wizard69

Member
May 3, 2001
251
0
I just got my motr rebuilt and i was wondering what the proper way to break it in would be?it is a 02 kx250(doubt that matters)I have never broke a bike in before so what should i do?thanx for any help
 

MONKEYMOUSE

~SPONSOR~
May 10, 2001
889
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Heat cycles, let the bike idle for 10-15min then let it completely cool down. Do this around 5 times. Then ride the bike around staying under 1/4 throttle, and then allow it to cool. Then under 1/2 throttle again let it cool. Then 3/4 throttle, let cool. Then you should be all set. That’s how I've always done it, haven’t had a problem yet. Oh also I would richen up your fuel mixture for breaking it in. Also do a search, tons of info on this site about this topic.
 

stangmata23l

Member
Mar 14, 2002
34
0
Everyone has their own way, but monkey mouse is correct.. heat cycles.

Richen up the tank. I would skip the 3/4 throttle part and instead, while riding under half throttle "blip" the throttle once in a while to get the engine into its powerband.

After a tank of gas (if even that much) you will be good to go.

Have fun!
 

Bizerk

Member
Feb 28, 2004
142
0
Won't the spark plug foul after leaving it idle for that long that many times? I just rebuilt two motors but have not started them yet because of the weather outside. Your input is greatly appreciated. Thanks!
 

Porstala F9

Member
Jul 30, 2003
345
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The spark plug may foul because of the combination of new parts + a richer mixture some people initially run, and the fact that you need to stay away from wide open throttle for the break in period. But I have personally never fouled a plug for letting the bike warm up for a while (not idle, but gently rolling throttle)

Like mentioned, everyone has their way. I personally just warmed the bike up for about 10 mins, and ride it around for about 10,15,20 minutes three times. One time under 1/3-1/4 throttle (fouled a plug there) - The next time under 1/2 throttle, and the next time about 3/4 throttle. And from there I let her rip. But I know guys around here that just warm em' up for a few minutes and ride them like they stole em
 

Coolector

Member
Nov 25, 2003
106
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Do you guys mean richening up the mixture by adding more oil?? Like from 32/1 to 25/1.Doesen't that actually lean out the fuel?? My2cents
 

MONKEYMOUSE

~SPONSOR~
May 10, 2001
889
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No, that won't lean out the fuel. In richening (sp?) the mixture your adding more oil, witch intern there will be more lubrication during the break in period. After you burn all of that tank go back to your normal fuel mixture.
 

Bodge

~SPONSOR~
Oct 4, 2003
481
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If your bike was good jetting wise and it has not gotten colder where you are since then there should be no reason to richen the oil-fuel mixture. Your engine needs the correct amount of Gas and oil to be lubercated properly. If there is too much oil and not enough gas then the engine will be lean fuel wise, which is not good.
 

MONKEYMOUSE

~SPONSOR~
May 10, 2001
889
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Again like said before every one has their own way in breaking in a motor.
 

adstott

Member
May 23, 2002
65
0
Making your bike more rich does not mean adding more premix. The definition of rich is the amount of fuel in the combustion chamber. So a more rich condition means you are getting more fuel then you were before. If you add more oil that means there will be less fuel which leans it out. I know it sounds bass ackwards but that's the way it is.
 

joe28kdx

Member
Sep 28, 2001
235
0
I warm my scoots up, shut it down, check torque on the head and cylinder, fluids.
Them I go for a ride, not a hard ride, just run the scoot. Nice easy trail.
Go home, recheck torque and fluids again and that's it!
I've rebuilt the top end, loaded the bikeup and raced! Many times!
Joe
 

fox_racer

Member
Mar 17, 2004
8
0
What i do is go in first gear for about fifteen minutes second gear for fifteen minutes and so on and so on but dont hold your throttle in one spot always speed up and slow down. DON'T hold it at one speed. And also mix your gas a little richer.
 

DEX

Member
Jun 11, 2003
178
0
Im no expert but I would think it has more to do with the RPM range then waht gear you are in. I would think it would be fine to be putting in third gear as long as your not revving it up to get there. I would think first would make it alot harder to keep it at a low RPM while driving for like 2 hours.
 

joe28kdx

Member
Sep 28, 2001
235
0
If your injection is working correctly, it doesn't need to be richned up!
Don't you think you put more stress on your engine, say the last lap of a muddy race after it's been hammering for 2 hour or when you and your buds have been ripping up the earth all afternoon?? The manufactures have tested the oil mix and know what to put in to keep them running.
Keep the RPM and load, (lugging it), to a mimuium unitl every seats in and the toleraces ease up and it'll be fine.
If you start screwing with the mix, you'l just load it up, them you'll have to clean it out by reving the BE-Jesus out of it, the spike in RPM will just hurt your new motor.
I don't even worry about a new motor, I've had them totalal rebuilt, ran @ a few minutes and raced. (I have dump my gear oil when I get any gear/crank/clutch work done, to get rid of any junk left in there.
All scoots, (2 smokes) are needle bearing design, they spin easy, the cylinders are for the most part hardned, (chrome plate, etc) so they are tough.
Keep the filters clean and dirt out of the engine and ride, don't loose sleep about how to break a new one in!
I've yet to find a, "off the assemble line" motor really tight, most times they are in the middle of the tolerences. If you have your cylinder bored, (old style cylinders), you had to watch piston/cylinders spacing. You gotta check the ring gap when you do a rebuild, but I've only seem/heard of a few that were too tight ring gap or wrong piston.
Joe
 

TravisP

Member
Sep 11, 2003
30
0
Actually adding more oil is leaning out the mixture i know it is confusing but if you have one gallon of gas 4 ounces of oil (32 to 1) ok take that same gallon of gas and add 6 ounces of oil in your mixture you now have less gas. A carb jet doesnt know the difference from gas and oil it meters the same amount of the mixture so you have less gas and more air which is leaner i know i didnt explain it well but trust me.
 
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