T-Maxx 2.5 after breaking it in.... some questions...

[Sasquatch]

OK my friend and I just broke in our new T-Maxx's yesterday...

Finally some good weather in Denmark..

Man do they accelerate....

Both trucks are almost identical regarding needle settings and performance. We followed the breakin procedure to the letter..

Now both trucks does the same strange thing...

After a little warmup and some high speed runs both trucks tend to stall when breaking with 75 - 100% power.

Sometimes they stall just when the truck comes to a complete stop, and sometimes first when doing a 1-2 mph 180 turn to get the truck back towards us.

It's just as if you need to keep some pulsating movements on the throttle to "keep it going" (or not to have to walk 200-250 feet to restart the truck) :\

And this brings me to the second problem. Well not really a big problem, but it is annoying... It is almost impossible to start up the trucks just after a cutout or stall.. But after approx. 1 1½ minute it fires up just instantly........

Does anyone have any ideas.....

The only ajustments we did was to lower the idle speed because both trucks just did'nt want to stand still after a few tanks of fuel during break in. And we leaned out the high speed needle to get some more performance.

Theres still a consistant trail of blue smoke comming from both trucks. They both shift to second gear without trouble. (phew are they fast.... )

low speed needle is on stock setting, because the fuel line pinch test is right on....

Please advice...

Regards from denmark:worship:

 

[SkyMaxx]

Sounds like they might be just a touch on the lean side. If you are getting a stall after running WOT for a bit, and then it just stalls...it is not getting enough fuel, thus too lean. Try richening it up a little bit, and see what happens.

As for the long wait before it re-starts, that is also a symptom of running too lean. What you are seeing is the engine "overheating". Soooo, it needs a little cool down period before the internals are ready to fire up again. Running too lean prevents some of that oil that is in the fuel from getting into the engine and helping with keeping it cool.

Realize, TRAXXAS engines tend to run on the hot side. Giving it a lean setting only makes it run hotter, and that is not always good for performance or engine life.

So, richen it up and give it a run or two and see what happens.

 

[Sasquatch]

OK. I just thought that if there is blue smoke and the truck is not having any problem going WOT. No cutouts or anything it was OK on the fuel mixture..

I will try to ritchen the HSN a bit....

That would actually bring me to just about factory default breakin setting on the HSN then...

Isn't it supposed to be set somewhat rich on the HSN from stock.??

Thank you SkyMaxx

 

[SkyMaxx]

If your engine runs great at the factory presets, then don't sweat it. Tuning the engine is as much art as it is science. Needle settings are going to vary and need adjustment throughout the year to accomodate differing weather conditions and temperatures.

The bottom line is to tune the engine for performance. Right now, it sounds like your engine isn't performing. So readjust the needles and see where things go from there. You might find that you only need to richen things up a hair to get the engine happy and still have the performance you want.

 

[Sasquatch]

OK. I'll try richening it up a bit today... The weather is actually quite good today and the forecast for the rest of the week calls for some nitro burning :cheerful:

Regards

Allan

 

[LarryA]

It could be as simple as the idle adjustment being set too lw. If the carb is completely closing then no air or fuel and "shutdown".
It's easy to overlook.

 

[Sasquatch]

Thank you for replying.... The idle is set only just so the truck doesn't "tick" forward. If I turn the idle up it wants to go forward.

During break-in tank 3 or 4 it wouldn't stay still.. had to turn the idle down a bit. So I think the idle is fine.

Actually i would like to have it further down so it sounds like on the DVD, but that seems simply impossible.....

