Runs rough after standing for 18 months

[Colin]

I have got back to my Valk after it has been standing for 18 months due to ill health.

It is desmogged and has standard vacuum petcock with a Danmarc. It starts and just about ticks over maybe a bit slower than usual apply any throttle and it splutters and stops. With the choke on it runs fine with the occasional backfire, with the choke half on it seems to run fine.

I presume gummed up carbs. Anything else I should look at before taking them all apart which I hope is a last resort.

[Hook#3287]

I would try a couple of cans of preferred carb cleaner first.

Berrymens B-12 is mine.

[Jims99]

I use the b12 and happy with it. Do a very strong dose at first (I’ve run 1/2 a bottle and 1/2 tank of gas) start bike and let it run long enough to get it down to carbs. Then I would let it sit and loosen things up for an hour or so. Then drive around at lower RPMs to finish off tank. Then do other 1/2 with a full tank and ride. Hopefully this helps, otherwise it’s removal time. Good luck.

[Earl43P]

I use the b12 and happy with it. Do a very strong dose at first (I’ve run 1/2 a bottle and 1/2 tank of gas) start bike and let it run long enough to get it down to carbs. Then I would let it sit and loosen things up for an hour or so. Then drive around at lower RPMs to finish off tank. Then do other 1/2 with a full tank and ride. Hopefully this helps, otherwise it’s removal time. Good luck.

What he said^, but my idea of a strong dose is stronger than his.
I really don't think you can OVER-dose Berryman B12. I know that I have put almost a whole can into a very low fuel tank (not a Valk, but still 2 carbed Honda GW1500) and started it, let it run at fast (choked) idle then let it sit, run it some more at normal idle (if it will), rode it and put more fuel in to dilute it and more B12 in each tank full. It took a few tanks but it got much better and I never touched those carbs. Put over 58k miles on that bike afterward but occasionally dosed it with the B12 when it needed it (when the idle would lope). People used to comment that my exhaust smelled rich....B12 was why.

Might also inspect/replace the air filter, mice tend to nest in there.

[GL15Brewer]

When I started mine after about 18 months I had similar issues. Are all your intake tubes heating up? My whole right side was cold. Had to tap the carb bowls with a wrench to get things moving again. I ended up doing a carb rebuild but it's proving to be quite a process. bikes getting old and have had to replace pretty much every hose on it.

[Colin]

Thanks everyone for your replies. Berrimans is not available in Spain. I got something similar (made by IATA) from my local car spares place and after about an hour of running it has cleared all the rubbish and is now running fine.