Another bike wont start problem...sorry.

[crowman99uk]

I have a yamaha fzr1000, 1988, pre exup with micron zorst and k&n filter, done about 57k, and its getting to that age where things are starting to fall off of it etc!
Anyhow, my problem, it all started about a week ago, i was out and about and noticed a funny noise which turned out to be the coolant boiling over and spitting it out through the overflow, I drained cooling system and refilled, was alright for a few days then done the same, I have since tracked this down to a dodgy thermoswitch which means the fan is not switching on when it gets too hot, so till i get a new one would a switch wired into it whereby i could manually switch the fan on and off be a reasonable solution? I know how to do this, just wondered if it was feasible.
OK, secondly and more importantly, the bloody thing wont start!
This has been threatening for a while, over the last 2 or 3 weeks when starting from cold (ie after being left overnight) it starts first time, i can run it for miles stop, and it will start first time, however, if i leave it for half hour + it struggles to start, normally starting and firing on 1 or 2, i then have to wait anything upto 2 minutes or so for the other 2cylinders to kick in, it will then run fine. Now however it wont start at all!
I try starting it with no throttle and the starter turns ok but nothing happens, doesnt even appear to be firing, but when i try starting on full throttle for a few seconds and then close the throttle firstly the starter motor slows slightly (also when on choke) then it tries to start then backfires and shoots a 3ft flame out the back, which looks really cool, but not really what i want to do. I drained the carbs, cleaned the fuel filter, checked fuel lines, fuel breather line, fuel pump and all are fine....any ideas anyone?
Also anyone tell me how to get to the spark plugs? do i have to remove radiator, oil cooler etc...seems a bit extreme just to check the plugs but i cant see any other way.
Any help / advice would be very much appreciated.

[finpos]

Well, as you said, it's knocking on a bit, so anything could be up with it!

best guesses though:

To fit a switch for the rad fan, pull the connector off the themo switch. It will have ither 1 or two connectors. If only one, run a wire from it, to a switch, and then directly to earth. If two, bridge the two connections via the switch. Use a big switch.

You might find a bike of that age is just struggling generally with cooling die to the radiator being furred up.

Starting:

The flames and misfiring two cylinders say to me that you have either a failing coil or low tension or high tension wiring associated with that coil. Check that first before worrying about fuel.

edit Oh, and I forgot, use a car battery to try and start it, see if it helps!

finpos.

[crowman99uk]

many thanks for prompt reply.

I will check coil etc tomorrow and will let u know, as for car battery, been using one because battery died while trying to start it.

once again, thankyou