Idle screw

[Cornholio]

Hey guys, I have a .18 cvr in my RC10GT and for some reason my idle screw does nothing. I've taken the carb apart and put it back together but the screw still doesn't adjust the idle gap. How do I get the screw to seat properly on the carb? Is there a trick? Obviously when I hit the break the engine dies, for me its no biggie cuz who needs brakes anyway? But, I'm trying to teach my son how to drive a nitro so I need to be able to brake properly for his sake. Any help?

 

[Nitro Nerd]

Are you certain the stop screw is in its groove? I'm not familiar with that carb, but most slide carbs have a groove in the housing, which allows the idle-stop screw to prevent it from going past where you set it. Below is a pic of one of my carbs. You noted you took the carb apart, so forgive me if this is something you're certain is set....but can't think of anything else that would prevent it from not working.

If that's not it, let us know...as it HAS to be something. ;-)

 

[Alan81]

Agreed with above. If your slide isn't set at the proper position, the idle screw will thread into the carburetor, but not engage the slide.

I'd bet if you force it when it's not set in the groove, your likely to bend the end of the needle.

edit : Noted that your carb isn't a slide carb, but the principle should still be the same. Perhaps you have the "rotor" installed 180 degrees from where it should be, and the slot is on the back side of the "rotor" instead of on the side with the needle ?

 

[Cornholio]

I've got the rotary carb but I can't get the stop screw to seat in the groove properly, that's my problem. It's probably very easy to do, I must be just missing something. I was just curious if there was a trick to putting the barrel back in a certain way so the screw catches it. I'm trying to be very careful to, so that I don't fudge up the needle.

 

[Alan81]

The only thing I can say is to look at the barrel while you're sticking it back into the carb and make sure that the opening for the needle aligns somewhere close to the middle of the groove. Once the barrel goes in, the needle should thread into the groove and allow for adjustment. The needle doesn't go in perpendicular to the barrel either, so take that into account when you're trying to align it.

Is the barrel seating fully into the carburetor body?

 

[Nitro Nerd]

Yeah, it can be a bit tricky. Alan81 above covered it. You'll get it unless something is damaged.

 

[Cornholio]

Update: I was able to get the needle aligned in the grove on the barrel last night but still after turning the needle all the way in, doesn't give me enough gap to keep my truck from dying during breaking. Soooo....after almost throwing it through the window I decided to drop by the LHS after work and let them have a peek. After telling them the problem they looked at me like I was an idiot...he says. "Turn the needle in so you get more gap dude". I said: "No kidding man, but it won't turn in anymore and it's only a .3-.4 mm gap or so showing..and that's not enough". So I give it to him and he takes the needle out, the barrel and the spring. Puts it back together, tightens the screw and gets almost NO gap at all! Yup, hes perplexed and flustered now and I DONT feel like such an idiot. So we decided to remove the needle spring and that gives it just a hair more of a turn in and MAYBE a .5 mm gap....I just put the truck back together but haven't tried it yet. He and his business partner are just guessing that maybe its a manufacture defect in the carb or needle??? Anyhow, I'll fire it up tomorrow and see how it goes..if it doesn't work, guess I'll be buying a new carb!

 

[Alan81]

Update: I was able to get the needle aligned in the grove on the barrel last night but still after turning the needle all the way in, doesn't give me enough gap to keep my truck from dying during breaking. Soooo....after almost throwing it through the window I decided to drop by the LHS after work and let them have a peek. After telling them the problem they looked at me like I was an idiot...he says. "Turn the needle in so you get more gap dude". I said: "No kidding man, but it won't turn in anymore and it's only a .3-.4 mm gap or so showing..and that's not enough". So I give it to him and he takes the needle out, the barrel and the spring. Puts it back together, tightens the screw and gets almost NO gap at all! Yup, hes perplexed and flustered now and I DONT feel like such an idiot. So we decided to remove the needle spring and that gives it just a hair more of a turn in and MAYBE a .5 mm gap....I just put the truck back together but haven't tried it yet. He and his business partner are just guessing that maybe its a manufacture defect in the carb or needle??? Anyhow, I'll fire it up tomorrow and see how it goes..if it doesn't work, guess I'll be buying a new carb!

Almost sounds like they didn't tap the threads all the way into the carb, OR the needle is too short for some reason (broken?). Check the length of the needle first, it would be cheaper than a new carb, but if it's the carb body that's defective, and it's a new buggy, the MFG should warranty it. :\

 

[Nitro Nerd]

First, thanks for the follow up - it always helps folks searching for a similar issue.

Second, good for your LHS guy! Guys with tenacity like that are rare these days (at least in my experience). One of my "mentors" in this hobby was my LHS guy, and to this day he was one of the few I'd ever let touch my vechicle - so kudos to that. ;-)

Third, I agree with Alan81. It sounds like you've performed your due dilligence here, so if the mod does not work, I recommend sending it back for a new carb. The good news in all of this, seems you've learned a lot about idle-stop screws. Sometimes the only way to learn is when something's not working. ;-)