Bought a tmaxx roller and put a new 2.5r engine in it, tons of problems, engine has been sealed new carb rebiuld kit, biggest problem is the inconsistanse. Todays problem was it ran great then acted like it was starving four fuel up top, then it would run great finally stalled wouldnt stay running without ezstart insertted Noticed what I thought were air bubbles in fuel lines. Tested glow plug, glowed bright orange. Still wouldnt stay running without ez start. I put new fuel lines on it yesterday checked fuel tank for leaks notjhing test drove it no problems yesterday. Now today this, its not the tune its way bto erractic, Iam an exact kind of guy and mechanicly inclined, this erractic engine has me baffled, still has good compression thanks for any input

I was having kind of the same problem with my jato 3.3,it ran horible kept ruinning plugs today,i was told it's the crappy fuel,wich i never thought about,so i was relieved.I was using 33% traxxas fuel.If you are maybe it's the junky fuel.

Not the fuel, its also being used in my slayer and i gave my friend a couple of tanks, Thanks

i had the same problems except with the easy start i used a glo igniter and the pull start i fixed mine with an mc-9 plug and 30% oddonel fuel i had to retune it after the change but have not had a problem since then except consistant runs and wheelies on demand hope this helps keep us posted on the situation

You have tuning issues, reset your needles to factory

When the fuel mixture ("tune") is all over the place, thats usually indicative of an air leak. You said you sealed the engine and rebuilt the carb. What exactly did you do to the carb to "rebuild" it? What did you seal on the engine and what did you use?

If the engine will not stay running unless you keep the glow driver on it, the low speed mixture is too rich. Air bubbles in the fuel lines means air is getting in somewhere. Perhaps the threads are stripped or the o-rings squished out on the carburetor (the two hex-keyed plugs will sometimes leak even if the o-ring is in place). I would put a drop of CA glue on the threads of the 2 plugs in the carb. I would also verify the main needle/fuel banjo fitting is good and snug. Next, I'd check the tank for leaks. Plug one fitting and blow into the other with the tank completely submerged in water and note any bubbles. Any bubbles means something is leaking whether it be the tank or the lid.

The fuel system is a sealed system, so naturally if there are leaks it will not perform properly. If you didnt push down on the carb while tightening the pinch bolt, pull the carb back off and clean it up. use a very small amount of RTV silicone on the top and bottom of the O-ring and re-install. Push down on the carb so there is good pressure on the o-ring and re-tighten the pinch bolt. Remove the fuel filter if present to eliminate it as a problem. With a properly installed carburetor, good fuel, good glow plug (try a new one?), and proper needle settings the engine should run consistently.

When tuning the carb (I dont like factory settings as a broken-in engine tends to not run very well if at all because its so rich) I would start with opening up both needles 1/2 turn from where they are and see how the engine behaves. If its obviously rich, lean the main needle down until WOT is nice and clean. Once it sounds clean at WOT, work the idle mixture needle until you get a nice clean transition from idle to WOT. Usually leaving the engine idle for 5-10 seconds and punching the throttle will give you a good idea where the idle mixture is. If it stalls, its lean and if its slow to open up and clean out its too rich. (also if the rpm's drop off slowly and eventually stalls out the idle is too rich)

What kind of fuel are you using, and what kind of glow plug (brand/#)?

Iam using 20% traxxas, I got it running good today I had to richen hsp out 4.75 turns from closed, stock is 4. lsp 2 out from closed stock is 1.75. I sealed back plate, carb, just like you suggested. carb rebluild was, new carb body and all new o rings. I use traxxas glow plug 3332x.. fuel system isair tight, thanks for input

First off, I'd dump the Traxxas fuel. It is not that great. I'd suggest using a better fuel - Odonells, Byrons, Blue Thunder, or Trinity Monster HP are good ones. I had many tuning problems with TRX fuel, but they went away with better fuel. Next, on the glow plug... if you meant 3232X which is a medium plug, it will work okay but you should use a Hot plug like a McCoy MC59 plug instead. Also, if you havent changed the plug in awhile, perhaps trying a new one will cure the trouble along with some better fuel.

You say the fuel system is air tight - did you physically check the tank by dunking it under water to verify it isnt leaking? It may look fine, but one small pinhole could cause issues. If it is fine (and I believe that it is, but you have to troubleshoot the whole system part by part), try different fuel and different glow plug. Note any bubbles in the fuel line. If there are still bubbles in the line while the engine is running, you have a leak somewhere still. If not, then you need to tune it better.

If I were you, I'd be getting some Byrons Gen2 20% nitro car fuel, and Mccoy MC59 glow plugs. You should be able to find a quart of it, otherwise get some Odonnels, or Blue Thunder. Set your main needle to 4 turns out, and set your idle mixture to 2 turns out. The engine should start and be very rich. Set your main needle, then set the idle needle only after the main needle is set for a clean WOT throttle. You will pull your hair out if you keep using Traxxas fuel. Trust me on this one.

Your right on glow plug number, thats what I use. I also have a slayer pro, no problems with fuel,maybe Ill try other fuel,still got 3 quarts. Heard on several forums thats its no good. Slayer is set at 4 and 1.75, runs great any weatherand that whats had me so baffled about the 2.5r on stock settings(same as slayer), runs good first half tank, then getst hot even in 40 degree weather. windshields gone for cooling purposes. Starting riching hsn Iam at 4.75 and It runs alot better, lsp at 2. Another problem that took me a few daysto figure out was a serve bogging, only sometimes. I was getting stuck in 2 gear, Tighting set screw up, fixed that but wouldnt shift. Some tweeking and I think Ive founds sweet spot. Unfortuntatly got a new one coming from ebay. along with spur gear upgrade. I did several makeshift leakdown tests for engine and fuel tank. Put my air compresser on fuel nipple closed off other one, took a fair amount of pressure to pop fuel cap seemed like a good seal. soapy water around engine while blowing into it(not with compressor) nothing. Thanks for detailed response, I bought this as a project, learning alot, but could have bought a new one with the money Ive spent. This hobby isnt going anywhere for me so its good to get your hands dirty. I cantbelieve it took me until Iwas 42 to buy a good rc. Starting to get into heli a bit , wife just rolls her eyes..</p>

The cap on the tank may be sealing fine, but I'd be more concerned with minute amounts of air being able to seep through a crack in the tank's seam or around the base of the two tank nipples. You should check your fuel tank's seal by submerging it in water. You will not be able to "hear" an air leak nearly as well as being able to see it.
The 3232X plug works okay, but I like the Mccoy's better. I get more use from them vs. the Traxxas plugs which I used for years. Using the proper heat range plug for the fuel being ran is pretty important to longevity as well as performance. As long as you keep your mixture right, plugs should last a long time. Some guys have run the same glow plug in Aero engines for multiple years and multiple gallons of fuel. In some cases, they may still glow but if enough of the filament is covered in combustion byproducts it will not ignite methanol properly as the platinum on the plug's element is what reacts with the methanol in a chemical reaction. (The combustion process deposits micro specs of "stuff" onto the coil much like carbon on a spark plug - enough of it and the plug will fail to perform optimally)

Don't feel bad about the wife rolling her eyes. To mind, its just a hobby. For me its more of a passion. By no means is it the end-all be-all for my spare time but it helps me relieve the stresses of everyday life that other things just can't do.

Some good glow-plug reading:
http://www.scootworks.com/rdrc/gloplugs.html
They don't talk about too many car plugs but the principles and cross-reference chart is good to have. I printed it out and set it aside for easy reference.