Power loss!!

[chris8886]

riding to and home from the show in birmingham on wednesday while on the motorway doing about 80, having been going for about 40ish miles or so (i think). i suddenly have a dramatic dip in power/drive!! the engine doesn't cut out, but the revs dip suddenly and rise again after a moment or 2. it does this a few times with revs at one point hit zero, but still the engine keeps running. i carry on as the problem seems to have stopped, but it re-occurs a couple more times on the way home, but in less dramatic fashion. i did take it easy the rest of the way home.

any help on this issue as to what it might be would be very much apprieciated, as i need to use it tonight!!

i have just had the chain and sprockets changed (i don't think this would be an issue!), the bike is due a service ie. oil and filter change etc. but the oil is not low. my bike is also restricted if anyone may think it has something to do with it!!

any help/suggestions are apprieciated!!

thanks

Chris

Was it cold and damp on that journey. Could be the carb icing issue. Mine tended to do it when held on constant throttle openings. Does it seem ok now?

99.9% sure it's nowt to do with the new chain etc.

[chris8886]

Originally Posted by petevtwin650

Was it cold and damp on that journey. Could be the carb icing issue. Mine tended to do it when held on constant throttle openings. Does it seem ok now?

99.9% sure it's nowt to do with the new chain etc.

it was warmer than it has been recently and it was damp. i don't THINK it was cold enough for things to have iced up!! i came to work on it this morning, but there's no motorways and the journey is pretty short

Sounds to me like fuel isnt getting in the engine thats for sure! Could be that you were running the fuel lower than it has been for a while and jelly like petrol (old petrol) might have been pulled through to the carb and blocked one for a few moments! Sounds ver like it might be.

So were you running it lower than it has been in a while?

[Biker Biggles]

As above,plus did any electrical bits fail at the same time?Curvys can chafe their wiring looms under the seat and cause all sorts of odd results including ignition failure.
But it does sound like carb icing/fuel starvation really.

Originally Posted by ThEGr33k

Sounds to me like fuel isnt getting in the engine thats for sure! Could be that you were running the fuel lower than it has been for a while and jelly like petrol (old petrol) might have been pulled through to the carb and blocked one for a few moments! Sounds ver like it might be.

So were you running it lower than it has been in a while?

That would be my thought to, perhaps some dirt in the carbs. If it continues, start by checking the wiring loom, as mentioned they can chaff. I'd then check that the foam pad under the fuel tank hasn't become unstuck and been pulled over the air filter, check the filter as well while you're at it. If you have not found anything and you are sure it's not carb icing then it might be worth checking carbs. One thing you can check before pulling them off is that the choke cables are not sticking and return to position when you release the choke leaver, they have a habit of rusting and seizing.

I'd check all this before pulling the carbs off, no need in having to do more than you need too.

Good luck getting it sorted.

[chris8886]

Originally Posted by ThEGr33k

So were you running it lower than it has been in a while?

i don't know is my rather lame answer to this!!

thanks for the words guys. what you say kind of makes sense to me!!

my final question is: do you think it'll be alright getting to portsmouth tonight and back again tommorrow morning (i'm coming from jst outside london and back to the same place)? or could this problem turn nasty and lunch the engine?

thanks again

[Biker Biggles]

Engine lunching on SVs is nearly always caused by abuse(like wheelying)or allowing the oil to run low,so you should be ok on that front.
If its carb icing you can tell by stopping the bike and letting the heat from the engine warm the carbs(takes about 30 seconds)and suddenly it runs fine again.Intermittant fuel starvation tends to happen at high throttle openings and "cures"itself as you throttle back.Wiring loom events tend to just happen,sometimes as you put weight on the seat.
If you are doing a long run on it I would run the fuel low and brim up with fresh just in case you had a cr&p tankful.

Is it a hesitation when you crack on the throttle, or just happens at constant throttle (i cant make out from your posts). I sometimes get a hesitation when I've been at constant throttle then wind some more throttle on, typically when accerlarating from around 4000 rpm. My bike is also restricted; could be something to do with that and the cooler air now its winter?

I do know that my engine feels alot better after a good thrashing through the gears a couple of times, but this isnt always possible in london traffic

Matt

[chris8886]

Originally Posted by Biker Biggles

Engine lunching on SVs is nearly always caused by abuse(like wheelying)or allowing the oil to run low,so you should be ok on that front.
If its carb icing you can tell by stopping the bike and letting the heat from the engine warm the carbs(takes about 30 seconds)and suddenly it runs fine again.Intermittant fuel starvation tends to happen at high throttle openings and "cures"itself as you throttle back.Wiring loom events tend to just happen,sometimes as you put weight on the seat.
If you are doing a long run on it I would run the fuel low and brim up with fresh just in case you had a cr&p tankful.

this makes me feel much better!! i have just filled it up having returned from brum. when i did throttle back it did seem to help to stop it, just that when you're in the outside lane doin 80 throtleing off that much and waiting a second or 2 can be a problem!! lol

Originally Posted by alpinestarhero

Is it a hesitation when you crack on the throttle, or just happens at constant throttle (i cant make out from your posts). I sometimes get a hesitation when I've been at constant throttle then wind some more throttle on, typically when accerlarating from around 4000 rpm. My bike is also restricted; could be something to do with that and the cooler air now its winter?

I do know that my engine feels alot better after a good thrashing through the gears a couple of times, but this isnt always possible in london traffic

Matt

no, it only happened when at a constant throttle for a long period of time when on the motorway. i will give it a good handful through the gears as usual before i start my journey on the motorway.