I've had my 89 K100RT for a few months now and occassionally I've found the engine will cut out. This only happens when...

• I'm approaching an intersection
  
• I'm throttling down (ie I've rolled off the throttle)
  
• Clutch is in
  

This problem is not an intermittant problem. I can replicate the cutout at any time by clutch in an roll off accelerator.

I've read somewhere of someone else having this exact problem but there was no solution offered.
Could it have something to do with the TPS, ECU or Hall sensors.

Engine operates quite well in all other respects. Starting and idle is no problem.
This is a big problem for me as at one time it left me in the middle of cross traffic with no power.
Any help will be greatly appreciated.
Cheers

Disconnect the TPS and leave it off. Go for a ride and see if that changes things. You wont do any damage unless you run flat out for a few miles but even then it's unlikely. You may even like the way it runs at low revs in 1st and 2nd gear.
Also with the TPS connected let the revs get below 2000rpm before you clutch in, say about 1500rpm in 3rd or 4th.
Let us know what changes if anything.  It could well be bad contacts in the TPS.

My '86 K75c has done that a bit since I reconnected the vacuum line to the Fuel Pressure Relief Valve (was disconnected when I bought the machine.
Made me think that it might be related to a fuel pressure issue but have never got around to finding a gauge and fittings to allow me to check this out.

Rick are you pointing to TPS due to the fact that one of its functions is to enrich the mixture when contacts close on throttle being fully closed? Or does that happen only when cranking for start up?

They only enrich the mix at start up and that comes from the starter button.
If the contacts are corroded or dirty and taking a while to close then it may be getting confused about closed throttle above 2000rpm.

Thanks RicK G
I removed the TPS connection. There was no difference. Engine still cut out on throttle down. But what I found was the middle connector was badly corroded. I gave the whole plug and socket a good clean and a squirt with wd40. The rubber seal in the top appeared to be a little squashed so I took that out and turned it around hoping it would make a better seal. Another test ride and the problem seems to be gone but will monitor this over the next week.

What I don't understand tho is that the engine should run ok with the TPS disconnected. Mine still cut out??
Is there something still amiss?

Many thanks again mate.

I think we have seen the tps with a few issues ...one in particular had been flooded with something and was shorting out between the wide open setting and the closed throttle setting ...must have felt very strange

I guess you are new to k bikes

can I suggest ...check all the rubbers around the throttle bodies ...in particular the tube from the crankcase to the plenum (above the throttle bodies ...about 16-18mm od  with a odd angular bend ) this sits behind the coils area ...if perished ..will leave the bike struggling at lower revs as it is an air leak as far as the system is concerned ...

other symptoms could be that it idles roughly ...but if the bike is new to you ...would appear to be normal ....erm.. ish   just because you have never seen it as it should be ...

just a thought that might help ....time and rubber deterioration

Captain Holister wrote:Thanks RicK G
I removed the TPS connection. There was no difference. Engine still cut out on throttle down. But what I found was the middle connector was badly corroded. I gave the whole plug and socket a good clean and a squirt with wd40. The rubber seal in the top appeared to be a little squashed so I took that out and turned it around hoping it would make a better seal. Another test ride and the problem seems to be gone but will monitor this over the next week.

What I don't understand tho is that the engine should run ok with the TPS disconnected. Mine still cut out??
Is there something still amiss?

Many thanks again mate.

All the TPS does is tell the ECU when the throttle is fully closed and fully open so it can cut fuel above 2000rpm when shut and go real rich at wide open so as not to smoke a set of pistons. The L Jetronic is very agricultural injection compared to what we get today.
If you disconnect the TPS it helps prevent what can be very bad snatching in 1st and 2nd gear because it continually hunts between under and over 2000rpm when riding slowly in the low gears.

As that has made none or very little difference I would have a close look at leaking intake after the filter as that will give incorrect readings from the Mass airflow sensor and make for lean idle and running at low revs.

While idling remove the filler plug for the engine oil and that will determine if there is a leak at the breather because the plenum chamber is connected directly to the crankcase to give negative pressure and prevent oil leaks and if air is getting in it will idle badly if at all.

Hi there, while playing with the injection setup, using the lean drop metod, I learned that an incorrect idle adjust, via the MAFS´s air by pass screw, will result in such engine cut out´s while stopping.
A more careful adjust solved the issue.
Hope this helps.

