How To: Run in a new engine. Run it HARD

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DvDRip

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ok it gets asked allot "how do I run in my new motor?" So I thought I'd put some info up and hopefully get stickied for easy reference.

Fell free to discuss all things running in and share tips on how you do it and any other tricks to keeping that brand new engine healthy :D This way we can keep all the new engine discussion in one thread in the tutorial section

A general misconception about running in bikes is people think you have to go easy on it and ride around slowly without stressing the engine, most pitbike manuals say to do this, well it's just not true.
The motor has to be loaded hard for the rings to bed in properly, basically I just accelerate hard from second all the way up to fourth, but don't let it rev out all the way in any of the gears... then once you hit fourth and before the motor fully revs out just drop the throttle and decelerate all the way down to low revs in 3rd, then accelerate back into 4th and slow down to 3rd again, then repeat going through 3rd and 4th.... don't hold the clutch when slowing down and don't use your brakes, just let the motor do it's thing


this write up is quoted from cactus in another thread and it sums it up pretty well with a technical explanation:

..................vvvcactusvvv................
The reason why you throttle on hard is to create high enough cylinder pressure to get behind the rings and force them out hard against the cylinder wall ... That wears the peaks of the honing off and gives the best possible ring seal ...

The reason why you throttle on , let the bike pick up some speed , then totally chop the throttle letting it slow itself down in gear without touching the brakes is :

When the rings are wearing in , fine metal filings are produced ... If you keep on revving the engine out ... those filings get blown down into the sump oil because the rings haven't sealed yet ... When you instantly back the throttle off , the strong vacuum sucks oil upwards past the rings ... That helps lubricate the bore , rings and piston to prevent metal welding or seizing ... but the main thing it does is pulls the fine metal filings up into the combustion chamber where they then get blown out of the exhaust pipe ... instead of sitting between the rings and causing problems or getting blown into the bottom end ...

You don't want to labour , stall or idle a new motor for very long the same reasons ... If the idle circuit is too lean , you'll heat the piston and rings up too much ... plus less oil gets splashed onto the bore or pumped up to the top end at idle ... The peaks of the cam lobes can also heat up too ... they work harden over time ...

As the rings wear in ... they get hotter than usual so they expand more ... if you idle for too long or labour or rev the motor too much , they can get hot enough to butt the ends up and scuff the bore ...

That's why it's best to do your run in for very short periods at first with intermittent cooling down in between ... as the rings and bore wear in , the friction and heat lessens and the end gaps increase slightly ... once everything is properly run in , the rings and their end gaps stabilize ...

The Chinese engine manufacturers have more than likely taken into account that a lot of owners won't do the run in procedure properly ... so they most likely set the end gaps on the wide side for safety reasons ...

Drag racers use "file back" rings so that they can set the end gaps to their own specs ... the smaller the end gap , the greater the ring seal , the greater the cylinder pressure and the greater the power produced per cylinder ... But with tight end gaps ... the bed in procedure must be done spot on ...

They also use "Zero gap" second rings (ZGS) ... Childs and Albert makes them ...

You want to wear the rings into the cylinder wall in a controlled manner without wearing them too much ... so the on /off throttling procedure should be done in short bursts first ... then the rev out gradually increased as you feel the engine loosening up ...

You'll know when the rings are beginning to seal better because the engine will start easier , idle better and you'll feel it start making more power ... plus it'll start running cooler ...

Then you can enjoy a sweet running , smooth idling engine that holds it's tune ... A properly run in engine will idle steadily all day long without stalling ... a poorly run in engine will always seem like it's out of tune ... oil contamination affects how it runs ...

