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Top to bottom rebuild break in?

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Three heat cycles seems to be the order of the day! warm it up let it run for a while, shut it down to cool off, repeat 2 more times, after that take it for a spin after warm up, with light blips of the throttle and let it cool off, couple more times and u should be ok for regular riding.

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Ive have a lot of experience rebuilding 2 strokes over the last 10 years between the 4 i have, and here is my procedure. 

 

1. Start bike let run at idle till reaches 100F, turn off let cool

 

2. Start bike let run at idle till reaches 110F, turn off let cool

 

3. Start bike let run at idle till reaches 120F, turn off let cool

 

(as you get into the third heat cycle you might need to coax along with a little bit of throttle but don't push above 1/8th to 1/4 throttle)

 

4. Start bike let run at idle till reaches 100F, then ride bike around camp for 5-10 minutes at 1/4 throttle first and second gear. turn off and let cool

 

5. Start bike let run at idle till reaches 100F, then ride bike around camp for 5-10 minutes at 1/4 to 1/2 throttle first and second gear. turn off and let cool

 

6. Start bike let run at idle till reaches 100F, then ride bike around camp for 15-25 minutes at max of 3/4 throttle second to third gear. turn off and let cool. 

 

Usually after that i baby the bike for the next few rides till i know its rock solid, then let her scream.

 

Every time i start my bike i let get to 100F before i take off, i have a inline thermostat in the coolant return line, i ride in the sand so riding around camp is easy but I'm guessing you get the point of why you run the bike gently at first. giving all the parts time to warm up and kindly break in before letting it run wild. the hottest i run my bike with in the first 5 hours of a rebuild is 165 and hottest after that is below 195.

Edited by knero250

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I let warm to operating temperature then cool. Warmed up again and rode 1/4 throttle for 2-3 minutes then proceded to ride the piss out of it. 25 hours and no problems yet.

 

A lot of people say warm up and ride the piss out of it right away to seat the rings.

Edited by problem_child

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I let warm to operating temperature then cool. Warmed up again and rode 1/4 throttle for 2-3 minutes then proceded to ride the piss out of it. 25 hours and no problems yet.

 

A lot of people say warm up and ride the piss out of it right away to seat the rings.

 

This might work for you, but I'm rebuilding large cylinder race motors. I've had the bottom end of two machined to accept the larger pistons. I prefer to be a little more cautious, ill run 100 hours on my cr250, 75 on my trx with a 310 PV cylinder, and 50 on my trx that have 350 PV cylinders on them. I haven't blown a motor in years, and i don't know if that because i maintain them or if its because i rebuild them regularly but i think one heat cycle, riding at 1/4 throttle for 2-3 minutes and then riding the piss out of it would cause for earlier rebuilds. 

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This might work for you, but I'm rebuilding large cylinder race motors. I've had the bottom end of two machined to accept the larger pistons. I prefer to be a little more cautious, ill run 100 hours on my cr250, 75 on my trx with a 310 PV cylinder, and 50 on my trx that have 350 PV cylinders on them. I haven't blown a motor in years, and i don't know if that because i maintain them or if its because i rebuild them regularly but i think one heat cycle, riding at 1/4 throttle for 2-3 minutes and then riding the piss out of it would cause for earlier rebuilds. 

How so? I kinda figured if somethings gonna break because of break in it's gonna happen then and there.

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How so? I kinda figured if somethings gonna break because of break in it's gonna happen then and there.

well allowing internals such as the rings to expand and cool will give you proper seating, the rings want to expand against the cylinder wall, but when you rebuild you will notice a small gap between the cylinder and piston. giving it time to expand and cool multiple times with out heating the engine to its max results in a slower expansion and is less stressful on the metal this will not cause them to become brittle and break. it may not happen immediately but over time can shorten the life of the rebuild. Also your bearing come from factory full of grease and slowly breaking them in allows for the grease to evenly displace and gives a better coating around the entire sleeve the balls are sitting in. to each their own, different strokes for different folks i just prefer to baby my motors a little more when I've just done a rebuild to try and help them last a little longer.

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I let warm to operating temperature then cool. Warmed up again and rode 1/4 throttle for 2-3 minutes then proceded to ride the piss out of it. 25 hours and no problems yet.

 

A lot of people say warm up and ride the piss out of it right away to seat the rings.

That's how all the old Ice Racers do it here. I've done it both ways, I rode a race with a bike I hand't even started on a fresh top end! It ran fine. 

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