TRX 3.3 on a TMAXX

[xp190]

Hi Guys

First time poster as well as first time Nitro RC owner.

I have a few general question which I would like to hear some comments on.

I bought a TMAXX (4908), used, from a guy who raced RCs for years.
The truck other than a few broken pieces was in decent shape.

I rebuilt it, replaced all the broken parts, cleaned it up good as new, put it back together, fired it up and it ran quite well, but I had a hard time tuning it just right.

It would bog down when I richened it a bit, and stall out when I leaned it just a tad, I figured most likely an air leak, so I replaced some orings, and sealed the engine. It holds an idle much better since, and is easier to tune.

Here is my issue.... Starting.

I watched some youtube clips and it seems nitro engines fire up almost instantly and run quite well, mine wont do this. I have the EZ Start system, and in order to get the motor to run I have to spend 2-3 minutes spinning it before it slowly starts catching, and eventually it will take, this is after priming the engine, so I know fuel is in there, just not getting burnt.

How hard is it to start a TRX 3.3, once it is broken in, on a cold day, say 10C, which would be 60F or so? I find it very frustrating that it takes so long to get it going.

Once it is running, It has plenty of power, I'm still working out a few tuning issues, but I think it should be fine.

Second question,

The engine seems to be leaking fuel through the EZ Start system, not the back plate, but the shaft, unless I missed something, it's quite a bit too, so it might just as well be suking in air through there, is this normal? Is there a way to seal it, or just replace? I ask because the truck gets real filthy because of this, and it's a hard to clean place.

Some more information for you experts.

I took the engine apart, it has lots of pinch at the TDC. I put in a new glow plug and it seems fine, but I'm going to start using a glow ignitor as opposed to the traxxas EZ start for heating it up, maybe it will help with the starting.

It seemed to run a bit hot at first, hence the orings and sealing the engine, it is doing much better now. I have a new fuel tank, so there should be no air leaks there, and fuel lines check out as well. Exhaust is sealed off nicely.

My main concern is starting it, if this thing had a pull start on it, I'd rip out at least 3 pull starters before it fired up, I'm glad it does not right now, but this can't be normal, can it?

Thanking you all in advance.

xp190

 

[Metalhead Matt]

Use a separate glow ignitor. The leak sounds like a bearing. With a separate ignitor, you can get rid of the blue and yellow wires and the wand battery will last much longer.

 

[xp190]

Thanks Metalhead

I got the glow ignitor, I haven't tried it out yet, but I'm hoping for positive results.

 

[SteelCityNitro]

I found that I had starting issues with my ez start when using a 1200 mah battery.. as in it wouldnt fire up as quickly.. I tried a 3600 and it made a big difference

 

[Old2.5]

iv got the 3.3 on my 2.5 and when it comes the factory it had factory needle settings of 4 on HS and 1 1/2 on LS thats factory seeting i would go from there

 

[xp190]

Thanks for the feedback guys

Old2.5 - I did initially reset it to factory defaults as per the manual, it fired up, but it took just as long.

I think SteelCity is on the right track, I'll know for sure when I try the glow ignitor, I don't remember what the battery in the starter wand is, but it can't be anything fancy.

But overall, it does not sound like I'm doing anything wrong with the motor to start it and the fact that it takes so long, does it?

Cheers

xp

 

[Metalhead Matt]

I don't think it's anything your doing. Unless your not quite getting it primed. Sounds like you are, though. The ignitor should solve your problem.

 

[xp190]

Hey guys,

a bit of an update. The ignitor works, works much better too, and as soon as I can figure out why the engine is stalling I won't have to use it as much.

From my last tuning session I left the motor untouched, it ran fairly well. Today, I went out and could not get it started at all, my starter battery discharged completely, I had to go back and charge it up again and try one more time.

I reset the hsn to factory defaults, it turned out I had it only two turns out from the last session. So I backed it up to 4 turns out, the motor fired up real nice, after warming it up for a bit with a bit of throttle, I decided to give it a run, it bogged down terribly and hardly made any power, so I started leaning it out.

After multiple restarts and very poor performance, I reached a point when I had turned the HSN two turns in, which would be only two turns out from completely closed, this got me some performance out of the engine, but still not what I used to see, didn't even go into second gear, but picked up quite well.

At this point, the motor was running at ideal temps, I leaned it out a bit more, and with almost no performance gains, still bogging out, it started overheating, so I backed off.

This is a little difficult to figure out, and I'm not sure why. If anyone could shed some light as to what might be going on, I'd appreciate it.

Some other notes. The LSN was flush with the carb as per the manual, but I noticed it is completely closed at this position, this might have something to do with why the motor dies when I try to idle it, some fussig around with the LSN proved to impact the idle a lot, but, at this point it makes no difference since there is no power out of the engine.

One additional note, it was real cold today, 5C, good weather for tuning since the motor got a lot of cold air flow, but perhaps it was too much, I don't know.

Any advice on how to troubleshoot this will be greatly appreciated, my goal is to run a full tank through the motor without restarting it all the time.

Cheers

xp

 

[TOCCHET]

the first thing i did with my t-maxx 3.3 was loose the cheesy start and put a rotostart on it,so much easier to start.sounds to me like your on the right path tuning wise,sometimes tuning can be a major pain to deal with,my 3.3 doesn't tune very easy lol,but once i get it runnin' good it screams.

 

[SteelCityNitro]

the carb is almost completely closed at idle, turn up the idle speed a little, that should help keep it running at idle speeds

 

[Old2.5]

your high speed wont do much unless you do somthing to your LSN so like i said earlier 1 1/2 on LSN and 4 on HSN

 

[xp190]

Hey Guys

Another update, this morning I took my truck for another test drive. I followed your suggestion, as well as some of my own findings, and things are looking much better.

I turned up the idle speed, this time around it kept on going and didn't creep forward, great improvement.

To start it up, I turned the HSN 4 turns out, it started real quick, I let it warm up a bit and then leaned it out 1 turn, it still bogged quite a bit, so another half turn and I tuned it from there.

I was able to get it to move quite fast, although on the beginning it would not shift into second, a bit more tuning and paying attention to the temps and smoke, and she was as fast as she should be on a cold day like today, so I was very happy.

Unfortunately, my clutch fell apart, again, the pins come out and get stuck in the clutch bell, I can keep going like this, but I'm stuck in second gear, and if I try to come to a complete stop, the engine dies naturally. I need to replace this faulty clutch.

I think I had to restart it 4 times in total on a single tank, 3 times because of the clutch, once due to a lean condition. Overall, not a bad run.

The engine seems to run a bit higher then the spec temps, I'm not sure what to make of that, but I always have smoke coming out, yet I think the engine overheats every now and then especially when I try to get it to go as fast as I saw it go on warmer days.

Slowly getting to my goal.

Old2.5, I think it's the other way around on the 3.3, the HSN controls everything and LSN is only a sub channel of the HSN, that's what the manual says at least.

Cheers, and thanks for all your help.

xp