Poor running when cold. (1999 Gen1)

[Martin.UK]

I have started to get a running problem with my 1999/2000 project bike.
When i start it from cold, The engine tics over but is running ruff untill it is up to temp.
when cold it wont rev pass 3k without holding back and it is pinging on warm up when revved like its missing.
Once up to temp it runs fine and revs as it should.
I have changed the spark plugs and balanced the TB's at normal running temp.
It starts from cold and hot ok, its just sounding like a bag of nuts when cold.
I also checked and cleaned the injectors and there is no air leaks any where.
Also the choke/fast idle does not seem to do anything untill it warmed up.
The only thing i've done before this started was change the fuel pump.
But it all worked as it should when i refitted it. Its just starts playing up a couple of days later.
One thing i am thinking, could it be the injectors playing up even though i've cleaned them and there spraying a fine miss when i tested them.

[sixpack577]

Sounds like the IAC sensor(idle air control) or the temperature sensor that turns the fan on(I think that model still has 2 temp sensors, the other sending the temperature to the guage)
Where is Greg with his '99 at?
Paging the old Kiwi
@Kiwi Rider

[Kiwi Rider]

Sounds like the IAC sensor(idle air control) or the temperature sensor that turns the fan on(I think that model still has 2 temp sensors, the other sending the temperature to the guage)
Where is Greg with his '99 at?
Paging the old Kiwi
@Kiwi Rider

The ‘99 model doesn’t have an IAC unit, the FI system is too early for that…. The “choke/fast idle” lever on the switch block is cable operated to the throttle bodies and actuates the throttle flaps manually to allow air in to raise the engine speed.
The symptoms described by Martin UK could possibly be caused by a dodgy coolant temp sensor, or even a poor connection at the CTS connector.
Yes they have a ‘coolant temp sensor’ that relays coolant temp info to the ECU, and also a ‘coolant temp sender’ that switches the rad fan on at the temp determined by the sender switch.. (100degC or thereabouts) it’s mounted in the radiator LH side lower tank, from memory.
My bike runs well even at cold engine temps on cold start up, will rev freely if required and I always use the fast idle lever to raise revs to 2500rpm initially for about 5 seconds. Then lower revs down to 1500 for another 30 seconds approx… then it idles sweetly at 800rpm. So that’s what Martin should expect on cold starts.
My first thing to check would be the fuel pressure and the fuel delivery, seeing as he’d just replaced the fuel pump.
there may just be a problem with that.
I’m sure he will get to the bottom of the issue.

[Martin.UK]

Happy days. I got the bike all sorted and its now running spot on both cold and hot.

I brought the cheapest set of TB's i could fine on eBay, which cost me £100 posted.
The set i brought were from a 22k mile 2006 Hayabusa.
Instead of taking everything apart i thought i would just change the injectors over.
So i removed the injectors from the new TB's and cleaned them and check they were spraying ok, which they were.
I then swapped them with the ones on the bike and they worked.
So there must of been a problem with the old injectors that did not like the new fuel pump i fitted.

So thats another problem sorted.

[Martin.UK]

So this morning i wanted to check that after a night of it sitting, that the bike would start and run.
I was a bit worried as you know what its like after having a problem or 2 with our bikes.
There was no need for me to worry as first press and it started. It runs great so i am 100% happy now.

[sixpack577]

Happy days. I got the bike all sorted and its now running spot on both cold and hot.

I brought the cheapest set of TB's i could fine on eBay, which cost me £100 posted.
The set i brought were from a 22k mile 2006 Hayabusa.
Instead of taking everything apart i thought i would just change the injectors over.
So i removed the injectors from the new TB's and cleaned them and check they were spraying ok, which they were.
I then swapped them with the ones on the bike and they worked.
So there must of been a problem with the old injectors that did not like the new fuel pump i fitted.

So thats another problem sorted.

Who knows, but the increased fuel pressure(back to the normal amount) with the new fuel pump, could have dislodged some old varnish or moved trash from the gas in the fuel rail or the injectors, pushing it further into the injector(s) gumming them up, disrupting their spray pattern and slowing the fuel delivery, so clean injectors fixed the issue.
Might as well clean the old ones at some point.
Injectors do die, but normally they will outlive the bike with just being cleaned on occasion.
You at least have a few spares, and likely an entire spare set.