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t-maxx feul help -
11-05-2005, 12:27 PM
hey guys I have a t-maxx and when i go to take off i have the throotle open fully and it slowly moves and then it takes off like crazy so I sent it to my hobby store and they tuned it and it did the same thing. now the feul I was using was traxxas top feul and it is about three weeks old and i noticed inside the feul bottle there was water bubbles in there. so if I get brand new feul do you think it will help or not.
thanks, traxxas thrasher 
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11-05-2005, 01:03 PM
its always good to use fresh fuel. 3 weeks in the can is fine as long as you always tightly close the cap. 3 weeks in a fuel bottle not so good. See, the fuel wants to suck all the moisture out of the air, keep it closed to keep it fresh.
Is your hesitation/boog happening after you idle for a few secs or every time u open up. Also does temp make any diffrence I/O does it change from cold to hot? Does it die out? 1 more, is this the trx2.5 motor? MBX5T - O.S. MBX5R - Novarossi Nomadio
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11-05-2005, 01:15 PM
the engine im running is a 2.5 and my dad went and picked me up some new feul on his way home from work so i tried it and it works a little better it isnt towing any more. it doesnt really die out but when i let it idle for 5 or more seconds it takes off a little slower but it isnt acting like its towing something anymore. I also think my engine is close to needing a rebuild or whatever because when i drive I have the throtle open full all the time which I need to stop and I have had 2 gallons through it. It also doesnt wheelie anymore even in the grass. like I used to have a hard time keeping the front end down.
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11-05-2005, 01:17 PM
Fuel is spelled "Fuel"...And an engine that is 2 gallons old shouldn't need a rebuild unless you really screwed up.
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11-05-2005, 01:23 PM
well I broke it in the right way according to traxxas and I used 20% "fuel" jk.
and I had my hobby dealer tune it. but it also could be because of my transmission why its not pulling wheelies. the shaft that holds the spur gear is bent a lot.
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11-05-2005, 07:52 PM
I figured it out my engine is bad the piston it rbbing against the sleeve and gets stuck at dead top end almost like it has never been broken in before. too bad cause I have only had 2 gallons through it and it is bad.
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11-05-2005, 08:01 PM
if it gets stuck at TDC then that means it still has good pinch and does NOT need a rebuild.
either that or you have some major scrapage on the piston/sleeve causing it to get stuck
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11-05-2005, 08:17 PM
Your motor should be tight at the top of the stroke... thats the "pinch" and is there to seal the combustion chamber.
I think Revo2k meant running way to lean or running without an air filter. At 2 gals your motor should be fine... I would set the needles at the factory settings as found on the traxxas page or atleast check where they are (Take note where they are now so you can put back if needed) then tune for performance as shown on that cd/dvd that came with the truck. Also make sure you check things like slipper being too loose or something binding in the driveline. the trx motor is a hard one to kill. take your time and check these things out. learn to tune your motor yourself under driving conditions. I cant see a hobby shop guy running a few tanks threw the truck to tune it properly. Also remember, a change in weather=a change in tune. Right BOYZ? MBX5T - O.S. MBX5R - Novarossi Nomadio
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11-05-2005, 08:22 PM
I think it has a little scrapage on the sleeve because i looked at the sleeve and there are parts where you can see that it was rubbing and also when i would go to take off I would have the throttle open full and it would act like it was towing something and the take off like a bat out of hell.
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11-05-2005, 08:27 PM
mx kevin when i would go to take off I would have the throttle open full and it would act like it was towing something and then take off like a bat out of hell. it wont wheelie for crap but it still has great topend great for bashing
  but not so great for racing 
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11-05-2005, 10:13 PM
Get the engine up to operating temp, and do the "pinch test"... Pinch the fuel line about 1 inch from where it enters the carb, and PAY ATTENTION to what happens. Count the seconds till it dies. 3 seconds, with a slight rise in RPM just before cutting out is perfect. If it dies in under 2 seconds (which I HIGHLY doubt from what you've described) your low speed needle (LSN) is too lean. (Low speed needle is located at the end of the slide where the linkage attaches). If it runs for 4 or more seconds before dying, the LSN is too rich. If you are unsure which way to turn to richen or lean the mixture, clockwise turns the screw in and leans the mixture, counter-clockwise richens the mixture.
It sounds to me like you are probably too rich on the low end, which will cause it to be sluggish at first, then take off quicker (assuming the HSN is tuned right) Also, Im sure everyone here will agree with Kevin. Take the time to learn how to tune your engine yourself. It can be expensive having the hobby shop always tune your engine. Especially around here, where the temps and humidity are always changing, which will affect the tune on a Nitro engine.
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11-05-2005, 10:26 PM
Quote:
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11-05-2005, 10:48 PM
You are right Squirrel. "Loading up" happens when the engine is idling, because the engine isn't burning the fuel fast enough to prevent the oil in the fuel from starving the engine. Another problem with an engine loading up, is it causes the engine temps to fluctuate more. The oil is what cools the engine while running. When idling, the oil buildup cools the engine slightly. In general, a well tuned engine should be able to idle for at least 5-10 seconds with minimal oil buildup and still be able to get a good start.
The higher your oil content, the easier an engine will load up. Oil is the only property in the fuel which DOESN'T ignite. That is why the side of your buggy/truck/car has an oily film after running.
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11-05-2005, 10:58 PM
yay i was right for once score a point for me!
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11-06-2005, 10:13 AM
hey thanks for all your posts but last night I took my engine apart and I noticed that the nut that holds the flywheel on was loose to where I could loosen it with my fingers. since that was loose my crankshaft was moving inside the crankcase and causing the rod to rub against the inside and it would become hard to get the piston to move up and down. also If my low speed is to lean does that lessen the amount of fuel that goes in or is the fuel amount controlled only by the hsn (high speed needle)?
thanks, kevin
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