RC10GT driving issue

[MN Mike]

The truck started up fine and idled fine, then i went to drive it it and on pavement it was okay.
when i went to grass it wouldnt move and revved a little then died.
It also couldnt get a higher speed than less than a walking pace.

I turned it off and put piston at bdc, but havent been able to tune or adjust anything yet.

Any ideas to what is the problem/solution?

Thanks =]

[GoMachV]

The first thing to determine is if it's mechanical or tuning/adjustments.

Assuming the engine runs and revs ok, engine off hold the left tire and the spur gear from turning, and try to turn the right side wheel. If it slips, is the nut on the slipper turning? That will tell you if the diff or slipper is slipping first

Assuming it doesn't run above idle, when you pull the throttle is the carburetor opening all the way? Take off the air filter and see if it is. If not, explore why. If it is physically opening but dies when you rev it or it lacks power you could be way too rich or too lean. Explore tuning the engine.


I don't want to go into huge detail until we know your true symptom

[MN Mike]

The first thing to determine is if it's mechanical or tuning/adjustments.

Assuming the engine runs and revs ok, engine off hold the left tire and the spur gear from turning, and try to turn the right side wheel. If it slips, is the nut on the slipper turning? That will tell you if the diff or slipper is slipping first

Assuming it doesn't run above idle, when you pull the throttle is the carburetor opening all the way? Take off the air filter and see if it is. If not, explore why. If it is physically opening but dies when you rev it or it lacks power you could be way too rich or too lean. Explore tuning the engine.


I don't want to go into huge detail until we know your true symptom

Thanks! Ill try that when i get home today and update afterwards

[Sixtysixdeuce]

I'm pretty sure you just bought that truck from me on the bay last week, especially since i mentioned this board.



If so....

The trans is in good shape, I had it open for inspection before I listed the truck. Slipper should be plenty snug for the moderate power of that engine as well, even with the larger tires. Diff is set to moderate tension, so it'll allow normal differentiation, but not slip excessively. That trans had been in my recently built runner black tub GT with an HPI Nitrostar .18 and had no issues, and that .18 is peppier than the OS .15 CV. There was nothing wrong with it; I only took it out of my runner to install a spare I'd just built with metal gears.

Minneapolis, MN is at 800 ft altitude, some 6,000 feet lower than what that OS .15 CV was tuned to here just North of Elizabeth, CO. That's why I included that tip sheet; with such an altitude change, you'll be wayyyyy too lean down there if you haven't adjusted the carb. Would go OK at part throttle and light load, but starve out at high RPM and/or heavy load. Turn the high speed needle counter-clockwise at least one full turn and go from there. As I said in the note, should get a trail of smoke for 10-20 feet of acceleration; if it acts like it is cutting out, it's still too lean. If it's doggy and smokes a lot, it's too rich. That engine is still pretty tight, too, with how little it's been run since the new piston & sleeve, so you'll want it to idle a tad high until it breaks is completely, or you may experience stalls, especially when coming to a stop.

This screw will probably be nearly flush with the shroud when you get it dialed in:



Sorry for the crappy arrow. Photobucket's editing feature leaves a bit to be desired.

I find most nitro engines I get are tuned to sea level, and they typically require substantial leaning to run right up here. The LRP Z.18S I just broke in today required 1-5/8 turns in from factory setting for a proper tune. As such, the reverse would be true when the engine is tuned here and goes to near-sea level altitude.

Also remember that changes in temperature and humidity often require small adjustments, although those OS CV engines are not overly wound-up, and as such are a bit less finicky than, say, the OS .12 TZ turbo engine in my GT2 or the Fantom FR-15 turbo engine I had in my TC3.

Just play with the tuning a bit, and she'll wake up.