TRX 2.5 cutting out at high RPM

[MotoGod]

OK so I have a buddy with a T-Maxx 2.5 that has been having issue after issue with it. It's been to the LHS at least 3 times, and while they fix the issue he reported.....they never track test it...or even bash test it so other stuff keeps cropping up. So I offered to take it home with me and try to work on it for him a bit to save him the 25 diag fee at the shop.

Last problem he was having at the track was a low idle and flame outs as soon as he took off. he had no tools handy...so I just brought it home with me. I have the idle set a little high at the moment while troubleshooting and it will sit there for quite awhile idling.....but I do have to blip it every 20 secs or so which I would expect since Nitro motors load up a bit when they idle.

As soon as I try and drive it, it seems to really rip around the yard from closed throttle to @ 3/4 throttle. As soon as I open it WFO, it will take off like a rocket ship to 10-15 seconds...then just flame out completely like someone cut the damn fuel line. I have checked for obstructions and found nothing. I'm going to replace the line tomorrow anyway, but it doesn't appear to be an issue.

I also reset the carb to factory settings, had no change there at all. I leaned it out from there so it wasn't chocking itself and still had the same issues.

One odd thing to report is after it cuts off, I have to remove the plug and use the EZ-Start to kind of clear out the motor before it will even attempt to fire up again. Almost acts like it's flooded, but no fuel actually comes out of the engine. Rathe odd symptom, but I think solving that issue will lead to fixing this motor issue as well.

I am bolting up my TRX 2.5 to it tomorrow to make sure the rest of the truck is in good working order before I do too much diag work to it, plus I really need to test this TRX 2.5 ;-)

Anyone have any ideas at all with the cutting out issues? Motor is not running hot at all. Highest I tempted it at was 190, and that was almost a full turn leaner than stock on the HSN, and @ 3/4 turn lean on the LSN from stock....and after the short high speed pass it will make. It also idled for a good 2-3 min before I even attempted the pass.

I'm stumped...and the only thing I can think of here is the HSN is gummed up internally so my only other thing to try here is either the carb off my 2.5 on his engine....or cleaning the crap out of his carb and trying again.

Any other ideas?

 

[itsalifeworthliving]

I'm really rusty with my nitro, but interested in finding out were this goes.

 

[Gabskee]

Though I'm not entirely sure, I believe I had this same issue with my TRX 3.3. After speaking with my LHS they told me my carburetor may have some dust or dirt in it. I completely disassembled my carb and thoroughly cleaned it, reassembled and returned the needles to factory settings. The problem has yet to come up again.

 

[ThunderTiger]

I had the same issue albeit with a different engine recently.

All i had to do was clean all the needles (hi speed/low speed) and clean the spraybar as well for good measure.

The other things i did just for good measure were to clean the fuel filter, swap out the fuel lines and blow some fresh fuel into the tank from the OUTWARD side (that supplies the engine) to clean the sintered filter in the fuel tank and after all that, i fitted a new GP (Glow Plug).

Problem cured.

----------------------------------------------------------------------------------------------------------------------------------

As to the TRX 2.5, been there done that waht a PITA !!!!.

After 4 hours of Pee-balling around in the field (so to speak) chasing the tuning all over the place (figuratively and literally) I gave up and went home.

In the end, it came down to dirty carburettor needles. PLUS, i had to tune the LSN as well as the HSN once i'd cleaned the needles.

 

[MotoGod]

That was the only thing that was making sense to me as well. He let it sit for a good 18 months or so...and I'm not sure he ever gave it a really good cleaning before he wanted to put it back in service. Carb cleaning it is.... ;-)

 

[olds97_lss]

The other things i did just for good measure were to clean the fuel filter, swap out the fuel lines and blow some fresh fuel into the tank from the OUTWARD side (that supplies the engine) to clean the sintered filter in the fuel tank

After seeing he's had it sit for over a year, I'd definitely do this with the tank as well. I've had this issue before with a tank I left sit in a drawer empty for a long time after using it.

Really just sounds like it's gummed up.

 

[Old2.5]

OK so I have a buddy with a T-Maxx 2.5 that has been having issue after issue with it. It's been to the LHS at least 3 times, and while they fix the issue he reported.....they never track test it...or even bash test it so other stuff keeps cropping up. So I offered to take it home with me and try to work on it for him a bit to save him the 25 diag fee at the shop.

Last problem he was having at the track was a low idle and flame outs as soon as he took off. he had no tools handy...so I just brought it home with me. I have the idle set a little high at the moment while troubleshooting and it will sit there for quite awhile idling.....but I do have to blip it every 20 secs or so which I would expect since Nitro motors load up a bit when they idle.

As soon as I try and drive it, it seems to really rip around the yard from closed throttle to @ 3/4 throttle. As soon as I open it WFO, it will take off like a rocket ship to 10-15 seconds...then just flame out completely like someone cut the damn fuel line. I have checked for obstructions and found nothing. I'm going to replace the line tomorrow anyway, but it doesn't appear to be an issue.

I also reset the carb to factory settings, had no change there at all. I leaned it out from there so it wasn't chocking itself and still had the same issues.

One odd thing to report is after it cuts off, I have to remove the plug and use the EZ-Start to kind of clear out the motor before it will even attempt to fire up again. Almost acts like it's flooded, but no fuel actually comes out of the engine. Rathe odd symptom, but I think solving that issue will lead to fixing this motor issue as well.

I am bolting up my TRX 2.5 to it tomorrow to make sure the rest of the truck is in good working order before I do too much diag work to it, plus I really need to test this TRX 2.5 ;-)

Anyone have any ideas at all with the cutting out issues? Motor is not running hot at all. Highest I tempted it at was 190, and that was almost a full turn leaner than stock on the HSN, and @ 3/4 turn lean on the LSN from stock....and after the short high speed pass it will make. It also idled for a good 2-3 min before I even attempted the pass.

I'm stumped...and the only thing I can think of here is the HSN is gummed up internally so my only other thing to try here is either the carb off my 2.5 on his engine....or cleaning the crap out of his carb and trying again.

Any other ideas?

wow sounds odd id say clean out the motor like all the bearings and how old is the motor traxxas says you should do a motor rebuild every 3 gallons of fuel

 

[ThunderTiger]

3 gallons ?? my 2.5 is waaaaaaaaaay past 3 gallons and still runs like a champ but thats with cleaning the carb out regularly and regular maintenance.

 

[knall]

3 gallons ?? my 2.5 is waaaaaaaaaay past 3 gallons and still runs like a champ but thats with cleaning the carb out regularly and regular maintenance.

I thought I read someplace that a traxxas 3.3 really starts to break in / come to life after 10 gallons? or is that 10 tank fills?

I am about 1 gallon through my used god knows how old 4909

 

[olds97_lss]

Pretty sure 10 gallons is a tall order for a traxxas engine, at least to still be in it's prime. I'd say more like 10 tanks, but that sounds a bit light. Even cheaper built engines do better after half a gallon or so. From most of what I had read, TRX engines start running much better around the 1 gallon mark. Many engines are that way.

 

[MotoGod]

I slapped the carb on this motor from the TRX 2.5 I have for sale in my thread....problem solved. So it's definitely a gummed up carb for sure. Now I'll clean it and just toss that carb on my TRX 2.5 ;-) At least it gave me a chance to test my TRX 2.5! Runs pretty well too!