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

[2revo1maxx]

Your lsn would have to be off by a country mile to cause that kind of overheating, but it will cause some serious idle issues. I would set the idle gap at 1mm or slightly less and the lsn at flush like it says in the Traxxas manual.

Your temp guage should have instructions on how to calibrate it for certain materials. If you want to check and see if it's anywhere near accurate you can point it into your mouth.

 

[Dr. Bogger]

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.

Okay, I just ordered some green slime.
I'll do all the sealing once I get it in the mail.

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.

Yes, I have a new fuel tank, stock pipe, and a new manifold on order.
If that doesn't fix it, then the damn is going to be thrown in the trash... Or maybe i'll just run it into the damn ground and watch it explode! lol

Your lsn would have to be off by a country mile to cause that kind of overheating, but it will cause some serious idle issues. I would set the idle gap at 1mm or slightly less and the lsn at flush like it says in the Traxxas manual.

Your temp guage should have instructions on how to calibrate it for certain materials. If you want to check and see if it's anywhere near accurate you can point it into your mouth.

Yes, exactly what i'm trying to say! I know its not a tuning issue, cuz i've reset it to factory settings, and even at factory setting it still overheats.. I had the HSN set 1 turn richer than factory settings, and it still overheated.

I say something is wrong with the fuel delivery system, just i can't figure out what. I have the rest of the parts I didnt replace on order, so I'm crossing my fingers like a pretzel lol

And yeah, my temp gun is accurate when pointed into my mouth...

 

[zrock]

I would have held off on new parts until you sealed the motor and tested that out... Be careful when pulling the carb out. The bottom o ring easily gets cut when pulling out.

 

[SchrodeMode]

Factory settings are just a "ballpark", they may be rich on one engine and lean on another. It is okay, to go richer. My 3.3 ran good when the HSN was 5 1/2 turns out, I've read about plenty of people who had to go a turn or two over stock.

 

[2revo1maxx]

The reason I asked about your fuel tank screws is because with one missing or loose it will cause the fuel to foam and you'll get bubbles in the line.

 

[Dr. Bogger]

Factory settings are just a "ballpark", they may be rich on one engine and lean on another. It is okay, to go richer. My 3.3 ran good when the HSN was 5 1/2 turns out, I've read about plenty of people who had to go a turn or two over stock.

That's good info! I'll keep that in mind.

I would have held off on new parts until you sealed the motor and tested that out... Be careful when pulling the carb out. The bottom o ring easily gets cut when pulling out.

Well due to the fact I sealed the original engine and it didn't help solve any issues, I doubt it is a engine leak. But I will seal it anyways, I'm just saying I have my doubts.

That's why I went ahead and ordered those parts. That's the last of the parts that are part of the fuel delivery system that i haven't replaced yet, so once I do that and seal the engine, if that don't fix the issue, then I will make sure to record a video of the t-maxx being blown up for ya'll to see!

The reason I asked about your fuel tank screws is because with one missing or loose it will cause the fuel to foam and you'll get bubbles in the line.

Yeah, that's not an issue for me.. But the fuel tank is gonna be replaced anyways, along with the pipe and manifold.

 

[hulkmaxx]

I would put money on it being a bad fuel tank for sure I have had tanks in the past test good but still not function properly.

 

[hotrodrob]

Finally someone who agrees

 

[Dr. Bogger]

So i got the fuel tank today, and installed it. It started right up, MUCH quicker than it did before. Seemed to idle much better too!

It's freezing out today (I'm back in NY, so its freezing out today), so I didn't have much time to tune it, but I'll be doing more tuning another day.

But all in all, I think the fuel tank was the culprit.

Thanks everybody for all your help!

 

[hotrodrob]

So now you have a spare engine,save the new one for summer and run the old one for winter

 

[Rolex]

Winter is not a happy time for tuning nitro engines.

 

[hotrodrob]

I usually do good unless its real cold,today it was 38 out and after ten minutes I had her dialed

 

[olds97_lss]

Yeah, if you keep them dry and block some of the wind over the cooling fins, they don't do too bad, within reason. Small blocks anyway. Never had good luck in the winter with big blocks though. Too much surface area to keep warm I guess. I still won't run when it's below 30F out. Just too damn cold and things get so brittle. I couldn't help it and ran my revo over christmas... as luck would have it, busted both front and rear bulkheads. I've had a revo (or variation of one) for 7+ years and never broke a bulkhead... EVER! Until 3 weeks ago that is. lol

EDIT:
Is hard to imagine that the revo is an 8+ year old platform... traxxas did a good job with that rig.

 

[hotrodrob]

Wow, revo is that old already! I remember like it was last week when I got a t-maxx the year traxxas released it and Still have that Maxx today,its an antique! I guess.

 

[2revo1maxx]

The revo is about 9 years old. I got my first one in the spring of '05.

 

[romper4444]

Haha when I read the op's original post I knew right off the bat it was the fuel tank. I was going to skip to the last page and just tell u 100% it's the tank. I've ran into this on others rc's when they come to me as a last resort. I figure I better read through the thread so I don't repeat what's all ready been figured out. Sure enough last page u got it. Good for u Op for sticking to ur guns and following thru the problem. Shame on all the guys telling u that u can't tune or to rip a brand new motor apart, ruin the factory seal and end up where u started. When the fuel tank or whatever it may be is the only thing that hasn't been replaced, well it's pretty obvious. I always say to myself when tracing a problem in any case no matter what I'm working on(being a diesel mechanic for me it's big rigs) keep it simple stupid!! People always too quick to make it complicated, or tear into a motor, even a brand new one in this case, lol. Now there's always the exceptions, like a new motor having an air leak, it can happen, it just don't happen very often with good quality products. Always really think it through. In this case it coulda saved the op the cost of a new motor

 

[Phins Fan]

^^Your right however he invested in a new motor before anybody had a chance to help. His choice for that investment and nobody was twisting his arm. Given everyones experiences he asked opinions and we gave them - right, wrong, indifferent it really doesn't matter. At the end of the day theres plenty of PROVEN gurus that will tell you to seal a perfectly new engine before running no matter the quality of the mill you are breaking in. Personally when I experience issues like this and not sure of the cause I always start with the cheapest "fix" and work my way up.Taking some of these small and insignificant steps will allow you to bash vs wrench your new rig. While I enjoy doing both I would always prefer to bash first!!

 

[2revo1maxx]

Before you throw stones Mr. Romper, check post #5, where the OP says this:

"Yes, i checked the fuel tank for leaks, and didn't find any."

What would you think after reading that?

 

[lesclaypool]

Before you throw stones Mr. Romper, check post #5, where the OP says this:

"Yes, i checked the fuel tank for leaks, and didn't find any."

What would you think after reading that?

That was the first thing that came to mind as well. When the OP states repeatedly that he knows how to tune, and his tuning isn't the problem, you'd assume then that he would know that a mechanical problem lies elsewhere. Why go for an engine and the tube of RTV when a tank can be leak tested in 1 minute. But he said he knows his tuning, and he checked everything.

When a guy comes asking questions, shouldn't he assume to get some answers?? These guys on this board know their crap inside and out. The amount of help offered in this thread alone is awesome.

 

[Childresshunt]

I know these guys on here have helped me many times and have saved me some money. The more you argue with their suggestions the less willing they will be to help take any suggestion and use it to your advantage