Stutttterrriiiinng

[GezTheHealer]

Not ridden my bike in a while, perhaps its getting back used to it, but under 4000rpm there's a noticeable delay/lag/stuttering even if I give it a decent amount of throttle. Upshot is I can't pull away as quick as I'm used to unless I slip the clutch and rev a bit higher. Over 4000rpm it seems fine. I have had about half a tank of fuel in it, probably some as old as November, the rest around January, so it has been over a month or so. I'm thinking it might be stale fuel doing this. Seemed Ok this morning, only noticed it in the afternoon after getting a minor service (oil). But the tank wasn't off, so unlikely a pinched fuel line.

I only get the stuttering under load, it rev's freely if in neutral. Maybe the cold weather and mix with old fuel?

Anyway I've put some Redex in the tank for the time being and will fill it up to full with newer fuel to see if that helps.

Thinking otherwise could be sparkplugs maybe. Looking online someones suggests IACV hoses, though IDLE seems smooth and fine.

Any thoughts welcome.

Thanks.

[Badger-Roy]

Not ridden my bike in a while, perhaps its getting back used to it, but under 4000rpm there's a noticeable delay/lag/stuttering even if I give it a decent amount of throttle. Upshot is I can't pull away as quick as I'm used to unless I slip the clutch and rev a bit higher. Over 4000rpm it seems fine. I have had about half a tank of fuel in it, probably some as old as November, the rest around January, so it has been over a month or so. I'm thinking it might be stale fuel doing this. Seemed Ok this morning, only noticed it in the afternoon after getting a minor service (oil). But the tank wasn't off, so unlikely a pinched fuel line.

I only get the stuttering under load, it rev's freely if in neutral. Maybe the cold weather and mix with old fuel?

Anyway I've put some Redex in the tank for the time being and will fill it up to full with newer fuel to see if that helps.

Thinking otherwise could be sparkplugs maybe. Looking online someones suggests IACV hoses, though IDLE seems smooth and fine.

Any thoughts welcome.

Thanks.

Id say it sounds like old petrol.
When I park a bike up I fill the tank to full to avoid condensation/rust inside tank, then when I start using it again I drain 2/3rds of the petrol out and refill with fresh then use the old petrol mixed with new each time I fill up.
Try topping of the tank with fresh petrol then going for a lively ride (whilst remembering your likely to be abit rusty yourself from not riding for a while).
The injectors could be gummed up but I'd say it's unlikely after just a few months parked up.
Personally though I wouldn't expect petrol to go stale to the point of being noticeable after just a couple of months, yes it'd be past it's best but should still be useable.
Dunno where you fuel up and Iv no evidence of this but iv been told/read that the reason supermarket garages can sell petrol cheaper than Esso etc who they buy it from them in the 1st place is they buy it at knock down prices as they buy older/stale petrol, if that's a fact and you fuelled up with it then the petrol in your tank could be older than you think.

[WR6133]

Any thoughts welcome.

Easiest to start with is fuel

Clear the breathers on the fuel cap (unlikely but it takes 5 minutes to do and remove from equation).

Drain the fuel filter in to a clear glass, you are looking for water. If there is any hint of it drain the tank.

If the above don't work then it's time to check the fuelling pipes, pump flow, etc. Was the air filter changed? If it was a line may have been pinched in the process or the airbox may not have been resat correctly.

I'd be shocked if the fuel is "stale". I've got a Novemeber/January mix in the ZZR and it's fine. Heck when I bought the thing it had a full tank of 9 month old and was fine. I wouldn't have thought IACV would have an effect at 4K RPM, I'm not that hot on EFI but I believe it should only effect idle.

If none of the above work then I'd be trying

TPS - When the TPS went on my GSXR I had a similar symptom but it was up at 8k RPM. Scour around the net you'll find a guide on checking and setting the TPS for your model bike. It's an easy but slightly fiddly job.
Coils - Does the tach needle bounce about a bit when it happens? Could be ignition coil related, though I'd check this last as it's a pain in the arse to properly test coils and also I don't think it's very likely as if a coil was dying you'd expect the problem to get progressivley worse under load.

Dunno where you fuel up and Iv no evidence of this but iv been told/read that the reason supermarket garages can sell petrol cheaper than Esso etc who they buy it from them in the 1st place is they buy it at knock down prices as they buy older/stale petrol, if that's a fact and you fuelled up with it then the petrol in your tank could be older than you think.

That one is a myth (my old man worked in the industry). Refineries don't store boatloads of spare fuel to go stale. The only difference between supermarket and garage is the detergents (including ethanol) added to the petrol, same base product from same refineries (Anything in this area will have come from the refinery in Fawley). Contamination usually comes from the forecourt tanks and there is a thought (which maybe a myth) that supermarkets wait longer intervals before cleaning the tanks.

