Curvy backfiring and running badly.

[Stooks]

Hi all, my sv has been out of use for nearly a year now due to it not working and im ready to give up. it started with it backfiring when i was decelerating it started backfiring unbelievable amounts and eventually cut out and wouldn't start at all. so i went through all the standard things like changing plugs, ht leads and coils, this did nothing. then i went onto the carbs, i cleaned them out twice. for some strange reason it burst into life on a friday about three months ago, i had it MOT'd and the mechanic said it was in perfect nick. after the MOT it ran really rough but after a few miles it sorted itself out. in idle it liked to cut out so i changed back to my after market exhaust (no baffle) and then it ran fine. on the monday i was riding it through town and whilst stopped at a set of lights it did its backfire spazout again! so i have replaced the battery, replaced the plugs as the previous ones had loads of carbon in it after a weekend riding and just to be certain ive got another set or carbs off a working curvy. it still didnt work so i put my old restricter washers in and it started and ran for about 10 secs but it was backfiring the entire time. ive put my stock exhaust back on but it wouldnt start again. i took the rear plug out and it black and covered in petrol. i havent checked the front as its a nightmare to get out. im really stuck and would appreciate if someone could help me before i through my bike in a ditch.

Sam

[andrewsmith]

I would be getting valve clearances checked. What's the mileage on the bike?

I'm thinking that the valves are either not sealing right or just open at detonation

[andrewsmith]

What state are the fuel lines in?

Is there an external fuel filter from the tank to the pump?

Was fuel you were using been in the tank for the last year?

[Stooks]

The valve clearences is a very good shout!! I knew they needed looking at but it never crossed my mind. The fuel is about 3 months old as when it ran for the weekend I only had a little fuel so I filled it with brand new stuff as it wasn't running very nice, after I rode it awhile and got the old petrol out it was fine. The fuel lines have no splits and no blockages. I'm not sure about the filter but I know the bike is defo getting enough fuel. Thanks for responding guys.

[21QUEST]

Hi

Are the carbs in balance? Do you have a carb balancer?
Choke working as it should ie not plunger not stuck and/or the O-rings sealing properly

I believe you are not far from me. I'm happy to come down and have a look if you want.
I can't do anything this weekend but we could possible arrange a time to suit between Monday and next weekend.

PM me if you want to take me up on the offer.

[Haircut]

It may be worth doing another clean of the carbs abd checking that the float needles are free and is working correctly.

[Stooks]

hi guys, thanks for the help. ive got a friend who knows his stuff about bikes and we have managed to narrow it back to a point before the coils as the spark only happens intermittent and its weak. so we have had a look and he thinks its the pulse generator?

[Stooks]

Hi guys! I've finally found the issue!! It was the cables that run from the altenator to the rectifier had melted on the exhaust! Abit of solder later and it ran as sweet as a nut!