps...

I'm back. I just read a couple threads on priming - that would make sense. I am just getting back into nitro trucks after being away for 5-6 years, I feel like I'm learning all over again. I have never had a pull start motor before, always used a starterbox and never had to prime a motor before I started it. I guess the other running issues when leaning it out is probably just tuning correctly. I was concerned about possible air leaks causing the motor to run erratically but I guess I should just spend some more time tuning before I get carried away.

Thanks for the replies.

 

[Maxx Trooper]

if ur tank doesn't have a primer button on it, cover the exhaust tip, and pull on the cord a couple of times. make sure the glow starter isnt on the glow plug. u should be able to see fuel going through the lines.

good luck,
later

 

[jon2]

you rebuilt the motor so I would use some rtv silicone and seal the back plate and carb so you know that end is covered. If you haven't replaced the lines , do it. You should cover up the stinger on the pipe and give the motor a few tugs. I like using clear lines so I can see fuel travelling in the line. If you don't see any fuel I would check the tank to see if it has any leaks. Let us know if your condition improves or not.

 

[olds97_lss]

Not to give you bad news, but I rebuilt my mach 15 on my xxx-nt and never got it to run right either. I didn't replace the con rod though, but I did everything else. I sealed the carb and back plate, replaced the lines, replaced the tank... no luck. It still did the same kind of stuff yours is doing.

You might want to check and make sure you put the head shim back on.

 

[RatzoRC]

If the motor was sitting for a long time, you might have oil build up in your high end needle valve.
Take the high end needle valve totaly out, put your finger over the pipe tip and pull a few times. (be carefull not to shoot nitro fuel in your face)
then reinstall the valve, and back it out about 3 to 3 1/2 turns from closed, and start it.
Then lean it out to where you want it.
Give it a try, you have nothing to loose.