Hoping not to sound dictatorial, All the issues you have describe will be service related and majority from the carbs.
It's a 22 year old bike and was most likely serviced well for the first few years. If the bike has spent it's life in Ireland then as you know the weather can be harsh on man and machine.
The carbs on these work well if treated to some love and care and an occasional service. You don't need to completely strip them (unless snowbound for a few months
) just clean and replace the emission tube and needle, the jets will last twice as long and if the filter is intact (fitted to the inlet of the T piece between the carbs) then a lot longer, replace the gaskets and using a quality balance, balance the carbs, remembering that if you've adjusted the valves or replace the exhaust/mufflers then that will effect the balance.
Replace the right hand side white circular plastic air cut off cover as the bike sits on the side stand to the left this plastic cover gets the sunlight, it is effected by UV light and gets micro cracks (and can bend
) resulting in a vacuum loss and poor running at low RPM, the one on the left hand carb lasts a lot longer. The choke mech has a tendency to stick slightly open, give the cable and mech a good lube.
The needle clip position is variable and can be quite different from bike to bike, I run a K&N filter and find I need to drop the needle one clip and it still runs a little rich, I'm looking at changing the main jets to help with the over fuelling, yet other bikes run beautifully set to standard, make sure the little centralising washer is fitted and if not make one and fit it, see link.
http://www.trx850.com/phpBB_forum/viewt ... ic#p119873
There is a foam collar under the tank that keeps the "air" forced into the intake for the air box, don't remove it just make sure that it's intact and not being sucked into the airbox inlet, they do have a tendency to come loose (old glue) and can restrict the air flow.
The ignition is fine on these, but a little soft, you will notice the Ignictec Ign is a great upgrade and will change the feel and sound of the bike plus it improves the low to mid range power delivery, the ignition on modern bikes either works or it doesn't, as a mech mate of mine said, "all ignitions issues are found to be in the carburettors". The leads are also most likely on their last legs, replace them, (see link)
http://www.trx850.com/phpBB_forum/viewt ... ds#p119623
