just finished the oil & oil filter change... quick question

Originally Posted by embee

The yellow one is correct, start it, let it settle down for maybe 30sec and then ride off gently. Don't use lots of revs or full throttle until it has thoroughly warmed up, just ride it "normally".

Cold bores will result in fuel and condensate being absorbed into the oil film on the cylinder wall, which contributes to oil contamination and wear. Letting it idle on "choke" (or enrichment with FI engines) simply lengthens the time the warm-up takes before the bore surface reaches a high enough temp to prevent this.

Aye - tis correct - and for every gallon of fuel you burn, you produce a gallon of water - when the engine is cold, this can get carried into the oil and with the components of combustion blowby, create strong acids that will eat away at your engine components - the sooner you can get the engine up to operating temperature, the sooner any water will evaporate off - engine oil hangs on to water ( that's why it goes milky when the engine is used for lots of short journeys ) unlike gear and hydraulic oils which drop it out fairly quick. Also lots of time on choke can wash the oil off the bores too which can also accelerate wear.

Cheers

Nana

[Paul the 6th]

interesting stuff guys - thanks for all the info/tips/advice

I used to let the bike warm up for about 3 - 5 mins when I lived with my parents because the bike was tucked down a driveway and I didn't have a loud exhaust. Now I've got my own place I'm a bit wary about advertising my bike with the loud can and right on the end of a cul de sac next to a public bit of greenery with a public footpath... so now I just fire it up and get moving with in a minute or so (taking it gentle along the way)...

thanks again for the info, much appreciated

Originally Posted by thefallenangel

Yes letting the engine warm up is good but don't forget about tyres, brakes etc. . needing to warm up too.

So do those friggin' carbs thats half the reason why i leave my bike to warm up for a few minutes on cold mornings, get some heat into the carbs (and airbox too) so the thing dosn't die on me when I pull to a stop for the first 10 mins

[yorkie_chris]

The carbs will actually get colder when running, on some dope burning engines you get ice on inlet manifold

Engine nice and hot stops fuel dropping out of suspension, if it's dying when you stop then balance carbs, up idle speed a little and maybe a little pro-FST

[embee]

Just to expand slightly, there are additives in good quality oil which are there to combat the acid build up.

When Oil analysis is done during development work, one factor determined (along with wear-metals etc) is the "Total Base Number" or TBN . This is the reserve alkaline content which is capable of neutralising the acids.

One measure of an oil's quality is the TBN, especially after a period of service involving repeated short runs. Obviously the amount of acids generated by the engine are also a critical factor, which is where the importance of the break-in procedure to minimise the blowby comes into play. Cheap oils often have poor TBN which means it's all the more important for frequent changes.

Acid oil tends to attack soft metals in particular, which is basically all the crank bearing surfaces (big-ends and main bearings typically). Also it will get to the pistons and ring grooves during those cold starts when a lot of moisture is being generated. The importance should not be under-estimated, there have been instances in the past, for example in low speed diesels, where engine failures resulted from acid attack of cylinder liners where the surface temperature hovered round the dew-point for too long (liners dropped in half).

[yorkie_chris]

embee I don't normally disagree with you... but aren't they buffer compounds rather than alkalis, to keep constant pH?

Originally Posted by yorkie_chris

The carbs will actually get colder when running, on some dope burning engines you get ice on inlet manifold

Engine nice and hot stops fuel dropping out of suspension, if it's dying when you stop then balance carbs, up idle speed a little and maybe a little pro-FST

Ah, gotcha. I've been told twice now about this magic pro-FST...

Originally Posted by embee

Just to expand slightly, there are additives in good quality oil which are there to combat the acid build up.

When Oil analysis is done during development work, one factor determined (along with wear-metals etc) is the "Total Base Number" or TBN . This is the reserve alkaline content which is capable of neutralising the acids.

One measure of an oil's quality is the TBN, especially after a period of service involving repeated short runs. Obviously the amount of acids generated by the engine are also a critical factor, which is where the importance of the break-in procedure to minimise the blowby comes into play. Cheap oils often have poor TBN which means it's all the more important for frequent changes.

Acid oil tends to attack soft metals in particular, which is basically all the crank bearing surfaces (big-ends and main bearings typically). Also it will get to the pistons and ring grooves during those cold starts when a lot of moisture is being generated. The importance should not be under-estimated, there have been instances in the past, for example in low speed diesels, where engine failures resulted from acid attack of cylinder liners where the surface temperature hovered round the dew-point for too long (liners dropped in half).

Normal Passenger car engine oil TBN levels are around 7 - commercial diesels can be around 10 - 12 as the engines run cooler and produce more acids - Gas engines and marine diesels using poor distilate fuel oils can be around 15 as these engines rapidly deplete the TDN additives.
Rule of thumb for change is 50% of the starting number. Low TBN means that the detergency is low, low detergent levels can contribute to deposits and corrosion - sticking piston rings etc.

TAN can also be measured - this is a measurement of the weak organic and strong inorganic acids present and indicate the oil oxidation.

Good to know there's someone on this group who knows about oils ( Embee ) ... makes a nice change

Nana

[embee]

Originally Posted by yorkie_chris

embee I don't normally disagree with you... but aren't they buffer compounds rather than alkalis, to keep constant pH?

Yes, you're right. Sorry, technical error

Awesome, I love these kinds of threads, learning about technical stuff