Spluttering, dammit
 

Time for me to ask for help... the short version is, my bike was perfectly alright till the other day but no for no apparant reason it stutters and won't rev above 5-6k. The longer version...

1999 curvy 20k on the clock, had it since almost new, have ridden all over the place on it this year with no problems. Got it out to ride to work on Monday, it was fine till I got half way there (10 miles on the motorway), then when I tried going above about 6k in 6th it wouldn't accelerate, just spluttered. It got worse and worse and cut out in the end, but after a mintue or two in a lay-by it started again and seemed more or less okay. Coaxed it to work, same thing home, thought it was fuel starvation so have cleaned the carbs, checked all the hoses etc, and nothing seemed out of order. Took it for a run just now and it's just as crap, it doesn't matter which gear you're in it starts spluttering at around 5k, worse on full throttle, but you can't get it to go any faster on part throttle. Low speed it runs okay, it sounds lumpier to me than it used to. So perhaps something in the ignition system? I put a voltmeter across the battery and got normal readings, so I don't think it's the regulator/rectifier interfering. Before I waste enormous amounts of time chasing my tail, any ideas? It had new plugs earlier this year when I serviced it, and has never so much as coughed before.

You got a fender extender? Was it raining?

check the foam sound deadener under your tank for any looseness, the vacuum from the airbox may be sucking it away from the tank restricting the airflow

^why?

bobit's thinking it could be running on one cylinder. But I doubt it, here.

RandyO's suggestion's a good one. Could be a vacuum leak? Or maybe fuel starvation? It's also similiar to what happens if you're disasterously lean. I'd lift the lid and have a root about, see if anything's amis.

Sticking chokes :idea:

oooh nooo

this sounds like oil starvation you are running without oil man !! and idd cause of that running on 1 cilinder can be a possibility

now i hope for you, you didnt already ****ed up your engine on the insite, i did it, and it costed me 1900 euros


good luck and first thing to do when taking your sv babe for a spin is checking the oil level!

Thanks for the replies, still no further on.

No rain, never had a problem in the rain, in fact I did 1700 miles last month on holiday, most of which was in the rain. Checked the tank foam, still stuck fast to the tank. Oil level is fine, engine is not dead yet.

Took it out for anotehr ride yesterday, basically above about 4k if you really wind it on then it splutters, if you back it off it's not as bad. Stripped the carbs today, cleaned everything - there was a bit of rust in the rear choke plunger, and found a tiny bit of fluff in the rear main jet (138 DJs by the way Windy), so was optimistic putting it all back together. Stripped the fuel pump, clean as a whistle, as was eveything else. Tried it again, still crap, but now with enough patience and lack of sympathy it will go above 5-6k then take off - but slow down again and the same thing happens. I'm obviously missing whatever it is that's at fault.

I recently cleaned the K&N and resprayed it with oil - but not K&N oil, just whatever the bike shop had, Putoline I think. Reckon it'd make any odds or am I being paranoid? Tried opening the choke while out riding, no difference, so doesn't appear the be leanness. All pipes etc. looked to be in good nick and in the right place etc.

FH, I'm well confused now. Help! Anyone heard of anythng like this being electronic? Any more suggestions?

Its not something daft like water in the fuel or mank in your fuel tank contaminating the fuel is it ?

Exact same thing happened to me, it was very intermittent and drove me mad until i lifted the tank and it almost fell off.
not the most obvious problem but worth checking out. i wished i had checked earlier as it would have stopped me from wastind several hours taking various bits off my bike!