Regards

Allan Jensen, Denmark

 

[LarryA]

With the engine not running, remove the air filter and turn on the receiver electronics and you transmitter. At your throttle idle position you should be able to see just a slight opening inside the carb throat. If the slide inside is closed with no opening then it will definelty shut off. The opening at an idle is generally about the diameter of a paper clip (about 1/32 inch). This can vary but that is a ballpark. I'm going to take a stab in the dark here and make a few possible check suggestions. It is possible that if the carb adjustment screws were turned in too far and bottomed too hard that they have a rideg on them. The needle screws are a consistant taper end. If the taper on the needle or even the seat get a ridge on them then adjustment precision goes down the drain. There is no fix if this is the case besides replacing the needle screws. They would probably need to be examined with very good light and a magnifying glass. Another possible cure is to chance carbs. I have a HPI on-road car and my brother a T-Maxx that we have both changed the factory carbs with OS carbs. The OS seem to be much easier (for me anyway) to get set up. Other than the these two things I don't know what would make it idle too high other than maybe an air leak. Assuming it runs ok otherwise, I would tend to exempt the air leak. Getting the engines to run good is the hardest part and when the weather makes a drastic change so can your engine's running condition. Tempermental little things to develope the power they do. Good luck with you probelm (or oppertunity).... 8-0

 

[Sasquatch]

OK. I will check that tomorrow. i did not get the time for doing it today unfortunately.

I have not at any time overtightened any needles (atleast i think I don't) I have not been even near full in or full out on either needle.....

But tomorrow. I will check and see before, hopefully final, tuning in the engine...

I will post back with ny results....

Regards from Denmark (once again) :breakdown

 

[Sasquatch]

OK now... today me and my friend went to a nearby hard packed gravel football field size area and tryied to tune in our T-Maxx trucks....

They still stall when coming in after some high speed runs. we both have to pulse the throttle to keep it going without stalling. It just dies out without warnning. And they're quite hard to start again. But after waiting for about 1 minute. They fire right back on...

I checked what LarryA suggested, and looked at the carb setting, and the opening is just about right. Besides that it always returns to a setting about almost closed. Never fully closed...

My truck got ritchned a little on the HSN. It was getting a little hot I think (we just placed an order for a temp gun and some accessories totay) as we have no idea what temparature our engines run at...

But still..... they stall. Now because we are coplete nOObs here we would appreciate some advice from all you experieced guys... :bow:

Else we only ajusted the idle speed to stop the trucks from stepping forwards...

What could be the problem for the stalling trucks ??? Do you need any further info from me to perhaps help in solving the problems...

LSN ajustment perhaps.. I dont know. The fuel line pinch test is right on I think.. 2-3 sek and speedup and it dies.... We have not ajusted them from stock setting. We didn't want to make things even worse. I've read alot on needle settings in different T-Maxx forums and there sees to be as many settings as there are trucks.

Best Regards

Allan, Denmark

 

[big kal]

You might try opening up the idle a little bit and lean out the low speed needle just a hair. This would also happen to mine. I found out from running it rich a lot of the oil would build up in my pipe. Also, if you haven't changed the glow plug since break in, now might be the time to put in a fresh plug.

Remeber, when you make any adjustments to the needle, you want to make a couple of high speed passes. The needle adjustments aren't instant.

Also, if you want to get rid of the ticking in your tranny, install a Traxxas FOC. It'll clear it right up and it's like only $11. Plus, you get better acceleration. Here's a link to the FOC.

Traxxas FOC

 

[Sasquatch]

Hey big kal...!!!!

When I open up the idle, the truck tends to go forwards on it self.... will the leaning of the low speed needle compensate for that ??? ... I mean that's what happened to you ? You had to up the idle AND then lean out the LSN... sorry if i'm too slow

I allready changed the glow plug after break in. I ude the O.S. # 8. They are great. The engine was broken in on there too. Never used the Traxxas ones, because they were unavailable (and still is almost all over) Anyway they're impossible to get in Denmark or any country near here... :constipat

Therefore we removed the stock glow plyg because we got the O.S. # 8 and wanted to break in the engine on the type of glow plug's we are able to get locally.

And yes. We always make some high speed runs after each ajustment så see the improvements / changes...

Regards from Denmark (once again)

 

[SkyMaxx]

I guess we need to go to ground zero...

What are your needle settings? High? Low?

Does this happen to both of your T-Maxxes in the same exact fashion?

First, the phenomena you are witnessing can be caused by one of two or three things.

