Erratic high idle.... (Video link in post #8)
 

I'm having a problem with my revo 3.3. It had a high idle problem so I did the leak test and found that my front bearing was leaking BAD. I bought the bearings today, dissassembled the motor... replaced the bearings and did a quick blow on the fuel line and heard no leak at all from the front bearing area. I didn't do a thorough check on the backplate and carb, and I wish I had now, but either way I started the truck up and this time the idle screw actually dropped the idle low enough that the truck didn't move on it's own.... for a little bit. After a few passes, I checked to make sure the HSN was set right, and it seemed perfect... decent smoke and shifting nicely, but then I brought it back in and the idle was high again and this time it was erratic. It seems to me like it's leaking air again, but I also know it could be in the tune. What causes a high and erratic idle, lean or rich LSN? This thing is really really starting to frustrate me.... I have a blast with it, it's just the idle and inconsistant acceleration that bugs me. I'll be driving it for a few minutes and when it's warming up it gets peppier and peppier, then it just starts getting doggy on the low end... GRRRR :flaming:

PS- I'd post a video of it, but apparently I don't have enough posts on this forum..... again... GRRR:flaming:

Sounds like you're moving in the right direction. I would have sealed the backplate and carb while it was out. You can try leak testing the engine while its running to see if it shows more leaks, but I seal all my engines from the start to just be sure. Carbs have been probs with these - pinch bolt can be tightened enough to crack body and let air leak when the throttle is pulled. These cracks are hard to see and find.

Takes 10 posts I believe.....

Thanx Duster. I'll try sealing it up today and letting it set till tomorrow or the next day and then I'll try it all over again.... I really hope I get this running right soon, before I get too frustrated and end up selling it dirt cheap.... I get upset too easily:nod:

I know about that.....put a Fantom FR18 in my 1st Tmaxx - wow, incredible power! Wouldn't run without igniter plugged in! I did everything you could think of, tuned it all over the planet, diff plugs, diff heat range plugs, anything and everything - nothing helped. Finally pulled motor off and as soon as backplate came off - saw why - half the bp gasket was gone, big air leak!

Just gotta walk away sometimes and start fresh again, later!

OK, I picked up some permatex ultra copper gasket maker..... Here goes nothin'.

I understand how to seal the carb, but how do I seal the backplate right? I am guessing you unscrew the back plate, lay a bead, and put the backplate back on. What about the pull starter? Any sealant there? What seals where the starter shaft goes through the backplate?

Thanx for all the help man

just a piece of free advice...

i fought this same issue,but my engine was 100% sealed...it would start,idle fine,then after a couple minutes the idle would shoot up,id turn it down with the idle screw to where it would idle great,but then when i would try to fire it cold it wouldnt idle...the problem was the clutch bell bearings were going bad...so dont rule those out either...amazing how the cost of 2 bearings is cheaper than the bottle of aspirin i needed for the headache it was causing me!!!

Thanx Bad.... When I pulled it apart I spun the bearings in my fingers and I didn't feel any resistance or notchy-ness.. How else can I check them? Maybe wait till the engine is hot and then try spinning the spur gear/clutch bell assembly?

OK, I'm gonna try the video thing again.......

http://www.youtube.com/watch?v=sq0jjeLFlcU

This isn't a video of the high erratic idle problem, this is just a test to see if the video link works for me now.

If it works then I'll post a video tomorrow of my idle issues...

If they're going to drag that badly, you'll feel it. If they spin free and the CB coasts to a stop rather than just stops, they're good.

Have you checked fuel lines for leaks - usually the 1st thing I do when chasing down prob like this is replace both lines with new. Blow into the pressure line and make sure the connection to pipe is open and clear. Are you using a fuel filter?

Clutch bell does spin freely and slowly stops... I have new fuel line that I bought a couple days ago so I'm gonna just put that on. I know the opening from the pressure line, through the tank, all the way to the carb is clear cuz I can still blow-prime the fuel system. I am not using a fuel filter...

If it persists then it might be your clutch shoes and springs. They should be replaced every gallon or so. Its like 7 bucks for the spring and the shoes and you might as well pick up some bearings for like a buck or two each to totally eliminate having the clutch be a problem! :)

What might be the clutch shoes and springs? The high idle? How does that effect the erratic idle?

There inside the clutch bell, the little plastic half circle things wrapped in a spring

And im saying that you should replace them if you have ran over a gallon, but have you actually checked them by taking off the clutch bell?

I was talking about the pressure line back to the pipe - that can get partially plugged inside pipe and then the pressure used to pressurize the tank is intermittent, it comes and goes. This would affect the way the fuel is feeding which could affect idle.

Case I've encountered - pipe plugged and engine was re-tuned to run, but when pressure would come back, it engine would see increased fuel flow and idle would go up until the pressure went back down.

I see what you're saying Duster.... I'm gonna replace both hoses. Eliminate everything that could be the problem, right.

Pinky, I know what the clutch shoes and spring are, I was just not understanding what you were saying it was causing. I wasn't seeing how that was causing my idle issues. I'll probably just replace them anyways, just gotta get this darn idle figured out..... Thanx for the suggestion though, I forgot about replacing them that often!!! Such a simple and cheap part to fix....