stmaxx25r

Ok, I finally got my Sport-T-Maxx tuned pretty good; at least on the HSN. I am now having trouble with starting the truck initially and especially after a rollover. I have to prime the engine and then let it "clear out" while cranking on the EZ start the whole time. I killed a brand new 7.2V (discharged) while trying to start my maxx. I then noticed the glow plug light on my EZ start controller wasn't lighting up. I have now killed 3 glow plugs in less than 2 quarts of fuel. What is causing this? What are some possible solutions? The one we killed when getting the tune right lost its upper glow ring. I have not checked this latest one but it still works, just not correctly. I assume the coil is partially out as well. I have a Traxxas Sportmaxx with the 2.5 Racing Engine (not 2.5R) and a factory 2spd tranny (came with truck). I also use 20% Traxxas Top Fuel and McCoy something 59 glow plugs. Thanks for your help!

DGMaxx

Running overly lean or rich can ruin a plug. What does the plug look like and what does the element look like? Have you checked the ground wire to make sure you have a full circuit? If the plug is wet you are too rich, if it is dry and element looks fried you are too lean. I've always had good luck with either traxxas plugs, OS LS3, or Duratrax LR3. Not sure if they will work on the 2.5 (.15) motor.

Danju

yeah for quite some time i had the same prob as you. every time i shut off the engine, a plug blew. i blew 6 plugs in 2 weeks and i finally figured i was running too lean. youve gotta keep a good eye on those traxxas engine, as they are very sensitive to each 1/12 of a turn you make. for traxxas engines, i recommend making very small increments when tuning.

twomanytoys

You can also try a colder plug.

ttoks

a colder plug will just retard his ignition timing and not fix the problem, that is a cover up for a deeper problem, i am willing to bet the low speed needle is to lean, even though you hasn't adjusted it yet, adjusting the high speed will inadvertently do the same to the low speed, so try richening the high and low speed needle slightly.

crazzyrevo

There is a nother reason for glow plugs like that .It good that you have a lot of play in your connecting rod/con rod ..

stmaxx25r

My plug looks dark and wet. It is not gray, glazed or fried looking. I believe I am running rich. Is this a LSN or a HSN adjustment I need to make? Should I use a different plug manufacturer? Thanks for the info!

IOWAREVO

Dark & wet is a sign of too rich. When my 2.5R was still running I used a MC-59. This plug seems to work well with most engine except the OS.


Here's a general guide on reading plugs:

1. Wire and surrounding bottom of plug wet, with like new shiny wire = rich side of optimum power
2. Wire and surrounding bottom of plug starting to dry and wire starting to gray = very close to optimum power
3. Wire and surrounding bottom of plug dry, wire totally gray but not distorted optimum power
4. Wire and surrounding bottom of pug dry, wire distorted = slightly lean "DANGER!"
5. Wire and surrounding bottom of plug dry, wire broken and distorted or burnt up = extremely lean possible engine damage!

stmaxx25r

Thanks for the info. I will tune my truck a little bit more lean. Is it the HSN and LSN? Or just one of those? I am thinking just the LSN since my truck doesn't take off very well.

IOWAREVO

Sounds like the LSN. Do a pinch test. (pinch the fuel line close to the carb.) If the engine dies immediately the LSN is to lean. It should rev up then die in about 2-3 sec. If it takes longer the LSN is to rich.

DGMaxx

LSN adjustments will help your starting but you should take it back to factory (HSN 4 out, LSN flush, and carb at 1mm). Start with the HSN, then tune the LSN, check your idle, back to HSN and then last shot on LSN. Make sure to keep an eye on temps when starting out since factory is just a base to start from, you could need to go rich or lean from there.

stmaxx25r

One thing about the "pinch test" is that my fuel line going to the carb is really short and hidden behind the engine head. I can't even begin to reach it to pinch the line shut. I bought some extra fuel line and I am going to extend the line. Will extending the line to the carb make any kind of impact on my trucks performance, reliabilty or tunability? Anyone done this on the 2.5? Got pics? Thanks again.

NitroVenom

^^ I have and all a longer fuel line will do is alow the enginge to stay running upseide. This is because when the truck is upsidedown, the fuel pickup on the gas tank is at the bottom so when its flipped over, there is no fuel getting picked up. So a longer fuel line will just alow the extra fuel in the lines to the carb and keep it running until you flip it back over. It wont have anything to do with the tunning. Just remember to prime the motor or it will take a while to start.

stmaxx25r

Thanks! I was wondering where you ran your line to keep it out of the way? Any pics?

Brent Davis

If you are blowing them alot, re-set your mixture screws to the factory settings which is 4 turns out from fully closed and set the low side to flush. If it then keeps blowing plugs, pull the back plate off and look to see if the rod is rubbing the engine block, if so, then it is throwing aluminum up to the plug and causing it to blow. I had a 3.3 that was doing the same thing as yours. I set the needles back to factory and it was still blowing plugs. I took the head off and the piston showed no signs of anything but when I took the backplate off, the rod was rubbing the block bad abd that was when I further inspected everything and saw specs of aluminum at the head and in the plugs.

Just my .02