The first would be an air leak in the system. I would discount this on the fact that it is happening the same way on two brand new T-Maxxes, but it is not beyond the realm of possibility. When you have an air leak and hammer on the throttle, the extra pressure from the WOT condition kind of compensates for the air leak and still pushes the fuel to the carb. Things to check: fuel tank for cracks, good seal at the carb throat, fuel lines for leaks, bad header gasket, fuel filter leaks, etc.
Things to do for each: Replace the fuel tank, buy a product called Air Seal and use it on the O-ring around the carb neck then install the carb, replace the fuel lines with new ones, replace the header gasket, check to make sure the fuel filter is properly closed and has a good seal.

Second, and the more likely scenario is needle settings are still too lean. When you drop the hammer and go WOT, the engine pushes the fuel to itself via the backpressure line. This creates fuel waiting at the carb. If the High speed needle is set too lean, when you remove the WOT condition that fuel is no longer pushed as hard and the engine will stall for a lack of fuel. This situation gets worsened by the overheat condition that running too lean tends to cause. The overheat condition creates back pressure into the fuel supply line causing it to be even harder for a lean engine to get fuel. Things to do to fix it: Take the needle settings back to factory presets. (when you do this be careful to not over tighten the needle all the way closed when trying to find a starting point for the count as you open the needle). Run the engine at factory presets. If the engine still stalls after a high speed run, then open it a little more. Run it a little more rich than you would think. Get the engine used to that for a couple of tanks, then lean it out a little at a time.

The final thing that I can think of, that most people discount, is the fact that your engine(s) even after following the break in procedure to the letter might still be breaking in. Sometimes these high performance engines need an extra tank or two before they truly break in. I know a friend who took nearly twelve tanks before his new .21 engine was broken in. Why? Most likely because he never got the engine up to a good operating temp often enough during the initial break in tanks. Things to do: Take it back to the factory break in settings on the needles, and run it around at WOT for a few ten second bursts and get that engine heated up. Then let it cool down a little with some nice easy not so WOT runs. Then repeat until the tank is empty. Let the engine cool down, refill the tank, and do it again. After tank two of this, try tuning it again from the factory presets. See what happens.

The bottom line: Your engine is starving for fuel after the WOT runs. You need to find out why. Is it an air leak? Do you need to run rich? Do you need to spend some more time breaking it in? Try the above and find out.

 

[Sasquatch]

Needle settings is stock on LSN.

HSN i actually don't know.... explanation

I was turning it counter clockwise to get to a starting point... Expecting about 4 4½ turns 5 max. out... after 5 turns counter clockwise without noticing it getting tight or anythinng I stopped turning it. I'm affraid of destroying it. How do I know when the HSN is all closed ?

I now set it 4½ turns out (from where i chickened out not daring turning it anymore ;-) )

Idle is 1 complete turn in from stock to stop the truck from stepping forwards..

And finally yes. The same thing happens to both brand new trucks.

When I come to think of it. We did not check if the factory settings was set correctly, but we assumed that what is stated in the users manual is true...

To tell you the truth I'm not hapy about me being able to turn the HSN 5 turns in without noticing any resistance or anything...

Please advice..

Regards

Allan

 

[big kal]

First, to close the HSN, you have to turn it clockwise and then only turn it until it's lightly seated. Once, it's fully closed turn it counterclockwise 4 to 4 1/2 full turns. That's where the factory setting is. To set the LSN, the screw has to be flush with the inner slide. Start from there and also put a sealant around the backplate of the engine, to seal any air leaks. Also, seal the o-ring around the carb.

SkyMaxx-I thought if your truck or car dies out from a high speed run was because of a rich setting? I guess I was wrong. I'm constantly learning, because I did notice an air leak on my backplate of the engine. Also, to check for an air leak, can you spray water on the back plate when the engine is running? I heard that if you do and the motor stops, you have an air leak there? Does it work the same for the carb also?

Sasquatch-Sorry for giving you bad/wrong advice in my previous post.

 

[Sasquatch]

hey !! kal....

Not to worry :-D

man am I stupid... turning the HSN he wrong way..

Just imagine the looks on my face when I could just keep turning and turning the HSN...

I'll det the HSN to 4 turns out (no mistakes this time hehe) and the LSN is allready set flush with the inner slide.

Later today I'll try these settings. Weather here is just gr8.8-0

Sasquatch out....