T-Maxx Tuning questions

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srbecker

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Tonawanda, NY
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  1. Bashing
I apologize for the noobish question, but I'm at the point where I mostly understanding tuning my T-Maxx but still have some confusion.

After reading all the posts on tuning and factory settings and blah blah, it seems that the main concesus is that 4 turns out on the HSN (factory setting) is usually a tad rich to start as far as break in, but can also vary depending on climate, temp, height above sea level and what not. Thats what is confusing me.

I purchased my T-Maxx in the end of January (in Buffalo), so it was cold out. I broke it in with aluminum foil on the cooling head on a 40 degree day, hits temps and what not, and was running fine for the most part at about 4.5 turns out on the high speed. Once the warmer weather hit, from what I understand, you would be able to lean out the engine a little bit because the air isnt as dense, however my truck is just the oposite.

Two 80 degree days in a row and this is how my truck ran:

Day 1:
Tank 1 - truck ran fine, tuned it by leaning it out a little bit (about 1/2 to 3/4 a turn) and all was well
Tank 2 - Awesome! Had power, popping wheelies, very faint blue smoke trail, all seemed well
Tank 3 - Started bogging at half tank when accelerating fast, however could accelerate slowly up to full speed, just not punch it up to full speed. I started measuring temps, and they were high (280-300).
Tank 4 - Played with HSN then LSN, nothing, same results anywhere between 3 and 7 turns out

Brought it in, played with it, started inspecting things and found this:
Capture.png

*Notice the small chip underneath the fuel plug

So I replace the carb body, set everything back to factory settings and:

Day 2:
Tank 1 - still bogged when accelerating quickly and high temps (too lean?)
- Adjusted HSN (in increments thoughout the tank) ending somewhere around 5.5 - 6.25 turns out (lost count)
- Adjusted low speed (after full speed pass) so that pinch test was about 4 seconds, then adjusted idler screw so it wouldnt creep when sitting still.

Tank 2 - everything seems to be running well, no bogging, deceent power, no wheelies though :(
- Spit test, spit sat in cooling head for about 2 seconds then started to sizzle
- Didnt have temp gun but judging by spit test, temp was probably pretty good
- Had a pretty decent smoke trail through all speed ranges

My question now is:
1. Is it normal/abnormal to be that far out on the HSN in the summer time?
2. Just lean up the LSN a bit if I want more power of the start? or Do I need to lean the HSN, then the LSN?

I apologize for the book I needed to right, but I just wanted all the facts to be presented so I can get the most help possible. I know there are many posts and how to's on tuning an engine and I have read them all, I just want to know if the things I am experiencing are normal or should my HSN be much leaner than it is (presenting the idea that I may STILL have an air leak somewhere?)
 
that seems a bit rich,4 turns out on the hsn is break in setting.try turning out your lsn out a quarter turn and go back and set your hsn back to fact. setting and start from there
 
I went through some tuning issues as well. Took it to the hobby shop I purchased it at and the shift point was off so even though I was rich enough the engine was still running hot due to the higher rpm's when I took it in the guy informed me of the importance of breaking new engines in with temp above 50 for best results. He set the hsn to 4 and 1/8 out and told me to never adjust the LAN from factory setting as long as the pinch test was within 2 to 3 seconds. Truck is running great for me
 
I wish I could say the same Trstern. Mine seem sto shift fine and everything with the current settings, which seems like it should be way too rich, bit its not....

maddmaxx, I will try your recommendation, but it just will not accelerate at factory settings, I keep trying but it always bogs down when I hit the gas until I richen it. Very aggrivating!
 
some times u have to adjust the lsn for humidity and altitude

---------- Post added at 9:29 AM ---------- Previous post was at 9:26 AM ----------

when you fixed your carb did you take out your hsn they are very easy to cross thread and will play hell on your tune
 
some times u have to adjust the lsn for humidity and altitude

---------- Post added at 9:29 AM ---------- Previous post was at 9:26 AM ----------

when you fixed your carb did you take out your hsn they are very easy to cross thread and will play hell on your tune

