Hey guys. Have just gotten to the stage whereby you are instructed to run in the RB7. I have been following the Kyosho instructions for the GX21 engine adjusting the needles/screws as instructed.

So far have ran 2 tanks of fuel through just basically standing still, then ran another tank just using 1/4-1/2 throttle in fig 8 shapes, allowing the engine to cool for at least an hour with the piston set to BDC each time.

It was just into the third tank where suddenly the throttle fully opened up and wouldn't slow down by the brake. The car mounted a curb and snapped the lower left wishbone (replacement parts ordered). I stopped the car by halting the flywheel.

Took the car into the garden, checked and the carb was closed as it should be. All fueling tubes were still connected properly. Started it up and the throttle ran away again so I killed it. This time I noticed the throttle was stuck open. Had to physically press the brake lever on the RC unit for it to close.

Checked all the servo linkages and all appear to be free running and didn't get stuck. Started it up again and all was ok. Ran it around for another 2-3 mins and then left it idling to finish the tank off.

I then proceeded to remove the glow plug and put in what I thought was after run oil. Turns out I had been using air filter oil... (Why are they both red!!). Anyway I then used the proper stuff and put the car away.

So the two obvious questions;

What do you guys think would cause the throttle to seemingly get stuck wide open, even though (the first time at least) the servo was in the correct, 'closed', position.

What damage could/would have been caused by using air filter oil rather then after run oil for the past 24 hours.

Aside from this, the engine appears to be running fine, just need to continue tuning but this is on hold until I get the replacement wishbones. Need to see if I can improve the turning circle, 'Large ship' comes to mind. I'm sure I can do something with the toe-in angle to aid with this.

Luckily I already removed the 'display' front wing otherwise that would have basically exploded into a million pieces! Gonna build the next few issues but really am after the race body as mine will be displayed on my wall in race bodywork as want to make it obvious it's a nitro model. Won't get much use as it feels far too fragile (even in race trim, that poor front wing!) so ill be using the hummer for general use which should be complete in the next few weeks, then onto the Skyrider :D

Cheers, good to know. I did do some googling and others who had done it by mistake got the same comment, it apparently would burn off within the first few seconds of runtime anyway as its a rather hostile environment for it!

I guess I could have nudged the trims by accident but didn't have to adjust them back. I did have it idling for 2 tanks of fuel so perhaps some deposits got gummed up somewhere as it was within the first 10-15 seconds of driving it in circles that this happened, then as I say after another start where it did it again the symptom didn't return. I do have an in-line fuel filter fitted so I know the fuel wasn't bad.

Would it be possible that there could be an air leak elsewhere in the engine therefore bypassing the carb. The engine could then get as much air as it wanted and would act as though the throttle was open?

I did panic and closed the idle screw by 3-4 turns so had to start that procedure again. Will wait to run it again until I have the new lower wishbone but just seems odd. I did think perhaps the needle valve got stuck open somehow but couldn't verify the theory. Weird.

Glad you've got it sorted out. At least it was something easy to fix