used tmaxx classic with 3.3 is all sorts of funky

[stretchnutz]

So I traded off a bandit for a tmaxx 3.3. Ran fine when got it. Took it home n cleaned her up and has puzzled me since. I got plugs, pull starter, spur gear, New air filter n the mantainence oils. Set the carb to factory since was set a lil lean n haven't.gotten it to tune since. I pulled the motor n checked for leaks, none, the bearings are fine and the clutch shoes look brand new. Once it seems to be in the "happy truck" spot it runs great till I shut it off. Then acts like nothing's tuned right. Another thing I didn't get is it wouldn't shift into second. Opened the tranny up and its converted to single speed. Figured maybe he used it for pulling hence the metal eyelet on the back bumper. Anyone has any tips or thoughts on this I would appreciateit.

 

[Phins Fan]

I would say an airleak is typically the biggest culprit for an irregular tune. When you checked for leaks did you reseal the backplate, carb, and pullstart/ez start assembly? If so what did you use for sealant? The 1 speed I couldnt help out with but that may affect tune as well. Does it have the high or the low gear only? Set at low gear I would imagine would cause overheating as its always runnin at higher RPM's. Opposite for high gear only as you may burn thru clutches trying to get the high gear to fully engage.

 

[jchampion99]

make sure you check your gas tank for air leaks too. if thats not it check your piston because i had a 2.5 in mine and it was a pain to tune in and come to find out the piston was broke on the bottom of it.

 

[stretchnutz]

I checked it this morning using the soapy water technique. Didn't find any. So I tore it apart to check the internals which all looked good (bearings, rod, piston etc.) And all the o-rings were in good shape. And not sure which gear I'm guessing the low speed cuz it gets allot of torque but only gets up to maybe 20mph. I'm planning on getting the parts to return it to a two speed trans. And may pick up a new carb or atleast carb rebuild kit for it so I can eliminate it being a factor. And thinkin bout it I might get a tube of high temp sealer just in case

 

[Kyleb]

If he has just locked it in 1st, it should be reversable. Should just be 3 screws in the primary gear. Did you happen to get any pics?

 

[stretchnutz]

I'll post some when I tear it apart again . And its not locked, I found it out when I pulled the rubber plug to adjust it.and there wasn't a set of screws there. There's only one set of gears in it. Someone changed it to a single speed in the past. I'm assuming the reason was so it would just be low geared for pulling since there's a steel hook on the back bumper and the rear diffs way more worn than the front.

---------- Post added at 9:34 PM ---------- Previous post was at 9:30 PM ----------

I know its hard to diagnose the problems when getting a used nitro since I don't know what its been through or the level of maintenance done to it lol. I appreciate eberyones input and suggestions though. Thank you

 

[Snook Man]

Once you shut it off will it restart when the engine temp is still up?

The single speed conversion is geared between what 1st and 2nd gear would be, it was probably not installed for pulling as most all pullers would increase the drive ratio for more torque.

 

[stretchnutz]

Ahhh. I see. And ya after it starts to run decent it doesn't want to start up again. I have to increase the.throttle trim to get er to fire. Which it could just be my tuning but the last nitro I had I built from frame up and it had the pro .15 and I got it tuned in 10 mins and rarely ever had to readjust it. And if I did it was like a 1/16 of a turn.

---------- Post added at 8:47 AM ---------- Previous post was at 8:45 AM ----------

Btw my hsn is about 3 1/4 turns out and the lsn an 1/8 turn.in from flush with inner ring. Running stock pipe and as far as it looks the stock carb.

 

[jose.28]

If the engine runs fine then when it gets to temp runs funny or it wont start when hot then that is the engine that is bad. I had the same problem with the 3.3 and it was no compression when hot. It did start after it cooled off

 

[Phins Fan]

I still lean towards an airleak of some sort. Buying a high temp RTV is a good start. make sure you do the pullstart/EZstart backplate, base of the carb, and even a little grease in the highspeed needle screw wont hurt either. Also buy some fresh fuel tubing. I don't agree with Jose that the motor is junk, especially if you tore it down and everything seems to be fine. Start with the cheap easy fixes before you drop $150-$300 on a new engine that didn't need to be replaced in the first place

 

[jose.28]

I still lean towards an airleak of some sort. Buying a high temp RTV is a good start. make sure you do the pullstart/EZstart backplate, base of the carb, and even a little grease in the highspeed needle screw wont hurt either. Also buy some fresh fuel tubing. I don't agree with Jose that the motor is junk, especially if you tore it down and everything seems to be fine. Start with the cheap easy fixes before you drop $150-$300 on a new engine that didn't need to be replaced in the first place

Wait! Let me clear my self.
I didnt say it was bad and if it came off like i did I'm sorry.
i had the same problem.
My 3.3 would run fine till it got to temp. Roughly 10 min in.
then the idle would go down and id lose alot of power then it would shut off.
To restart it i would have to open throttle some more and push the botton untill it started. It was a pain. If i let it sit for about 10is min it would start and get full power but it would do the same thing again shortly.
I spent days looking and i ended up rebuilding the carb and checking everything and also replaced the back plate seal.
Days later i found that i was losing compression when hot.
Got a new engine and also a sleeve and piston as i have a few 3.3s
I then swapped out the same piston and sleeve along with the rod and broke it in and never had that issue again. Have a half of gallon thru it so far.

I'm sorry i came across to wrong way.

 

[stretchnutz]

I am definately going to tear it down n seal it up with high temp sealer n possibly rebuild the carb. Just to rule them out for sure. I've been working long hours since i work at budwieser n its almost 4th of July so I haven't.messed with it much. Did a lil earlier for an hour or two and I swear the lsn and hsn don't matter, I've been just about every where within flush on inner and putter ring on lsn using clock dial method of incriments and everywhere between 2 3/4 to 4 1/2 turns out on the hsn. I know the 3.3s are picky but damn lol. I'll recheck the piston and sleeve when I tear it down again to make sure there's still a pinch n no lil cracks. (Although didn't see any last time). Might look into seeing if my lhs has the kit to change it back.to a two speed tranny so the reak in tuning settings will be more accurate.......oh how I miss the trips to hobbytown because i wanted a part instead of needing one lol. Gotta love the world of nitro.rcs, 30 % play,30% maintenance, and 40% scratching your head at hobbytown wondering how long the next part will last lol

 

[stretchnutz]

Ok yall are gonna love this newb mistake I made. Upon teardown to seal it with rtv I found I put the piston in backwards with the notch towards the exhaust side rather.than intake side lol .

 

[jose.28]

Ouch I'm not sure but it may be bad for the piston and sleeve.
I hope that was the issue for you. Let us know how it runs after fixing that.

 

[stretchnutz]

I will tommorow after the sealers had time to cure. N I hope not lol. I think it just affected the ability to seperate the stages between the combustion and intake/exhaust sequence. After flippin it around n sealin it up she def seems to be harder to turn over by hand

 

[stretchnutz]

We'll fired her up, took three pulls ( I consider that damn good since didnt do any priming) and after about four adjustments or so on the tuning she had a nice line of smoke, good rpms, and ballooned the front tires. (Rear diffs are worn). Everything ran great tillll I noticed it gettin real blotchy n discovered my da stripped out the fuel inlet on the carb lol. So off thursday to get a carb but I feel she ran 100 times better till that. Goes to show even if you think your motor is sealed, just put some rtv on it anyways . Thanks all for the opinions n help on it.