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Revo 3.3 Idle Problem

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Old 06-20-2008, 11:31 PM
  #1
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Default Revo 3.3 Idle Problem

My revo idle's fine when its first started, but after a tank of fuel it starts to rev up and down. Why is it doing this? I've tried playing with both the fuel trim and low idle trim, but increasing the throttle trim seems to be the only thing that steadies it. Even then its changes after time. I'm sure I'm doing something wrong and would appreciate some advise.

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Old 06-21-2008, 01:20 AM
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Default RE: Revo 3.3 Idle Problem

sounds like you have an air leak[:@] Im going through one of those myself. What i hear around here is spray soapy water over the hoses and carb/engine then take the hose off the tank and blow into it. Do you see any residue around the carb or flywheel?
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Old 06-21-2008, 08:06 AM
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Default RE: Revo 3.3 Idle Problem

This seems to be a common problem with the TRX 3.3 engine, I have seen it in many other posts. Could be the front main bearing or seal around carb and/or your EZ-start back plate. Do what equlizer said, then you know where the leak is coming from.
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Old 06-21-2008, 08:51 AM
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Default RE: Revo 3.3 Idle Problem

Thanks equilizer

I will look into it. Will I ever get this thing to run perfect for just one day.[&:]

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Old 06-21-2008, 06:03 PM
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Default RE: Revo 3.3 Idle Problem


Quote:
ORIGINAL: equlizer

sounds like you have an air leak[:@] Im going through one of those myself. What i hear around here is spray soapy water over the hoses and carb/engine then take the hose off the tank and blow into it. Do you see any residue around the carb or flywheel?
From the sounds of it, I would say u are definately right. Definately sounds like a air leak to me as well. Because whenever the idle surges up and down like that as u are describing, that is definately a classic telltale sign of a air leak.
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Old 06-21-2008, 08:37 PM
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Default RE: Revo 3.3 Idle Problem

My guess if its a leak, its your front bearing.
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Old 06-21-2008, 09:01 PM
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Default RE: Revo 3.3 Idle Problem

Quote:
ORIGINAL: Mspeed

My guess if its a leak, its your front bearing.
Where ever the air leak is its a big one to cause surging like that, I've seen this in full size cars not nitro engines though.
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Old 06-21-2008, 09:35 PM
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Default RE: Revo 3.3 Idle Problem

i disagree on the air leak
if the air leak were bad enough to cause the surging you are describing then
imo, there would be symptoms from the time the engine started , not just after it warms up
although i could see the symptoms getting worse with heat i just don't see going from no symptoms
to full blown big air leak after the engine warms

i think that you have a tuning problem
read this link from the late ron paris, he talks about what i believe is your problem in the
carb needle balance section near the top of the link
http://www.nitroreview.com/hintstips...ngTechTips.pdf
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Old 06-22-2008, 06:12 AM
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Default RE: Revo 3.3 Idle Problem

If there was a small crack in the block it would get worse with heat expansion. When my brother decided to retire his TRX 2.5 engine, after warm-up it would lose wheelie capability because when the engine was cold the piston seal was tighter. You know 9 out of 10 mechanic's would diagnose surging as an intake air leak, I think we should all start the process of elimination here and not skip the obvious signs.
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Old 06-22-2008, 06:46 AM
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Default RE: Revo 3.3 Idle Problem

Just a lean bottom end needle will cause it to surge at idle, whats with all the grim posts have you tried to re-tune it again ?
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Old 06-22-2008, 06:55 AM
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Default RE: Revo 3.3 Idle Problem

the key things you said were "get worse" and "obvious signs"

get worse implies that there are symptoms to begin with and he says there are not
and with nitro rc's (especially with - no offense intended - newbs) tuning is the most obvious problem

this is not a 1:1 car so, while there are similarities, there is very little direct translation

using your example, yes a surging in 1:1 engines strongly indicates an intake air leak
but
it's also highly unlikely that the 1:1 owner was out there adjusting the engines carb settings

sure there are things that happen that could cause his symptoms - like a cracked block
but that sure is...well...less than obvious

i still think this is a tuning issue
reset the carb to factory settings and retune it
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Old 06-22-2008, 08:59 AM
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Default RE: Revo 3.3 Idle Problem

Thanks for all the advise peeps.

I haven't had a chance to run it yet to check for air leaks. Damn work.