..................^^^cactus^^^................

another important thing to remember when running in a new motor is set the valve clearance before the first ride and after the run in, the gaps are often way off from factory and while the motor runs in and loosens up the gaps close surprisingly fast.
Setting valve clearance can be very intimidating to those new to pitbikes, but it really is dead simple and only takes 15minuts, and is vital to keeping you engine healthy...
here's some guides to help with valve clearance:
YouTube - How to check valve timin on Honda 50 70 cc motors
http://www.miniriders.com.au/motor-tutorials/24965-how-set-valve-clearances-horizontal-engines.html
QingQi (Qlink) 200GY Illustrated Valve Adjustment - MyChinaMoto

It's also important to run a good 4t mineral oil, so don't use the shipping oil, don't use synthetic or semi-synthetic..... For this I recommend Castrol Activ 4T
 
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DvDRip

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A bit more info from Cactus Jack.....
It's all pretty simple if you put your mind to it ... When the engine is run at idle speed there's more time for the oil to get squashed out from in between the parts ... and that creates more friction ... not good for a new motor ...

ie if you drive a car slowly thru water , the tyres squeegy the water out and maintain grip on the road ... but drive thru at a higher speed and the water will lift the car off the road causing it to aquaplane ...

The same thing applies to rocker arms running on cam lobes and pistons in bores ... When they are moving slower there's more time for the oil to be squeezed out ...

A good explanation of why valve clearance is so important, quoted from cactus of course ;)
As to why the valve clearances should ALWAYS be checked regularly ... ESPECIALLY on a new engine ...

New valves tend to sink into the seats as they wear in ... and that causes a loss of rocker arm to valve stem clearance ... as a result of the lack of clearance ... compression escapes past the valves ...

The high pressure leak can burn the exhaust valve when the heat mixes with oxygen in the pipe by using the same principal that oxy acetylene cutting torches use ... the excessively hot exhaust valve stem can seize in the guide ... a hot valve head can also cause detonation ...

Leaks back past the inlet valve also cause a loss of compression ... the pressure waves of the blow back mess up the signal at the carb ... making the rider THINK that the carb has gone out of tune ...

The symptoms will be hard starting , rich running , hiccing , popping or back firing thru the carb ... The engine will stall often at idle ... and idle poorly ...

New valves tend to lose clearance at first ... but once they settle in they hold their clearance for a longer period ... The REAL culprit is unleaded fuel ... My XR75 engines never lost any valve clearance in over two years running on leaded or lead replacement fuel ... and they only run .002" on both valves ...
 
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jordzan

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Nice one DVDRip thanks mate .... great info there.
 

synergy17

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nice write up dvdrip/cactus jack

should help a few, i definatly learnt somthing from it. :)
 

sparrow334

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ive always just held mine wide from the first time ive ridden them if you run them in slow they will be a slow bike iv never had a problem with any of my bikes
 

Peter1230

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so me racing my engine for the first time i rode it may not have been so bad afterall?

mind you it was my first race ever so i wasnt pulling 1st places haha.. at the back of the pack.
 

wogtaz ryder

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Mite of been.

I would of after a couple practice laps , change oil . then after first race or 2 change oil again...

But when your racing it you dont really let off the throttle completely .. so it mite not of been good..
 

roost666

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nice post guys, I seen a dude rock up to our last grasstrack race we had, rolls a brand spanker white 2010 YZ250F out of his van, lined up and give it hell all day.

I just rode mine pretty much normal just without hitting the limiter, haven't had any probs yet
 

DvDRip

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pete that was probly not so good, holding it wide open in one gear is a no-no for running it in , the idea is short bursts of hard accelerating then decelerating, first race I'm guessing you probly were'nt too hard on it and at least it better than letting it idle for 30mins or riding round at low revs for a whole tank of fuel like some fools on here have done
 

Dreadful

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yeah good work ..... I don't hold it wide but I do rev it hard on and off .... I do that till the header gets hot enough to change colour .... I was told this helps the piston and rings to bed in better.
 

pbk

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another good thing to have is a magnetic oil drain plug because when you irst run it in you will be surpised by how muh metal shavings come from the gearbox and the more metal shavings there would mean more wear and tear

so get an oil drain plug when you buy the bike there pretty cheap too
 

wipeass

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you recommend castrol active 4t. its 10w-50 is that right? and do you recommend using that oil throughout the bikes life?
 

luke.a

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this may sound stupid but is it possible to run it in while i have it sitting on a stand?
 

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