T-Maxx Troubles

[cjquadrider]

My T-Maxx 2.5 just got out of the shop to get completly fixed. Took it out today and it started up with a bit of priming and about 5 seconds on the starter. It ran for a bit and shut off, it was hard to start again. but once i did, it ran once again for a bit and started to bog down, once i stopped, it just shut off, i checked the temp, it was a whopping 300 degrees :\ i tried starting it again once it got down to about 130 degrees, and it wouldnt go, it was cranking over just fine and was constantly on the verge of starting, but just would go. The battery in my igniter and starter were just charged and the glow plug is brand new. I have no idea what is wrong with it. Any thoughts?

 

[Nitro4910]

You need to tune it, your running lean.

Tuning flow chart.
https://www.rcnitrotalk.com/forum/showthread.php?t=60832

 

[cjquadrider]

Are you sure? Thats sounds right, but i just got it back from the local hobby shop and one of the main things they did was tune.

 

[SC-REVO]

High temp over 270 ( danger-danger ) if your at 300 you are lean, no question. You need to tune that carb. But it back to factory spec. He gave good advise. Set you HSN first, the LSN, then idle. It need fuel to run and lube rotating assembly.


"It's more than a hobby...it's an addiction!"

---------- Post added at 12:55 AM ---------- Previous post was at 12:54 AM ----------

Oh just cause they said it was done, I would still double check it, just to be safe.


"It's more than a hobby...it's an addiction!"

 

[cjquadrider]

Thank you guys so much. I will do that and see what happens.

 

[cjquadrider]

I got my truck out this morning, and tryed i
Using that table from the link you gave me. It started up easy, didnt run for a minute so i did what it said. And i couldnt get it started again. But if i wait a long while then the engine will strt right up again. I have no idea what the problem is.

 

[HobbyGuyMod]

You may be flooding it a bit. You might have went to far and you are now running rich

 

[cjquadrider]

I dont know if i was flooding it. It definately sounded like i was. But i turned 1/8 turn clockwise. Which is leaning it right?

 

[Ballen]

everybody else gave good advise but if it did not work that means something else is wrong.

just because it was at the shop does not mean they checked it out real good.

I took mine to the shop and asked them to tune it because I could not get it .they set it back to factory ,adjusted it a little never did a test run and sent me up the road .check the compression .take the motor off leave the glow plug in and see how easy it turns by hand.
If it turns kinda easy thats low compression.
How much use has that motor had. Sounds like the same problem mine had when it was beat,toast , crispy.when a motor is worn out ,it will start and run for a min or two and then as soon as it gets warmed up it starts to boog down, motor dies,and then won't restart untill it is compleatly cooled down .when it gets heated up everything expands and you have less compression.What happens when it gets cooled down the sleeve contracts and it has compression again. Piston/sleeve $45-60
or resize the old ones for a toatal of abot $26

 

[Phins Fan]

How about an airleak? Theres plenty of people out there that end up finding 1 and fix all the headaches

 

[cjquadrider]

That sounds like it is very plausible. I'm just going to take it back to the obby shop and tell them that they didnt complete their job. I hope i can get it going good soon, if not, i will probably just upgrade to the 3.3! Thanks everyone for your advice and i love that chart. I will definately use it in the future.

---------- Post added at 7:49 PM ---------- Previous post was at 7:48 PM ----------

their might be an air leak, i know the engine does leak nitro. and i told the hobby shop to fix that, guess what, they didnt. so would an air leak also be associated with a nitro leak?

 

[Kyleb]

I found the 3.3 Trx more finicky and harder to Tune Maybe you should keep the 2.5 on it and try to learn how to tune first. If you get a new 3.3 and dont know how to tune it will greatly affect the engines life span.. Just a thought

 

[cjquadrider]

I somewhat know how to tune. But when my dad bought the truck new he broke it in well but never tuned it. So from there, it went downhill my da never let me touch it. And now I'm basically the only one to touch it and havent had a very good time trying to clean up his mess (tune it properly after many years of neglection).

 

[SSX]

so would an air leak also be associated with a nitro leak?

not necessarily but its not helping matters.


when i stripped my eb4 down for a total clean/rebuild i had problems starting the engine. took a while on the pull start but ended up blowing down the fuel tank pressure hose to get the fuel up to where it needs to be....fired right up.

problem was my main fuel line was too long really,and i had a poor seal on the exhaust manifold...... it made priming a right pita.

an air leak might be plausible if your not getting enough pressure in the fuel tank to drive the fuel up to the carb to keep it running, that will cause some issues, so i would change the fuel and pressure lines.

check the carb is sealed/seated correctly.

are you using an air filter?

 

[SC-REVO]

Ya I agree, next step for me would be checking for leaks, I would do the soapy water test. Or like you said "years of abuse" I would jump in by replacing or reinstalling several things. Remove your resonator inspect boot-clean pipe and header install with new ties, check psi line from resonator to tank- I trim a small portion from each end, check the nipple fittings in tank and make sure they are snug-careful not to over tighten, get close to tank lid and listen for noise of seal releasing, check fuel line going to carb. The carb sometimes (ok all the time on Traxxas) leak a little making it hard to tune. You can use high temp RTV. When it cranks is the nitro smell really strong and smoke?

"It's more than a hobby...it's an addiction!"

 

[cjquadrider]

I can smeel the nitro a bit. But no smoke. Just straight nitro. So i definately am flooded.

 

[SC-REVO]

Yes. My Jato is a pain in my... Anyway it will turn over 6 to 8 times ( when cold ) before it even acts like it will crank. But I know this, so I resist to temptation to pull the throttle until it fires. If I pull it to soon its flooded.

"It's more than a hobby...it's an addiction!"

 

[SSX]

i flooded mine out this afternoon, i had hydraulic lock for a sec....had to remove the glow plug and pull the starter a few times. put the glow plug back in and re-primed...fired right up.

if you can smell fuel from the exhaust outlet and its not smoking at all you are defo running way too rich or your glow plug is goosed.

these little engines only need fuel, air and compression to run so the problem should be fairly simple.

might be worth doing a compression test.

 

[cjquadrider]

Half of those things that you said, i have no idea what they are. How would i go about doing a "soapy water test"?

 

[SSX]

Half of those things that you said, i have no idea what they are. How would i go about doing a "soapy water test"?

Step 1.

Be sure that the high-speed needle is open at least two turns out and the throttle is at fully open.



Step 2.

Install one end of the fuel tubing on the carburetor nipple. You're going to be blowing into the other end of the tubing to pressurize the engine crankcase.



Step 3.

Place your thumb over the carburetor intake to prevent air from escaping, then blow into the fuel tubing while brushing soapy water around the base of the carburetor, on both sides of the pinch bolt, around the fuel fittings, at the high and low speed needle valves, around the front bearing and even around the back plate.

If any bubbling occurs you've got an air leak.


common air leaks seem to occur around the carb pinch bolt. Applying a dab of rtv/silicon over both exposed sides of the pinch bolt will fix this type of leak. RTV is also great for sealing any leaks around the base of the carburetor. Simply remove the carburetor and run a small amount of RTV around the base of the carb where the leak occurred. Reinstall the carburetor and allow the RTV to ooze out between the crankcase and the carb body. For leaks around the high-speed needle valve fittings, usually re-tightening the high-speed needle assembly will take care of these. Leaks directly at the high speed or low speed needle usually means there's a damaged O-ring that must be replaced. Many people don't realize that the front bearing can leak air. That's why nearly every high-end engine uses a rubber sealed front ball bearing.