kochj

I have this engine and I have had perhaps 2-3 gallons threw it.
When I 1st had the engine (bought it new) no idleing problems.

The engine is in a Associated NTc3 Factory.
I took apart the engine and here are the findings:

Some were on the entrance to the crank shaft below the carb.
carb insulator is cracked.
I took everything out of the case and presure checked for leaks with a air tool hose.
The front bearing leaks air when blown threw with about 20lbs of Presure...

The car will idle if I lean (clockwise) the idle needle in quite a bit and take a Hot OS Turbo plug running 20% car fuel....
But not for long.... It will sit but when slowly advancing the throttle and keeping the speeds slown (like running on a tight coarse) it will flame out....

It seems the wear on the crank shaft is caused by this:::::::\\\

When I start the car, sometimes the fuel gets flushed out of the carb (flys out and sprays on the airfilter)
I didn't notice this before and I guess that this then caused any fine dirt to soak and then when the engine would start, it would suck any fuel off the air filter, and then
pull the fine dirt with it....

When I try to turn the engine over by using the fly-wheel to turn the engine over while mounted on car by hand, I can hardly turn it over......
I have experimented with different head shims that came with the engine to no difference....

I tried using hight temp silicone to seal up the carb, but no help....

Anyone think that the engine is worn out??? It seems that if a engine was sucking air I would have to richen the idle??? The main fuel valve is set at 1-1.5 turns out and the midrange needle is screwed in about 1-turn...
I didn't notice much if any oil comming out of the front bearing when running engine on the car..

These setting don't seem to be out of the ordinary...

With the severly leaned idle and hot plug it will do pretty well...

Any risk of damage with these settings or is it time to replace some parts? (piston/cyl, rod, or crank)

I will try to post some picts when I get the time..

Thanks

Bax

My Feedback: (11)

It sounds like the piston/liner fit is starting to go. We'd bet that performance will come right back if you install a new piston/liner assembly. When the compression starts to go, idle and acceleration are the first things that deteriorate.

R/C cars very commonly have the piston/liner fit go quickly. That's due to quite a number of factors: dirt, over-leaning, low-oil fuels, bad breakin procedures, and so on. Typically, the average R/C car engine barely lasts a few gallons' worth of fuel due to those factors...all under the control of the modeler.

It's normal to have some leakage through the front bearing. That's how it gets lubricated. You'll notice a small "stripe" of fuel under it on the chassis, and possibly a "stripe" on the body above.

kochj

Thank you for the information Bax!....

This was my 2nd or 3rd nitro car/ truck engine since then I have had many.....

I think the main culprit was the carb, spiting fuel on the aircleaner, and then sucking the dirt in when it was ran with the wet airfilter.


Would a guess that this would be a "Run at your own risk" but would a O.S. Engines 12TZ(P)-T5 ABC or the O.S. Engines 12TZ Speed Spec 2 ABC
Cylinder & Piston Assembly work in this? or are there just too many variables involved and be better to go with the Cylinder & Piston 12TR (P)-T (stock) setup...
It is cheaper anyway...

Thank you again...

Justin K.

Bax

My Feedback: (11)

Use the stock assembly. We don't "mix and match" parts, and things like cylinder/piston assemblies don't transfer from one engine to another.