I really believe its a tuning issue because i'm a newb at this. I have a rc sloutions roll cage, so I doubt I craked the block. My fuel lines are likewise protected. I will check for the air leak but have not noticed any fuel or oil coming out of the front bearing. As I mentioned, playing with the throttle trim will usually steady it for a while, then its off again.[:@]
I put a fuel filter on the gas line and I'm going to clean it today. Would a dirty fuel filter cause such a problem? But then again, why would it run fine when first started if it was the fliter. Ansewered my own question I guess.

Thanks for all the great tips
Off work at 5 and will be testing then.
Will keep you posted.

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Old 06-22-2008, 02:51 PM
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Default RE: Revo 3.3 Idle Problem

I have had great success with my 3.3's in the past, but unfortuntly I have finially run into a not so great one. Usually it just takes time to learn how to tune, but if you get one of these problematic engines, then your in for a treat if its your first nitro experience. I am starting to think the new batch of 3.3's with that new head on them might have some issues with them, but well see. Tune and tune some more then let us know and go from there.
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Old 06-22-2008, 03:48 PM
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Default RE: Revo 3.3 Idle Problem

It could be the stock carburetor. The block is aluminum the carb is composite. When the block gets nice and hot it can expand larger than the o-ring(s) can compensate for because the carburetor does not expand with heat. One way to remedy this is to get some red automotive RTV silicone and put a THIN layer around the seam to quell any air leaks, or you could get a new seal set. http://www3.towerhobbies.com/cgi-bin...?&I=LXDGB6&P=7

I'm not saying this definitely is the problem but it sounds like it considering it only surges when it's heated up and the fix is cheap so you might want to try this.

Alternatively you could buy a better carburetor that is made of aluminum, I've heard doing this makes the engine run like a beast without tuning problems.
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Old 06-22-2008, 10:45 PM
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Default RE: Revo 3.3 Idle Problem

Well, it turns out my engine was simply overheating. Re-reading the owners manual can pay off from time to time.

While waiting for the battery to charge, I read that overheating will cause fluctuation, so I richend the fuel a quater turn and there you have it. It was even hotter outside tonight than the last time I ran it, but the adjustment worked. I guess when I was trying to adjust it the other day, it was already overheated so naturally I wouldn't matter what I did.

Alas, no more catwalk power however.[]

Thanks again for all the tips and help. If this doesn't fix it in the future, I'll know what to look at now.

Cheers
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Old 06-23-2008, 04:14 AM
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Default RE: Revo 3.3 Idle Problem

Glad to hear you figured it out.
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Old 06-23-2008, 04:38 AM
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Default RE: Revo 3.3 Idle Problem

Yeah, always best when it doesn't cost you money to remedy the problem. [sm=thumbs_up.gif]
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Old 06-23-2008, 05:34 AM
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Default RE: Revo 3.3 Idle Problem

you may have fixed your problem - which is good
but it still sounds like the engine is out of tune - which is not so good

reread the manual and the paris racing link i posted
reset the needles to factory and tune the engine per those instructions
i think you'll find that you regain some of that lost power
and still keep from the overheating/surging issues you had

tuning is a process, not a hit and miss turning the needles 1/4 turn this way or that
learn to tune properly and you'll get better performance and a lot more satisfaction from the hobby
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Old 06-23-2008, 07:56 AM
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Default RE: Revo 3.3 Idle Problem

I actually did reset the low speed idle to factory settings and then adjusted it after a few runs. I also leaned out the fuel towards the end of my runs and recovered most of my previous power, but not all. When it pinched the gas line, it turned off in exactly 3 seconds, which is according to the book near perfect tunning. I know I could of leaned it more, but keeping my engine in good condition is more important than catwalking to me.
I should also note that I drilled holes in the windshield and side windows on the body cover, and that may be attributing to my engine running cooler. I will testing how far I can safely lean it today.

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Old 10-08-2008, 05:57 PM
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Default RE: Revo 3.3 Idle Problem

dsd
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Old 10-08-2008, 06:05 PM
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Default RE: Revo 3.3 Idle Problem

dsd to you to.[sm=72_72.gif]

Don't know what it means but cheers all the same.
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Old 10-08-2008, 07:00 PM
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Default RE: Revo 3.3 Idle Problem


Quote:
ORIGINAL: SureToCrash

dsd to you to.[sm=72_72.gif]

Don't know what it means but cheers all the same.

dsd!! what the fock does that mean?!
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