Why does my bike cut out when cold & idle?

rat_race

It's not really a problem as I overcome it with normal driving, but I'm more curious why the following occurs.

Firstly, it's a 2010 Ninja 250, so it's fuel injected. Good oil, good plugs. Well maintained.

If I turn the bike on, and let it idle, the automatic choke will keep it at 3-4k revs and this would gradually decrease to 1.5k -- the normal idle speed. Never cuts out like this.

If I turn the bike on, and rev it a bit (even after giving it a few seconds) -- and not much revving, just up to 5/6/7k (bike goes to 15k), and not for long or aggressivley, and then I let the bike idle again, the revs can go down to 1k or below, and the bike struggles and can cut out if I don't rev it it again. Idle should be 1.5 -- which it is once bike is warmed up.

Something similar can happen if I drive for a minute or so and get stuck at lights; the idle (which should be around 1.5k) hovers around 1k, and the bike starts to struggle. I often give it a few revs around the 2-3k mark to keep it happy and warm it up a bit quicker.

Bike is fine once warmed up.

Why does the auto choke not kick in when the bike is cold and I'm not revving/moving? Maybe this is normal behaviour?

Could it be related to the battery? Havn't changed it yet, seems fine. I can't see how it's related, but maybe...

gctest50

needs this

http://www.ecotrons.com/products/small_engine_rhb31_vz21_turbocharger/

rat_race

Super I'll get one from Santy!

But seriously...anyone have any advice?

goodlad

I had similar with my SV and just turned up the rev setting for the automatic choke.

two wheels good

It may be worth adjusting the Throttle Position Sensor. I don't know the procedure for a Ninja but I'm sure you'll find it online.
Also check the air filter is clean.

ZX7R

If it has an automatic choke would reving it not cause the auto choke to dissingage

robot7080

I'd say have a look at the air filter also but it sounds like a choke issue to me. Is it possible that by revving it up while it's cold you're causing the ECU to turn of the choke because it'll think you're going to drive it on the roads and then it's taking time to kick back in? Could be completely wrong on that but it's just a brainwave?

Maybe just let it warm up for 5 minutes itself and don't use the rev range as a guide - use the actual engine temp to tell you??

rat_race

ZX7R wrote: »

If it has an automatic choke would reving it not cause the auto choke to dissingage

That makes sense, but, you'd think it would come back on when the bike stops. I mean, otherwise, what is the point? Most people take off on a bike right away...even the manual says not to let the bike warm up (I know it is better to wait though -- they just say that for environmental reasons)...

two wheels good wrote: »

It may be worth adjusting the Throttle Position Sensor. I don't know the procedure for a Ninja but I'm sure you'll find it online.
Also check the air filter is clean.

Didn't know they could be adjusted. I have adjusted the throttle idle dial so when the bike is warm it's at 1.5k. It was fine for a long time, but I had to adjust maybe a year ago -- possibly due to cable wear? Didn't know there was anything else that could be adjusted regarding the throttle.

Air filter is good, almost new. If that was the problem, why does a warm bike not produce the same problem? Not doubting you, just curious...

robot7080 wrote: »

I'd say have a look at the air filter also but it sounds like a choke issue to me. Is it possible that by revving it up while it's cold you're causing the ECU to turn of the choke because it'll think you're going to drive it on the roads and then it's taking time to kick back in? Could be completely wrong on that but it's just a brainwave?

Maybe just let it warm up for 5 minutes itself and don't use the rev range as a guide - use the actual engine temp to tell you??

Makes sense about the ECU...that's what I was already thinking, and what ZX7R said too. But seems a bit strange that it's not a bit smarter...

professore

Check the fuel filter too.

rat_race

Thanks. Wonder if it could be that the valves need adjustment too?

Wossack

My understanding; metal expands and oil flows better when warm. Both reduce internal frictional losses in the engine, and so make it easier to start when warm (and idle better etc)