Sticking Carb

[nitromad]

Hi - I have an STS .28. I've noticed that the carb does not close completely on the idle bar unless I give it a push. The result is a very high idle (and subsequently overheating without an airflow) and an inability to adjust idle speed (as the adjustment is not actually adjusting anything but space). At the moment I am having to keep the LSN too rich to keep the idle speeds and temps artifically low, and the result is very boggy performance off the line. The advice I've received is that they stick sometimes but eventually loosen up through use. However I've probably run 20 tanks through it now, and the problem is not getting any better. Are there any suggestions as to how I can fix this?

I'm also planning to seal my engine, which I have never done before. Would someone be kind enough to maybe post a few pics of how to do it? - I've read descriptions but I never fully understand and I don't want to fuse anything I shouldn't. Pictures would be a huge help.

Thanks!

Chris

 

[SMaxxin]

Have you tried turning the carb for your sticking throttle problem? If the carb is at the wrong angle it can cause your carb to stick and/or not completely open. Loosen the pinch nut at the base of the carb neck and you will be able to turn the whole carb body, it might be tight at first but it will turn.

 

[jon2]

Is there any binding on the throttle/brake linkage?If you remove it from the carb can you move it back an forth without feeling any restriction? Manually moving the carb, can you feel any restriction?Let us know.

 

[nitromad]

Hi - thanks for the replies. I had to turn the carb around as it came set up for a monster truck with the slide on the wrong side. It's currently in the same position as my old engine - with the slide parallel with the throttle arm (if that makes sense?).

I can open and close the throttle manually, and the air gap looks fine. However I know it is not closing as far as the idle bar, because the idle control has no effect at all on idle speed. If I push the slide a little firmer, I can feel it move in a fraction more (and I suspect this is the true idle). When the engine is running, this brings the idle down. The problem then is it seems to get stuck in that position and I have to pull it out again fairly hard(as the servo isn't strong enough). So its almost like it doesn't want to quite close properly and when it is made too, it gets stuck. I'm planning to pull the carb apart to have a look - is there anything I can do to alleviate this (instead of buying a new carb)??

I'm sorry but I'm not sure what you mean by binding? I've attached a pic of my throttle arm to help. You can see the position of my carb in that too. I've since adjusted the brass throttle arm (name?) so that is pointing foward, not up as in the pic.

Hope this helps

Chris

 

[jon2]

Hi - thanks for the replies. I had to turn the carb around as it came set up for a monster truck with the slide on the wrong side. It's currently in the same position as my old engine - with the slide parallel with the throttle arm (if that makes sense?).

I can open and close the throttle manually, and the air gap looks fine. However I know it is not closing as far as the idle bar, because the idle control has no effect at all on idle speed. If I push the slide a little firmer, I can feel it move in a fraction more (and I suspect this is the true idle). When the engine is running, this brings the idle down. The problem then is it seems to get stuck in that position and I have to pull it out again fairly hard(as the servo isn't strong enough). So its almost like it doesn't want to quite close properly and when it is made too, it gets stuck. I'm planning to pull the carb apart to have a look - is there anything I can do to alleviate this (instead of buying a new carb)??

I'm sorry but I'm not sure what you mean by binding? I've attached a pic of my throttle arm to help. You can see the position of my carb in that too. I've since adjusted the brass throttle arm (name?) so that is pointing foward, not up as in the pic.

Hope this helps

Chris

I know on my old TMAXX I had the Sirio 23 on it and found the throttle linkage was not allowing the carb to open all the way. In fact it would actually try to keep it closed. I found out the carb needed to be angled differently and the throttle arm changed out.

Let us know what you do.

Jon

 

[Monkey Wrench]

If you find that adjusting the carb angle and linkage do not solve your problem, try polishing the barrel LIGHTLY with some metal polish. My OS .18TM on my Revo had the same problem, but after I polished it, slides to the idle stop smooth as silk.

You can also add a throttle return spring to pull it closed when you let off the throttle. I'd try that first before polishing it.

 

[nitromad]

Thanks for the replies. I've had a play moving the carb around and also adjusting the throttle linkage, but I think the real problem is in the carb sticking at full idle. The throttle return spring sounds like a good idea, but I still think the problem of sticking would be an issue.

So tonight after work, I'll take the carb apart and use some light polish, and try and get that puppy opening and closing better. I'll let you know how it goes....

Thanks!