Best regards

JAP

RicK G wrote:They only enrich the mix at start up and that comes from the starter button.
If the contacts are corroded or dirty and taking a while to close then it may be getting confused
about closed throttle above 2000rpm.

Thread tangent: I've heard/read this starter button enrichment also works at higher RPMS and can give a K bike at wee bit of an extra boost. (I think Don Eilenberger posted about it somehwere.)

Probably engages the starter too but I don't think the sprag isn't going to catch up to an engine running at high RPMs.

Something I've always meant to experiment with but just never remember to try when out riding....

duck wrote: I've heard/read this starter button enrichment also works at higher RPMS and can give a K bike at wee bit of an extra boost. (I think Don Eilenberger posted about it somehwere.)

I've also been reading that fairytale.....the starter button circuit isn't energized
unless you but the bike in neutral or pull the clutch.

duck wrote: Probably engages the starter too but I don't think the sprag isn't going to catch up to an engine running at high RPMs.

The ground connection on the starter relay coil is disabled when the engine is running higher than 711 rpm's.

mmm .. .may or may not help but . . . .had this exact scenario with a nissan pulsar. It was the airflow meter not working properly. When I dismantled my K @110ks, did the rebuild, 6 months later it would not idle. The airflow meter was the issue. Hope it is not that but prob worth investigating

regards

Inge K. wrote:

duck wrote: I've heard/read this starter button enrichment also works at higher RPMS and can give a K bike at wee bit of an extra boost. (I think Don Eilenberger posted about it somehwere.)

I've also been reading that fairytale.....the starter button circuit isn't energized
unless you but the bike in neutral or pull the clutch.

duck wrote: Probably engages the starter too but I don't think the sprag isn't going to catch up to an engine running at high RPMs.

The ground connection on the starter relay coil is disabled when the engine is running higher than 711 rpm's.

Agreed on the start button power, etc..... It was just something I read a while back and never really looked in to.

RicK G wrote:

While idling remove the filler plug for the engine oil and that will determine if there is a leak at the breather because the plenum chamber is connected directly to the crankcase to give negative pressure and prevent oil leaks and if air is getting in it will idle badly if at all.

Rick,
I am about to tune my TB's or at least check them (waiting for carbtune to turn up).

Have adjusted the valve clearances (substantial adjustment on 2 valves-both exhaust).

Have checked inlet manifold for leaks (aerostart spray) - all good.

TB linkages have blue paint on them, hoping it is factory setting and not from PO - we will find out I guess once carbtune arrives.

After reading your above comment I did the test and the engine cuts out immediately. Does this indicate a "Z" pipe leak and if so is it possible to replace or refit the pipe without removing anything - it looks as if it would be fairly tight to get into. Or is it better to remove the air intake system to get at things a bit easier 

Regards,
Mike

If it cuts out or runs really bad then it is a good indication that there is very little air getting in elsewhere.  It shows that the engine has good vacuum in the crankcase and not much air is getting through but as soon as you pull the plug out it goes lean and stalls. I didn't put it very well in the last post. If there is a heap of extra air getting anyway then you will notice almost no change when the plug comes out.

RicK G
I think I jumped the gun a little there.
The problem is still happening. Only cuts out when decelerating in any gear except 5th, above 2000rpm and when the clutch is engaged. Doesn't seem to happen at low revs.
Disconnecting the TPS makes no difference.
How do I get to the contacts in the TPS?
What I've noticed is that the ignition light comes on just after the clutch is engaged and the revs start to drop.

I've pulled the oil filler cap while idling. It either runs very rough or cuts out which, from what you said, is what should happen.

Just a long shot but my starter switch is missing the green button and spring which holds the switch open. It seems to still work ok.

Cheers

Other usual suspects:

1) Bad/dirty ignition switch

2) Bad fuel tank connector

Captain Holister wrote:RicK G
I think I jumped the gun a little there.
The problem is still happening. Only cuts out when decelerating in any gear except 5th, above 2000rpm and when the clutch is engaged. Doesn't seem to happen at low revs.
Disconnecting the TPS makes no difference.
How do I get to the contacts in the TPS?
What I've noticed is that the ignition light comes on just after the clutch is engaged and the revs start to drop.

I've pulled the oil filler cap while idling. It either runs very rough or cuts out which, from what you said, is what should happen.

Just a long shot but my starter switch is missing the green button and spring which holds the switch open. It seems to still work ok.

