I am hoping that the wonderful K100 folk can help
I have read the similar threads on lumpy running and will do the following

1. check I have not disturbed the Fuel injection module wiring under the seat when I removed it to change the battery - I removed it whilst still attached to the loom as I could not get the clip undone - will check I have not damaged the wires
   
2. check all the perishable rubber bits (the Z rubber bit?)
   
3. check the idling set up
   

I wonder if there are any other "idiots guide to fixing your K100 when its running lumpy" tips (I am the idiot, not you lot)

A bit more background - 

• the old battery was flat (cos I left it on the bike all winter in the shed and started it a few times but did not run it)(told you I was an idiot)
  
• I charged the old battery (whilst still in the bike) enough to start and the bike ran lovely, no probs. went out for 20 miles, got home, would not start again to drive back into shed
  
• changed battery - new gel pack with enormous cold cranking
  
• started on choke, ran lovely until choke off, then went lumpy
  
• rode at speed for 20 plus miles, no probs but stalled whenever at stop and runs lumpy at low revs. (held throttle open to idle at 1.2k and it hunts/hesitates)
  

All thoughts greatly appreciated

It's possible that your new battery is defective.

Before you attempt anything concerning idling, drain the fuel from the tank, put the old fuel in your Aston Martin and refill the moto's tank with clean fuel. Then try starting it.

Next time you intend to leave the moto idle for an extended time, disconnect the battery's negative ground cable from its attachment point at the transmission and cover its terminal so it doesn't ground on the frame.

Learn to disconnect the electronic fuel injection control's plug from the unit. It's attached by a hook on its left end (within red oval) and a latch on its right end. Look into the hole at the top of the box. Push the latch to the right (toward the rear of the moto). Grab the plug at the end indiated within the green box, pull it outward so the plug is pivoting on the hook then disconnect it from where its hooked at the left end . You might have impaired its connection during your handling of it and it might need to be re-seated firmly.

Thanks Duck

I still have the old one. (although it is dead)

A logical test would be to install the old battery, jump start the bike and see what the tickover is like then.

If the tickover is fine then its the new battery that is somehow at fault 

Seeing that the problem occurred on replacing the battery, it would seem logical to test the new component first

will try that and see what gives

Thanks Laitch

I will try to disconnect the Fuel injection box as you say and refit to see if that makes a difference

I think I will do that first, then check out the battery dodge

The bike ran perfect on the fuel in the tank before the current problem and I topped the tank up with 97RON fuel after the problem had started, wondering if a bit more bang might clear the problem, but it didnt

Aston Martin? my other car is a van!

bimbler wrote:The bike ran perfect on the fuel in the tank before the current problem . . .

The moto ran perfectly for only twenty miles after sitting in a shed for months. That's not stellar performance. Removing and replacing all the fuel eliminates fuel that might have been diluted by condensation. That's why I recommended replacing all of it. Have you ever looked into the tank and examined its condition? Sure, the new battery might be defective but evil forces are at work during a moto's idleness; they must be expelled!

The remedy is probably a simple one—loose battery and ground connections, a clogged fuel filter finally giving up the ghost in a fit of depression caused by neglect, loose fuel hose connections within the tank, a new battery with insufficient charge.

Pull the fuel filter out and try to blow through it. (Free! )

When fuel filters sit the fibers in them can swell and restrict flow.

I'd replace it anyhow just for peace of mind.

I'll put my bet on the fuel and the filter too.

Have you checked the four pin tank connector to make sure it is making a good connection?  That connector is infamous for causing trouble.

You mention that the bike sat all winter.  Around here that is about 4-5 months if we're lucky.  That is long enough for the crap fuel they sell now to suck up a bunch of water and make some varnish, both of which can make the engine run rough at idle. 

I would suggest draining the tank completely, mopping up any remaining fuel with rags and refilling it with fresh fuel that has a good fuel system cleaner added to it.  I use either Chevron Techron or Seafoam both when I put my bikes into hibernation and as a Spring tonic when I put them back on the road.

If you don't have a pump to remove the fuel an easy work around is to remove the fuel return hose where it connects to the tank and direct it into a container.  Start the engine and as it runs the fuel pump will pump the fuel into the container.  If you aren't sure which hose is the return, it is the one connected to the left side at the front of tank that ISN'T connected to the injector fuel rail at the other end.

Thanks all for the advice

I checked and reseated the Fuel injection model
I cleaned the plugs (which were a bit oily) and cleaned them
I checked/tightened the battery terminals

I have ordered new plugs and fuel filter and will drain the tank before fitting

It ran better but is still not happy

Whilst looking for plugs I came across a conversation on the motobrick forum that a number of you here were contributing to. 

http://www.motobrick.com/index.php?topic=9512.0

really useful stuff

I have opted for NGK D8EA to avoid any possible preignition and extend electrode life

Try putting a Harley badge on the tank and grow a beard.
RT

I had a very similar symptom with mine and cured it by pinching the return line at the tank while revving the motor. Start it up, hold the line pinched shut for a few secs and whilst the rpm is up release the line. Did this multiple times and my bike went back to normal. Worth a try.

bimbler wrote:Whilst looking for plugs I came across a conversation on the motobrick forum that a number of you here were contributing to. 

http://www.motobrick.com/index.php?topic=9512.0

really useful stuff

I have opted for NGK D8EA to avoid any possible preignition and extend electrode life

Between BMW and NGK they know a hell of a lot about the right plugs to use D7EA is the recommended plug and that is what I have always used regardless of the temp or any other factors. My current K75 is still on the set of plugs I put in 60K ago

Yep NGK are tops. I just changed my wife’s Golf plugs, still original VW made by NGK. Been in since new in 2009 and after 80k miles still looked fine and ran fine.

Hey Nobbylon - thanks for the tip

Being a mechanical novice I am always up for testing less technical fixes first. I will try your fix as described

I ran projected tip DP8EA in Australia's heat (as compared to Old Blighty's damp cold) for a while in my 8V K100RS. They seemed to be slightly more sooty than when I used D7EA, which is what's in there, and running clean, these days. There is no valid reason to use a one step colder plug in a touring and commuting K100.

As an aside, when BMW came out with the new series K40 'wedge' engine in 2004 it had Bosch plugs. Within a coupla years the part number was superseded to an NGK number. Of course there are many factors as to why a company use a certain product, but this sparkie remains the most common brand in a wide range of BMW models, both car and motorbike.

I’ve read bad things about Bosch plugs (made in Russia) so never use or recommend them.