Throttle setup problems on RC10GT

[Jasper Jones]

I have an RC10GT with a Crezcenzi brake system and an O.S. .15CV. I am having problems setting up the throttle and brake linkages. I can not get it set so that I have full brake and full throttle. If I set everything up for full brake, I get only part throttle. If I set it up to get full throttle, I can't stop the truck. I also have a problem with the engine cutting out when I hit the brakes. What do you guys recommend?

[Jasper Jones]

Also, if I have it set to be able to get full throttle, it will not return to idle, it will idle way too high (it is open too far).

[rocknbil]

Welcome aboard Jasper!

Actuall this is pretty common, the correct setting on a GT is a pretty narrow band. What you have to do is play with different rotations on the servo horn - rotate it one tooth this way or that, expirament with putting the throttle pivot in different holes closer or farther from the center until you get it right. One thing that will help is to get rid of the stock linkage and install the OFNA linkage seup (http://forums.radiocontrolzone.com/attachment.php?attachmentid=40221) on the GT. Play with it long enough, you'll find the "sweet spot."

As for it dying when you brake, if when you hit the brakes the throttle opening still stays open at least 1mm, there could be a couple things. One, you have to remember that if the idle is too high, it will cause premature clutch engagement that puts drag on the engine; when you hit the brakes it's enough to stall it. Failing clutch bearings can also cause this. Address these mechanical issues first before going into tuning.

Second, if this is all good it is probably mis-tuning, either running roo rich or too lean overall or just at the low end. If you have acceptable high-end performance, what does it do from a dead stop? If it "gurgles" at all, the low end probably needs to be leaned out a tick; if it takes off like a hot rocket it may be too lean on the low end.

Lastly (and many put this first) it may be the idle screw adjustment, but never "up" the idle for a mis-tuned engine, then you have two problems. At idle with a stock clutch, the GT should "lurch forward" at no more than slow walking speed, like an auto transmission car in drive. If it moves too fast - the idle is too high. With an MIP 4-in-1 clutch, it shouldn't move at all at idle.

If it's idling too high, it's possible your transmitter trims are set so it's holding it open - remove the air filter and with the electronics on, verify that the carb opening doesn't move at all when you go from the idle position to the brake position. If it does, this may also be what's causing the stall. Adjust the trim so it pushes the throttle opening all the way against the idle screw stop - that is, as closed as it could be, with the idle screw holding it open at least 1-2mm. Once this is done, with the air filter back on and the engine running, you can fine-tune the idle screw so that it will run as low as possible at idle wihout lurching forward too fast. When you hit the brake, the additional drag caused by braking should not stall the engine.

So excessive drag, low end tuning, and LASTLY idle setup generally is what causes the stall when you hit the brakes.

[Piggy89373]

Bill, this is the brake system he was referring to:
http://img.villagephotos.com/p/2005-1/942577/Picture006.jpg
Jasper, there's a fine line you have to deal with on this setup. As you see in the pic, I'm just half a hair from being at WOT. But, when I hit the break, it'll lock up the rear end if I let it. Really, it's a matter of play. However, if you look at the instructions, Dave Creszenzi recommends using the stock servo setup. I think the purpose of using longer horns to allow further travel with less servo movement. (if it makes any sense).

It's funny you posted this, I had just finished putting on this brake yesterday and had fidgeted with it to come up with the setup you see.

For any other GT owners, I highly recommend using this brake setup. It'll definitely lock up the brakes if you want to. Another good one to get from Dave is the clutch nut. (which can be seen in the pic). Just throwing in a quick plug for a good product. :D

[rocknbil]

But his problem was with the throttle. Not the brake. And dump that funky stock servo horn setup. :D

[Piggy89373]

his problem dealt with the brake interfering with the throttle. I like the original stock servo horn...it's still a pretty white. :D

[rocknbil]

Meh, I get the same thing with the stock linkage, it's the throw to the carb. I just can't stand those wobbly throttle pivots, the OFNA linkage is smooth and solid. And it comes in white.

[Piggy89373]

Bil, got link on the Ofna stuff? BTW, here's the link for the Crescenzi Brake (http://www.rc10gthobby.com/cr_brake.htm)

[rocknbil]

Meh. Me lazy. Search Tower.

:D

Here's a blue set. (http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXBM06&P=7) The come in all colors.

My previous link shows one installed. I usually get them on eBay NIB for about five bucks. You'll need to save or fashion a brake rod, but look at the pivot slider system, very smooth and solid. :D