500 lb. koolaid man

I decided I ought to start a thread for my questions on the t-maxx I bought today, since I'm familiar with hpi trucks but not traxxas.

Yesterday I saw an add on craigslist for a t-maxx with no pictures wanting $150 saying it has a hop up motor and a spare motor too. I went to look at the truck today and it looked like a good deal, but the one way bearing was shot(They didn't know) so I offered him $125 and he accepted my offer. I got the truck, transmitter, o.s. .15CV with a nice medal pipe, traxxas .15, glow plug igniter and charger, an almost full gallon of 10% traxxas fuel and a spare glow plug. The reason he sold the truck(it was his 13YO sons) is because they had problems with keeping it running, the person they bought it from said it just needed a good tune, and I believe that. The o.s. .15 does seem to have OK compression, but I've heard that that means either the engine is shot, or it will run great because some engines with OK compression run excellent. The spare motor(traxxas .15) seems to have good compression although it's a little gummed up so it's hard to tell. On the way home I picked up a new 1 way bearing at a hobbyshop($28). Then realized it had no air filter, so I picked one up at my LHS($5.50). I think overall, I got an amazing deal on the truck. It's in great shape.

Questions:

1. It's having trouble steering(front wheels off ground) and I hope it's just low battery voltage to the RX so I'm going to change the 4 AA's first and see if that helps. Are they in the box labeled traxxas, do I need to remove two allan head screws(blue) to get to the batteries?

2. There is a 3-position switch on the transmitter where your thumb would normally be placed. Is this for reverse? And why are there 3 positions on it and not just two, does the truck not shift by itself? The switch itself is a little weird to me, do all t-maxxes have one on the stock tx?

3. Is it a good idea or bad idea to roughen the shaft before I put the new one way bearing over it?

4. How should I kill the engine(once I get it running)? On my xtm x-cellerator that I used to own you were supposed to pinch the fuel line, and never cover the exhaust to kill the engine. On my savage, it's the opposite. Which method should I use?

Thanks for the help!

jatoracing33

1. its probly the batterys, and im pretty sure you just unscrew the 2 screws.
2. the switch is reverse, all traxxas vehicals with reverse have it. it shifts by itself when its in forward, but you need to manuely shift it into reverse
3. im not sure. i read somewhere on traxxas's site that says the shaft should be smooth with no scratches or anything
4. you can kill the engine either way. putting your finger over the stinger is easier but it hurts with a metal pipe (trust me...i have a perfect circle on my finger)

Excell0602

1. yep undo those blue screws and in there are the AAs.

2. don't know

3. don't know

4. I just pinch the fuel line because thats what it said to do in the video.

Hope this helped

Edit: Darn it you beat me by 1 minute

500 lb. koolaid man

Thank you both for the help, that knocks out 3 of the 4 questions I've had so far. I'll check the batteries tonight, and I guess I'll pinch the fuel line to kill the engine.

So the 1 question left(for now) to answer is... sand the shaft or don't, because I know it's either a very good idea and will make the bearing wear out less quickly, or it's a bad idea and will mean short bearing life. I'll wait for an answer before I start yanking on the pullstart because of course it's better not to guess, I want the bearing to last a long time. Thanks in advance for any replies.

DaveG55

#1 - you already know
#2 - that is an aftermarket switch. I'd guess that a previous owner had a problem with the stock switch and replaced it. The stock one is usually orange plastic and only has two positions. As long as flipping the switch changes from forward to reverse ypu'll be fine.
#3 Is the shaft damaged now? If not, don't bother sanding the shaft. If it's damaged then, yes, sand the imperfections smooth. If it's not damaged then try it w/o sanding. If the owb slips then you might try a light sanding to give the bearing a place to grip better.
#4 - Stop it how you want. There really is no "best" way. I prefer blocking the exhaust but my preference has nothing to do with a "best way for the engine". It's more to create a habit for me so I always reach for the same thing in case of emergency and the exhaust is easy to get to on any car/truck/boat. If there really is a "best" way then I'd have to say that it would be to stop the flywheel rather than pinch the fuel line or block the exhaust. The newer Savages come with a lever that stops the flywheel. I do not think that there is a real easy way to do that on a T-Maxx though.