Cheers

The TPS is designed to send a signal to the ECU that the throttle is closed and if the ECU determines the RPM is above 2000RPM then it will cut the pulses to the fuel injectors so you have better engine braking and save fuel.
It should not matter which gear you are in it will do it at all times so what you are seeing there is quite normal.
As you said when you pull the filler plug it runs bad or stalls is also a good sign in that if there are any air leaks then they are very small.
The ignition light coming on like that isn't really much to worry about some of them including my K75 have a very faint charge light all the time. There is a fix for it by inserting a diode in the blue wire to the alternator with the arrow to the alternator but if all it does is flash on then go off again it's OK.
Check the voltage across the battery at 2000rpm it should read 13.8 to 14.2 volts with 14.2 as optimum charge.

The alternators weren't really big enough and later models from 1994 on had 50 amp which were a big improvement. Might pay to get one and Duck is the man to talk to about that he knows the ins and outs of all that.
There is a link to a site about "so you just bought a BMW what now" on the portal page. Have a look as Ted has done a great job putting it together and it gives you a good insight as to what will need doing to get your new possession to top shape.
One other to visit for good info is Ducks site K Bike Tech there is a wealth of good reading there.

RicK
OK. I understand how the TPS works and it does then appear to work the way its supposed to BUT the engine should not stop when the clutch is engaged. My reason for mentioning the ignition light coming on was to point out that, not only has the fuel been cut in deceleration, but the electics stop also which means when it gets back down to 2000rpm there's no ignition and the engine needs to be restarted.
Sorry but I must be missing something.

Duck
I'll check the ignition switch.
Also, what is the fuel tank connector?

Bare with me guys, I'm not a mechanic.
Appreciated all your help.
Thanks

Depending on the model it will be at the rear and comes out the rear from under the tank with a 4 pin plug which is usually behind the right side cover. That's the late model. The earlier pre 1986 it is front left under the tank next to the outlet and return lines for the fuel injection.
This thing with the clutch is getting a bit muddled.
Am I right in that when you are approaching an intersection where you need to stop, you roll off the throttle and when you get below 2000rpm then pull the clutch lever in the engine stops. Then do you need to put it into neutral to restart or does it start just with the clutch lever pulled in.

RicK G wrote:Depending on the model it will be at the rear and comes out the rear from under the tank with a 4 pin plug which is usually behind the right side cover. That's the late model. The earlier pre 1986 it is front left under the tank next to the outlet and return lines for the fuel injection.
This thing with the clutch is getting a bit muddled.
Am I right in that when you are approaching an intersection where you need to stop, you roll off the throttle and when you get below 2000rpm then pull the clutch lever in the engine stops. Then do you need to put it into neutral to restart or does it start just with the clutch lever pulled in.

This problem has happened 3 times now while breaking heavily from speed. In one incident a car did a u-turn in front of me... I roll off the accelerator, pull in the clutch, apply brakes... engine stops. The engine starts easily in gear with the clutch in. This doesn't appear to be intermitant as I can replicate this anytime.

This does not happen under normal operation ie just pulling up at lights etc where I've knocked it down 2 or 3 gears, revs near idle then pull in the clutch to stop.

Cheers

See if it happens with a full tank of fuel.

RicK G wrote:See if it happens with a full tank of fuel.

Full or near empty... same problem.
I've cleaned the tank connector and tweeked the contacts a little. Its nice and tight but the problem is still happening.

How do I get to the TPS contacts you mentioned? Looks like I just undo the 2 retaining screws and unclip it apart. ??

Seems to me its a fuel issue. Something is cutting the fuel as soon as the clutch is engaged when the throttle is off. The engine can be doing 5,000rpm with throttle off and when the clutch goes in the ignition lights come on like you'd just hit the kill switch and the engine dies. I can start it in gear with the clutch in or just let the clutch out and it roll starts.

I can hear the TPS clicking in just as the slack is taken up on the throttle cable and off again when released. Maybe the throttle cable needs adjusting?

OK this is not a huge problem as its rare that you'd need to engage the clutch any longer than necessary to change gears and now I'm aware of the problem I can avoid it.... but it shouldn't happen, and those times when I need to brake hard and engage the clutch I end up with no power.... engine is dead after an emergency stop.

Anyways, I'll leave this one out there.

