Proper Initial Run In & Break In Proceedures
Posted: June 22nd, 2007, 12:36 am
Jerry Hall is a very well respected engine builder and Tuner. These are his thoughts om 2 stroke engine break in...
....this is what the man said...
1. If the ring is round, and the bore is round... the ring is seated..... period. If you find excessive blow by, get a new machinist.
2. No, you cannot "Heat Treat" anything inside your motor by following some heat cycle ritual you saw on Thumpertalk....
3. So, what are you trying to accomplish then? In a nutshell...... you are trying to acclimatize the piston to the bore..... I'll explain.
Obviously, when the engine is cold, everything is at room temperature. Once started the piston heats quickly, while the cylinder takes a while to catch up as it has both greater mass, and cooling water running through it. At some point the piston will reach a final " No Load" temp of perhaps 300 degrees, and so will the cooling system if we dont start riding.... so monitor things closely and shut off the bike once it gets pretty warm ( Coolant starting to come out of the overflow..)
Great!!! You just did your first run in. The only real purpose is to check your work and see if the engine runs, and is doesnt leak.
At this point you should do two things... retorque the bolts and hoses, and put as large a pilot jet and the engine will take for your riding conditions.
Now, for the breakin- and the reasons behind it.
First imagine your getting into the jacuzzi, and its 103 degrees.... Do you just hop right in? NOWAY! The twig and berries must be slowly acclimatized to the elevated tempreture, or severe discomfort will be the only result... Your piston is no different.
Once you have checked your bolts, and jetting the pilot up, find a fairly large riding area... start the bike, and warm it up. Once done ...... Ride.
The goal is to get the jug up to operation tempreture, then increase the piston temp in stages, up to max operating temp.
How is this done?
1. Once the engine is warm, make a few hard acceleration runs in FIRST GEAR ONLY! This will bring the piston temp up to about 350 degrees.
2. Then make a few runs through first and into second.... 375 degrees.
3. 1st, 2nd, and into third...... 400 degrees
4. 2nd and 3rd.... 425 degrees
5. 3rd and 4th.... 500 degrees
6. 4th and 5th..... 675 degrees.
What you have effectivly done is the mechanical version of lowering yourself into that jacuzzi I mentioned. As the temperature of the piston increased, you very slowly brought the piston to full size, and any micro " highspots" were allowed to mate together for brief periods of time, and then the throttle was closed and EXTRA OIL was allowed into the engine by the oversized pilot jet to both cool and lubricate.
NOTE! No increase was made to the needle or main jet as this would hamper the ability to get the piston temp up to where it should be.
Jerry stated that on his dyno, he can accomplish this drill in about 10 minutes. On a bike it should take about 20. Once done, go hammer that thing!
Excessive running in the garage does nothing.
Putt-Putting ( Babying) the motor for the first hour does nothing.
Some exotic battery of timed heat cycles, cooling off, more cycles, more cooling is hogwash.
The basic fact is that by slowly bringing the piston to size, and at a controlled rate, it's allowed mate to the cylinder wall properly where it can have a long life.
Smiley
....this is what the man said...
1. If the ring is round, and the bore is round... the ring is seated..... period. If you find excessive blow by, get a new machinist.
2. No, you cannot "Heat Treat" anything inside your motor by following some heat cycle ritual you saw on Thumpertalk....
3. So, what are you trying to accomplish then? In a nutshell...... you are trying to acclimatize the piston to the bore..... I'll explain.
Obviously, when the engine is cold, everything is at room temperature. Once started the piston heats quickly, while the cylinder takes a while to catch up as it has both greater mass, and cooling water running through it. At some point the piston will reach a final " No Load" temp of perhaps 300 degrees, and so will the cooling system if we dont start riding.... so monitor things closely and shut off the bike once it gets pretty warm ( Coolant starting to come out of the overflow..)
Great!!! You just did your first run in. The only real purpose is to check your work and see if the engine runs, and is doesnt leak.
At this point you should do two things... retorque the bolts and hoses, and put as large a pilot jet and the engine will take for your riding conditions.
Now, for the breakin- and the reasons behind it.
First imagine your getting into the jacuzzi, and its 103 degrees.... Do you just hop right in? NOWAY! The twig and berries must be slowly acclimatized to the elevated tempreture, or severe discomfort will be the only result... Your piston is no different.
Once you have checked your bolts, and jetting the pilot up, find a fairly large riding area... start the bike, and warm it up. Once done ...... Ride.
The goal is to get the jug up to operation tempreture, then increase the piston temp in stages, up to max operating temp.
How is this done?
1. Once the engine is warm, make a few hard acceleration runs in FIRST GEAR ONLY! This will bring the piston temp up to about 350 degrees.
2. Then make a few runs through first and into second.... 375 degrees.
3. 1st, 2nd, and into third...... 400 degrees
4. 2nd and 3rd.... 425 degrees
5. 3rd and 4th.... 500 degrees
6. 4th and 5th..... 675 degrees.
What you have effectivly done is the mechanical version of lowering yourself into that jacuzzi I mentioned. As the temperature of the piston increased, you very slowly brought the piston to full size, and any micro " highspots" were allowed to mate together for brief periods of time, and then the throttle was closed and EXTRA OIL was allowed into the engine by the oversized pilot jet to both cool and lubricate.
NOTE! No increase was made to the needle or main jet as this would hamper the ability to get the piston temp up to where it should be.
Jerry stated that on his dyno, he can accomplish this drill in about 10 minutes. On a bike it should take about 20. Once done, go hammer that thing!
Excessive running in the garage does nothing.
Putt-Putting ( Babying) the motor for the first hour does nothing.
Some exotic battery of timed heat cycles, cooling off, more cycles, more cooling is hogwash.
The basic fact is that by slowly bringing the piston to size, and at a controlled rate, it's allowed mate to the cylinder wall properly where it can have a long life.
Smiley
