Can't Start RC10GT

[snmhanson]

I just finished putting my RC10GT together. I have an OS CV-X .12 engine in it and everything appears to be connected and adjusted correctly. I was able to get it started once and let it idle for about five minutes and then it died. I haven't been able to get it going since. There is compression when I pull and I can see fuel in the line but it just doesn't turn over. I removed the glow plug and tested in with my glow starter also pulled the engine with the glow plug off several times in case it was flooded. I adjusted the needle valve per OS instructions - two full (360 degree?) turns from closed - and I have the minimum throttle opening set to the recommended ~ 1mm. I didn't mess with the mixture control valve at all. I can't think of anything else, any suggestions? I've went through one complete charge on my glow starter trying to get it to work. The only other bit of info I will add is that I initially had the tubes betweent the fuel tank and carb and muffler crossed but I did get it started for the five minutes after I switched them. Thanks for any help on this.

Matt

 

[snmhanson]

OK, I've got it running now. I adjusted the mixture valve and leaned it out a bit. My only real questions now is is it normal to need to open the needle valve when you start it cold? The routine I take to get it initially started is prime it (quite a bit) by covering the exhaust hole, open the needle valve and pull away at the starter. It takes several pulls to get it going and sometimes I need to open the throttle a bit but after it starts running I am able to lean out the needle valve up to one full turn. Once it's warmed up it runs great and is easy to start for the most part. I don't mess with the mixture valve and I get a bit more smoke when I'm on the throttle but it doesn't seem too excessive. I have good accelleration all through the power band. Does this sound like normal engine behaivor? Thanks.

Matt

 

[Rolex]

No, there's no need to open a needle valve. Once they are set, and you get good low and high end, all you need to do is raise your throttle trim and start it.

 

[Mr T-Maxx]

^^Yeah, what blinky said^^

You mention that the truck is new or at least just assembled. Is the OS new also?

Until an engine is properly broken in they can be a bear to get running and keep running, but as Rolex mentioned your current practice is definately not the normal procedure.


Keep us updated.

Mr T

 

[rocknbil]

. . . My only real questions now is is it normal to need to open the needle valve when you start it cold? . . .

Actually you usually will, and here is why.

The optimum running conditions for these little engines is actually a pretty narrow band of mixture. Variations of barometric pressure, ambient air temp, and humidity from day to day and even within the same day are going to require adjustments to maintain an optimum running condition.

This includes engine temperature. Generally speaking, when you start an engine it's going to need a different mixture than when it's up to full running temp five minutes later. You get it running and fully warmed up, adjust the high speed needle (only, usually) for performance, and off you go. Usually this setting is a bit more lean than when you started it up.

So. Next day, the needle is in a slightly lean position, when you try to start it you might have to enrich the mix by half a turn or more to get it running and warmed up.

A few other tidbits - don't let the "factory setting" or how far off from it you are concern you. This is a general starting point and you'll seldom actually wind up here. Most OS engines I've owned run anywhere from 1-3/4 to 2-1/2 turns out, but I had one that liked to live at over 3 - 1/2 turns.

There are many methods of tuning but this works for me. Get it up to temp and adjust only the high speed needle for high speed performance: that is, from about 3/4 throttle to full throttle, on the track. Now play with accelleration from dead stop to 1/2 to 3/4 throttle, making TINY adjustments to the low speed setting, like one tick at a time, giving it 30 seconds between changes to settle in to the new setting. The goal here is to be able to dump the throttle from a dead stop and not have it bog down or flame out but give you a clean acelleration up to mid high speed.

Once you get the low speed setting where you want, you will seldom have to change it. When you adjust the HSN, you are affecting all the fuel entering the engine, across the entire power band, including low speed. Generally if the LSN is set right, it will proportionately rise and fall with this adjustment, so you'll only have to tweak the HSN every time you run.

 

[snmhanson]

Thanks for all the help. I've been running it a little more and it seems to be running better each time. The car and engine (as well as the driver/tuner) are all new so maybe it was just going through normal break-in stuff. Also, I don't think I was priming the engine enough. I was basically priming just until I got fuel to the carb, no more. Now I am giving it a few more priming pulls and it seems to be starting up much better.

As far as engine settings, I think my mixture setting I think. I get some smoke coming out of the muffler under throttle and can barely see any when idling. My low end acceleration seems to be good. When pegged the car almost wheelies over and the front tires skip along the ground until it gets up to speed. I've been setting my needle valve at 1.25-1.75 turns out, does this seem too lean? To set it I basically keep closing it until the engine starts hesitating under heavy throttle and then back it off about 1/4 of a turn.

Thanks again for the help. I think I'm figuring it out now.

Matt

 

[Rolex]

As rocknbil mentioned, the HSN does need to be tweeked for optimum running due to temp and humidity changes, but not until the engine has started and warmed up. Messing with needles before the car is warm can only make starting more difficult. And, true, some engines go through a period of what's called 'the break in blues' where they can get stubborn.
It sounds like you're getting good punch on the low end. Just to make sure the LSN is not too lean, drive it till it's up to temp, then at idle pinch off the fuel line close to the carb. It should speed up and then shut off between 3 - 4 seconds. Less than that and it's too lean on the LSN, and should be richened up a bit.