Cheers

Have you checked the sidestand / clutch inhibitor @ the end of the gearbox. Just a thought. Also (not sure here) but is there a microswitch at the clutch lever, or, even more thought says check the connections relating to the gear selector display mechanisim,

Be made wrote:Have you checked the sidestand / clutch inhibitor @ the end of the gearbox. Just a thought. Also (not sure here) but is there a microswitch at the clutch lever, or, even more thought says check the connections relating to the gear selector display mechanism,

A 1989 K100RT does not have any switch associated with the sidestand. The "clutch inhibitor" is the switch on the left switch block that blocks the starter from working unless you pull the clutch in. This is on all K100s. Even if the GPI (gear position indicator switch) was unplugged it would not cause the engine to stop.

One thing that has crossed my mind about this problem is that it is when you do a hard stop. which is why I asked about the full tank or not. I was thinking of fuel running away from the pump under extreme braking.
Maybe the ECU (engine control unit) under the seat is not secured well and is getting knocked around and this is causing the connections to be O/C under brakes, also is the battery secured well. It appears to me that most likely what you are looking for is a physical thing that is moving under hard braking and causing a momentary Open Circuit of the electrical system that feeds power to the ECU.
All I can suggest here is to have the bike idling on the stand and pulling and wriggling connectors to see if you can make it happen.

RicK G wrote:One thing that has crossed my mind about this problem is that it is when you do a hard stop. which is why I asked about the full tank or not. I was thinking of fuel running away from the pump under extreme braking.
Maybe the ECU (engine control unit) under the seat is not secured well and is getting knocked around and this is causing the connections to be O/C under brakes, also is the battery secured well. It appears to me that most likely what you are looking for is a physical thing that is moving under hard braking and causing a momentary Open Circuit of the electrical system that feeds power to the ECU.
All I can suggest here is to have the bike idling on the stand and pulling and wriggling connectors to see if you can make it happen.

This happens at any time RicK. Not just when I do a hard stop. It's just that that's when you're most likely to engage the clutch for a prolonged period of time... under heavy braking. As I have said I can replicate the problem anytime and it does happen just by pulling the clutch in at high revs but not at low revs (<2k). That's why I've been thinking it's something to do with the TPS.

It caught me out yesterday as I approached a T-intersection (give-way) on a down slope in 2nd gear and engaged the clutch, I didn't notice the engine had stopped. I rolled on out to turn right and went to give it some throttle to resume in 2nd gear but had no power. So now I'm in traffic with a bus bearing down on me having to restart, get it into 1st and get around the intersection. Anyone watching must've thought I was a real Noob.

I've put the meter on the battery as you suggested and I'm getting 13.89v @ 2000rpm (but I have read that the alternator output changes at higher revs (??). I might try to rig a meter up so I can see whats happening as I ride around. Another thought was that I might get the battery tested even tho it starts fine and I'm getting 12.8v

The engine runs fine in all other respects except for the odd backfire (more like a fart) which was pretty bad till I replaced the exhaust gaskets and crank vent hose but from what I gather, a little backfire now and again is normal (??). Also I think I'm getting rather high fuel consumption at around 7 lit/100k but I'm not a sedate rider. The user manual says 5.2 lit/100k but whats really normal?

Thanks for everyone's thoughts on this. I guess an answer will appear someday.
Cheers

RicK G wrote:...  It could well be bad contacts in the TPS.

How do I get to these contact? Can I remove the TPS and open it up without too much trouble? Looks like you just undo the two retaining/adjustment screws and it unclips apart??

It caught me out yesterday as I approached a T-intersection (give-way) on a down slope in 2nd gear and engaged the clutch, I didn't

I think you mean when you disengage the clutch like as when you pull the lever in to the handlebar. Am I right?

RicK G wrote:It caught me out yesterday as I approached a T-intersection (give-way) on a down slope in 2nd gear and engaged the clutch, I didn't

I think you mean when you disengage the clutch like as when you pull the lever in to the handlebar. Am I right?

My mistake. Yes. I disengaged the clutch.

