stuttering idle speed

[yorkylancs]

Chris,went with what the dealer said 1 on the front and 1.25 on the rear,it was still doing the same ie,1200 revs then a sudden drop to 800,then back up just as quickly,was a bit dissapointed to say the least,as my hunch had not paid off.Went back to thinking about what else i had done,i bought some ht cable off ebay a while ago,it was cheap and a nice red colour,could that be it i thought.So i swapped it back to the other i had used,fired it up and the sudden drop off was not as bad,but it was still hunting a bit.Took it for a run and the revs stopped pretty constant even from giving it some,down to a standstill and setting off,it is still stuttering a bit,maybe losing 150 revs,but this is better than before,will try your settings Chris and see if it makes it a little better.I also re routed the carb breather pipes,but that was before i changed the ht lead.Thanks all for your help.Rick

[tony.mon]

Yorky, how often does it do this?
I'm wondering if it's the old "cough" through the airbox they all do.
If it's only once every minute or two, that'll be it....

If it's this, you can sort of feel the thud at the back of the tank as it happens; if you ride with your nadgers on the tank it's more noticeable

[sirch345]

Chris,went with what the dealer said 1 on the front and 1.25 on the rear,it was still doing the same ie,1200 revs then a sudden drop to 800,then back up just as quickly,was a bit dissapointed to say the least,as my hunch had not paid off.Went back to thinking about what else i had done,i bought some ht cable off ebay a while ago,it was cheap and a nice red colour,could that be it i thought.So i swapped it back to the other i had used,fired it up and the sudden drop off was not as bad,but it was still hunting a bit.Took it for a run and the revs stopped pretty constant even from giving it some,down to a standstill and setting off,it is still stuttering a bit,maybe losing 150 revs,but this is better than before,will try your settings Chris and see if it makes it a little better.I also re routed the carb breather pipes,but that was before i changed the ht lead.Thanks all for your help.Rick

Rick,
Interesting about the HT leads. At least you seem to be going in the right direction with the problem now being less.

Is what you're experiencing as Tony suggests

Another couple of thoughts are, how long ago were the spark plugs replaced The air filter you replaced recently was it a standard filter Have you had the TPS (throttle position sensor) unplugged recently and you forgot to reconnect it

Another possibility is petrol gone off if the bike was not started for a long period, and carbs weren't drained.

Chris.

[yorkylancs]

Nah Chris,dont think its a cough like Tony suggests.The plugs have not been done for a bit,but looked ok,and were gapped ok,have some new ones on order,the air filter is brand new and standard,and the TPS is connected.Yesterday it was all ok,but went for a run today,and it cut out 3 times fortunetely near home!Its the same sympton again.Gutted i checked the pilot screws again,and im pretty sure the front one was much more than the 1.25 or whatever it should be,this got me to thinking it had loosened itself,therefore giving me the poor running at low revs again,especially as nothing had been changed from the previous day.I have put a mark on it so i can see if it moves,and if it does it is out with the loctite!I suppose these jets dont get moved to much,and am wondering and maybe clutching at straws but what do you reckon?Cheers lads.Rick

[sirch345]

Nah Chris,dont think its a cough like Tony suggests.The plugs have not been done for a bit,but looked ok,and were gapped ok,have some new ones on order,the air filter is brand new and standard,and the TPS is connected.Yesterday it was all ok,but went for a run today,and it cut out 3 times fortunetely near home!Its the same sympton again.Gutted i checked the pilot screws again,and im pretty sure the front one was much more than the 1.25 or whatever it should be,this got me to thinking it had loosened itself,therefore giving me the poor running at low revs again,especially as nothing had been changed from the previous day.I have put a mark on it so i can see if it moves,and if it does it is out with the loctite!I suppose these jets dont get moved to much,and am wondering and maybe clutching at straws but what do you reckon?Cheers lads.Rick

Rick,
I reckon, that the pilot screw should not be moving on it's own. So you really need to know if it is for sure. Marking it is a good idea.

I've never had one out on the Firestorm, but I assume they are held in place by a spring which fits around the thread of the adjuster, along with a washer and an "O" ring. If it is moving about I wonder if the previous owner undid it to far and it fell out, losing the spring, or may be the spring is broken.

My advice would be, if the pilot screw is definitely moving on it's own, you could ask Chris (Jonesy) if he would check out his spare set of carbs, to see what exactly is under the pilot screw.

One thing I meant to say (if you don't already know that is) is do not tighten down too tightly the pilot screw when screwing it all the way in, if you do you could damage it's seating.

Chris.

[Pete.L]

Std settings on mine with std exhaust was front 1hr 20 mins open from full closed and rear 1hr 40 min.
If you have race pipes on you need to run a little richer, open the jets a little more than suggested.
It's also possible, if your mixture needle isn't in need of some thread lock, you might have a worn seat or a bit of dirt stuck in the float bowl valve.
Open the drains on the bottom of the float bowl and catch the fuel in a glass jar and have a look to see if you have any dirt or sediment present. A carb clean might be in order.
Check the colour of your plugs. If they are very black and sooty make sure the choke leads are correctly seated and returning properly after putting the choke cable back in.
Lastly, a blocked air jet on your slow idle circuit in the carb can give the same symptom.
Just some ideas to think about.

Pete.l

[yorkylancs]

Chris,have had them out and they have a spring tiny washer and a small rubber o ring,in that order,have used some loctite locking compound on them,hopefully they should be better,if not will fit them new plugs,and maybe get some new ht lead.Thanks Pete,i have cleaned the carbs,but you never can tell.Not sure of owt else i can do,apart from take it to a dealer and thats not on is it!

[sirch345]

Chris,have had them out and they have a spring tiny washer and a small rubber o ring,in that order,have used some loctite locking compound on them,hopefully they should be better,if not will fit them new plugs,and maybe get some new ht lead.Thanks Pete,i have cleaned the carbs,but you never can tell.Not sure of owt else i can do,apart from take it to a dealer and thats not on is it!

Rick,
Ah well, that's that theory is out the window then, although really the air screw should not need thread locking if the spring is doing it's job.

It's quite possible you have a leak from your HT leads or spark plug caps. Run the bike when it's dark and have a look to see if there is any arcing out from the leads and/or plug caps, if they are you'll see a spark jumping to earth (engine metal casings etc). Trying a new set of plugs is a good idea too.

You say you cleaned your carbs, did you use carb cleaner and leave the carbs unused for a time so they dried out

Chris.