[Badger-Roy]

That one is a myth (my old man worked in the industry). Refineries don't store boatloads of spare fuel to go stale. The only difference between supermarket and garage is the detergents (including ethanol) added to the petrol, same base product from same refineries (Anything in this area will have come from the refinery in Fawley). Contamination usually comes from the forecourt tanks and there is a thought (which maybe a myth) that supermarkets wait longer intervals before cleaning the tanks.

I must admit it's not a line of thought Iv ever actually believed in as I can't help thinking grumpy customers would have started court cases by now if it was true and 90% of petrol I buy myself is from Tesco in amesbury but thought I'd chuck it in to the mix as an idea. .
A thought Iv just had is on my triumph trophy if the battery's not 100% that has some weird and wonderful effects on the bike including runnng crap at low revs and the engine completely cutting out if the lights are switched on. I fitted a new battery and it ran perfectly again.

[Last Train]

I fired up my S1 a couple of weeks back.
It had been sat for quite a while, outside too, and really didn't like it.
Was fine after 10mins or so, but leaving them sat idle isn't really a good idea.
I felt quite fortunate that it sorted itself easily but i will flush some redex through anyway.

[Trev]

Easiest to start with is fuel

Clear the breathers on the fuel cap (unlikely but it takes 5 minutes to do and remove from equation).

Drain the fuel filter in to a clear glass, you are looking for water. If there is any hint of it drain the tank.

If the above don't work then it's time to check the fuelling pipes, pump flow, etc. Was the air filter changed? If it was a line may have been pinched in the process or the airbox may not have been resat correctly.

I'd be shocked if the fuel is "stale". I've got a Novemeber/January mix in the ZZR and it's fine. Heck when I bought the thing it had a full tank of 9 month old and was fine. I wouldn't have thought IACV would have an effect at 4K RPM, I'm not that hot on EFI but I believe it should only effect idle.

If none of the above work then I'd be trying

TPS - When the TPS went on my GSXR I had a similar symptom but it was up at 8k RPM. Scour around the net you'll find a guide on checking and setting the TPS for your model bike. It's an easy but slightly fiddly job.
Coils - Does the tach needle bounce about a bit when it happens? Could be ignition coil related, though I'd check this last as it's a pain in the arse to properly test coils and also I don't think it's very likely as if a coil was dying you'd expect the problem to get progressivley worse under load.



That one is a myth (my old man worked in the industry). Refineries don't store boatloads of spare fuel to go stale. The only difference between supermarket and garage is the detergents (including ethanol) added to the petrol, same base product from same refineries (Anything in this area will have come from the refinery in Fawley). Contamination usually comes from the forecourt tanks and there is a thought (which maybe a myth) that supermarkets wait longer intervals before cleaning the tanks.

Nice one Chris, quick and simple guide to checking it out ........ now can you come and get my stepthru running properly?

[WR6133]

now can you come and get my stepthru running properly?

You're ahead of me mine isn't working at all! It's the next project once I (imminently) get the GSXR back together. My 2 stroke knowledge is extremely limited but, if it's running like a bag of nails, do you have the baffle (+wadding) when mine was running (badly) I'm sure it was the lack of baffle making it erratic (based on having set everything else as per spec and rebuilt the top end).

[Trev_P]

Not ridden my bike in a while, perhaps its getting back used to it, but under 4000rpm there's a noticeable delay/lag/stuttering even if I give it a decent amount of throttle. Upshot is I can't pull away as quick as I'm used to unless I slip the clutch and rev a bit higher. Over 4000rpm it seems fine. I have had about half a tank of fuel in it, probably some as old as November, the rest around January, so it has been over a month or so. I'm thinking it might be stale fuel doing this. Seemed Ok this morning, only noticed it in the afternoon after getting a minor service (oil). But the tank wasn't off, so unlikely a pinched fuel line.
I only get the stuttering under load, it rev's freely if in neutral. Maybe the cold weather and mix with old fuel?
Anyway I've put some Redex in the tank for the time being and will fill it up to full with newer fuel to see if that helps.

Thinking otherwise could be sparkplugs maybe. Looking online someones suggests IACV hoses, though IDLE seems smooth and fine.

Any thoughts welcome.

Thanks.

more than likely the fuel as already said, with this modern stuff the ethanol evaporates, not like the good ol stuff - 4 star leaded, that used to last years before it went a bit funny if it did you just top it up with number 7 paint thinner
once you fill it up I reckon you will notice it getting better after a few miles

[GezTheHealer]

Cheers all, I'll check the breather, and mix in some newer fuel and try a bit of an italian tune up and see if I have any joy. It would be nice if the redex helped it out. It didn't have an air filter, only an oil filter so I don't think they even had the tank off. Fuel filter sounds like a good place to look. I may just not be used to it and labouring the engine, but I don't remember it riding like this.

Thanks for all the pointers guys, and all the steps WR6133. I'll let you know how I get on.

[BB]

Good luck