I did swap all the needles from the old carb body to the new one, but I was sure not to cross thread any of them. All needles and plugs are in straight and snug. If I have an air leak, it has to be either with the pull start or the exhaust. I am 99.8% possitive it is not on the carb side of the engine. I guess it is possible for a leak on the cooling head/engine block mating, so ill check that too, but at this point, its gotta be exhaust or pull start. Maybe Ill just tear the whole engine apart this weekend while its raining and seal everything. Just the weird part about it all is that it was running fine at 4.5 turns out and then suddenly changed. Now I'm 6 turns out and runs fine, but I shouldnt be that rich.
 
traxxas engines are funny like that sometimes.when i got in this hobby i broke more things kicking it and throwing it than running it,lol.seal it make shure the boot on the carb is good and seal the base of the carb.your best bet is to throw that thing in the trash and buy a good quailty engine.thats what i did and never looked back no more headaches
 
Well I can only assume by the following pictures that I had an air leak, and in more than one area as well:

IMAG0359.gif

IMAG0360.gif

IMAG0361.gif


So, after replacing the dented manifold and cleaning and sealing the entire engine, I am back together and ready to attempt tuning again. Hopefully this time it runs both cooler and better.
 
I might have missed it but you keep saying high temps but I dont see where you posted the actual temps. How hot is hot? TRX engines have a history of running on the hotter side of the spectrum on a normal basis. On a couple occasions you mentioned that it bogs when you first gas it. To me that sounds to rich on the LSN.
 
he was running the hsn at 6.25 out thats way to rich
 
Well I was running between 6 and 7 turns out as maddmaxx said, and still hitting temps around 280-300. Had blue smoke and it ran decent, but running that rich and getting decent performance with high temps means there had to be an air leak, which I am pretty sure there was. Since then I have completely sealed the engine, hopefully get out today and run a little bit
 
I went out yesterday, outside temp was just above 50, maybe 52. I retuned after sealing the engine and now I am hitting temps more in the 250-270 range which I know its not all about the temps, but atleast I can be comfortable knowing I am not doing any major damage to it. I'm currently at 5 turns out which isnt bad, but I think I can lean that out a little bit and richen the LSN a little, but we will see. Ill tinker with it next time I get out to run it. My front bearing might be on its way out (little gas spray near the freewheel) but at this point I am just going to run her until she dies and upgrade the engine to either an OS .21 or Picco .26 Are their any additional mods I need to do with the .26? Better tranny or any driveline changes?
 
thats normal for the front bearing to leak a little as for the piccos i was thinking about getting a .26 myself. i here nothing but good things about it,they say its a drop in.I mean hear sorry gramer police,lol
 
Good to know Maddmaxx. I dont mind upgrading the engine, but if I have to also do drive shafts and metal gears in the trans, I think I would opt out and stay with the .21. Ill do more research I suppose, but I am in no hurry as my engine is only on 1 gallon so far.
 
Keep the 3.3 going until it dies, for a practice engine. 5 turns out on a 50° day is average for a 3.3. You and I will have to meet over in batavia sometime after you get that .21, I'll help you dial 'er in.
 
Did ya get the 21?
I'd be happy to help you tune it sometime if you do....unless you're a young kid who can't drive out to batavia lol.
 
Keep the 3.3 going until it dies, for a practice engine. 5 turns out on a 50° day is average for a 3.3. You and I will have to meet over in batavia sometime after you get that .21, I'll help you dial 'er in.

Sounds good man! I can always meet before I get a new engine too, just to do some bashing/fun driving around... Not to many people I know have RC cars, so its pretty boring driving by myself lol
 
Did ya get the 21?
I'd be happy to help you tune it sometime if you do....unless you're a young kid who can't drive out to batavia lol.

No I didnt get the .21, just running what I have for now. I'm 24 and have my own vehicle lol so no worries.
 
Ok I'll let you know sometime when I'm gonna go bashing. I don't really know any good places in Batavia, but there must be something.
 

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