Ex demo advice

[Redmurty]

there all bench run in any case

cheers Spud

[djl50]

My S10 was an ex demo bike with 1000 miles on the clock when I purchased it, now has 7000 miles and running like a dream. Very robust engine so if the deal is right I would go for it.

[-Ralph-]

You'd need to thrash a modern bike right from zero miles to glaze bores or feck up the piston rings, and as Redmurty says they are all run for the first time at the factory. A lot of manufacturers now say there's no need to run them in. The worst that will happen in an engines early life is it might use a little bit of oil, but again no more than the manufacturers state is normal, and it should be checked regularly anyway. The 600 mile oil change is as important as the running in.

[bond_yzf]

Thrashing the bike won't glaze the bores

[mrdelmonti]

Yep you aren't going to glaze the bores by using the engine as intended. I've helped rebuild a few race engines (car engines) they all get thrown together, started and then taken out on the track to bed them in. Engines that are used in the running period in the same way they will do afterwards tend to give higher power outputs and run just a little sweeter.

As for an ex demo I wouldn't worry about it, it'll be fine.

[bond_yzf]

http://www.mototuneusa.com/break_in_secrets.htm

Good bit of reading

[Mike54]

You'd need to thrash a modern bike right from zero miles to glaze bores or feck up the piston rings, and as Redmurty says they are all run for the first time at the factory. A lot of manufacturers now say there's no need to run them in. The worst that will happen in an engines early life is it might use a little bit of oil, but again no more than the manufacturers state is normal, and it should be checked regularly anyway. The 600 mile oil change is as important as the running in.

What causes bore glazing is prolonged light loads, not heavy loads.

Also, modern engine bores are flat rather than in peaks and troughs, so rings don't get worn like they would in new engines from times gone by. modern processes and tight tolerances ensure that a cylinder walls are uniform so "running in" isn't really especially important anyway, and as others have said, they're all bench run anyway so there is little harm to do really. Modern engines shouldnt use oil either in the first few hundred miles, there is no reason for them to.

[AndyB]

I'm a great believer in taking it easy for the first 100 miles on a new bike but that's only in case there's been a cock up during the PDI or a brand new bearing lets go but after that point any problems have usually come to light. With a brand new bike you've also go to remember that you've got shiny new tyres until they've gone through a couple of heat cycles but none of this matters on an ex demo bike.

[-Ralph-]

Fair do's, sounds like you guys know more about it than me.

I was always told bore's glaze because the piston rings aren't flattening the peaks and troughs properly (because the engine was thrashed in early life), so firstly there's rough surface for the gum to stick to, and secondly the piston rings aren't scraping the cylinder walls properly to remove all the excess petrol and oil that makes the glaze.

I guess if modern engines don't have the same peaks and troughs on the cylinder walls then that's less of an issue becasue piston rings will make a good seal from day one, and giving it a good handful would burn up any excess petrol and oil anyway.

In which case there's even less to worry about in buying a demo bike!

[Mike54]

You're right Ralph, but they're not flattening the peaks and troughs of the cross hatch because its NOT been used at heavy load, it's only been used at prolonged light load so chemicals in the fuel have "glazed" the bore

These days tolerances are so tight and machine tools so good that most bike engines cylinders dont even have cross hatch anymore, they're already flat. The motoman thing was relevant back then (1999 I think) and for a few years but not so much these days. Bottom line is that a new engine in a modern bike is going to be pretty much bulletproof unless there has been a mistake in manufacture. A few people riding it (as in the demo) is really not going to hurt it