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Running in?


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In my drag racing days, we used to run them in at very high revs..... both 2 and 4 stroke.

The (highly tuned) 2 strokes never lasted long no matter how you did it. LOLOL

I would say, run it in. ( it only takes an hour )


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Hi Matt,

I cant comment on your machine, or on what your engine manufacturer would suggest. However, I own a PJ Volution 2 (2 stroke) and within the documentation supplied with it, is the following extract..


· The Parajet 2 XT 172 engine has been run-in prior to shipment. This means that your

Volution 2 is ready to fly. It is important however that excessive throttle is NOT used

for at least the first 10 hours of flying. For example, do NOT depress the throttle fully

for more than 30 seconds at a time. A well run in engine will outperform an engine

that has been run at full power for long periods right from the start. You can

potentially damage a new engine with excessive throttle.

Hope this helps,


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I would say running in is a good idea (iaw miniplane instructions).

As im sure you know, inside your engine there are high tolerance components, hammering around at considerable RPM.

Letting everything settle and wear in over a period of time should see everything lasting in the long run.

However, as Simon rightly points out - motor bikes seem to react better to a 'thrashing' from early on. Im not sure how its so different between bike and car engines, but this does seem to be the way it is.

As for me, Im hoping that the thing that gets me into the air will keep me there for years to come, so its 'softly softly' for me for the first few hours! :D


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In my youth...........not that long ago it seems (some say I will never grow up) :P:P

A Part of my work involved working with small plant hire equipment

and as a test one time when we had a new make of disc cutter 10 of them.....I took the time to correctly run five of then in....the other five got no attention whatsoever apart from making sure they started and the identification number stamped onto them ......Because if they didnt Start within 5 pulls they usually got thrown across the building site several times :shock:

every one of the run in machines broke down before even one of the ( THRASHED from the first second )

machines broke down.......To me that was all the proof I needed... :?:?

....A Paramotor engine is very much the same as it works at very high revs nearly all the time...in fact if a engine in anything works harder than a disc cutter engine I would be surprised ...Used and abused comes to mind ... :twisted::twisted:

What we need is disc cutter engines in paramotors (if they made them just that little bit bigger) :idea::idea:

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Working with outboard engines all my life i've seen different results when it comes to new engines, i've seen new engines being thrashed from the very beggining and done 1000hrs but then again i've seen others which have been religously run in and not lasted more than 50hrs, however i think the type of material used on the cylinder walls makes a big difference, but then again i cant really comment as paramotors tend to rev alot higher than an outboard engine.

At the end of the day you dont really have a choice on the matter if youre dealing with a new engine because you have to follow the instructions given by the manufacturer, if you dont follow the instructions effectively youre voiding the warranty.

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I've not built an engine for many years but when I did I always ran in for a reasonably short time but paid most attention to warming the engine up gently from cold throughout it's life. I think that has more importance than anything.

Interesting one that .....when an engine is cold it wears all the moving parts quicker than when its hot and up to temperature.........So if you rev the bollocks off it from start up it gets up to working temp quicker :shock: so by the time its been gently warmed up over a longer period of time its worn more :!:

I dont know which way is better......only that thats my take on the subject :P

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Running in and warming up are both about balance. It is true that an engine wears more when cold, but it will wear much more if run hard when cold.

Oil in a cold engine will not move around so easily as in a hot engine, so some areas of a bearing will be starved of lubrication. Under low load, the area which is lubricated may be sufficient to support the whole bearing and virtually eliminate the metal to metal contact which causes wear.

Correct running clearances are only achieved when the whole engine is up to temperature. A fast warm up will heat some parts (e.g. piston crown) quicker than others (e.g. cylinder) causing incorrect clearances and increased wear.

There are at least two approaches to running in. Race engines are often pre-heated before starting, then run hard immediately. This seems to work if the goal is to get maximum power from the engine, possibly at the expense of reliability.

I would expect that reliability is more important to us. With this in mind, it is probably better to follow a gentle build up strategy, warming the engine under minimal load and increasing load / rpm over a period.

Engines supplied as 'run in prior to shipment' have had the first and most sensitive part of this process carried out.


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