Question about warming up engines (not boxers)

[Mouse]

I'm having a discussion on another internet site about warming up bike engines - not specifically air cooled boxers, just in general.

I maintain that the best way to warm up any engine is to use it "normally" from cold - that is to say, with a bike, you would start the engine and ride off immediately, being gentle with it until the temperature was in the normal range.

Other people claim that you shouldn't ride until the engine is warm, thus they leave their bikes idling for 5 minutes before riding off. Of course some people think the best way to warm the bike up is to thrash the nuts off it at 6am, but we'll ignore them

Am I right?

And more importantly, why? I've always believed this advice to be good, but never really known the mechanical reasons behind it. I know for example that if you leave the engine running with the choke open, the rich micture will wash the bores of oil causing increased wear. But is there a good reason not to let a cold engine idle with a normal mixture?

Cheers

 

[cookie]

you are totally right, that's why all manufacturers recommend doing it that way.

the reason you don't warm engines up by leaving them ticking over, is that they warm up faster when used as intended. that way all the parts expand to their normal tolerances quicker = less wear.

 

[riverking]

A few reasons but mainly..


Oil pressure - it takes AGES to distibute when cold at idle - a FEW revs is better
More importantly..

Crankshaft loading - the shaft needs to be loaded up in one direction rather than 'jiggling about' with light forces in opposite directions - it b*ggers them quickly - once saw a very expensive 16 cylinder diesel wrote off for the reason that it was only ever 'test' started for 15mins once in a while (standby generator)
(a bit like the old fixed wheel pushbikes - better to load the crank with both pedals pushing than to prat about on/off backwards & forwards if that makes sense)

 

[(RIP) Kaister]

I don't think there is a truly right or wrong.

Start an aircooled two stroke up and ride it away quickly and it'll 'cold-seize' ie the piston will expand quicker than the barrel and nip up near to the studs.

Kawasaki set their engines to rev the nuts off on choke so they warm up quickly with lots of oil flowing.

All racing teams start engines and warm them up to full operating temperature before letting them out of sight.

Most road bikes have enough tolerance to allow for any method - after all, they have to work when operated by monkeys.

I favour the warm up for a bit , then ride method.

 

[Mouse]

I'm not sure something that's valid for a race bike always translates directly to real life - race bike engines are rebuilt every few hundred miles, for a start. They're trading longevity for peak performance.

Anyhow, thanks for all the info!

 

[Flaps]

I've always let the bike warm up for about 15-30 seconds before pulling away, enough time to put on helmet and gloves. This, apparently, allows the oil to flow around the engine before putting it under load. I turn off the fast idle when one bar shows. I have been told that when the engine is cold it is best never to over rev it (I limit myself to 3-3.5k) or, and this is the most important, never let the engine labour.

 

[(RIP) Kaister]

Most road bikes have enough tolerance to allow for any method - after all, they have to work when operated by monkeys.

did you miss this bit ??

 

[Mouse]

I didn't miss that, but this is a hypothetical debate about the "best" method, not what "will do" for everyday use. I'm just tyring to understand the engineering behind the issue, rather than getting strict advice on what to do

 

[Le singe]

Motomartin,are you saying us monkeys don't know how to operate machines?

 

[riverking]

I didn't miss that, but this is a hypothetical debate about the "best" method, not what "will do" for everyday use. I'm just tyring to understand the engineering behind the issue, rather than getting strict advice on what to do

If you really want to know, look up 'TRIBOLOGY' on the internet - keep you going for years

 

[Beemerboff]

Honda reccomend that you warm up the engine at varying revs until it will run without the choke, then drive off .
So , dont warm it up at a tickover , and dont drive with the choke out.
Both for the reasons already posted.