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T-max 2.5 engine issues

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Old 04-20-2003, 12:39 PM
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eletrick
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Default T-max 2.5 engine issues

I have been having a bunch of trouble with these engines, as of late. They are very hard to get started, even with a glow igniter.
I've spent many hours trying to figure it out.

They also die often, then almost never restart when hot. I thought it was only one of the 2.5's we have, but yesterday at the track, all five did almost the same thing.

Items tried: started fresh with factory carb settings, dialed in for many hours. Changed fuel tank, and lines. Removed carb, changed orings and cleaned. Thought it was bad fuel, but the Savage's run fine on it, even still opened new bottle.

I think this is a piston and sleeve issue, I would say these engines have about 2-3 gallons through them. And if it is a piston and sleeve issue, these engines are not as good as they claim.

Anyone else having these problems?

Richard Newman
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Old 04-20-2003, 01:12 PM
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JBrannon
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Default T-max 2.5 engine issues

The factory stteings are too lean, back the main out 1 more turn and try again.

Joe
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Old 04-20-2003, 01:30 PM
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eletrick
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Default T-max 2.5 engine issues

thats not it. tried the needles (both) from both extremes. I have benchmarks from all the trucks on our track since they were new, this is a wear issue ( I think).

They ran to good to just fade out like this. The fuel line thing I doubt is a fix (traxxas board), if the fuel line was the deal, it would
have been a problem all along. I'm going to try it, since I've been trying everything else, one more thing can't hurt!

If it doesn't work, I will order a piston and sleeve. Its funny traxxas's board has a "how to" section on changing the piston and sleeve, and has since the trucks release.

Richard Newman
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Old 04-20-2003, 04:55 PM
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Default T-max 2.5 engine issues

Okay, I replaced the fuel tubing, in a loop, just like the
other guy did. Still has a starting issue. I put the needles back to factory settings, and still nothing.

Broke down the first engine, major wear. Has cavity on one side of the sleeve, and the reverse mark on the piston. The rest of the
inside of the engine looked good.

I will order the parts Monday and post what happens next!
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Old 04-20-2003, 05:48 PM
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Default T-max 2.5 engine issues

Yep I feel the same way eletrick! I got sick of going to the track and watching all those nice buggies run laps for days without ever stalling or not idiling. I went and bought a Sirio .18 but
I havent broke it in yet. The Sirio has got to be better than this
engine.
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Old 04-20-2003, 06:03 PM
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Default T-max 2.5 engine issues

I'm going to rebuild this one, this time. But if this is the life time of this engine, the trx15 was a longer lasting engine. Hands down.

Richard Newman
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Old 04-20-2003, 06:15 PM
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Default T-max 2.5 engine issues

I had similar problems to you for a long time and it was quite frustrating for me.

What ended up working for me was setting the high end very rich. I ended up with my needles set at 2.5 low end and 4.5- 5 on the high end.

I don't think it's an engine problem, but more of a carburetor problem. I say this because I was at the track yesterday and a guy was having all kinds of problems with his T-Maxx. It turns out his was too rich and to get it to not stall when giving it throttle we had to bring the high speed needle all the way in to 2.75 - 3 turns out. Anything more and it would stall from too much fuel.

Also if the low end it too rich it won't start, it will just spit fuel out of the exhaust. On this guys T-Maxx we had it at 2 turns out and it was too rich and wouldn't start. With it at 1.5 turns out it would start with no problem.

Basically there is no standard setting for the T-Maxx. It seems that settings vary wildly from Maxx to Maxx. Also don't forget that temperature and elevation make a big difference in needle settings. The T-Maxx seems to be very vulnerable to any changes in the weather or elevation.

I think the internal engine problems people are starting to see is because of the wild tuning that they do to get it to run. They go from very rich to very lean and back which can be very hard on an engine.

The other fixes are to run a longer exhaust pressure tube (with a loop near the tank) and a longer fuel tube both that go around the back of the body posts to the other side of the engine. This keeps the fuel from heating up as much before it gets to the carb, which may be part of the air bubbles in the fuel lines that many people see.

It's frustrating but it can be worked out. When I had my T-Maxx at the track (in the process of trading it for two trucks) I was able to run a full tank time after time with out it stalling, unless the truck flips upside down and the marshals don't get to it quick enough.
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Old 04-20-2003, 07:02 PM
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Default T-max 2.5 engine issues

I've had these five trucks running like a clock, since they were released. The tuning is not an issue, but, I have spent many hours going from extreme to extreme to prove this is not the case.

I've been in r/c for many years, setting this carb is no problem.
These trucks ran to good, to start having the "t max flu".
And with other trucks doing the same thing, it leads me to believe its a wear issue (especially after tearing one of these down).
The trucks have about 2-3 gallons of fuel put through them.

The fuel line thing sounds good and all, but when the engines cold, this is going to do nothing. but thats just my 2 cents worth.

Richard Newman
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