Idle speed on a Honda CBR250RR?

[overworkedmonkey]

Now I have ridden a number of bikes in my past life and the CBR250RR seems to be the most different. Whilst riding i.e. in second gear, I seem to have to keep the throttle open rather than blipping through the revs which means I am constantly between 8 - 9k in the rev range whereas on previous bikes I could close the throttle and the bike would de-accelerate slowly as opposed to immediately which it does on the CBR250. Is that common and normal? Is it ok if I am constantly within a range?

[tri boy]

Old CBR250RRs are bottomless money pits.
Sounds like yours is in need of a top up. MHO

[overworkedmonkey]

What is that opinion based on?

[tri boy]

What is that opinion based on?

Based on?
This is KB.

My theory is a bit like physics. ie speed time distance etc.

So, old 250 sprotbikes that get thrashed regularly = Faults, Repairs, Frustration.
Oh, and many years working as a m/cycle mech has given me unwordly powers of deduction.
Plus, this is KB.

[overworkedmonkey]

Based on?
This is KB.

My theory is a bit like physics. ie speed time distance etc.

So, old 250 sprotbikes that get thrashed regularly = Faults, Repairs, Frustration.
Oh, and many years working as a m/cycle mech has given me unwordly powers of deduction.
Plus, this is KB.

Based on your powers of deduction, how should the bike behave?

Also am seeking facts as opposed to theories so would be grateful if you could point me in the right direction.

[Slyer]

The bike should slowly decelerate.
You're saying that there is no engine braking? It's like you've got the clutch in when you get off the gas?

[overworkedmonkey]

The bike should slowly decelerate.
You're saying that there is no engine braking? It's like you've got the clutch in when you get off the gas?

There is engine braking. What I mean is that the bike seems to decelerate (engine braking) immediately if I close the throttle. Now what I am doing is to blip to match the revs as I drop a gear, letting the clutch out slowly and opening the throttle slowly to avoid engine braking.

[Slyer]

Then all is well, they're meant to do that.
A badly tuned/adjusted bike will do as you described for your old bike.

[overworkedmonkey]

Then all is well, they're meant to do that.
A badly tuned/adjusted bike will do as you described for your old bike.

Sweet. Thanks mate.

[Katman]

Triboy is onto it.

20 year old multi-cylinder 250s have had 20 years of being raped.

Those who purchase them are destined to valleys of tears.

[overworkedmonkey]

Triboy is onto it.

20 year old multi-cylinder 250s have had 20 years of being raped.

Those who purchase them are destined to valleys of tears.

I would agree however what if they have been regularly serviced. See many KB'ers here noting riding their bikes well into their 100,000 kms or more

[SMOKEU]

Old CBR250RRs are bottomless money pits.
Sounds like yours is in need of a top up. MHO

They're not much different from a CBR250R in terms of the mechanicals. I've had mine for about 2 years and I thrash the absolute phuck out of mine. The only thing that has ever gone wrong with mine is the fuel pump died. Try thrashing an old WRX or turbo Skyline like that and then you'll see what a real money pit is.

[SMOKEU]

It should also idle at around 1500RPM, regardless of what gear you're in if you pull the clutch in fully. The idle adjustment screw is very easy to access, it's tucked in by the left fairing and no tools are required to access it or adjust it.

[overworkedmonkey]

It should also idle at around 1500RPM, regardless of what gear you're in if you pull the clutch in fully. The idle adjustment screw is very easy to access, it's tucked in by the left fairing and no tools are required to access it or adjust it.

Thanks SMOKEU. Been reading the service manuals and some of the other material online and it is suggested that the choke not be used when starting the engine unless it fails to start. It suggests to start the bike, open the throttle below 6,000 revolutions for a couple of second and let the bike warm up. Take it that it should be at 1500 RPM after it has started warming up. Also take it that if it is below 1500 RPM, I should adjust it so that it stays at 1500 RPM.

After it has warmed up after 3 -5 minutes, ride off slowly and it should be warm enough in 5 - 10 minutes to have the bike go through higher revolutions.

