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TRX 2.5 help!!!

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chrisexv6

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OK, finally got my truck all back together after upgrading almost everything :) (except the engine, maybe thats the mistake!!).

Now it will only run for 1/4 tank or so, and it cuts out. Hard to restart too, so my guess is overheating. However, I can't figure out why.

Everything has been sealed (backplate, carb, carb endcaps, etc). Everything is on tight (head screws, manifold screws, etc). Fuel lines and tank checked out OK under pressure. The only weird symptoms I have are glow plugs with shiny but crushed/broken elements, and the top of the piston looks a little darker than normal (a dark brown on it instead of a golden brown, it also seems to be "sludgier" than normal, the stuff on it is thicker than I'm used to seeing).

LSN is stock, maybe a tad on the rich side. HSN is 5 turns out (I have a Sirio pipe on the engine, so I figured Id run it rich to make sure it doesn't cause overheating).

It basically gets real hot, real quick, and I can't figure out why. The only other thought I have is possibly something binding up in the drivetrain, but when this thing runs, its runs like mad!!! Really fast (possibly indicating a lean condition, but with my needle settings, I can't see why), no trouble getting it into 2nd, etc. It has a FOC, so I can only spin the spur opposite of the engine when its just sitting there, but when I do it spins freely and doesn't feel like its having any trouble.

Sorta disappointed, but I also have a Fantom on order. id like to get the TRX running if I can, I want to prove that there is nothing else on the truck causing this, so that I can be sure it wont wipe out the Fantom as well.

Thanks in advance!!!
-Chris
 
Originally posted by chrisexv6
OK, finally got my truck all back together after upgrading almost everything :) (except the engine, maybe thats the mistake!!).

Now it will only run for 1/4 tank or so, and it cuts out. Hard to restart too, so my guess is overheating. However, I can't figure out why.

Everything has been sealed (backplate, carb, carb endcaps, etc). Everything is on tight (head screws, manifold screws, etc). Fuel lines and tank checked out OK under pressure. The only weird symptoms I have are glow plugs with shiny but crushed/broken elements, and the top of the piston looks a little darker than normal (a dark brown on it instead of a golden brown, it also seems to be "sludgier" than normal, the stuff on it is thicker than I'm used to seeing).

LSN is stock, maybe a tad on the rich side. HSN is 5 turns out (I have a Sirio pipe on the engine, so I figured Id run it rich to make sure it doesn't cause overheating).

It basically gets real hot, real quick, and I can't figure out why. The only other thought I have is possibly something binding up in the drivetrain, but when this thing runs, its runs like mad!!! Really fast (possibly indicating a lean condition, but with my needle settings, I can't see why), no trouble getting it into 2nd, etc. It has a FOC, so I can only spin the spur opposite of the engine when its just sitting there, but when I do it spins freely and doesn't feel like its having any trouble.

Sorta disappointed, but I also have a Fantom on order. id like to get the TRX running if I can, I want to prove that there is nothing else on the truck causing this, so that I can be sure it wont wipe out the Fantom as well.

Thanks in advance!!!
-Chris
Click to expand...


Ok first things first. What are you talking about with the glow plug? Is that the result after you are running the mill? If so I am confident to say you are WAY TOO LEAN! Why don'y you richen her up a bit or better yet bring it all back to factory settings.
What is your temp in area? If it is hot like in the 70's and up use a medium plug. what percent fuel are you running? Second do you have a temp gun? No. GET ONE!

IMO just cuz the mill gets too hot doen't mean its a paperweight.

Let us know so we can help you!

Jon
 
I have a temp gun, way too hot (330!!!).

As far as the plugs, I've read that a crushed element in itself does not imply too lean. Either way, I have the LSN at factory, and the HSN too rich. If anything, it should be too rich the way I have it right now.

Weather was low 60s, very little humidity. Running a brand new (well, three after i broke two of them) MC-59 plug.

Might not be a paperweight yet, but I think its getting close!!!

-Chris
 
What percentage fuel are you running? The compressed coil in the plug indicates retardely high compression, too much for the engine to handle.

Did you happen to take the head off for any reason? If so, did you put the head shim back in? Are you using an aftermarket cooling head?

To high nitro content (>20% is to high for most applications) will also cause to high of compression which will crush the glow coil.
 
Nope, stock head, with the shim intact. 20% Nitro (Trinity Monster HP to be exact).

The *only* thing different about the head is that I changed to one I had from a used TRX that I bought. The shim is intact however, and is in place.

I assume Traxxas didnt change the head design at anytime, so I dont see why this would make a difference.

-Chris
 
That's weird man. Do you have a temp gun? Then all I can think of is to damn lean.

But I had a bumb 2.5, so anything I did to it didn't do any good anyway.
 
Did you seal the engine with a sealant? copper silicone stuff?or some kinda of fuel proof sealant?

I did thi s with my mahc .15 being really carefull, I thought It would not have aleak and run like a champ. Turns out when I screwed everything in, some of he sealant got inside the engine. Cleaned it out, and it ran great.
 
I used Ultra Copper. When I pulled the backplate off, I noticed that some got on it, but it was on the round part that pushes into the block. I dont think it would affect anything, but I guess you never know!!

I'm still searching for other possibilities. Any good suggestions on checking the drivetrain for binding? The truck rolls freely, but I notice if I put it on one side and spin the front wheel (say the front left), the rear left also spins, but it sounds a tad noisy and it doesn't spin as fast as just turning the front or rears together. Dont know if this is normal, or if it indicates a larger issue.

And any other engine advice would be helpful too :)

-Chris
 
you mean richen :)

but what I dont understand is that I was so rich to begin with, why was it overheating.

5 turns out on the HSN and factory on the LSN should NOT be overheating.

-Chris
 
I think that all the suggestions are good and valid but I wouldn't run it until you are pretty sure you have solved the problem because 330 will burn up a mill in no time flat. Is it possible you tightened one of the needles so tight that it messed up the needle and isn't giving the proper amount of fuel? Good luck.
 
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I've also had my needles walk on me while the engine is running. The first time I saw it was on a friends maxx with a 21 thunder tiger on it. We would fire it up, it would have great power for about 2 minutes then all of the sudden, overheat and die. So, we would back the screw out 1/2 turn and try again. Eventually it dawned un us that the screw was screwing itself in.

I had the same thing happen on my OS 21 RG. Except mine was walking out instead of in. So it would get so rich that it would sputter out and die.
 
I'm not 100% positive, but I might have found the issue.

Someone must have broken into my home and tore down the 2.5, and when they were nice enough to put it back together for me they put the backplate on upside down.

Serisouly though, what are the implications of the backplate being on upside down? Right now I'm guessing it all makes sense..........the backplate has cutouts to "finish off" the ports for the engine. If they werent where they should be, it was in effect reducing the displacement of the engine, causing too high compression, causing a busted glow plug or three. At the same time, it was hindering the flow of oil back into the sleeve, causing the overheat.

Sound about right?

-Chris
 
Or it just caused you an air leak. I'd check the bottom of your piston. Normally there's a cutout for where the backplate goes in to clear the piston skirt. It's been so long since I've looked at a 2.5 I don't remember though. You may have damaged your piston a bit which would obviously cause some issues.
 

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