I just reread the entire thread (helps me focus on it) and it certainly does look like the over and under 2000rpm fuel cut out is involved in the equation. The TPS only tells the ECU that the throttle is closed, it's up to the ECU to determine what to do. It is unlikely that the feed to the ECU to monitor the engine speed is not working as it most likely wouldn't start if that were the case.
If the contacts in the TPS were dirty and only intermittent then inspite of what I said earlier the ECU would not know the throttle was closed so will do nothing to cut the fuel because it still thinks (heavy word for a collection of components) there is open throttle.
I think (collection of brain cells working here)   your next move will have to be to try a different ECU or at least cleaning the contacts on the plug and receptor on the ECU.
If you do need repairs I know this guy does do them http://www.cdirepair.com.au/

Can one of the Aussie brotherhood make a spare ECU available so the OP can test it? I was thinking the OP's problem might be a not properly fitted computer connector. Earlier people has issues with humidity in the injection computer and the ECU?? Grasping at straws here :-)

When you mention ECU, what are we refering to here. My Haymes manual referes to the Ignition Control Unit which is mounted under the tank behind the steering head and the Fuel Injection Control Unit mounted below the tool compartment above the battery.

I'd like to check out the TPS first and I've ask this question prev. but... is there any issue with taking the TPS off and opening it up to check the contacts? I would just like to proceed with caution.

Cheers

ECU is what Haynes refer to as the fuel injection control unit.
I don't see why you couldn't open it, I have never had the need to open one but by the drawing I have I seems a fairly straight forward switch unit.

Captain Holister wrote:I'd like to check out the TPS first and I've ask this question prev. but... is there any issue with taking the TPS off and opening it up to check the contacts? I would just like to proceed with caution.

Cheers

There isn't much to these TPS units and, even if you opened it for inspection, there are no serviceable parts inside.  The clicking sound comes from a microswitch.  If it's broken, the cost of a new one is the same as a used TPS.  The WOT contacts are regular exposed bronze metal.

This shows the internals of the TPS:


Test your unit by
(1) removing the harness connection
(2) use an ohmmeter between Pins 1 and 2 (Green and Blue in the diagram above).  With the throttle closed, you should read zero ohms.  Crack the throttle and the measurement should jump to infinity
(3) use an ohmmeter between Pins 1 and 3 (Green and Red in the diagram above).  With the throttle closed, you should read infinity.  Open the throttle fully and the resistance measurement should drop to zero just as you reach the end of the movement.

If all these tests pass, your switch is good to go.  If ANY test fails, buy another switch.

Captain Holister wrote:How do I get to these contact? Can I remove the TPS and open it up without too much trouble? Looks like you just undo the two retaining/adjustment screws and it unclips apart??

You access the TPS contacts by removing the harness connection on the top of the switch. There is a wire retaining clip that needs to be carefully prised off the connector housing, just like on an injector. Once free, the contact housing simply slips off.

You remove the entire TPS by undoing the two screws that secure the TPS to the TB assembly. You are advised to perform the tests above while the TPS is attached to the TB assembly though.

robmack wrote:Test your unit by
(1) removing the harness connection
(2) use an ohmmeter between Pins 1 and 2 (Green and Blue in the diagram above).  With the throttle closed, you should read zero ohms.  Crack the throttle and the measurement should jump to infinity
(3) use an ohmmeter between Pins 1 and 3 (Green and Red in the diagram above).  With the throttle closed, you should read infinity.  Open the throttle fully and the resistance measurement should drop to zero just as you reach the end of the movement.

Thanks robmack
TPS checks out okay. Could it be that there needs to be an adjustment there? The microswitch clicks in right at that point when the throttle slack is taken up.

ECU connections all look clean.

The odd thing is that this problem only occurs when the clutch is disengaged ie the clutch lever is pulled in.

RicK G wrote:I just reread the entire thread (helps me focus on it) and it certainly does look like the over and under 2000rpm fuel cut out is involved in the equation. ....  I think (collection of brain cells working here)   your next move will have to be to try a different ECU or at least cleaning the contacts on the plug and receptor on the ECU.

Captain Holister wrote:ECU connections all look clean.
The odd thing is that this problem only occurs when the clutch is disengaged ie the clutch lever is pulled in.

Just thinking as well.  The TPS is functioning normally and even appears to be adjusted properly by your description above.  The clutch switch is pretty much out of the picture when the bike is running so it can't be that circuit.  The Hall Effect sensors feed engine RPM to the Ignition Control Unit (ICU) under the tank.  Rick thinks the symptoms are pointing towards problems with the engine electronics recognizing over/under 2000 RPM.

Although the contacts to the ECU are clean, you haven't eliminated the ECU itself as a failing unit.  Swapping in a known working unit would be a good move.

