Hello All,

Going through the bike in a bit more indepth, I have discovered that the fuel hoses are suspect and would like to replace them



I see that normal 1/4 inch reinforced hose to fine to use, but i am a little concerned that the return hose( the one that is routed behind the plenum box), has a hex nut connector on it. i have yet to strip the bike this far to confirm this, if it does can normal hose be fitted onto it or must I get from BMW?



Many thanks

sae 30r10 is the stuff your looking for ....8mm internal diameter ...(you may need to get new hose clips as the later brew of rubber is a bit thicker , better and less whiffy than original) ....you might need about a metre in all ...the feed side , the bit from the rail to the presure regulator ...then the bit from the regulator to the return valve-coupling

also look to getting some 12mm (internal )air conditioning - cold return pipe type insulation, does wonders for keping the warm out ...if you live in a hot climate or ride around the city ...cheep as chips ...just be carefull around the radiator



hope that helps

If you can see your way to do it get 2 quick connect hose clips in 8mm and it makes the tank a whole lot easier to get of.

thanks all.



what i could find is 1/4 inch fuel hose non conductive, 250PSI W.P hose made by goodyear. I got 2meters as that is the minimum the shop would sell it for. I paid R50/m ( in real money about 4.50 pounds uk ) for it.



now just to remove everything to get to the hoses that run behind the plenum box as viewed from the left of the bike.

I like the idea of a quick coupler and the insulation of the hoses.

hope it works will let you all know.

you might find that working from the right hand side ...and undoing the air box could be helpfull to get to the presure regulator area behind the throttle bodies , rather than undoing the whole tb assembly .

thanks yes that is excactly what I intend to do. those throttle bodies look like a mission to get off.



this bike is a real drama to get the fairing off to do anything- I am learning as I go I suppose!

Hi All,

just to let you know, I got the right side fairing off now and removed te airbox to gain access to the other side of the intake plenum - 1/4 inch hose is not quite the right size.no matter what I do the hose will not fit on the fuel pressure regulator , especially on the injector rail side. I am going to try and get a lightly bigger inner diameter hose.

also i see there is a some type of sensor mounted to the alumininium cross bar - it has a single connector and looks like its earth is is too mounted on the bar. the sensor looks like an oil pressure switch, but has a piece of hollow vacuum hose attached to it at the one end, which leads out to under the battery. Do any of you know what this is- i cannot find it in any description of the fuel system anywhere?



thanks

i think thats the vacuume switch ....discontinued after 85 or something

i think you can safely remove it and block the vacuume take off that feeds it ...

some of the other members could confirm this .

the reason for removing it ? just another place that could become an issue with rotten rubbers ..

thanks, but the "vacuum" hose is not connected to anything?

could it be some sort of air temperature/ or air pressure sensor? the wire going to the plug is brown and the "earth" wire is green?

it probably ..used to be connected to the take off on number 1 ? but disconnected ?

RSMITH wrote:thanks, but the "vacuum" hose is not connected to anything?

could it be some sort of air temperature/ or air pressure sensor? the wire going to the plug is brown and the "earth" wire is green?

A brown wire on a K series is always earth the green goes to the multi pin plug at the ECU under the seat.
The vacuum switch was used on the early models but was discontinued. Apparently no changes were made to the ECU when the switch was removed so if you have one just feed the thing to the garbage bin.

Hello Charlie 99,

I am not sure I follow you? where is the take off for no 1 situated?



I think what I should do is take a pic and post it so you can see what I am refering to.

if it can be taken off then I will probablly just leave it on incase it does have an effect.

The take off on #1 is in the same position as the vacuum tube for the FPR on #4

thanks- I will a have another look tonight when I get home from work and try and figure it out.



now just to get the right size hoses- no one has slightly bigger than 1/4 inch.

once I got the airbox out- the bike itself is not that bad to work on- I have worked on this bike before with my dad, but never on my own, and have also worked many bikes before, The K seems fairly straight foward- I just have to learn all the "tricks"

Hose is 5/16 or 8mm

managed to find some 5/16 for R60 ( approx 5 pounds uk),

ah well at least i can use the hose I got yesterday on my other bike, and for syphoning petrol.

just keep it as a spare in the cowl at the back .....when or if you need to remove the tank on the side of the road .....just use the ends from out to return on the tank so you dont loose fuel ...but 1/4 is pretty small

that is exactly it-

I see taking the removing the tank is a pain in the backside, and now i can drain the fuel out of the tank easily with the piece of hose!

Here's a trick that saved my sanity when I was replacing the fuel hoses and rubber bits on my 1985 K100RS: a very small ratchet wrench and appropriately sized socket can be used to free the clamp that fixes the duct between the top of the airbox and the plenum.