[SMOKEU]

Thanks SMOKEU. Been reading the service manuals and some of the other material online and it is suggested that the choke not be used when starting the engine unless it fails to start. It suggests to start the bike, open the throttle below 6,000 revolutions for a couple of second and let the bike warm up. Take it that it should be at 1500 RPM after it has started warming up. Also take it that if it is below 1500 RPM, I should adjust it so that it stays at 1500 RPM.

After it has warmed up after 3 -5 minutes, ride off slowly and it should be warm enough in 5 - 10 minutes to have the bike go through higher revolutions.

You'll probably do more harm than good by letting the engine idle for a few minutes while it's cold. Start it up, and as soon as it starts behaving itself, ride away gently.

[overworkedmonkey]

You'll probably do more harm than good by letting the engine idle for a few minutes while it's cold. Start it up, and as soon as it starts behaving itself, ride away gently.

When you say behaving I take it you mean when it's at 1500 RPM? What sort of harm can I do letting the engine idle?

[SMOKEU]

When you say behaving I take it you mean when it's at 1500 RPM? What sort of harm can I do letting the engine idle?

Many old carbied bike engines will stall if you try and ride them unless the engine has had a minute to warm up from a competely cold start.

Basically, if you let the engine idle for several minutes when it's cold to warm up, it takes much longer to warm up than if you ride it very gently for a few minutes. The longer the engine is cold for, the more wear and tear occurs. When the oil is cold, it becomes thick and may not have sufficient pressure to cover all of the engine.

The same rules do not apply for 2 strokes.

[overworkedmonkey]

Many old carbied bike engines will stall if you try and ride them unless the engine has had a minute to warm up from a competely cold start.

Basically, if you let the engine idle for several minutes when it's cold to warm up, it takes much longer to warm up than if you ride it very gently for a few minutes. The longer the engine is cold for, the more wear and tear occurs. When the oil is cold, it becomes thick and may not have sufficient pressure to cover all of the engine.

The same rules do not apply for 2 strokes.

So gently would mean under 6,000 RPM? Having read some of the forums, it has been suggested that the CBR250 should not be ridden constantly under 6,000 RPM. Any truth to that?

[SMOKEU]

So gently would mean under 6,000 RPM? Having read some of the forums, it has been suggested that the CBR250 should not be ridden constantly under 6,000 RPM. Any truth to that?

Just don't take it over 10,000RPM until it warms up properly. These bikes don't like low revs when they're warmed up properly.

[overworkedmonkey]

Just don't take it over 10,000RPM until it warms up properly. These bikes don't like low revs when they're warmed up properly.

So would the temperature gauge indicate what is considered warmed up properly? Like a car does it have to be in between of cold and hot?

[SMOKEU]

So would the temperature gauge indicate what is considered warmed up properly? Like a car does it have to be in between of cold and hot?

Yup. Water tends to warm up faster than oil though.

[overworkedmonkey]

Yup. Water tends to warm up faster than oil though.

Interesting. It does take a while for it to warm up. When you said it does not like low revolutions when warmed up, why is that?

So how do I know if there is sufficient water or does it only have to be a coolant?

[SMOKEU]

Interesting. It does take a while for it to warm up. When you said it does not like low revolutions when warmed up, why is that?

So how do I know if there is sufficient water or does it only have to be a coolant?

CBR250 engines, by nature, are designed to be revved very hard. They don't like cruising along at 50kmh in 6th gear.

On the right hand rear fairing there is a hole where you can see the water level. It's meant to have antifreeze in it so it should be bright green.

[overworkedmonkey]

CBR250 engines, by nature, are designed to be revved very hard. They don't like cruising along at 50kmh in 6th gear.

On the right hand rear fairing there is a hole where you can see the water level. It's meant to have antifreeze in it so it should be bright green.

So what if you are cruising especially on long straight roads say at 50km/h on the second gear? Based on past experience, was told that the throttle should be opened and closed. It should be held open constantly. Not sure why but am curious to know the reason.

Cool. Should it be completely topped up?

