TMaxx 2.5 Engine/Truck rebuild - RC Groups
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Jun 19, 2010, 11:33 PM
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TMaxx 2.5 Engine/Truck rebuild

I got this Tmaxx in my shop last week. The guy paid $100.00 for it it needed some cleaning he said and during further inspection the engine was froze. So here was how I spent my morning today.

This Tmax had been sitting for a year So here is what I did. I wanted to show that a little bit of time and effort and little bit of know how can get a dusty old truck back to top condition. I have about 3 and half hours in this truck from start to finish. The tool I used were basic. A screw driver, metric hex wrenches, toothbrushes,soft wire brush,break cleaner(non chlorinated) and gloves. I need a heat gun to get the sleeve out of the crankcase an air compressor is a HUGE help but not necessary. The blue goo in the bottom of the tank is what was left of year old fuel in the tank. The engine would not turn over at all. A key to any build is to get organized .That is a struggle for me but how ever you can do it will help.

The engine was first. If this is your first engine go slow and label all of the screws. A manual is available from Traxxas on line it will show you how to do it step by step. You can use break cleaner to get the gunk out of an engine or even Nitro fuel .I have an old jug of fuel It works well for getting the crap to dissolve. I wanted to inspect the bearings to see if any damage had been done. That is why I took out the piston and sleeve. I wanted to get a good cleaning and more important a good lube on the bearings. There was some rust on the crank so I used a wire brush and removed it all. This is why after run oil is so important. You will get years of use out of any engine with that simple step. Remove all fuel after every run and after run oil every time.

You don't need much heat to get the sleeve out heat the out side of the case evenly and get a wooden dowel to get it out don't use a screw driver if you gouge the case or sleeve you might as well call it a day. Gloves are handy here the case is going to be hot. With the engine apart it is time for a good cleaning. I used the soft wire brush to get the baked on oil and fuel off and some rust on the crank. A good soaking in the brake cleaner loosen up the gunk you could use Nitro fuel. It works very well.

After all parts were clean it was time to put it back together. I lubed everything with after run oil as I put it back together.
Last edited by mredzadventure; Jun 20, 2010 at 12:19 PM.
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Jun 20, 2010, 11:27 AM
Kowalski !.....Options
mredzadventure's Avatar
Here is the rest of the assembly. After a engine tear-down cleaning,rebuild and lube. I cleaned the rest of the chassis.
Old tooth brushes and soft bristle brass wire brushes work great. The air compressor is one of the best tools a man could buy. I think they rank up there with the wheel ,fire and BBQ grill for tools that changed the world.

The kid size toothbrushes are great for nooks and crannies. I get the cheap brass wire brushes at Harbor Freight they are a soft but not as soft as a toothbrush and work well for aluminum and steel parts. The air compressor works wonders here for getting all of the dirt out everywhere. Multiple blasts of air and break cleaner and attack with the brushes is all is needed here. Then I use WD40 on the plastic parts little is more here some on the brush scrub and blow off the excess with the compressor. Plastic loves this stuff. Everyone has opinion on WD 40. It works for me.

I used after run oil during the assembly of the engine to lube the entire engine. I also Rem Oil. Its a gun oil made by Remington available at sport shops and even Walmart.
It's very thin and penetrates into the smallest of bearings and races. The pounding that firearms take during there normal use is extraordinary so I have been experimenting with it for the last year to see how it works.

My carburetor test is simple just plug both ends and gently blow into the fuel inlet with some fuel tubing and listen for leaks. it seems to work for this style of carb anyway. The arm and boot will move in and out as you blow into it. I have tested a few of these this way and seems to work .

The Tmaxx is a great truck. I have tore down and rebuilt 7 of these a few things every stock Tmaxx needs.
Any part from RPM is a good investment.
A 6 volt battery pack will work wonders for your steering and throttle and brake.
The Hitec 645 servo or equivalent for steering is a must it will make the Tmaxx s much more responsive you won't believe it. A great investment. I like to add ball bearings to the steering of any Traxxas truck it will tighten it up and make it more precise. If you have an older Tmax the sealed ball bearings are a great addition they will keep a lot of the dirt out of the moving parts. Look on ebay you can find some great deals on bearings for the Tmaxx.

