Most likely culprit? Valve clearances or carbs?

[850 Combat]

If your pilot jets haven't been removed, I would recommend you get them out. I've never been able to clean them well while they're still installed in the carburetor. If you're having trouble getting them out, soak them with penetrating oil overnight and then go back at them. Kroil has worked the best for me, but it can be hard to find locally. Of course, you can always buy it online.

I was never able to get the #3 pilot jet out of my 850 and I always wondered if it was that big of a deal... Well, I finally just went ahead and drilled it most of the way out and then used an easy out to get the rest. Replaced it with a brand new jet and it ran much better. Got rid of some idling problems and a small flat spot right off idle. Made the bike much more pleasant to ride. I think the jet was only $3-$5 shipped off of eBay. Genuine Mikuni jet too.

Cleaning the pilot jet is not always enough. You have to verify that all passages are clear. The pilot circuit gas an air inlet is in the bell mouth. There are progression holes at the butterfly in the opposite end of the carb, upstream of the idle screw. All the components are connected by internal passages which can clog. It is a good idea to spray carb cleaner in the the three openings you can access, and visually verify that it sprays out all of the other openings. You can access three openings:

Idle screw (remove the screw)
Pilot Jet (Remove the jet if you want) (I do)
Pilot air jet

Spray carb cleaner into each and verify that it comes out of the idle opening, progression holes, and the other two openings you can access.

The GS850 High Res manual on Cliff's site has an excellent diagram on how the pilot circuit functions on page 14-30 (PDF page 301).

My guess is that the pilot circuit is still the problem. Blowing air is not definitive at best, and may have a potential to create a problem with the diaphragm. I wouldn't blow in in the main jet air inlet anyhow.

In my personal experience, its not worth trying to run a stock system without the airbox and filter.

[GelandeStrasse]

This project is going well now I have a better understanding of what's required. I'm waiting on parts right now. Shims, dynojet kit and pod filters. I'm having to use pod filters because the bike didn't come with an air box plus I like to keep things simple and easy to work on. To get the jetting right I'll probably need to remove the carbs quite a few times. Easier without an air box in the way.

I'm wondering if I'll need to put a shield over the filters to stop rain water ingress?

I've got the carbs stripped completely to component parts and soaked and blown out, all the passages including the tiny pilot holes by the butterflies are now flowing carb spray nicely. I bought a small 'easy out' to remove the pilot jets. Got them out without damage or drilling!

Any tips on jetting out there? Anyone done this the same way, pod filters and jet kit? Planning to follow the dyno jet instructions but any tips gratefully received

Edit: Hi forum mods, any chance this thread could be moved into 'projects'?