Weird T-Maxx Issues - Hard to Start, Unstable Idle, Impossible to tune

[Dr. Bogger]

Do me a favor and quit being so stubborn.
Your engine is running lean, from an air leak or bad tuning etc. Look for exhaust or fuel tank problems, then check your engine for air leaks.

---------- Post added at 9:48 AM ---------- Previous post was at 9:46 AM ----------

Are all four screws in your fuel tank? Or is it missing one?

I know the engine is running lean, but it is not due to bad tuning, and its not due to the engine cuz that's why I replaced the engine in the first place.

And when i got it, the fuel tank was missing 3 screws so i bought new screws for it.

Check your exhaust boot for splits or holes also check your fuel tank lid seal. When you open the lid and close it you should feel suction. Check your header for cracks as well. All of these thing will cause the problems your having.

The exhaust boot is brand new and is fine. No cracks at all.
Fuel tank lid seal is fine. Adjusted properly also.

The exhaust manifold (header) does have a dent in it, but no holes or cracks.
Will this dent cause these types of problems?



I've been talking to Traxxas tech support and they are just about out of ideas as well.
I'm about ready to throw this thing out the window

 

[frickenjoey]

I know this may be a silly question to you but,
when you put the "New" engine on it did you break-in the engine?
It really does sound like you have an air leak on the engine.
- Do you see bubbles in the air lines? If so are they coming all the way from the tank or starting some where in between?
- What fuel are you running,
- What temp of glow plugs?
- Does the engine still have good compression?
- Are the cooling head bolts tight?
Unless the dent in like half way through no it would not cause that problem.

 

[Dr. Bogger]

Best/worst. Post. Ever.


EVER!

I'm just saying, the redcat i have is tuned fine, and runs fine.. My Traxxas just won't even stay running.

you said you replaced the entire engine complete with carb. You did not say you sealed the new engine.. Start with the basics seal the engine completely... Takes 10 min and then you have eliminated the air leak possibility completely... Just because its new does not mean its totally sealed

Also check your fuel tank o ring if that is leaking you will never get a proper tune

No, i only sealed the old engine, and I figured sense this engine was new it wouldn't need to be sealed. I will try this when I get home from vacation. I'm leaving tomorrow.

The fuel tank o-ring is fine. I've check it many times over.

I know this may be a silly question to you but, when you put the "New" engine on it did you break-in the engine?
It really does sound like you have an air leak on the engine. Do you see bubbles in the air lines? If so are they coming all the way from the tank or starting some where in between?
What fuel are you running, howabout what temp of glow plugs? Does the engine still have good compression?

Yes, I broke the engine in (the best I could with the stupid air leak that's going on)

No bubbles in the fuel line unless the fuel starts running low. That's the only time i see air bubbles.

I'm running Torco C1 20% Fuel.
I'm using the Traxxas 3232X Glow Plugs
Yes, the engine still has good compression.

All honestly it would appear you DO NOT know how to tune an engine as there has been plenty of solid and legit suggestions by quite a few seasoned members who have not only helped me with my tuning incompetence but others as well. I agree with 2 Revo. QUIT BIENG SO STUBBORN!!! You can't start a thread asking for help and then tell everyone they dont know what they are talking about or that they are not helping your situation. The best way to get help around here is to not shoot down everyone elses suggestions but rather take them with pride and thanks.

Good luck with your tuning situation..

I was not trying to shoot down anyone's suggestions.. Its just I stated in the original post that i know how to tune an engine, and it is not a tuning problem at all.

I can tune a Nitro Engine very well. I can re-build a engine. I can rebuild a transmission. I can tear down and rebuild the entire RC Car.
But it's my car that's being stubborn, not me! xD

Check the nozzle on you exhaust pipe where it goes to the fuel tank and make sure it's not plugged up. I had one plug up on me and I had to drill it and run a wire through it to get it clear.

Yup, already checked that.
The only two things left that I haven't replaced are the pipe, the header, and the fuel tank. but the fuel tanks seems to be fine, so unless i'm missing something, idk what else it could be.

---------- Post added at 11:58 AM ---------- Previous post was at 11:55 AM ----------

I know this may be a silly question to you but,
when you put the "New" engine on it did you break-in the engine?
It really does sound like you have an air leak on the engine.
- Do you see bubbles in the air lines? If so are they coming all the way from the tank or starting some where in between?
- What fuel are you running,
- What temp of glow plugs?
- Does the engine still have good compression?
- Are the cooling head bolts tight?
Unless the dent in like half way through no it would not cause that problem.

Yes, the cooling head bolts are tight.
The rest of the questions I answered above.