[SMOKEU]

So what if you are cruising especially on long straight roads say at 50km/h on the second gear? Based on past experience, was told that the throttle should be opened and closed. It should be held open constantly. Not sure why but am curious to know the reason.

Cool. Should it be completely topped up?

I normally cruise at anywhere between 7,000 - 16,000RPM. If you're cruising at 50kmh keep it in 3rd or even 4th gear.

Coolant should be topped all the way up to the top. It has an overflow so you can't over fill it.

[overworkedmonkey]

I normally cruise at anywhere between 7,000 - 16,000RPM. If you're cruising at 50kmh keep it in 3rd or even 4th gear.

Coolant should be topped all the way up to the top. It has an overflow so you can't over fill it.

Cool. Is there any reason why you would cruise on the lower gears i.e. 1 or 2?

How often does the coolant have to be changed?

[SMOKEU]

Cool. Is there any reason why you would cruise on the lower gears i.e. 1 or 2?

How often does the coolant have to be changed?

Just cruise at whatever revs feels the best to you.

Coolant only has to be changed every few years. I should do a coolant flush on my bike.

[overworkedmonkey]

Just cruise at whatever revs feels the best to you.

Coolant only has to be changed every few years. I should do a coolant flush on my bike.

Cool. Just have to mindful to rev above 6,000 RPM.

How would I know if I have to change it?

[SMOKEU]

Cool. Just have to mindful to rev above 6,000 RPM.

How would I know if I have to change it?

If you don't have sufficient proof in the form of receipts from a reputable mechanic, you can safely assume that it hasn't been done in quite a few years.

[overworkedmonkey]

If you don't have sufficient proof in the form of receipts from a reputable mechanic, you can safely assume that it hasn't been done in quite a few years.

Fair enough. Thanks for all your help.

[overworkedmonkey]

One more question though, is it ok to keep the throttle open all the time while cruising?

[SMOKEU]

One more question though, is it ok to keep the throttle open all the time while cruising?

You have to keep the throttle open otherwise you won't be developing enough power to go faster than jogging pace. Try driving a petrol car and then backing off the throttle(s). The same thing happens on a bike.

[overworkedmonkey]

You have to keep the throttle open otherwise you won't be developing enough power to go faster than jogging pace. Try driving a petrol car and then backing off the throttle(s). The same thing happens on a bike.

So I don't need to open and close (close it partially) it all the time? Is there any reason the need to open and close (close it parially) would rise?

[xen]

You don't want to hold it at a constant rpm when you're breaking a new engine in but all other times no worries.

[overworkedmonkey]

You don't want to hold it at a constant rpm when you're breaking a new engine in but all other times no worries.

I take it when you refer to new you mean, a brand new bike from the shop. Any reason as to why that is?

[SMOKEU]

I take it when you refer to new you mean, a brand new bike from the shop. Any reason as to why that is?

There's a special technique for running in a BRAND NEW engine. This also applies to engines that have been freshly rebuilt. I won't go into details, but if you're buying a second hand bike then don't worry about running it in.

[overworkedmonkey]

There's a special technique for running in a BRAND NEW engine. This also applies to engines that have been freshly rebuilt. I won't go into details, but if you're buying a second hand bike then don't worry about running it in.

Thanks. I am curious though. Why would you need a special technique?

[Slyer]

Because when you are first running an engine it is freshly molded and assembled. Under normal use of the engine a fair amount of metal is worn down in the engine in this new state.
Be too harsh on it and you can permanently damage it, be too easy and it won't break in properly.

There's a million discussions on it. But the official word from manufacturers is to just not exceed a certain rev range until after 1000km.

[overworkedmonkey]

Because when you are first running an engine it is freshly molded and assembled. Under normal use of the engine a fair amount of metal is worn down in the engine in this new state.
Be too harsh on it and you can permanently damage it, be too easy and it won't break in properly.

There's a million discussions on it. But the official word from manufacturers is to just not exceed a certain rev range until after 1000km.

Very interesting. Did not know you had to break into a new engine. I would thought they would have been designed to simply ride off without a care in the world.

[Slyer]

The same thing goes for cars but to a lesser degree as they don't rev to 16k rpm :bleh: