jptech

New to nitro cars.

This is a new buggy. I spent a half hour running 3 tanks through the engine to break it in. I've been trying to tune it for a few days. I don't believe I've got it right. When I pinch the fuel line, it revs and dies within 3 seconds. It idles very high. If I lower the idle, it dies when I apply brake. I have to set my throttle trim all the way down or the buggy wants to take off at idle. The engine is running a bit hot. After about 10 runs back and forth on my street at full throttle, it's running about 245F and cools to about 235F after a few minutes. When running, I'm getting smoke from the gear. It's turned colors a bit. It makes a noticeable sound while running. I have no idea why it's doing this.


When I set my throttle trim at 0, the car wants to take off unless I apply brake. I have to turn up the brake screw on the throttle rod to keep it in place with the throttle trim all the way down. From my understanding it should free roll unless I apply the brake. And when I apply the brake it should stay still. Is this correct? Thanks.

Powerslide_AZ

From the looks of your clutch bell which does not look too happy from the discoloration , looks like you may want to investigate the clutch. If you have the stock two shoe clutch with one spring that goes all the way around , perhaps the spring came undone and or broke causing the shoes to engage the clutch bell causing it to move. Whether its this symptom in some fashion or not , it would be fair to say at this point you may need to pull that clutch bell and see what's going on inside.

jptech

Thanks for the quick response. The shoes are made of white composite. They are slightly burnt. The bell has a line on it. How did the clutch burn? Do I need to replace the shoes and the bell?

Powerslide_AZ

Without physically looking at what your seeing I would say you should consider changing out both as that would be relatively cheap and for piece of mind. Also just curious does everything else look good mechanically ?, i.e. other gears and such. I would suggest you may want to go with the aluminum shoe setup they offer for this model.

jptech

Here are the shoes and the clutch bell.



I cleaned both with some fine grit sandpaper and reinstalled them.

The car seems to be running cool enough now and my best guess was they got caught somehow.

The clutch will generate a bit of heat , but I don't know if that was too much. I want to replace the clutch, bearings and all soon though.

ijpom

Hi Jptech,

Welcome to the forum.

It looks/sounds like you are high idling and braking simultaneously. This will lead to a worn or burnt clutch before necessary.

I'd probably start by undoing the brake adjustment that was just made to slow the buggy's idle, and work on slowing the idle via the engine tuning.

Tuning will include adjustments before engine is started or radio is on:
Ensure idle gap is 0.5 to 1.0 mm when fully closed (if not use the idle adjustment screw to set it in this range - I assume HSN, LSN and IDLE are known to you)
Adjust the throttle linkage or servo arm position to get the carb pushed fully to idle BEFORE the brakes come on.
Remove the servo arm from the servo, and start the radio tx/rx and set the throttle trim back to the middle of it's range.
Now put the arm on the servo at it's closest position that has idle carb/no brakes. You should have enough trim to adjust it either way.
Start engine and carry on tuning.

You may want to check/measure where your idle position is first, so that you have knowledge of that before it is changed.
That knowledge may help you find your best starting setting again.

Happy running.

jptech

excellent reply. I am actually rebuilding the transmission today as well because I chewed up the spur gear.

I have a clutch bell, shoes, and spur gear arriving today. I agree that my idle is high and I am pretty sure the brake is engaging too much.

I believe I may have the screw on the servo arm too tight which is causing the brake to be engaged.