I ran the truck last night. It took a bit to get it started even with a new glow plug. All of the oil I used took a bit to get out of the combustion chamber. It fired and after few more bumps and it was idling pretty good. I set the mixture back to the factory specs and it was a little to rich so it had a hard time accelerating. I leaned it out a bit and that seemed to do the trick. I am not real happy with the compression but that is what can happen when you don't take care of business. It starts well but I think this is the last summer this engine will see before a rebuild or trade in for a new engine. It runs good but not great. The idle goes away a little when it gets to temp and it needs to run on the rich side to maintain a good plume of smoke and tone. I would say the engine is a 3 out of 5 stars good but not great. If this were mine i would be looking into the 3.3 at the end of summer.

I am no expert or guru on any of this stuff but who really is. There are a million different way's to improve any truck.This is just how I do it it and works for me. I just wanted to show what a little time and effort can bring back a dusty old truck to a good running vehicle that you can have a blast running. I focused on inexpensive upgrades that will make a noticeable improvement that I have actually used. Any other ideas are welcomed. There are no stupid questions in regards to R/C in my book we were all new once.
Last edited by mredzadventure; Jun 20, 2010 at 12:37 PM.
Jun 21, 2010, 09:38 PM
rc racer
dialed's Avatar
Great job on that Maxx! I have not touched one since the truggys hit the market and took over at the track, I enjoyed reading this...
Jun 21, 2010, 10:22 PM
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mredzadventure's Avatar
Thank you. It's just one of my adventures from the workbench. My dream is to open a Hobby shop and not sell a single thing I had fun doing it. They guy was tickled when I dropped it off tonight. I was hoping to show how straight forward a engine rebuild was. I had more time in taking pictures and typing.
Jun 22, 2010, 02:02 AM
Registered User
nice clean i know how time consuming fixing up a nitro can be after being left for over a year, i just fixed a mates GV models rex x for him, to clean the engine out i first pulle the heatsink and top of the engine off, the carby, and backplate, i then just poured metho through it while turning the motor over by hand from the flywheel, the let it air dry over night, the car is pretty fast, but still nitro =s
Jun 22, 2010, 10:32 PM
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mredzadventure's Avatar
Methanol is a great solvent a little pricey the brake cleaner is cheap and does a fair job .I will also use old fuel and give it a good soaking. I know I should be getting more into the electric but I keep buying nitro stuff and fixing it up. The electric is way more convenient and clean. When I was younger the top speed and power was nitro . Electric is getting into the realm of fantasy becoming reality. I will make a move over at some point.There is about an engine I love.
Jun 23, 2010, 06:24 AM
Registered User
yeh i know what you mean nitro has that not wanting to let go of sensation, but once you make the change you will never go back, well not to constatly driving the nitros
Aug 31, 2010, 02:17 AM
Registered User
Hi mredzadventure I was looking for information on how to tear down a nitro engine then i found your post. i have a used tmaxx with the .15 engine that just won't start and upon inspection and asking around, it also seemed to have lost compression as well. LHS told me it might be the piston and sleeve. this is my first nitro and im beginning to regret it real hard. i got this used and not knowing too much about it, i ended up with a non working truck. oh well lesson learned for me. so now i am planning to open the engine and see what i can do to it. i do hope i can still make it run. i could only wish that you live in Anchorage Alaska. that way, i would beg for your help hehehe. Great post, very informative for newbies like myself.
Aug 31, 2010, 02:39 PM
Kowalski !.....Options
mredzadventure's Avatar
Thanks for the kind words I actually lived in Sitka when I was a little boy. MY aunt still lives there. Small world

The Traxxas.15 is a good motor. The piston and sleeve will run about $50.00 to replace. Traxxas has a trade in program you send them your old engine plus some money and they give you a brand new engine.

They also have a power up program where you trade in your old engine and some money for the next bigger size. you could trade in the old .15 for a brand new 2.5R
You will need a kit to make it work

This is the route I am going to go My Tmaxx engine died as well.

But you may have some issues with the drive-train with the powerful motor. You can exchange the .15 engine for a new one for $65.00 plus shipping. Look here.

Good luck keep us posted.The Tmaxx is a fun truck

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