Hi group, it seems like I've had a good bit of mileage before these problems On a86 k100 rs . First , I rode up a steep gravel road for twenty minutes in first and second gear ( temps 70-80 F) and the temperature warning light came on maybe halfway up, when I stopped at the top and parked with the engine slightly uphill the coolant started overflowing from the reservoir at the back of the bike. I never heard the fan turn on while going uphill or before I shut the bike off at the top. I let it rest for a couple hours  and reattached the rubber cap and rode home without any issues. I had replaced the temperature sensing switch   a year ago because it wouldn't start. 

Another question I have is the bike will occasionally cut out at high speed like it is running out of fuel but will come back on by itself and this has happened a few times after starting to go downhill right after cresting s hill .I've looked on the forum and it sounds like it could be anything from the Hall effect sensors to the ignition switch , valves needing adjusted and oh yeah the temp sensing switch ( I've already replaced ) Fuel tank has been cleaned , fuel filter and pump  replaced, deteriorating rubber parts replaced , all in the last few years . Maybe someone has a new take ? Cheers

Check the electrical plug connector into the fuel tank. If everything is cutting out then it may be at the ignition wiring but if only the engine is cutting out then the ignition should be ok.

Fan temperature sensor is not the same as then engine temp sensor that controls the starting of the engine.

But check your fan will actually rotate, it may be seized. They tend to do that.....

Ok sorry I installed a new temperature relay .. . The fan will spin but the wiring connector came apart very easily for only being able to get one hand on it and I see the fan side connector has a plastic male plug that wasn't connected to any slot . Any how there is another post in the electrical forum that should help with troubleshooting the fan that I just saw. Thanks

How much gas in it when it cuts out? If it's very low then the gas can wash around in the tank and starve the fuel pump under some circumstances.

Plenty of fuel so that shouldn't be the cause. I have had that happen on steep twisty up hills before, that's not encouraging but at high speeds in traffic I don't like my bike cutting out , at all! !

Fuel slop inside the tank going uphill with falling fuel level will cause the intake to suffer fuel starvation when the fuel slops away going uphill as the pick up is at the front of the tank. I live up a steep hill........DAMHIK

A side note on fuel starvation: If you are running out of fuel then you can get another mile or two out of your tank by riding with the bike tilted to the left. DAMHIK.

you can get another mile or two out of your tank by riding with the bike tilted to the left.

Yeah. Done that a coupla times coming off the freeway. I start to worry a little when you can hear the pump sucking air.

Flip2 wrote:....
Another question I have is the bike will occasionally cut out at high speed like it is running out of fuel but will come back on by itself and this has happened a few times after starting to go downhill right after cresting s hill .I've looked on the forum and it sounds like it could be anything from the Hall effect sensors to the ignition switch , valves needing adjusted and oh yeah the temp sensing switch ( I've already replaced ) Fuel tank has been cleaned , fuel filter and pump  replaced, deteriorating rubber parts replaced , all in the last few years . Maybe someone has a new take ? Cheers

One way to tell if the ignition switch is being an arse is if the instrument lights flicker or go out. Usually when this happens the 'brake light' warning comes on when ignition power is restored.
But I seem to remember someone (Rockman I think???) had a similar problem while cresting a hill and I think there was a solution. Check out his posts.

Holister wrote:

you can get another mile or two out of your tank by riding with the bike tilted to the left.

Yeah. Done that a coupla times coming off the freeway. I start to worry a little when you can hear the pump sucking air.

Flip2 wrote:....
Another question I have is the bike will occasionally cut out at high speed like it is running out of fuel but will come back on by itself and this has happened a few times after starting to go downhill right after cresting s hill .I've looked on the forum and it sounds like it could be anything from the Hall effect sensors to the ignition switch , valves needing adjusted and oh yeah the temp sensing switch ( I've already replaced ) Fuel tank has been cleaned , fuel filter and pump  replaced, deteriorating rubber parts replaced , all in the last few years . Maybe someone has a new take ? Cheers

One way to tell if the ignition switch is being an arse is if the instrument lights flicker or go out. Usually when this happens the 'brake light' warning comes on when ignition power is restored.
But I seem to remember someone (Rockman I think???) had a similar problem while cresting a hill and I think there was a solution. Check out his posts.

In my case it turned out to be the hall effect sensor. Going uphill it would warm up a bit and cut out, then cool down a bit going downhill and run again. Replaced the HES and all good again. One of the sensors was actually loose on the plate so it was a wonder it went at all.

Ok , getting back to my fan I realized the wiring is damaged on the end of the wiring harness before the connector that connects to the temperature sensor.
The parts fiche for this bike 86 k100 rs shows 2 connectors at the end of the engine wiring harness-
one goes to the temperature sensor and does anyone know what /where the other goes to ? I do have a short section of tubing (15cm) coming up from the engine right under the fan that someone has put a screw into it.
If I remove the harness and cut out the damaged wire and solder a new piece back in place and maybe shrink tube it would this be acceptable in general ?

The fan itself will not turn on by powering it directly from the battery yellow/purple) and grounding the brown wire. So I'll take the fan out and have a better look at the wiring and the tips for rebuilding (thanks for the downloads!!)

Due to the OEM's fans passion for seizing it is a good idea to fit an override switch. If you flip the fan on once a week it helps stop the fan from seizing and gives you the comfort of knowing your fan is working. If the fan is seized take the opportunity to replace it with a fully sealed one. I fitted a Davies Craig fan probably 19 years ago and it has never missed a beat.
Regards Martin.

Cut'n'splice is okay, if done properly - the heatshrink is a Good Idea (tm). I think you're talking about the temp sensor and the fan connectors, but telling us the wiring colour codes would help a lot.

As for the tube: I think that was part of the California emissions regs but it sounds like someone has removed the gubbins. It needs someone else to confirm/deny that.

Yes, the tube on the front of the motor is CA related emissions junk. Very common to have that blocked and not an issue.

Yes, the fan connector wiring is violet/yellow (12V+) and brown(ground.) Solder/heat shrink repair should work just fine.

It should run when you jump it so it sounds as though your fan might be kaput.

Aftermarket fan:

http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/fans/fans.htm

YOk thanks for the info, the damaged wire is on the engine wiring harness before it connects to the temperature sensor( purple green wire)and not the fan like I posted, sorry  ! Will take a better look at the fan soon and see if it can be brought back to life .  I see the bosck fan motor is available for $80 (usd) but will compare with other new complete fans and maybe that override switch .

PYes my old fan is cooked, one of the brushes was less than 1/4 inch and the other one looked new comparatively , anyhow ordered that fancy spal fan and wanted to know what kind of connector set up to use since the new and old connectors won't match ?

When I did mine I just cut the connector off the old Bosch fan and spliced it onto the wires for the new one.  Soldered and used shrink tube for a nice job.

The wires feeding my coolant /water temp sensor were damaged and while I was repairing them I added a new wire at this damaged area to the wire connected to pin E of the temp relay( not joined to the wire to pin 10 of the efi-the other wire of the temp sensor) via a switch connected to the grounding point under the tank. This did not work to ground E , no fan power. 

I grounded pin E by temporarily sandwiching a wire in with pin E in the loom with the relay connected and this worked for getting the fan to turn on after grounding the wire. So am wondering why the first set up didn't work and also wether it's possible to push the female connector out of the base of the relay  in order to add a wire in at this connector
for my switch to ground pin E. if not that what is the easiest way to join a wire to pin E in the loom , a simple splice below the relay?