please help with engine prob

[Mach.21]

Ok, I'm perty good with tuning engines but this one threw me for a loop. Its a stock traxxas 2.5 t-maxx engine (on a traxxas t-maxx of course) i can't figure it out... i got it and it didnt run so i took every thing apart and all and the compression is good and i can't get it to stay running so of course i put all the needle setting to breakin settings which is 2 1/2 hsn 1 3/4 lsn and when i get it stasrted itll run for about 1min and 30 seconds and itll die and it is about 400 degrees(i know that is way to high) Just help me with this prob please :shrug: :shrug: :shrug: :shrug:

btw its also 14degreese f here

 

[olds97_lss]

More than likely, rolex will speak up, but in the mean time here's my take on it...

Take the carb and backplate off, clean the contact points, apply RTV silicone sealant to get an air tight seal on the contact points of the backplate and carb neck. Pull off the engine head and make sure you have at least 1 shim between the head and piston sleeve. Without a shim, your going to get horrendous air leaks no matter what.

Check the fuel tank for cracks. Empty it of fuel, put clean lines on it. Pinch one line with your fingers to seal it, then blow pressure into the other line. While blowing (try to build up pressure inside the tank, pinch the line your blowing into to seal it as well. Hold it for 10-15 seconds, the let go of one of the lines. You should hear a hiss of air come out. If not, you have a leak somewhere. Take the tank off the truck and submerge it in water while pinching one line and blowing into the other to see where the bubbles come out.

Replace the fuel line. Check in-line fuel filter for leaks (if you have one).

Answer a few questions:
What fuel (brand, oil/nitro percent)
What glow plug
How cold is it where your running it

If you have checked these things, then just wait for rolex... He's the resident genius with the 2.5 engine.

 

[Rolex]

Okay, I'm back......I was outside for about an hour. Sorry I'm late.
Before you pull things apart, RICHEN your LSN. If that's too lean, that engine will go over 300 in 3 minutes at idle. When the LSN is too lean, NOTHING you do with the HSN will bring it to a good temp.
When you richen the LSN, you'll also have to adjust the idle. There's a little 'happy' spot where those 2 needles play well together. By the way, do the idle adjustment with the throttle trim all the way down. Only raise the trim for cold starts and warm up.
I hope you have a temp gun. Let it idle, and keep checking the temp till it stabilizes and doesn't rise any more. On a warm day, it should be about 200-210, somewhere in that ballpark.
When it's running, and the temp stays good, get back to us here for the final 'tweeks'.

 

[olds97_lss]

I guess I just like taking stuff apart...

 

[Mach.21]

well i have done the fuel tank thingy its good no leaks..
The glow plug type isTraxxas 3231 Heavy duty long glowplug and gasket Medium temp.

The fule is Byron Race 20%

And its 9*F here

So i should also put rtv silicone on the carb o-ring area and the back plate

 

[Rolex]

Don't tear it down yet. Try what I suggested, then get back to us. Once I know if it's running there will be other symptoms to indicate an air leak, if, in fact it even has one. At this point, if you tear it all down and seal it, you might still be dealing with the same problem. There's an order of checking things when troubleshooting, and with that engine, it's almost always the carb settings.
Trust me on this. At the track they've started calling me "The Wizard of Two Five" meaning that I can get some VERY pesky 2.5 traxxas engines to start and run right.
Oddly enough, I've never had to touch the 2.5 in anyone's Revo.

 

[atye]

the 2.5 factory setting is 4 turn not 2 1/2 low speed is flush with inner housing

 

[Candyman]

Good catch atye. I just noticed his settings. Factory on the HSN is 4 turns out. And low speed is flush. Good eye....

 

[.21Rc10GT]

That may be a problem. The 2.5 doesn't really need much tuning past factory settings. Maybe a little leaning, but not much.