 

[frickenjoey]

I would re-seal the engine and let it cure up for a day then try it again from factory settings. You have an air leak. You say have checked everything else in the system so that is pretty much all that is left.

 

[Dr. Bogger]

I would re-seal the engine and let it cure up for a day then try it again from factory settings. You have an air leak. You say have checked everything else in the system so that is pretty much all that is left.

Okay, ill give that a try when I get home.
Do you think it could be an exhaust problem? Has anyone ever heard of a pipe not producing enough pressure on the fuel lines?

 

[Zdragon71]

Yes i have and usually due to the silicone boot being cut.

 

[Dr. Bogger]

Yes i have and usually due to the silicone boot being cut.

Yeah but the silicone boot is brand new. No cuts in it at all

 

[frickenjoey]

Which would mean it's probably not the exhaust. I would seal the engine. Engine removal to install is not more that 45 minutes. Hopefully that will fix the problem

 

[olds97_lss]

How old is your fuel? What tires/wheels are you running? What gearing are you running? What pipe are you running? Have you checked the clutch spring, bearings, shimming of bell?

Once you breach 280F, tuning/idle/running/stalling will be erratic regardless what you do until the temps come down.

Almost sounds like your fighting with a few things. Ruling out the air leak gets rid of one, but that leaves a few more possible issues including drag somewhere, too tall of gearing, too tight of gear mesh, too large of tires in too rough of terrain, unruly aftermarket exhaust...

IMHO, the t-maxx/revo should never have had a 2.5 (anything less than a solid .18) in them. Even on their best day, the 2.5R is barely enough to do the job if your not on pavement or a track. Which then lends itself to running overly hot (260F-280F as normal) when compared to other engines in other rigs or the same engine in a lighter rig more suited for it. As the temps creep up to 300F, tune becomes bad because the fuel is detonating/boiling in the engine as it comes in which just compounds the issue with less power and messed up tune.

 

[Mn Monster]

sounds like a air leak or your lsn is set wrong.

follow these and see how it performs

https://www.rcnitrotalk.com/forum/showthread.php?t=102688

https://www.rcnitrotalk.com/forum/showthread.php?t=60832#flowchart

---------- Post added at 2:51 PM ---------- Previous post was at 2:49 PM ----------

Yeah but the silicone boot is brand new. No cuts in it at all

are you using zip ties on each end of your boot?

 

[lesclaypool]

When you're tuning, how much are you turning the needles at a time?? Only move them in 1 hour increments at a time. I've seen it time and time again where guys get pissed off and start cranking half a turn this way, half a turn that way..

I'd start with putting some 'Green-Slime' on the needle o-rings to rule that out. Then move to the TX/RX on(engine not running) and set up your linkages so on neutral throttle trim your idle gap is no more than 1MM, and make sure it stays that way(doesn't close further) when you apply the brakes. Then check that your carb is opening fully on WOT.

Run some good fuel, maybe Byrons or something simliar, shoot for 30% / 9%-11% lube.

Once that's settled, follow this tuning guide. https://www.rcnitrotalk.com/forum/showthread.php?t=76808

 

[2revo1maxx]

I forgot one thing, what kind of temp guage are you using? Is it set properly to read anodized aluminum?

 

[lesclaypool]

I forgot one thing, what kind of temp guage are you using? Is it set properly to read anodized aluminum?

That's a really good point - in my line of work we use temp guns all the time, but when pointed at copper pipe(and other materials) you get some crazy readings.

One other thing I wanted to point out - you mentioned 'you know its not the tune or the engine, because the other engine was doing the same thing'. Well maybe...just maybe(no disrespect), the reason you were given the truck is because the guy that had it before you didn't have a clue, and maybe there was nothing 'wrong' with the engine you took out in the first place??

 

[Rolex]

The engine is not lean.. if you read my post above, i had the HS Needle set at 5 turns out, and it still reached temps of over 300F.

Unless I missed it, until Mn Monster's post #30 I didn't see any mention of the LSN. If that is set too lean you'll have idle problems and NOTHING you do with the HSN will take care of the overheat.

 

[chickenman242]

I'm still wondering if the fuel outlet on the tank has been checked
I had the same problem on my maxx when I first bought it, turns out the outlet on the stock tank was slightly blocked by some plastic when I finally found that out I drill it out and the problem went away
Just a thought

 

[Dr. Bogger]

How old is your fuel? What tires/wheels are you running? What gearing are you running? What pipe are you running? Have you checked the clutch spring, bearings, shimming of bell?

