Do you warm your bike up before heading off?

[Badjelly]

The next factor is the oil. Not so important with hi-tech oils as it used to be but oil does need to be warm and up to it's rated viscosity before it does its job properly. If you kick it to life and boot it off down the road there could be parts of the motor running in very little useful oil.

Sorry to be a boring tech geek, but I was doing a bit of research on gearbox oils recently and can't resist the opportunity to share.

That should be "down to its rated viscosity". The viscosity of oils decreases with temperature. And the effect is surprisingly large. The quantity used to characterise the change of an oil's viscosity with temperature is the viscosity index (VI):

http://en.wikipedia.org/wiki/Viscosity_index

It's an arbitrary scale on which a good mineral oil without viscosity-improving additives will score 100. Synthetic oils go up to 400 (less change in viscosity with temperature). From my reading of various tech sheets, the kinematic viscosity of a VI 100 oil will drop by a factor of 10, yes 10, between 40 C and 100 C.

[Cajun]

I heard a number of different things, and alot of it varys from bike to bike, from carb to Fi.

personally i fire it up, warm it up for abotu 10-20 secs before taking off, and take it nice and easy until its warmed up.

Alot more Carb based bikes do not like working correcctly warmed up a bit, where FI bikes are happy to get on and go once turned on.

Where i have heard other storys of some bikes (vtr1000f) that warning up on sidestand lots, can cause issues quicker than if not.

So personaly perference depending on your invidual bike.

[98tls]

In theory i would say an oil pump finds it much harder to get thick/cold oil to where it should be if the bikes left to idle for long periods when cold,even at fast idle the pump isnt really working hard.A few blips on the throttle will get oil circulating better.

[Magua]

Full choke for around ten seconds, then I leave it to idle while I put my gloves and helmet on.

[Mort]

I tend not to mainly because :

• I only use the bike on a minimum of 50 Km journey
• It runs/drives fine whilst warming up
• Its warmed up within 2 minutes
• I don't thrash it from cold
• I use synthetic oil because its better for cold starts
• If I'm doing a track day I make sure the engine is properly warmed up before going out

[CookMySock]

In theory i would say an oil pump finds it much harder to get thick/cold oil to where it should be if the bikes left to idle for long periods when cold,even at fast idle the pump isnt really working hard.A few blips on the throttle will get oil circulating better.

Usually the pump will be up to working pressure in seconds, and then its relief valve will bypass, even at idle. Once the oil has thinned a bit due to warming, the relief valve will close off, pushing all or most of the oil through the engine, until the revvs rise and it will relieve again.

The problem is, thick oil presents quite a high loading to a high speed bearing. Full explanation http://www.joegibbsdriven.com/traini...er/082106.html

Key sentence ;

In an operating bearing, if it becomes necessary to increase speed, ZN/P will increase and it may be necessary to decrease oil viscosity to keep ZN/P and the coefficient of friction in the design range.

The only way to decrease oil viscosity is to let it warm up properly, or put a thinner oil in it to begin with.

The bottom line is, if you revv an engine hard with a too-thick oil in it (oil is too cold or wrong SAE rating) then you will spin a bearing in its housing.

Further reading ; http://www.google.co.nz/search?q=%22...ture+viscosity


DB

[breakaway]

Whats the difference in the bike sitting still and motor doing 2000rpm (choke on) and the wheels going round and the bike doing 3000prm?

Pull in the clutch when you're rolling around doing 3000 RPM and see what happens.

[98tls]

Usually the pump will be up to working pressure in seconds, and then its relief valve will bypass, even at idle. Once the oil has thinned a bit due to warming, the relief valve will close off, pushing all or most of the oil through the engine, until the revvs rise and it will relieve again.

The problem is, thick oil presents quite a high loading to a high speed bearing. Full explanation http://www.joegibbsdriven.com/traini...er/082106.html

Key sentence ;

In an operating bearing, if it becomes necessary to increase speed, ZN/P will increase and it may be necessary to decrease oil viscosity to keep ZN/P and the coefficient of friction in the design range.

The only way to decrease oil viscosity is to let it warm up properly, or put a thinner oil in it to begin with.

The bottom line is, if you revv an engine hard with a too-thick oil in it (oil is too cold or wrong SAE rating) then you will spin a bearing in its housing.

Further reading ; http://www.google.co.nz/search?q=%22...ture+viscosity


DB

Interesting read.Yea i know its sad i find reading about oil interesting Was reading an article the other day on the internet about oil pumps etc and had a chuckle when they tested an aftermarket oil pump on a Harley,seems a few in the states had had problems after having there bikes idling at around 900 rpm with oem oil pump because it sounded goodupon testing the oil pump at those rpms it showed it wasnt pumping bugger all if at all anything.

[Toaster]

When my bike was in one working piece I backed it out, started up and left it running while I farted around with gloves, helmet and fumbling for the garage door remote.

Usually has a bit of warmth in it after a nice slow ride down the gravel drive to the road listening to the deep rumble of the v-twin.

[EJK]

My bike stalls on the lights if I don't warm it up... Low power bike you see?

[yod]

like the toastmeister said; i start her up and then let her run while i'm arsing around getting gear on....can't hurt, can it

[CookMySock]

a nice slow ride down the gravel drive to the road listening to the deep rumble of the v-twin.

hehehe, ooh.. hehehe, ooh, hehehe, ooooh. Yep.

My bike stalls on the lights if I don't warm it up... Low power bike you see?

/me points at teh choke.. just enough so the revs rise a little bit..

DB

[FilthyLuka]

My bike stalls on the lights if I don't warm it up... Low power bike you see?

It happens, talk to Xerxes about traffic lights and stalling

/me points at teh choke.. just enough so the revs rise a little bit..

You really shouldn't ride your bike with the choke on...

[Biggles2000]

Starting:
The initial few seconds after hitting the starter is the critical time for engine damage mostly due to low oil pressure. Modern oils are great things they flow easier when cold and stick better to the internal bearing surfaces than the old types of oils. We used to say that starting a motor from cold caused 100km of wear. Reving the motor up from cold with no oil pressure causes damage and shortens the service life of the vehicle.

Warm up:
After the oil pressure comes up it is usually fine to ride off but do not let the motor race until the motors temperature has come up. This lets the internal tollerances to standardise, the pistons to fit the bores, the oil flow to increase as the oil thins (cooling), the tyres to warm up etc etc etc. Think of this as a race warm up lap.

Some motors do not seem to be damaged by bad starting, like the old low power push rod toyota motors, but even now the new vvt performance toyota motors won't let the motor operate over 6000rpm until the motor has trached 75 dec C.

Yes I do carefully start all my motor without reving them and I do let them warm up while I put my gloves and lid on. I also ride slowly until the motor has warmed up to its operating temp.

[fridayflash]

I habitualy warm my bikes as i do my car and van,for a few minutes at
least,but i have wondered if this is always best? hmmm