I have just brought a K100 trike conversion. With it I inherited a bad missfire that makes it unrideable. The trike has had extensive work Compression check, valve clearances, fuel rail acid dipped, new fuel pump and filter, new plugs, coils leads and caps. Anyway checking for the missfire I noticed the fuel pump was not priming. I checked the fuses and one was blown. I replaced it, the fuel pump primed up and the missfire improved considerably. But not for long, now the fuel pump is not priming but the fuses are ok. I took each one out and tested them with a multi meter.  I am now wondering if it is a relay.

My electrical knowledge is limited. Does anyone have any clues to the cause of the problem. Is it a relay, and exactly where can I locate the relay. Is there any way to test it

Cheers 
Steve

The four pin connector that resides under the RH side of the tank is a known source of problems. Cleaning with Deoxit can sometimes remedy the problem. Alternatively replacing the whole connector with a good waterproof one will fix it. You can also pull the pump and bench test it. I am currently running a Chinese copy pump which has so far proved reliable. See http://www.motobrick.com/index.php/board,8.0.html
Regards Martin.

Another thing is to check the through connector in the bottom of the tank which feeds 12V from the bike into the fuel pump in the tank. Mine had gone high resistance, stopping the pump from working.

@MartinW wrote:The four pin connector that resides under the RH side of the tank is a known source of problems. Cleaning with Deoxit can sometimes remedy the problem. Alternatively replacing the whole connector with a good waterproof one will fix it. You can also pull the pump and bench test it. I am currently running a Chinese copy pump which has so far proved reliable. See http://www.motobrick.com/index.php/board,8.0.html
Regards Martin.

Thanks Martin, the plugs looks like it has been replaced with a Strip / block connector. I will get a new plug so I can rule that out completely.

Cheers 
Steve

@Basic2 wrote:Another thing is to check the through connector in the bottom of the tank which feeds 12V from the bike into the fuel pump in the tank. Mine had gone high resistance, stopping the pump from working.

Thanks mate I have the tank off now so I will check it out. How exactly can I check if it is as you say ' High resistance' 

Cheers
Steve

Take the pump out of the tank and use a multimeter to check the continuity of the wires between the 4 pin plug and the terminals on the pump. On mine the positive feed to the pump had gone high resistance, and would vary between several megaohms when you moved the wires near the through connector.

@Basic2 wrote:Take the pump out of the tank and use a multimeter to check the continuity of the wires between the 4 pin plug and the terminals on the pump. On mine the positive feed to the pump had gone high resistance, and would vary between several megaohms when you moved the wires near the through connector.

Sweet thanks for that, I have the tank off now, I'll take a look, it's going to be a couple of days before I can look at it again though due to work commitments.

Steve

Cool trike

The 4 pin configuration on the male end of the Petrol Gauge Level Sender

1.Brown-is ground continuity to the larger diameter ring terminal

2.Green-is 12V continuity to the smaller diameter ring terminal

3.Yellow-is fuel level

4.White-is 4 litre reserve indicator

Remove the ring terminals from the fuel pump to perform the continuity test for #1,2

@volador wrote:Cool trike

The 4 pin configuration on the male end of the Petrol Gauge Level Sender

1.Brown-is ground continuity to the larger diameter ring terminal

2.Green-is 12V continuity to the smaller diameter ring terminal

3.Yellow-is fuel level

4.White-is 4 litre reserve indicator

Remove the ring terminals from the fuel pump to perform the continuity test for #1,2

Thanks volador, Yes the trike is interesting, I haven't had a decent ride since I picked it up a couple of weeks ago due to the missfire. I have seen another in New Zealand based on the naked K75. Both Mine and the K75 were built by  ' Trikeworks ' a well known trike builder here in NZ.

The colour coding is very helpful thanks

Steve

@stevenh wrote:I have just brought a K100 trike conversion. With it I inherited a bad missfire that makes it unrideable. The trike has had extensive work Compression check, valve clearances, fuel rail acid dipped, new fuel pump and filter, new plugs, coils leads and caps. Anyway checking for the missfire I noticed the fuel pump was not priming. I checked the fuses and one was blown. I replaced it, the fuel pump primed up and the missfire improved considerably. But not for long, now the fuel pump is not priming but the fuses are ok. I took each one out and tested them with a multi meter.  I am now wondering if it is a relay.

My electrical knowledge is limited. Does anyone have any clues to the cause of the problem. Is it a relay, and exactly where can I locate the relay. Is there any way to test it

Cheers 
Steve

The photo you have up shows RT/LT fairing.

These were all 2V engines and the fuel pumps on these do NOT prime. They only get power when you press the start button. Nothing happens when you switch on the ignition. On 16v engines you will hear the pump as soon as you switch on ignition and bring kill switch to on position.

To check the relay swap the horn and fuel pump relays and see what happens. They are the same and will swap. All in the box under the fuel tank. These ones are not screwed in or bolted in, just pull them out.

Another point you haven't mentioned is the big plug into the Fuel Injection Control Unit under the seat, a known dodgy point and worth checking pins are clean and the plug is correctly seated.

@92KK 84WW Olaf wrote:

@stevenh wrote:I have just brought a K100 trike conversion. With it I inherited a bad missfire that makes it unrideable. The trike has had extensive work Compression check, valve clearances, fuel rail acid dipped, new fuel pump and filter, new plugs, coils leads and caps. Anyway checking for the missfire I noticed the fuel pump was not priming. I checked the fuses and one was blown. I replaced it, the fuel pump primed up and the missfire improved considerably. But not for long, now the fuel pump is not priming but the fuses are ok. I took each one out and tested them with a multi meter.  I am now wondering if it is a relay.

