retune old pro21R

[morry pike]

Hi can anyone help,iv'ebeen given a thunder tiger lotus its about ten years old and do you think i can start it no a new gloplug new pull cord and it will not go,So i think reseting the needles is my first port of call but i have searched the net on how to tune it but to no avail the engine is an older style pro 21R modern nitros have a idle spd screw in the end of the the throttle plunger but this doesn't.it has three screws all on one end of the carb and i dont know the factory settings any ideas welcome:\

 

[ThunderTiger]

Ok, here goes,

Low speed needle = 6 1/2 turns out from being screwed all the way in.

High speed Needle = 2 3/4 turns out from being fully screwed in

Idle speed screw = set so that carb slider has a 1mm gap

Here is the "Factory" version (from the manual)

Here's my Version listing the HSN, LSN & ISS

HSN = High Speed Needle
LSN = Low Speed Needle
ISS = Idle Speed Screw

And here is my version of the manuals "1mm" gap setting.

The above details are all FACTORY settings, for running, you need to have the following (AVERAGE) settings.

HSN: 2 1/4 to 2 3/4 turns out.
LSN: 5 turns out (or 1/2 to 1 turn out from the screw head being flush with the carb body)
ISS: Set to give 1 mm gap (As detailed Above)


NOTE When the engine is running again, turn the ISS Anticlockwise to lower the idle speed enough that the clutch is not engaging, yet the engine still runs when the brake is applied.

 

[morry pike]

thats brilliant i have it all sorted now thanks a bunch .its a bit smokey but thats an original engine in there 10 years old testament to the engines will last when looked after

 

[ThunderTiger]

No problems. These .21's are easy enough to tune, but can be an absolute pig if they want to be.

Heres a little known fact, there is a third "Screw" hidden behind the throttle slide ball, where you clip the servo to engine link.

Do you have a pic of it by any chance ?

 

[tkiefer]

Followed your direction but can't keep it running

I have a pro21R in my Mirage that is old. I bought it used (sat for 3 years). I took it apart and cleaned it completely out. I put new glow plug and it starts decently easy, but I can't keep it running. The needle up by the fuel line is supposed to be around 2 1/2 turns? and the needle that is on the carb itself is supposed to be 5-6 turns? is this correct? I have these settings and I try tuning from there with no luck. I'm new to RC cars though and have never tuned an engine with more than one needle (I'm used to planes). Does the needle that is hidden under the carb slide effect anything? or are you referring to the idle screw? Thanks in advance.