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Old 06-25-2004, 10:23 AM
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Jugg2Driver Jugg2Driver is offline
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Here is a nice step by step guide on how to break-in your nitro motor.
All credit for this goes to Grinch!

DO NOT take the motor out of the box and crank it over
Turn the motor over using the fly wheel and set the piston to the bottom of its throw
Put 4-5 drops of afterrun oil on the piston face thru the exhaust port
Give a little shake to distribute it over the piston and liner and turn the motor over by the flywheel 5-6 times to lube the piston in the liner

You will feel the flywheel notch as the piston reached TDC (Top Dead Center) thats normal and eases after a few runs. it can take a little bit of effort to turn it past TDC.
All Engines rotate COUNTER CLOCKWISE when you look at the motor from the front (Flywheel)

Next up set your needles, the GS21 is set as follows, but read the instructions that come with your engine, they are all different.

High Speed needle (By the fuel line) 2 1/2 turns out from closed (Closed is where it can nolonger be turned with very light pressure)
Low Speed Needle (On the end of the slide on the carb) set the screws bevelled edge flush with the slide case
Idle adjustment, there should be a 1mm gap inside the air intake on the carb. (where the Air filter attaches to)

Starting the engine.
Radio ON
Truck ON
check all controls respond, and test failsafe if fitted (Get one!)

place the truck on a stand or something to raise it off the ground.
Fill the tank
Prime the engine by putting you finger over the exhaust outlet and slowly pulling the starter cord, fuel will be sucked along the fuel line. (not too slow thos, it has to be splashed about inside the engine)
When fuel reaches the carb, pull 4 more times (1 pull = about 8 inches of cord. never pull ALL the cord out)
leave it to stand for 20 seconds.
Attach glow starter.
Pull engine over rapidly the engine should start in 3-5 pulls. if not add a little throttle trim to open the air ways.

Once the engine is running

Remove the glow starter
Set trims to neutral if not there already and set the idle, it should be fast enough not to struggle, but the wheels should be easy to stop (ie the clutch is not engaging)
If it stalls, start it up again, dont adjust anything except the idle speed. we are trying to get the fuel splashed over the internals here, not set it for racing.

Run 1/4 tank like this, restarting as needed

Getting moving

Place the truck on the floor with the engine running and gently move the throttle up. You may hear the engine bog, if it does, go slower, if it stalls, turn the low speed needle in 1/4 turn.
Get the truck moving at 1/4 throtlte, it will sound sick :) run the rest of the tank (3/4 at least) going slowly between 1/4 and 1/2 throttle.
At the end of the tank it will stall (may rev up first), using the fly wheel move the piston to Bottom Dead Center and let it cool right down.

Tanks 2 and 3
Start the engine, get her moving (should be easier) run between 1/2 and full throttle. If the engine stalls turn the High Speed needle in by 1/8th turns until it doesnt stall You want to be able to go full throttle, even tho it wont be fast.
Best way is to do full throttle away and 1/2 throttle towards you. Every few circuits run at a lower speed to let the lube get back in (1/4 throttle) The engine should be getting hot as it runs now

At the end of tank 2, put the piston to BDC and let it cool, repeat for tank 3.

Tank 4
Start her up and run her to warm her up. Reduce the high speed needle by 1/8th trun (Clockwise, we are leaning the mixtuer now)

Run the truck for 30 seconds at full throttle, then do a heat test.
I like the spit test, its cheap. Put a little spit right on the engine head by the glow plug. You want it to boil off in 2-4 seconds. If it dont your temp is wrong. if it hisses and spits, add 1/4 turn to the High Speed needle and repeat, if it sits there remove 1/8th turn and repeat. If you have a Temp gun, a Temp of about 200-250F is ballpark



Repeat until you have the high speed sorted, the engine should sing with a high pitched steady whine and not sound like it is choking or bubbling fuel thru, you WILL know when this occurs, then add 1/16th turn to the High Speed Needle (better to be ritch then lean). you may experience what is known as 'clearing out' this is when the engine seems to suddenly find 'second gear' and revs right up. This is a good thing, it means the engine is getting enough lubrication, but not too much fuel as to bog it down.

Tuning the low Speed Needle

Once the HSN is set, we can tune the LSN. Get the engine warm (running temp) then do punch tests.

The Punch test.
Let the engine idle for 15 seconds then punch the throttle WOT!
If the truck hesitates before launching, turn the LSN in 1/16th turn and repeat
Keep an eye on your idle speed, the LSN can effect it.

once the truck launches like a mad man off the line after a 15 second idle add 1/32 turn back on to the LSN.

Always watch temps and check them regurlarly
Always run an air filter in good condition and with oil on it, 1 bit of grit can kill your engine
Use a fail safe. or Throttle Return Spring or BOTH! the last thing you want is your truck breaking a child leg or something cos of radio problems.
You may need to tweak the HSN from time to time, that ok, just be patient with it.
Always set the piston to BDC if the engine is being allowed to cool
Always use after run oil after a run. 3-5 drops down the carb and crank her over 5-6 times. :)
Always remove unused fuel from the tank for storage, and crank the engine over with the starter on to burn off any fuel in the engine, crank until it simply wont fire, then afterrun oil it. Nitro fuel is Hydroscopic, that is it attracts and absorbs water, and that means rust in the engine if you dont remove the fuel and after run it
Dont Chase Dogs, you will win
Dont run in enclosed areas, these thing get up to speed in seconds!