Enjoy your new truck.

One more thing... That header pipe looks home made to give the truck a rear exhaust. I would guess that you may get better performance if you went back to a stock header and the side exhaust. Some people don't like that though so it's up to you.

500 lb. koolaid man

Thanks for the help Dave.

Now I have a new problem. I replaced the rx batteries and all the electronics seem to work fine now, but It's having trouble centering the wheels. Here's what happens, With the wheels off the ground, I turn the steering wheel on the transmitter right and the wheels turn left, I center the steering wheel and the wheels go perfectly center, so I then turn the steering wheel to the left and then let the steering wheel center but the wheels stay to the left of center(quite a bit). I looked at the servo while doing this and it appears to be where the problem is, it's not slop in push rods. Is this a transmitter setting that's incorrect, a bad servo, or what? All help is very appreciated.

DaveG55

If it's the stock steering servo it was never know to be all that powerful.
Try taking the servo arm off and see if the servo will center then. You might also see if the servo saver is too tight. Or maybe something in the linkage is binding???

500 lb. koolaid man

It's the servo saver[:@] The servo returns to center, I just checked. Does anyone know how to fix the problem or do I need a new servo saver? I would much rather prefer to "fix" this one or whatever the problem is if possible. Thanks for the help.

500 lb. koolaid man

I tried to start the motor and it runs great, however I didn't actually run the truck around since it's raining. I discovered that the center position on the controllers switch is neutral, rather unique.

Idle is very low, I have to hold the throttle way in to get the motor to idle and not stall. Which needle adjusts it? I circled(squared) the one that I think it is, am I correct? Thanks.

Mz

yep thats the idle needle.
to achieve a good idle, its really a mixture between the LSN, and the idle screw just in case you didn't know that already.

bob5429

if turn that screw to the right it should bring up the idle. that's how it is on my os 18

jatoracing33

yea...sounds right to me...wont hurt to just try it out...the worst that can happen is it will stall

jkdv8

My Feedback: (1)

since its rear exhaust you could just hit the flywheel with your foot. thats what i do with mine unless im putting it up for the day then i just let it idle out of fuel. also flip the cooling head around. make it cool better.

500 lb. koolaid man

Thanks for all the replies. I got the idle to where it should be, and got it tuned to where it was ripping down the street, shifting into 2nd perfectly. When I punched it I think the front wheels came off the ground a little, then again when it shifted. So it's "running" good now. However, the steering still needs some work.

Takeoff on the truck is rough. when I give the engine throttle, it takes a little bit too much gas to engage the drive, then it jerks forward as in every half second go stop go stop(looks similar to an electric car twitching) until I give it more juice and the drive is then fine. But I can't even take off in grass, I have to start on gravel then drive to grass. Maybe the "reverse/forward bar" isn't in it's max position. But has anyone ever had this happen before or know what the problem would be? Thanks.

edit: jkdv8, your right, the cooling head is on backwards. I guess someone probably had the motor apart and accidentally put it back on backwards. I don't see how it would help with cooling to turn it around to how it was, but I'll take your word for it and turn it. Thanks for pointing that out.