There is a connection between the ECU and ICU (Yellow/Red from Pin 8 to Pin 1), I think for the ECU to get information about engine RPMs.  Possibly the problem is with the ICU or the connection to the ICU.  It might be worth your while to lift the tank and service the connector that goes to the ICU.

I'm starting to strongly suspect the ECU more as this goes on.

I'll check out the ICU contector in the morning.

Kaptain, 
     I have a buddy with the EXACT SAME problem on a 92' k75. I initially changed the fuel filter...crisper idle....no resolution. I'm putting in a new fuel pump on today and will report the results.

Nope. She still dies when the clutch is disengaged. I noticed that if I pushed the "choke" lever to wide open, it seemed to be fine. (I understand that the "choke" on K bikes is more like a little arm that holds the throttle open)

Although she idled way to high, this seemed to keep her alive. I'm adding a Dakota digital speedo/tach combo tomorrow and once I calibrate the speed sensor I can report the high idle rpm.

*note that if it starts to die in the normal choke position and I let the clutch lever back out the bike will not die

I would go back to basics, start from the very first bits - valves properly adjusted/throttle bodies verified 'equaly set' and no air leaks of the rubber stubbs and fuel injectors. Make sure all parts are very clean (by-pass screws and holes?). The go further from there.

MikeisonTV wrote:Kaptain, 
     I have a buddy with the EXACT SAME problem on a 92' k75. I initially changed the fuel filter...crisper idle....no resolution. I'm putting in a new fuel pump on today and will report the results.

Hi Mike
WOW... I thought I was going crazy.

You can see from the thread that we've been eliminating possibilities one by one. I think RicK G is onto something with the ECU not recognising under/over 2000rpm as signalled by the TPS. IMHO I think we'll find this to be the issue eventually. Robmack has suggested cleaning contacts at the ICU which I've done but I've decided to give all connections a proper cleanout with electrical cleaner which I bought today. So the tank will be off tomorrow and I'll be going over as many connections as I can get to from the ICU back to the ECU. Once that's done and problem still exists I'll swap out another ECU and see what happens.

Other thoughts I had were to nip the idle speed up a notch and see if that makes a difference. It idles nicely at around 960rpm ±30 at the mo.

Also, I need to get the battery tested. Although its seems to be working fine, it could be a different story under load.

I would have to check again but I'm sure mine still cuts out when choke is on. I'll report back on that.

MikeisonTV wrote:*note that if it starts to die in the normal choke position and I let the clutch lever back out the bike will not die

I can confirm this. (I'm asuming that by "normal choke position" you are meaning the choke is off??)
Also when I see it about to die I can give it a bit of throttle to save it.

I look forward to hearing back re your high idle speed.

Question for Rick... How does applying the choke affect the TPS signal? I'll need to get the wiring diagram out tonight before lights out.
EDIT: Just had a quick look and it seems that the TPS clicks just as the second stage choke position is engaging.

Cheers all

The 'choke' basically opens the throttle a bit. If you clean contacts, make sure you clean the ones of the injection computer and of the ECU. Do you still have the automatic blinker cut-off working?

ReneZ wrote:I would go back to basics, start from the very first bits - valves properly adjusted/throttle bodies verified 'equaly set' and no air leaks of the rubber stubbs and fuel injectors. Make sure all parts are very clean (by-pass screws and holes?). The go further from there.

Thanks ReneZ
My strategy so far is to inspect/test/clean what appears to be logical and eazy to do. All the rubbers I can see look to be in good condition. I've recently replaced the crankcase vent hose. Valves and throttle synchronisation is not something I'm up for atm. Bought this Old Girl last April and I cleaning everything as I gradually go over it (what are the "by-pass screws and holes?)

I have to say that in every other respect the Old Girl runs very well. I use it for daily commuting as well as the longer hauls and it will cruise all day on a trip from Lennox to Sydney (750km/8½hrs) nonstop except for fuel. Done that return trip a couple of times now plus others. It never misses a beat and I get around 6.5 Lit/100km highway. I tend to fang it quite a bit and it's never failed me so far.

