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T-Maxx 2.5 runs good, then runs bad

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rossb

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My neighbor has a T-Maxx 2.5 and he is having some problems with it. When he cold starts it the truck seems to run good. I helped him tune it and the WOT temps are in the mid 200s with a nearly full tank and the pinch test causes a stall after about 3 seconds. The tune seems to be good. After it runs for a bit all of a sudden it starts to run like total crap. It has no WOT power and it will not shift to second gear. When all of this is going on the temps drop down to the 180s. We tried switching to a new glow plug when it started to act up but that did not help at all. I removed the glow plug and it looked perfect in my ignitor. If the T-Maxx sits overnight again it starts up ok, runs good for a few minutes, and then runs like crap again all of a sudden.

I pulled his motor last night and sealed his back plate and his carb. The little o-rings on the carb and back plate look substandard to me, much less beefy that what is on my S-25. We did not try to start it yet with the sealed back and carb.

Is this common with the T-Maxx 2.5? I checked his fuel line and fuel tank for a leak and I did not find one. I blew on the fuel pressure line and plugged the fuel outlet line at the end where it feeds the carb and I could not feel any leaks. The air filter looks good and there are no leaks at the exhaust. Is there anything else I should check?
 
You say that the truck runs good after a cold start. Does that mean you are able to run WOT without any gurgling? If so then you may be running the mill lean.
 
you need to lean it out a bit, if it is only hitting 180 when going WOT, u definetly need to lean the hsn down.

bryan
 
Sealing the engine seemed to do the trick. It ran good today and it was consistent.
 
Last edited:
WHat did you use to seal the engine? Will any type of silicon do?
 
So, if the Maxx 2.5 isn't getting around the 240-250 degree mark when warmed up, it's running lean?? I'm still learning to tune mine on my own, but it's running good from idle to a wot, at wot, good amount of smoke, about a 2-3 second delay on the pinch test, but the temp is only getting to about 200 when fully warmed up. I only leaned the hsn about a 1/4 turn from factory setting, after that it runs crappy at wot. I also have the lsn at 1 1/2 out from closed. I think I'm just making this more difficult than it really is, but it's easier to tune my damn Harley than this thing!!
 
diavolos said:
So, if the Maxx 2.5 isn't getting around the 240-250 degree mark when warmed up, it's running lean??

No, I did not say that. If you are running lean your temps will be high.

The truck I fixed was just dying when it got up to temp. The temps ended up dropping because it was not revving anymore.
 
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