Thanks for posting this up Matt, i would have never thought of it. It should be noted however that if you ask 100 people how to break in a nitro engine you will get 99 different answers and the 2 the are the same will be wrong :lol:

This works for me on my .21 Engines. The key is simply this: you cannot break and engine in without making it work!. Letting it sit and idle thru 8 tanks is doing nothing other than wearing the piston and liner out cos they are cold and wasting fuel. The reasons i say idle 1/4 tank thru is simply to ensure the engine is fully lubed before getting the revs up.

Originally Posted by toyranosaur View Post
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Old 05-07-2005, 06:53 PM
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toyranosaur toyranosaur is offline
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Another way I got from a guy who used to do this to break in motorcycle engines quick-like for racing after a rebuild: He'd take off the air cleaner, crank it up, and let the thing suck a handful of Bon-Ami cleanser (Like Ajax.) He said it broke that piston-to-cylinder-wall fit in quicker 'n crap through a goose! I would never try this on one of my engines, but I'm sure it'll work fine for YOU guys! :lol: Chris
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Old 05-10-2005, 08:08 AM
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I wouldnt use ajax in a Nitro block.... besides anything else without piston rings they break in pretty quick as it is.....

might be helpful on something like an zenoah 23cc petrol engine tho....(for 1/5th scales)

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Old 06-18-2005, 03:01 PM
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Another trick is to mark your flywheel when the piston is bottom dead center. I use a ziptie sitting thru the glow plug hole. Once its at the bottom mark your flywheel. This way you can put you piston at the bottom the first few tanks while you cool the engine. Theres nothing worse then the motor seizing on you. I have seen a couple motors destroyed because of this.

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Old 11-14-2006, 12:39 PM
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Losi Has two ways to break in their LST2 engine and i did the standing idle method. I didnt notice a difference in performance or premature engine wear. so is Losi Wrong or what?
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Old 12-19-2006, 03:56 PM
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A technique that I used to perform on my motors before breakin is called honning the cylinder...I only say "used to" because I have been too lazy to do it lately. I origonally read about this in RC Boat Modeler.

I typically remove the cylinder head but it is not required. Spray a puddle of lightweight oil, WD-40, afterun, etc, down onto the cylinder though the glow plug hole. Rotate the crank shaft so that the piston is cycled up within the cylinder until it starts to get difficult to turn. Don't rotate the piston through compression, just rotate the crank back the other direction until it becomes difficult again. Repeat, occasionally dumping out the oil and replacing with fresh.
What this is supposed to do is remove some of the high spots on the pistons ahead of the break in process. You will notice that the piston will get shinier as the surface gets honed. When it becomes easy to get close to top dead center stop and flush the motor out with more oil.
I have found that break in is a lot easier after this especially with the higher end motors that previously would need a dose of heat gun to loosen up enough to start. I haven't noticed any decrease in life between rebuilds as a result of this process.
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Old 11-07-2011, 05:20 AM
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Did you just buy a new RC Nitro Car? Well here are some tips and necessities to maintain your nitro engine.

Tip 1

you should always break in a new nitro engine before you start using it for races or going full throttle. If not, you can severely damage your nitro engine and the repair cost isn't going to make you smile.

How do I break in a Nitro Engine?
Step 1. First, prime the car. (Plug your finger at the end of the exhaust pipe and pull the pull start without the glow plug ignitor in the engine head)
Step 2. Start your car (Pull the pull start with the glow plug ignitor in.)
Step 3. Let your car run for a full tank of gas
Step 4. Start your car again. Do figure eights with your car at 1/4 throttle.
Step 5. Let it cool down and then, you’re ready to go.

Tip 2

Use 20% Nitro fuel. It will give you the most power in your engine. Preferably Traxxas Fuel. They have great products.

Tip 3

Make sure you tune your Nitro engine. If you do, it will give your engine more power and a longer life time.

Tip 4

Make sure you have spare glow plugs. They can go bad any day or second. They tend to die during the break in process Tip 5

Keep your body on. It will definitely protect your car from damage. (Physical Damage) And especially if you race in the dirt, it will protect your engine from getting dirt into it.
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Old 11-07-2011, 10:05 AM
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I actually have been using the 3 tank idle method for about 20yrs now.
1st fill up the tank with FRESH fuel
2nd Install a McCoy MC-59 plug
3rd Start it up and start richening it to the point it will barely idle with the glow plug ignitor on it.
4th Put a really big towel under it and then put the car on the ground facing a solid wall(preferably a inside corner of two walls)
5th listen for it to start reving when its getting low on fuel

6th let engine cool with piston at BDC and repeat the process for the next two tanks

After the third tank I start turning the needle in until it gets to about 160degs and run it for one tank like that with short on and off throttle bursts
On the 5th tank I start getting it up around 200degs
and on the 6th and final break in tank I get it up to temp and tune the low end..

I get about 5-7gallons of fuel out of a engine this way, in face I had a ofna engine that I literally wore thru the chrome and you could see the brass sleeve. The reason why I run it that rich is because you are actually "lapping" the piston to the sleeve and the extra fuel and oil carries all that material back out of the engine. If you do this method you can look at the rag thats under the exhaust and see all the shiny silver metal that was carried out.

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