Cheers

The switch in the TPS is way late it should click at the latest by the time the choke is half way to the first detent, as early as you can get it by using the choke lever.  You will also need a very free returning throttle grip and cable, if the cable or grip bind a bit then it makes the TPS switch slow to react to a closing throttle.
On my K100 I had a very bad problem with it in that it was almost unrideable at slow crawling traffic speeds and it turned out the grip was binding on the switch block when I had my hand on the grip riding but when standing  next to it and twisting the throttle all was OK. Took me a while to figure it out. Just re glued it onto the tube and all was OK.

Also, I need to get the battery tested. Although its seems to be working fine, it could be a different story under load.

MikeisonTV wrote:*note that if it starts to die in the normal choke position and I let the clutch lever back out the bike will not die

I can confirm this. (I'm asuming that by "normal choke position" you are meaning the choke is off??)
Also when I see it about to d

1) it's not the battery, at least not likely on this end as I just put a new one in last week for him

2)your assumption of the choke is correct. All the way off I sometimes get the cut out. All the way on, with a high idle, it prevents it

I think Rick G might be on to something with the cable sticking. I am going to add some oil to the inside and lube the chain where it connects.
(I had to replace it on my own k100)

Look forward to your ECU swap test, but hope that's not it as it's the more expensive end of resolution

MikeisonTV wrote:I think Rick G might be on to something with the cable sticking. I am going to add some oil to the inside and lube the chain where it connects.

Don't oil BMW cables as you would with other motorcycle control cables. They have an interior plastic liner that gets ruined when you attempt to lubricate it .  You should check the cable routing and make absolutely sure that there are no kinks or tight turns in the housing that might cause the interior cable to hang up.

To start, I've replicated this problem with the choke lever fully over to the 2nd detent i.e. still dies with choke fully on.

RicK G wrote:The switch in the TPS is way late it should click at the latest by the time the choke is half way to the first detent, as early as you can get it by using the choke lever.

So how can I achieve this if the TPS is clicking in right on throttle off position? Does this mean the choke fast idle speed needs adjustment? This is something I've not checked.

RicK G wrote:You will also need a very free returning throttle grip and cable, if the cable or grip bind a bit then it makes the TPS switch slow to react to a closing throttle.

I recently lubed my throttle control. It was very dry and was binding and I was finding it increasingly dificult to apply throttle. I've checked the release actiont just now and it's snapping back quite well on release.

RicK G wrote:Just re glued it onto the tube and all was OK.

Not sure what you mean by this

MikeisonTV wrote:2)your assumption of the choke is correct. All the way off I sometimes get the cut out. All the way on, with a high idle, it prevents it

That's different to mine which cuts out whether choke is on or off.

BUT something I have noticed while on one of my test rides the other week and after giving it a bit of stick was that it became intermittant i.e. it didn't cut out every time I throttle off>clutch in. The engine was nice and warm as I'd just had a good fang up the hinterland for half an hour to vent my frustrations

I used a meter to set the TPS. one with a needle not a digital or you could use an LED across the switch, you need to have a very on/off signal and a digital meter is slow to respond to that.
I set all the throttle bodies up and syncd the butterflys then set the TPS so that when at the stop it was off and as soon as I put a .010" feeler gauge under the stop screw it turned on and pull it out it clicked off. That was a far finer adjustment than any other way.
The big problem with the genuine BMW bowden cables is that they have a teflon lining and work very well until someone lubes them then they gather dust and that works as an abrasive on the teflon and in no time they don't work very well at all. If you can replace them with genuine and don't lube them and they go for 20 years.  It is counter intuitive but it works, especially after years of Japanese bikes.

What I did was remove the right grip and clean it and the twist grip plastic tube then glue them together again so there was a gap to the switch block.

Thanks RicK
Re: Setting throttle bodies (??) up and syncing butterflys. My Haymes manual indicates specialist equipment needed unless you can suggest another method???

Re: cables: I've only bought BMW cables and I certainly don't oil them but as I've posted above, I have lubed the throttle control handlebar assembly.

Re: glueing throttle grip. I'll take a look at that to see what condition mine is in.

Thanks mate

I only re glued my grip because it had worked its way up against the switch block and was binding a bit when I had my gloves on and my hand was pushing it up a bit more so I glued it so there was 1/4 inch clearance.
You may not need to adjust the butterflys but get it idling smoothly by adjusting the idle screws (the big brass ones) then set the TPS. Even using the choke to adjust it as the choke lever will only move the throttle very slightly for about a 1/4 turn, it is far more sensitive than the twist grip for setting the TPS.