Yes, a small / short ratchet is a tool that make life much easier when working in this really tight places.

Rick G wrote:

RSMITH wrote:thanks, but the "vacuum" hose is not connected to anything?

could it be some sort of air temperature/ or air pressure sensor? the wire going to the plug is brown and the "earth" wire is green?

A brown wire on a K series is always earth the green goes to the multi pin plug at the ECU under the seat.
The vacuum switch was used on the early models but was discontinued. Apparently no changes were made to the ECU when the switch was removed so if you have one just feed the thing to the garbage bin.

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sorry to flogg a dead horse on this vacuum switch thing.

i am in the vincinity again having to pull out the air box to sort out my "choke" light problem

I left it as I found it and following me riding the bike a bit I am not getting such good fuel consumption as I would like/Hoped for

can you kind fella's maybe tell me a bit more info about this vacuum switch? and maybe confirm that the vacuum hose does indeed connect to TB no1 in much the same way that the FPR vacuum hose connects to TB no4

many thanks

you could probably just plug the take off on number 1 vacume take off ....

test the temperature sensor ....at pin 10 of the "fi "computer under the seat ,,,there is a graph of the values in the efi trouble shooting link on the portal page ....if it was lossy or high resistance it could run the engine richer than expected .



good luck !!

I have an early 85 k100, it originaly came with that vacuum switch. It controls timing advance during mid throttle. Not necesary, so I eliminated it, no ill effects. That said,the hose ran to #1 tb. As you look at the throttle bodys they all have a small brass tube coming out of them covered with a rubber cap., these are used to sync the throttle bodys. If your throttle body rail is of the proper year to use the vacuum switch #1 will have another tube in the same spot as #4 has the pressure regulator hose hooked up to. The tube on #1 also needs a cap to prevent leaks HOPE THAT HELPS!

I found this same switch/sensor when replacing the fuel pressure regulator on my late 1984 K100RT - the wires to it were disconnected when I found it and that didn't seem right to me, so I cleaned and reconnected said wires and reconnected them to the switch. My bike ran ok once I had re-assembled everything else but I have now realised after reading this post that I have no tube connecting TB1 to this unit - it has been blanked off with a rubber cap !
Obviously the previous owner had already disconnected said switch at some point and blanked off the number 1TB as there is no pipe leading from it so I am guessing that by reconnecting the electrical connection to this that I have effectively shot myself in the foot - could this explain my poor idle speed I wonder ? The bike always idled fine before I replaced the FPR etc and reconnected this (discontinued) sensor

thank you all for your input.

yes I see on the the #1 TB there are two vacuum outlets that are both blanked off. Strange that I never noticed the lower one before- it points out straight to the side parrallel with the ground.

I will re-route the vacuum on the switch and plug it in to #1 TB. it also explains why the vacuum hose for the switch is so long.



re the temp sender, I made a quick measurement this morning before I made my way to work, we are in winter and the ambient temperature in my little workshop where the bike is, was approx +1.5c at 5:30am, I got 7.71k ohms. so if i go according to the graph on "K100 Trouble shooting" by Bertrand Vogel aka Crazy Frog- looks like there is my problem.

I hear the latest 4month post office strike is now over - so maybe I can order stuff from overseas.



thanks all again - much apprecciated.

apologies just would like to add - I measured the resistance of the coolant temp sensor/switch at the switch itself and not through the pins and got 7.71 k ohms

rs ....dont forget it is a double ended arrangement ....so to do the measurement properly you must measure only one of the probes - contacts and earth .

if in fact you measured both the terminals you would in fact be measuring both sensors ....or double the value

please concider this and reveiw your findings .

quite often the earth contact ie : the water stub could be corroded between the thread of the sensor and earth .....this might sound strange ...but if it were lets say 50 ohms extra (as an example) it could affect the normal running temperatures when it gets up to 80 odd degrees c when it would measure a lot less and the percentage of error is much greater than when cold ...

hope this helps

OK . I think I follow you?

what you mean is that I should only check the resistance on one pin at a time and earth and not together when measuring at the sensor itself?

just to be clear that I am checking the correct one- the sensor is the 2 pin square plug type that is screwed into the engine mounted behind #1TB near the bottom left of the radiator when looking foward through the radiator to the front wheel?

or is the actual procedure for cheking done via pin 10 and earth and thats that?

thanks again.

Check it at the sensor and at the pin 10 that way you may pick up an inconsistency in resistance if one is there.

yep thats the idea .....

the pin 10 on the computer is the easiest way .....that way you are checking for any corrosion accross the temp sensor connector as well... so in the end you should be able to clean it all up ...back to standard and good running mixtures .

the other leg goes to the temp switching relay for the fan control ......also worth testing .

good luck