stevo1957

Gidday all,

By way of background, I purchased a XXX-NT roller s/h and to it, have added some new servos, receiver and my Epic .18 big bore engine that I used to have in my Terra Crusher.

The XXX-NT is the Adam Drake edition and has the aluminium Adam Drake tuned pipe.

I have also fitted a HPI roto start backplate.

Here are my problems:

1) Very hard to prime.
I have checked the tank and lines for air leaks and have none.
I do notice that when I cover the pipe and prime with the rotostart, it does take quite a while for the fuel to get to the carby.
Also, when it does reach the carb and I remove my finger from the pipe, I get a gush of fuel exit the pipe. Not just a small amount, but a huge squirt!
I also notice that when I stop the engine by blocking the pipe, that likewise, when I remove my finger, fuel again gushes out in considerable quantities.
I'm wanting to know if this is normal, or whether perhaps my pipe may be mismatched to my engine.

2) Hard to keep a tune or idle.
When I do get it started, it absolutely flies until it gets hot and then the idle goes quite high.
I notice that even with a reasonably rich setting with fuel and smoke pouring out of the exhaust, that temperatures rise quite dramatically. If I richen it up any more, it will not start.
Even when the temps get high, a large amount of unburnt fuel is still exiting the exhaust.
If I stop the engine to adjust things, it is hard to restart.
Compression when it is cold is quite strong, but I don't know the correct way to check compression when it is hot.

3) No brakes!
Despite a digital radio with heaps of adjustment and new servos, I just can't get enough movement in the servo to really pull hard on the brake linkage.
I put a high torque Futaba servo on the steering side and a normal ball bearing Futaba servo on the throttle / brake.
Are there any secrets to getting effective brakes on these trucks?

So what do you guys think?
Any ideas?

Thanks in advance,

Cheers,
Steve

ThunderbirdJunkie

My Feedback: (3)

try blowing into the pipe's stinger instead of the finger method

you have an airleak. I'm figuring in the o-ring of the tank lid.

no, just proper linkage setup. are you using the actual XXXNT brake linkage/servo horn and all that, or are you using some generic piecemeal crap? Try getting the actual Losi hardware. or at least shortening your brake wire.

econ909

try reseting your low and high speed needles.. count how many turns it takes to close it then write it down then reopen them back up. you might have a dirty clogged "carby" take it apart replace the o-rings if possible

stevo1957

Thanks for the replies.

Yep - I'm runing original brake bits and linkages.

It's almost as if the servo isn't going far enough around to pull the rod far enough. I've check the radio adjustments and have it the best I can.

How fast should these things stop, anyway....on a pin...or is there a few metres required to pull them up.

I've also checked the needles and gone from stock. When I put the engine in, I also cleaned and rebuilt the carby.

Thanks again,

Steve

gerwen

This really sounds like you have a blockage in the fuel delivery somewhere. Nitro coming back at you is what's telling me that. Is there a fuel filter on the tank that could be cleaned? How about a fuel filter between the tank and engine? Could be blocked.
Perhaps the carb is gummed up as well. Clean all these up with denatured alcohol or nitro cleaner and compressed air if you have it. It's a good idea to replace all the fuel lines while you're at it, fuel tubing is cheap so there's no reason not to.


You need to solve your fuel delivery issue before troubleshooting this. Then set your carb back to factory settings and see if you still have a problem.

No secrets, just fiddlin'. How much pressure do you have to put on the linkage by hand to get effective braking? Depending on the type of brake disc, if something like fuel or wd40 got spilled on it, it could be much less effective. Pull it out and clean it and the pads up. Then it's just a matter of getting the linkages set so it can go to full throw, and setting the epa on the radio to pull as hard as you need to. If you're not using a 5 cell hump pack, switching to one can give your servos a little more oomph and that may help.

gubbs3

My Feedback: (1)

The reason the tank upchucks so much fuel is because of a poor design. If you look at where the pressure line enters the tank you'll notice it follows a tube to the bottom of the tank. This means when you stuff a lot of pressure into it when covering the exhaust, when you remove your finger from the stinger the pressure is released, from the bottom of the tank, meaning fuel. The new RTR's and AD2's have a new tank which has the pressure inlet on top of the lid to correct this. In other words, it's normal.

stevo1957

Guys,

Thanks for the replies.

My fuel line is OK and I have no leaks or blockages. Carby was pulled down and rebuilt before I put the Epic in.

Brake disc, pads and linkages are all new.

The design of the pipe issue makes sense. I actually just popped on my stock Terra Crusher plastic pipe that used to run with the Epic. Primed quite easily and no spew of fuel during priming or stopping. Some one out here in Australia suggested that the Adam Drake pipe was only for .12 - .15 engines, so perhaps with the Epic, the pressure was all wrong.

I'll have a really good play with the radio adjustments next and see if I can get some better brakes.
How quick should the XXX-NT stop, anyway?

Thanks again for the suggestions.

Cheers,

Steve

ThunderbirdJunkie

My Feedback: (3)

my AD2 is the hardest stopping ST i've driven...and i've driven lots.
your linkages are maladjusted...it's your linkage that is the problem, not the radio settings.

flynvy5

My Feedback: (2)

i was thinking maybe the fuel lines are back wards not hard to do with the older tank if you don't pay attention

gt5500

Your problems with the tank is the bad design, have a look under the pressure pipe inside the tank and you will see a plastic pipe that goes to the bottom of the tank. This causes fuel to go up the pressure pipe and out the exhaust, the exhaust design is fine. The best thing to do is stick an allen key in the pressure inlet on the tank and then using a screwdriver lever the plastic pipe inside the tank and it will snap clean off.