Hi all. I have a 1990 sporty with a 89ci S&S stroker kit. Due to work it's been sat for 18 months with very little running. A few weeks ago I took it for MOT and it ran badly. I installed new plugs and added a little octane boost to the fuel tank. This seemed to cure the problem. Two days ago however I took it out and it's worse than ever. It ticks over lovely and so long as I don't open the throttle anymore than just a fast idle it runs along ok. But as soon as I Rev up to speed up a little it coughs and splutters and I have to roll off the gas and crawl along. It's fitted with a S&S SHORTY a K and N CLEANER. Any advice would be appreciated

 

After sitting for 18 months I'd guess it's bad gas. Drain it.

 

That's my first thought. Start with draining old fuel and adding fresh. Hopefully the carb is not all gunked up. YD

 

Thanks for the advice. I have already drained the old fuel and replaced with good quality petrol. It has made no difference at all. At tickover the bike purrs like a content kitten. And will even rev up with mechanical delight. Although the Rev counter does fluctuate and bounce when doing so. Take it for a ride and the whole picture changes. Medium acceleration causes the bike to miss and splutter. Drop the throttle off a bit and it stops doing it. The bike has a screaming eagle coil and a compufire ignition system. Thanks

 

The next step would be to re-build the carburetor.

 

Hi all. I've rebuilt the carb. It did have a little debris in the bottom of the float bowl but nothing major. Put it all back together and hey presto, still the same. So it's not fuel related. I'm leading towards the coil as I've replaced the plugs and the leads. Anyone?

 

Don't know if you've checked or not, but see if your battery and ground connections are clean and snug. A loose ground wire will make the bike act crazy.
You should test the coil before you go replacing it.

 

Many thanks to replies. Especially the last one. I found the problem right at the end of the earth strap off the battery.