Break In Break-in? should I stay under 15mph...

crowvise

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Break-in? should I stay under 15mph...
...while going downhill if I'm not using throttle to obtain overage?
...or should I coast under 15mph using brakes downhill?
 
Break-in? should I stay under 15mph...
...while going downhill if I'm not using throttle to obtain overage?
...or should I coast under 15mph using brakes downhill?

I would say that as long as you are coasting in neutral, you can go any speed downhill during the break in...
 
Assuming we are discussing a Chinese 2-stroke kit:
Go as fast as you want to, just do not hold a fast or steady speed for longer than 100 yards or so. Vary your speed and throttle position for at least the first 2 tankfulls.
It is best to run the engine hard in short bursts to let the piston rings break in properly.
Never ever under any circumstances during the entire life of the engine coast down hill with the throttle closed or near to closed. The only lubrication that the engine gets is the oil mixed in with the gas. With high engine speeds and a closed throttle the engine will starve for lubrication. Hold in the clutch and let the engine idle while coasting down hills.
Also with a new engine, first time out, ride it for 15 minutes or so then stop the engine and let it cool down completely.
Second ride do the same for a half hour ride.
Third time do the same as second ride.
After that you should be good for long rides.
 
I built a mount to aid in the break in process. Haven't used it yet. Are you saying I shouldn't tape the throttle at approximately 12-15mph for a half hour? how often would I need the 'burst'(ie. could I have it taped 5; 10; or 15 minutes then give it a 10 second burst? I don't like having to go slow on the road and not be able to quickly get out of sight in the event that an inquisitive war pig decides to draw a battle line.
 
You can do smoky rolling burn outs if you want to, just don't hold them for longer than 3 seconds or so. The engine absolutely must be under a load, hauling your hiney down the road to properly break in. I never said go slow. Vary your speed from slow to fast to slow to medium to slow to fast..... you get the point.
Just starting the engine in a stand with a fan or something blowing air on it is quite possibly the worst thing you can do to it.
 
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I'll take your word 4 it. You, and a small handful of others, helped me w/ my clutch problems in your responses to others w/similar problems.
But for curiousity's snake: what is the science behind using/not using the stand idea?
 
Also with a new engine, first time out, ride it for 15 minutes or so then stop the engine and let it cool down completely.
Second ride do the same for a half hour ride.
Third time do the same as second ride.
After that you should be good for long rides.

Do not forget the cool down rests, they are very important. Let it sit for at least 45 minutes. A total cool down of more than an hour is best.
 
I'll take your word 4 it. You, and a small handful of others, helped me w/ my clutch problems in your responses to others w/similar problems.
But for curiousity's snake: what is the science behind using/not using the stand idea?

Piston rings are not manufactured perfectly round, and neither are cylinders.
They must be properly broken in, or married, before you can expect the best sealing efficiency.
In order for the piston rings to properly marry with the cylinder wall the engine needs to have a load on it.
With the engine just running static in an engine stand at any speed there really is not much pressure applied to the piston. Yes you might get screaming RPM's out of it, but that is not really working the engine, just abusing it.

When the engine is under a load you are putting resistance to the piston's ability to get pushed down by the pressure from the expanding gasses created by the combustion process. These gasses seek out every nook and cranny trying to escape. They will create pressure behind the piston rings, actually getting into the piston ring lands (ring grooves), forcing the piston ring outward away from the piston and pushing the piston ring's sealing surface tightly against the cylinder wall.
When a cylinder is brand new or freshly rebuilt they are finish honed. This honing process not only precisely sizes the cylinder to the piston size, it also leaves a fine cross hatch of ridges in the cylinder finish. Quite similar the the face of a hand file. It is important that the piston ring gets worn down by this rough surface before the surface gets worn smooth.
If this does not happen, the piston rings will never be able to properly seal against the combustion pressures and you will get what is called piston blow by. The pressurized gasses will blow by the rings and down the sides of the piston ultimately reducing the available pressure to push down on the piston and make power.

There are many differing views on the whole procedure.
This is the one that I mostly adhere to and It has not failed me yet.
I did not learn the procedure from this site, but It best describes the whole gist of how and why.
FWIW I do not agree with his take on heat cycling when it comes to these cheap Chinese engines (complete cool down between runs).
http://www.mototuneusa.com/break_in_secrets.htm
 
Thx man. You made my brain sigh. It craves details. (Like cold mountain water in a dry desert plain. -) My mechanic buddy takes offense if you ask any questions like that. Also for asking or bringing up someone elses opinion. Says angrily, that as long as he has been working on motorcycles, my doing so demeans his intelligence. Anyway, i also read the article last night. Going to subscribe. Would you say the other topics are as noteworthy/credible?
 
Thx man. You made my brain sigh. It craves details. (Like cold mountain water in a dry desert plain. -) My mechanic buddy takes offense if you ask any questions like that. Also for asking or bringing up someone elses opinion. Says angrily, that as long as he has been working on motorcycles, my doing so demeans his intelligence. Anyway, i also read the article last night. Going to subscribe. Would you say the other topics are as noteworthy/credible?

it's too bad that your mechanic feels that way because I know for me, the more I understand about a portion of something-- like what GearNut explained about cylinder sizing and shaping-- the more I understand about the overall picture... the more I respect what's going on...

I now know not just that "it is important to break in your engine" but what exactly is HAPPENING during the "break in"...

As for the cool-down time, the written directions that came with my kit recommended a 20 minute cool-down between one's first few shorter rides. It doesn't say WHY you should though.
 
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