Since I bought my S1W a couple of weeks ago I've not really touched it , anyway I took it for a short ride and it it ran great once past 3k but below that it was missing really badly, it's fitted with a mikuni and felt like a blocked pilot jet.
I've not delved in yet just wondered what I should look for first, the battery is old and week too.

If it were mine, I’d stick I big glug of RedEx in the tank and let it run through the carb to clean it on a good run.

The Mikuni website has a nice document to tell you all about the way the carb works (I’m sure you know already)...

http://www.mikuni.com/pdf/hsr_tuningmanual_021003.pdf

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08 Specialized Langster

Mine was doing that, oil from the breather pipes had run down behind the adaptor ring holding the air filter on and clogged up the pilot air passage.

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Wear the fox hat

Thanks for that tip I'll whip the carb and filter off this weekend and give it all a good clean .
Thanks for the mikuni link I've printed that off too so I know what's what.

Got the carb off and the pilot jet was blocked solid so I left it in carb cleaner overnight and then had to blow it out with my compressor and put it all back together excited thinking that was it cured .
The bike now feels like it runs on one cylinder 1-3 revs and fine above that and lumpy at tick over, I've ordered some new plugs and see what happens next, even though it runs shite it was still really promising .

Thank you for the update Howard

Mine also had a dodgy wire on the coil, looked ok from a distance, but was broken right at the connector.

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Wear the fox hat

Mine also, but if this is the cause I would also expect the Tachometer to be unstable.

It may be worth getting the whole carb body ultrasonically cleaned to ensure that it is all clean?

Had a good look at the coil and connectors and all looks and feels well , took it out for another run tonight and now I'm convinced it's running too rich on the mikuni.
I screwed the air mixture screw in and out and that made a big difference but still not rideable so now I need to find out where I should be starting with the jetting i.e. Pilot ,main and needle ?

Pash has a formula for that.........c'mon Nick

I’ve told him what to do but he hasn’t done it...

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08 Specialized Langster

I'd rather find out where I should start with the jetting then pop the carb in the ultrasonic cleaner then I know it's right as I've only just bought the bike and never had it running clean .