I am hoping you may be able to assist me in a problem I am currently experiencing with a K100RS I am 'recommissioning' for a friend? Its a bit of a ratty old beast but he just uses it for long distance commuting and it is generally sound. It only has 59k on the clock so is approaching being run in.

On starting the bike from stone cold, all is well for 5 or 6 minutes when the engine will suddenly cut out completely. When you try to start the engine directly afterwards the starter button engages the fuel pump but not the starter motor or, if my ears are working as well as they should, the starter relay. It seems that, whatever the fault, it is disabling the starter motor circuits completely.

When you leave the bike for 30 minutes or so, it will fire up, but cuts out very soon afterwards. The longer you leave the bike to cool down the longer it will run on a restart.

The battery is fine and measures 12.8v. There is plenty of fuel.

One issue is that the gear indicator never registers Neutral and so you have to pull the clutch in to start it up. I think that is just an age thing and should create a fault such as the one that is occurring. The clutch switch works perfectly.

Reading previous posts I thought it may be the Hall Effect Sensor but doesnt this usually start with a msfire on two cylinders and, in addition, why would it disable the starter circuits.

I also thought of there possibly being water in the fuel that mixes when you start the bike but, again, why would this disable the starter motor.

In my own mind it must be an ECU problem and, if it was my bike, I would get a 2nd hand item off Ebay to try it out. However it isnt my money I am spending so I would like a few opinions first.

Many thanks for your time in reading my ramblings!!

cheers

Richard Akrill

welcome to the forum richard

a verry wierd prognosis huh? ....

i think i recall seeing a discription of "overheat" cutout being at about 110 deg c .... basically the engine would not run .....i recon it might be a fuel injector control module safe guard ...

if this were the case , it might pay to measure the cables to the temperature sensor (located on the water stub which projects out of the engine casing proper ...then distributes to 2 pipes ..one a bypass and the other a standard feed to the radiator core the temperature sensor lives there ...and can be accessed by removing the right hand side lower fairing ..behind the radiator )

i would be looking to measure the number 10 connection on the under seat computer for this reading ...the other side to earth ...use 20,000 ohms or more as the scale for reading resistance .....

at 20 odd degrees c ...or colder the value should be over 2,000 ohms

but durring the stop event ...possibly under 100 ohms

um..... possibly this has a thermostat issue ....being blocked - failed , creating an over heat type situation (if it was blocked completly the water temp would quickly rise ...and take forever to cool properly )

measure the same locations after it fails to run .....

alternativly it could be a water pump issue ...again similar results to water circulation and cooling

question? does the radiator fan come on durring or before this fail to start event ? ( many problematic issues even just in that = age and corrosion to electrical connections )

well thats my guess at the moment ...until more information surfaces


i would advise you to get some deoxit " which is a marvelous anti corrosion cleaner to electrical connections


good luck !!!

Thanks for your very quick reply.

There is no sign of the engine getting hot at all. In fact, given that we are sunbathing here in about 5 degrees Centigrade, I would only say that the engine is barely warm when it cuts out after a few minutes.

try checking fuel pressure pump may start failing as it warms up also the pressure regulator maybe sticking dropping fuel pressure as well.or the pump maybe sucking crap up thus blocking it then releasing them when it stops

have fun

there is another co relationship between the air temp sensor (in the air flow meter ) ....and good running

you might have to do a "member introduction " post as required etc and a few more posts to get to the links -permissions for the download pages ...where there is a flow chart for efi issues ...which might be highly recomended

in any case ...do the measurement and see if there is a short cuircuit between the temp sensor and ground ....cant hurt can it ?



yep good suggestions toto.....

I just knew it!!!!!!!!!!

I think it's fixed itself!!!! I ran it for 15 mins last night with no sign of it misfiring or cutting out. I'll suggest getting some deoxit to the owner but knowing him - he wont!

I'll keep you informed.

hmm good for the moment ...but untill you prove the fault ....it will come back at some time



hope it works out ok mate !!!

whoohooo time for a beer or three

So here we are 4 months down the line and my friends K100RS is back in my garage. After my last experience with the engine cutout he took it away to have it MOT'd which, despite it cutting out outside the MOT station - it passed.

