Aggressive acceleration on start-up - plz help

[Shwarr]

Hello everyone,

So after 10 plus years I finally dig out my Savage 25 monster truck to see if I could get it started again. After sourcing new and clean fuel, giving everything a good clean down, and reading as much as I could from here on restarting HPI’s after many years I gave it a go.

For some reason, it does start, but then accelerated immediately up to full speed before switching off.

I reset everything back to base HPI Savage 25 suggested setting (HSN 4 1/2 turns etc) but it has just carried on accelerating extremely aggressively on start-up before cutting out. Looking back i seem to remember it used to do this 10 plus years ago when I was a kid and trying to run it in ....

As a chance I decided to squeeze the accelerator to see if that would help. It stays at full chat, then simmers down, nearly to an idle before cutting out once again.

Thinking that it could be tubing issues I have ordered a replacement fuel tank, tubing and a new glow plug. unsure as to how successful these will be when they arrive but figured I seek some guidance on here aswell. Anyone else experienced this? Any hints and tips for me?

cheers,
J

 

[Piccions93]

Try to start it with the electronic off. This for being sure that the engine does not rev up due to the throttle servo.

Remove the air filter, how much space there is for air? It should be about 1 mm at idle..

 

[Shwarr]

Try to start it with the electronic off. This for being sure that the engine does not rev up due to the throttle servo.

Remove the air filter, how much space there is for air? It should be about 1 mm at idle..

Good idea about the electronics off. Will try tomorrow morning with that one.
I have been trying to achieve about 1mm using the idol needle. Am I right with this one? Or should it be a combo or HsN and LSN?
thanks,
J

 

[Piccions93]

The idle minimum air flow can be regulated only through the idle screw, the one with the spring. It should be regulated with the servo horn disconnected, because the servo can keep the carburetor opened even if off. Disconnect the servo horn, regulate the idle screw, than turn on the electronic, set throttle trim to 0, finally replace the servo horn.

 

[Shwarr]

The idle minimum air flow can be regulated only through the idle screw, the one with the spring. It should be regulated with the servo horn disconnected, because the servo can keep the carburetor opened even if off. Disconnect the servo horn, regulate the idle screw, than turn on the electronic, set throttle trim to 0, finally replace the servo horn.

So I actually didn’t realise I needed to disconnect before altering. . . Daft question but Screwed in is less air flow or more?
Cheers,
J

 

[Piccions93]

Disconnecting the horn is the best way to do a good setting. Anyway, the idle screw works like this:
Clockwise = more air flow, more nitro, more rpm at idle speed

Counterclockwise = less air flow, less nitro, less rpm at idle speed