Piston & Sleeve Issue T-Maxx

[logboyaz]

Please advise:

I am rather new to the sport of nitro monster trucks, since coming from a background of older r/c electric cars (Gold Box RC10,etc.) I thought that I would start out with something used and go from there, so i found a T-Maxx that I thought was in really good shape. The first time that it was used by me it ran for all of 5 mintues and then shut off when I hit the brakes. I tries starting it, but nothing happened until it cooled down. From reading information on the internet and visiting a local hobby store it would appear that I need a new piston and sleeve. I guess I am trying to find out if that is indeed the case or can I mess with the tuning? I live in Phoenix so the temp is very very hot right now 109 degrees, would this have anything to do with it? If I do need to change out the piston and sleeve, where can I get instructions to do so and or would it be better to by a new 2.5 engine?

[zueslilbuddy]

you got a pm

[JTMaxx]

You would be better off using the Traxxas engine replacement warrenty then trying to fix this old engine. Trade in you can get a TRX 3.3r engine for about $150.00 bucks.

If you pull the head and inspect the piston and sleeve you will probably find scratches which is the problem you are having with once the engine comes up to temps it just stalls.

Link to engine replacement plan, I traded in a TRX 2.5 for the 3.3 and got a decent deal even with the shipping the old engine back.

Many HobbyTown USA will do it on the spot if you bring the old engine and there a few other hobby shops that offer this service. Strip the clutch assembly and Fly wheel then bring the engine in for replacement. Call in advance to see if it is available. Otherwise call Traxxas support and ask them the best way.


http://www.traxxas.com/products/nitro/erp/trx_erp.htm

[IMADMAN]

If the engine dies when you hit the brakes check your carb linkage to make sure the barrel does'nt close all the way in the carb.when you it the brakes. There has to be a small gap to let air in. Go online and download a T-maxx manual if you don't have one already, it goes over all the basics, also check your needle settings. If the engine has very little compression then it may be time for a sleeve pinch or P/S replacement.

[logboyaz]

The guy at my local hobby store told me that there was very little compression for my engine and that this was one of the signs of Piston and sleeve failure.

Can anybody confer?

[JTMaxx]

Pull the engine apart and confirm the problem. Once dirt gets into the engine it really leaves damage. If an R/C runs ok then comes up to running temps then craps out you may have piston/sleeve damage. Compression is good until after a few minutes of running.

I had a fairly expensive Picco engine this happen to from running a cheap air filter and it would rock for about 2 minutes then just die. I pulled the piston and saw scratches all over it.

[IMADMAN]

You can hold the engine by the flywheel, (make sure the piston is all the way down) if the engine falls under it's own weight( the piston will rise all the way to the top with no resistance) then your compression is very low.

[logboyaz]

Any instructions on how to rebuild or fix these types of engines or at least how to take apart to look inside?

[rccardude04]

Try richening the thing first. Sometimes if you're too lean, especially in a hot climate, it'll die like that. You'd be suprised sometimes how engines will run on low compression.
As far as taking it apart, you really just remove it from the truck, pull the 3 screws off the ez-start or 4 off the pullstart (whichever you have), then the 4 screws behind that which hold the metal plate on with the shaft sticking out of it. Then take the 5 bolts out of the heatsink head from the top and you're inside. If you really want to remove the piston/sleeve, you have to get the sleeve out. Do NOT use anything metal to help though or you'll definately need a new piston/sleeve when it goes back together. Use a Zip-Tie and turn the engine over to wedge it out. Then you should be able to drop the piston/rod off of the back of the crank.
Your rod will probably also be almost worn out if the engine is. I'd do the traxxas engine replacement program. You get a new one, free pullstart, new air filter, new one-way, carb, etc. for only like 30 bucks more than a complete rebuild (piston, sleeve, rod, wristpin).
-Eric

[logboyaz]

How do i enrich the truck? If I do go with a new motor should I get the 3.3 or 2.5R? Does changing the engine mean I have to break it in again? Sorry for the stupid questions, trying to learn as I go.

[rccardude04]

Richen the mixture by turning the screw sticking up from the carburetor counterclockwise like 1/4 turn (90 degrees, or 3 hours on a clock).
The 2.5R would be easier to drive than the 3.3. The 3.3 is a really strong engine and if you're still pretty new at the whole thing, the 2.5R might be a little bit better choice. Plus it's easier on transmissions and tires :)
As far as break-in goes, whenever you change a major engine component or the engine itself, you have to break it in at least to some extent. New piston/sleeve/rod = complete break-in, new rod = short break-in.
New engines do require a complete break-in procedure.
Only stupid questions are those which come after you broke it. :)
Also, you might read the "nitro guide" or whatever it's called at the top of the Nitro forum. A few of us spent a bit of time on that thing a while back and most of your questions will probably be taken care of in there. There's also an FAQ running around that I typed up and you should be able to find it if you do a search. We can't get them to sticky it up top :p
-Eric

[logboyaz]

Thanks for the information and the understanding. I will definitely look at the "Nitro Guide" you spoke about. I love my truck, I just want to use it longer then 3 minutes at a time. Thanks Again!