Unfortunately after that the bike died whilst in County Durham and it has taken a few months for him to get it back to me. Apparently when it stopped at the roadside it would just about start but would not rev. I am told that is symptomatic of a blocked fuel filter which we are going to change. Of course this is where the tank decides to spring a leak but I have some Permatex on order and I think that will be an easy fix.

I was wondering whether the blocked fuel filter and the engine cut-out I experienced could be related? There was a lot of crap in the tank which may, or may not, have fallen in when we removed the filler cap. If the petrol pump was straining to get fuel through a blocked filter, could it be feasible that it was failing (either due to overwork or large pieces of dirt in the intake) and then 'fixing' itself after a few hours 'rest'?

The main question is - if the fuel pump has failed, will it disable the starter mechanism as per the symptoms described in earlier post?

I think this may be the 'last chance saloon' for this bike and, if it doesnt mend in the next two weeks, the spanners will be coming out and it will find itself spread over about 50 adverts on Ebay!!!

Go on - give an aging K a fighting chance - it would be a shame for it to be stripped down.

A sudden cut out and a disabled starter relay could be related to the ignition ECU
(under front of the tank) and/or its connector, as the starter relay coil is grounded through the ignition ECU.

The temp sensor on the water outlet stub behind the radiator is the most likely thing. It will give a bad signal to the ECU as if the engine is overheating and cause the ECU to cut the engine and wont allow it to start untill it has cooled enough.
I can't think of any other single component that will stop the engine and prevent the starter motor working for a while.
You said that the longer you leave it before a restart the longer it will run after the restart, this points to a temperature related thing and if that sensor is shagged and thinks the engine is hot when it is only just warm then it could cause that problem. It would not be a bad connection in a plug point but possibly a chaffed and earthing wire because if the resistance the ECU reads from that sensor is zero or close it will be seen as a very hot engine.
But then again the K komunity needs organ donors.

+1 Inge. Sounds very similar to a problem I had in the early days. Swapped out the unit for a second hand one then all sorted.
88KE

i had a similar issue with an ecu... it would let you drive for about 10 minutes ...as the motor got hot it would die . letting the motor cool down would let you go for another 5 minutes ,etc

was caused by the mechanic not connecting up the earth stap , resulting in a verry high voltage being created ....the only thing that solved it was replacement .

Bloody mechanic! Prolly paid him good money too, eh!?

yep knew nothing about it till the headlights were bright as ...um "hid lamps" ...fail !!!

Imagine all that voltage going to waste.

Well - since the last installment I have drained the fuel tank (again) and installed a new filter and a replcement pump. The original pump was getting really noisy so we thought it better to replace than risk it dying. There was a lot of crud in the tank which I spent a long time removing.

Ive put it all back together and it seems to work but - the new pump sounds just like the old one and is noiser that the rumbly engine at tickover.

Any suggestions?

Lots of weird K-brick problems seem to relate to poor connections in various wiring looms. There is a standard edict to use contact spray and clean ALL accessible wireconnectors before trying to find more esoteric problems. At the same time you might look for corrosion at the frame grounding points - and if found, clean off and re-attach and cover with vaseline or similar non-acid grease.

Check the metal body of the pump isn't touching the inside of the tank as that will act like an echo chamber and amplify the noise.

if its a early version check the return fuel line ....the early series had a spring and ball bearing in the return line flange assembly ....suposed to stop back flow ....it can become verry noisy when the pump is running ... one of the "fixes " was to remove the spring etc to eliminate this issue ... use a screw driver as a stethescope to pinpoint the location of the noise in any case ....

I finally have ended up owning my mates K. I had done so much work on his 1200 Bandit and Aprilia Caponord that he owed me a fairly large amount of money. So instead of demanding money with menaces I suggested I took the K off his hands. I had no idea how much it has deteriorated in the preceding 3 years. It was a real mess.

So in an attempt to avoid splitting it for parts or scrapping it I decided to customise it in the style of a Street Scrambler I had seen on on a French website.

I think it's turned out pretty well!!

Have to admit, that does look nice.

Keep an eye out for it at the Dragon Rally in February then. With a bit of luck it'll be there.

I recognise your K100 from last year - we were all admiring your spotlights!!!

I hope it's as good as last year but a bit of snow wouldnt go amiss. I was on my CCM 604E last year but it felt like cheating.