The fuel is brand new, not even a week old.
Tires / Wheels are stock.
Flywheel, Clutch Shoes, Clutch Bell, Spur Gear, and Slipper Clutch, were all replaced with brand new, stock traxxas parts.

sounds like a air leak or your lsn is set wrong.

follow these and see how it performs

https://www.rcnitrotalk.com/forum/showthread.php?t=102688

https://www.rcnitrotalk.com/forum/showthread.php?t=60832#flowchart

---------- Post added at 2:51 PM ---------- Previous post was at 2:49 PM ----------



are you using zip ties on each end of your boot?

I will try that when i get home from vacation.
And yes, i am using zip ties on both ends of the boot.

When you're tuning, how much are you turning the needles at a time?? Only move them in 1 hour increments at a time. I've seen it time and time again where guys get pissed off and start cranking half a turn this way, half a turn that way..

I'd start with putting some 'Green-Slime' on the needle o-rings to rule that out. Then move to the TX/RX on(engine not running) and set up your linkages so on neutral throttle trim your idle gap is no more than 1MM, and make sure it stays that way(doesn't close further) when you apply the brakes. Then check that your carb is opening fully on WOT.

Once that's settled, follow this tuning guide. https://www.rcnitrotalk.com/forum/showthread.php?t=76808

I currently only turn the HS Needle 1/8th turn, and the LS Needle 1/12 Turn at a time.

Where do I buy this green slime? I've heard about it, but never used it.

Idle gap and linkages are set properly.

I forgot one thing, what kind of temp guage are you using? Is it set properly to read anodized aluminum?

I am using this:
http://www.amazon.com/gp/product/B009RUPQGW/

How would I set this for different types of material?

One other thing I wanted to point out - you mentioned 'you know its not the tune or the engine, because the other engine was doing the same thing'. Well maybe...just maybe(no disrespect), the reason you were given the truck is because the guy that had it before you didn't have a clue, and maybe there was nothing 'wrong' with the engine you took out in the first place??

Yeah, I replaced the engine cuz i couldn't find any other issues with it.
But the new engine is doing the same thing the old one did.
I did keep the old engine so I can use it for parts if I ever need to.

I'm still wondering if the fuel outlet on the tank has been checked
I had the same problem on my maxx when I first bought it, turns out the outlet on the stock tank was slightly blocked by some plastic when I finally found that out I drill it out and the problem went away
Just a thought

I have a new fuel tank and stock pipe (The plastic one) on the way. Once I get them, i'll be able to rule them out and hopefully find the cause.

Unless I missed it, until Mn Monster's post #30 I didn't see any mention of the LSN. If that is set too lean you'll have idle problems and NOTHING you do with the HSN will take care of the overheat.

I reset the LSN to stock multiple times when trying to tune. I can't even seem to find a proper tuning area for neither the LSN or HSN.

 

[outlawbrett]

Check the lower o-ring on carb. the larger diameter one. id pulled out stock carb couple times an then replaced with losi carb. still had the same issues ur having. pulled carb out again an noticed a very, very small tear in o-ring. replaced it and it ran perfect. also, check the seal on ur copper o-ring on glow plug.

 

[Dr. Bogger]

Check the lower o-ring on carb. the larger diameter one. id pulled out stock carb couple times an then replaced with losi carb. still had the same issues ur having. pulled carb out again an noticed a very, very small tear in o-ring. replaced it and it ran perfect. also, check the seal on ur copper o-ring on glow plug.

Will do

 

[olds97_lss]

I'd tear the engine completely down again clean all contact areas with DA and reseal everything with hightemp rtv:
- backplate
- carb neck
- carb cinch bolt
- HSN housing/banjo fitting for the fuel inlet on the top and bottom

Let it cure for 24 hours, lube the HSN and LSN o-rings with green slime:
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXSF70&P=ML

Loosen, then remove the cooling head and button (can't recall if traxxas is a one piece or 2, think it's one, so disregard button removal). Clean the contact points well with DA and a q-tip, then reinstall the head by gently tightening the head bolts, then tight each one 1/4 turn in a star pattern until all are tight. Make sure proper head shims are installed (check 2.5R manual).

Then reset the carb to factory settings and try again.

If that doesn't ferret it out with everything else you've done, then I would be at a loss.

 

[hotrodrob]

I keep reading the same thing over and over again,dude if uve replaced everything except the tank and its Still giving u problems ,......"then buy a new friggin tank" and watch what happens,I know uve checked it and didn't find anything but it must be the tank if uve literally replaced everything except that and are Still having the same proems,if u Dnt wanna buy one drive down to schenectady and ill let you borrow a new one,no prob let me know.