DaveG55

The jerkiness and poor take off you're experencing is likely two seperate but related things.
The jerkiness is just a T-Maxx quirk. It's related to the forward and reverse shifting/safety lock-out mechinism in the tranny. You can avoid most of the problem by not taking off slowly. A firm trigger finger will get past the jerky part. Or, a foc will fix eliminate the issue completely. But if you like having reverse, like I do, then there is a mod on the Traxxas forum called the "no buck, constant engagement" mod that will completely get rid of the jumping on take-off snd let you keep reverse.
The poor take-off is most likely a slipping owb in the transmission - I chased that problem for two weeks once. The owb rides on the main input shaft inside the primary gear. It is there to allow the truck to coast when you let off the throttle but if it starts to slip then initial acceleration is poor to nonexistant. The part is about $25 and I highly reccomend replacing it rather than trying to clean it.

nitrorcjunkie

I think jkdv8 meant turn the head 90 degrees, not 'around'.

jkdv8

My Feedback: (1)

your welcome koolaid. yeah what nitrorcjunkie said. 90 degree flip in either direction not 180. my fault.

tommythecat

My Feedback: (2)

I didn't read through everything so forgive me if this was already covered.

Looks like you got a great deal. That is the old pro .15 version of the t-maxx which many owners say was the most durable of all the models.

Do not sand the starter shaft. They need to be perfectly smooth and do not require any roughness for the one-way to grip. Sanding it will likely introduce tiny scratches which will likely cause OWB's to fail prematurely. If you cannot get a fresh clean OWB to grab the shaft well, then a new shaft is in order, and sanding the old shaft will only cause problems with your new OWB, not improve its engagement. But before you do anything, just clean the OWB, relube it with a little full synthetic oil and reinstall it. That usually works.

As for the jerkiness on take-off, that is perfectly normal. As Dave-G said, the no-buck mod is an option for cleaning up the take-off. IMHO it is the best cheap mod you can perform on a t-maxx. One longer pin in the forward gear, and a little grinding to remove the pins from the F/R shifting bell and your t-maxx has a nice smooth forward engagement...

500 lb. koolaid man

Thanks again for the help everyone.

Another problem: Every time I start the truck up for the first time of the day it starts up relatively quickly. After it stalls(or I kill it) I can pull and pull and pull on the pull cord(glow igniter in place) and it will not start. After I wait 20min. or so and most of the time it starts up again first pull. it gets really old really quick[sm=frown.gif] Anyone know what the problem is? Thanks.

MORE SPEED

could be because it is too hot

MORE SPEED

500 lb. koolaid man

You might be correct. But I have to wait until the engine is COLD to start it. When it's hot it also feels different, like the pull cord is easier to pull(I think that's just because of the heat creating expanding and contracting), and it's like I have to wait for the real "pop"(more compression) to come back in order to start it. I think my brand new one way bearing is already starting to go because I've pulled the pull cord so much.[:@]

Ahh, a thought just popped into my head but it's not a good one, is it possible that the engine needs to be cold to start because it needs that much compression/pop to start since the engine itself has low compression? The strange part is the engine runs strong when I get it to run.

Thanks for the help.

iamnot

that hard to start when hot/starts easy cold means one of two things. either you're not on the tune yet or the p/s is almost worn out. if you're pretty sure of your tune then you might be getting a new engine sooner than you'ld planed i sure wouldn't bother with trying a rebuild.

500 lb. koolaid man

Thanks for the help iamnot. You're rite that a re-build wouldn't be worth it. I'd get a new o.s. .18tz before that[8D] but luckily I have a spare trx .15 that was included when I bought it, seems to have good compression, so hopefully that will end up saving me some money.

Question:

My piston appears to be black in the o.s. .15(it was most likely like this when I got it). Carbon I would assume. Can someone please tell me what this means, and what I should do?

Thanks.

500 lb. koolaid man

I took a picture of the piston(top) since I had the head off to turn it 90 degrees... So I figured to post the picture here. Hows it look? Thanks.

500 lb. koolaid man

I'm still having trouble with the .15 stalling then not being able to restart until the engine is cold, I tune by performance(sound & smoke+not too lean) and due to the engine troubles possibly due to motor temp. I'm just curious since I have a temp. gun, what is the temperature range of an o.s. .15(or any .15 I guess) supposed to be around once the engine is warmed up?

Thanks.