running in your 2 stroke engine properly

Running-in an engine has always been one of those little mysteries to a newcomer, where to an experienced racer it is a chore that we do without even a second thought.

I recently came across the following instructions in a Yamaha kart engine box and it certainly expanded a little on my own usual brief words of "take it easy for 30 laps". Thankyou to the original author, whoever you may be !!

Running-in is usually done over three ten minute sessions.
1st session : Low speed on straights, with **full throttle through slow corners. Ensure some smoke is blown from the exhaust. Allow the engine to cool.
2nd session : Low to medium speed on straights, **full throttle through slow and medium corners. Allow the engine to cool.
3rd session : Medium speed with occasional high speed bursts on straights. Allow the engine to cool.

* * Full throttle through slow corners helps the engine reach temperatures that the engine normally runs at during a race. Many people do not 'load' the engine enough when running-in the engine, resulting in a seizure the first time the engine is run hard.
If the track you intend running your engine in on has long straights, you may want to consider reducing your rear sprocket teeth by about five to ten teeth. If at any time you feel you may have over accelerated the engine, choke it immediately * *.

Following sessions : Run a number of slower laps ( similar to a roll-around ) to allow the engine to come up to temperature before long sustained full throttle openings are held, otherwise the piston may expand at a greater rate than the cylinder, resulting in a seized engine. Always try to run your engine slightly rich - it only takes ONE run at too lean a mixture to damage your engine. If the setting is too rich the worst that can happen is a fouled spark plug ( slightly cheaper to rectify !! )

Note ::
My suggestion for a watercooled engine is you should do three fifteen minute sessions .

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So ur saying that after 3 ten minute sessions the bike should be fully ran in.

Some people will tell you otherwise. It is quite unsure about the proper run in, some say 30 laps others say 2-4 tanks.

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Ive been told 3-4 tanks and ride bike for 5-10 minutes then let engine cool for 10 minutes and so on and so on.

Running in a motor is something that no one can agree on. Everyone has different theories.

Also Jeremy, the motor will not sieze if u don't let it slowly warm up.

Using a 2 stroke hard right after starting - at best, is very hard on it. The piston/rings expand faster than the cylinder.

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Custom CAG Style Bike
14.5 to 1 compression 5 port head
Run on AV gas
Ported Piston
.005" Copper Base Gasket
Fatboy Exhaust
Balanced FC 10mm Crank
6mm Reed Spacer
BW Reeds
Ported stock carb: 15-16mm straight though,
tapered to 19mm
Jet size approx 80 to 84
Advanced Timing
Lightweight Flywheel

there's a gap in the rings to allow for exspansion

a mate of mine who is into his bikes told me he has always just taken it easy for 10 - 15 minutes then just held it flat strap for a minute or so and that was it. the only time it didn't work was on a kx 250 which blew up.

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cheapo 1/4 fairing with:
triple stage carbon fibre reeds
14/14 rep
alloy starter
fatboy
rocket key (not anymore all chewed up)
ngk bm7a
high flow fuel filter and lines
boost bottle
(by 1/4 fairing i mean 1/2 with a lot of plastic cut away to fit the new fuel tank and have a better turning circle)

Everybody has their own theory on how it should be done. I use the heat cycling method very similar to the original post in this thread. If I were to wait until I used 4 tanks of fuel it would take me two months to run the motor in.
I think every method has it's own + and - but one thing is for sure. Never flog a new motor from the word go (although there would be some that say it's ok).

Another point to make is to just not ride and ride without looking at the internals. I try to pull the barrell off every 4hrs of running time, clean up the piston and usually fit a new ring. Also every 6 months I renew bottom end bearings. By doing this and keeping it fresh on the inside you get longevity out of the motor.

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Make mine a double !

my bike has been runnign 4 like 4 years and hasnt missed a beat and since me my mate or his mate owned it ( lol its 4ht hand now) it hanst been cleaned out like that