My electrical knowledge is limited. Does anyone have any clues to the cause of the problem. Is it a relay, and exactly where can I locate the relay. Is there any way to test it

Cheers 
Steve

The photo you have up shows RT/LT fairing.

These were all 2V engines and the fuel pumps on these do NOT prime. They only get power when you press the start button. Nothing happens when you switch on the ignition. On 16v engines you will hear the pump as soon as you switch on ignition and bring kill switch to on position.

To check the relay swap the horn and fuel pump relays and see what happens. They are the same and will swap. All in the box under the fuel tank. These ones are not screwed in or bolted in, just pull them out.

Another point you haven't mentioned is the big plug into the Fuel Injection Control Unit under the seat, a known dodgy point and worth checking pins are clean and the plug is correctly seated.

Thanks Olaf. you are correct it is an LT. Are you sure about the fuel pump not priming. I replaced a blown fuse and was sure I heard the pump priming once the fuse was replaced ( in saying that it is not priming now).

I will check the control unit, and relays. Thanks for the info

Steve

When you turn the key to "on", the pump doesn't operate until the start button is pressed. If the motor doesn't start the pump will run for a couple of seconds after the starter button has been released and the starter has stopped.

@Basic2 wrote:When you turn the key to "on", the pump doesn't operate until the start button is pressed. If the motor doesn't start the pump will run for a couple of seconds after the starter button has been released and the starter has stopped.

Right so that might be a good way to test if my pump is working then. Maybe a quick jab on the start button and see if I can hear the pump. If so could I assume my wiring and connections are all good. ?

Another little test I have used.

If you press the start button and the engine actually fires at that point, keep the start button pressed and if this keeps the engine firing it means your fuel pump is getting power and the fuel circuits relay etc should be ok.

If it cuts out then after you release the start button then you have a different focus. At this point the system is now relying on the signal from the Hall Effect Sensors [HES] under the T cover at the front of the engine. Most common issue may be the connections and this eventually goes through the Fuel Injection Control Unit [FICU]under the seat which is a common area to get some issues mostly related to poor electrical contact or the plug not seated correctly. On your 2v at the front of the petrol tank is another unit, under the headstock, Ignition Control Unit [ICU]. This also has a plug connector that may need some cleaning. It has two nuts and it slides backwards to come out, in case you are wondering how on earth do you get this thing out.

As an owner of the earlier 2 valve...

the standard move for me is to half press the starter button at least once to prime the fuel line - the pump will be heard.

Bike will / seems to start easier with the priming

You stated earlier: "I replaced a blown fuse and was sure I heard the pump priming once the fuse was replaced "

This will happen if the starter button is pressed too hard and is stuck in (the shaft under the green button is metal... and creates a circuit across two pins... and can get trapped between them). Mine does this occasionally. Just pull it back out.


Stupidly, I hadn't noticed mine did this the last time I rode it. So I thought that the starter relay was welded closed...Up with the tank, out with the relay, failed to open it, in with a replacement...same problem! Then I noticed the starter button stuck in.


Had a good ride after that.

G

Thanks everyone for all the feedback on my missfire problem.    I have plenty of good info and a 3 day weekend coming up. I plan to go over pretty much everything mentioned here. Hopefully I'll end up wit a good result  

Cheers
Steve

"the standard move for me is to half press the starter button at least once to prime the fuel line"


What GF said

Well over the weekend I took my tank off and went through all the electrical connections on good advice from many people on the forum. Although the fuel system had been Refurbished new pump, fuel rail injectors.  I thought I would take a quick look in the tank while it was empty.

I was horrified at what I found. The fuel pump looked like a generic car fuel pump, just sitting loosley in the bottom of the tank. no anti vibration mount, no fuel filter, the fuel strainer had become detached, the original hoses replaced with thin hose. The wiring to the pump was crap.

I have decided to pull it all out, and buy an aftermarket kit from the U.S.

Can anyone tell me the correct kit for my 1987 K100 LT.  With the return hose or without the return hose. I believe it is the kit without the return but I'm not sure 

Here are a couple of pics, seeing is believing

https://www.pinterest.nz/pin/566398090635958990/

https://www.pinterest.nz/pin/566398090635958987/

https://www.pinterest.nz/pin/566398090635958965/

Cheers 
Steve

Hi Steve,
My 11/87 K100 CJ had a 43mm diameter pump mounted in the vibration damper, and a sock filter. The OEM 12V feed to the pump uses ring connectors, not spade connectors.

I would suggest that (inside your tank) is not an uncommon sight. The rust and general mank should be remedied by 10 X 2 litre bottles of white vinegar ... Aldi $1.19 each (if I remember). Soak for several days and plastic scourer should clean it up.

Neglected bikes frequently suffer from vibration damper decay... The plastic mount is usually okay but the rubber often presents in a tar like state due to old fuel and ethanol usage. Plastic mounts can be obtained easily - it's just the cost of the damper that forces skin flints (like me) to try alternatives.

Is the pump working? If not, I have twice run into "jammed impellers" in the bottom of the fuel pump. Solution is to remove it, pinch the aluminium outer housing crimps flat and slide the inner out (may take some persuasion ... like a hammer handle and rubber mallet...handle against the bottom of the pump and light tap with something heavy (the mallet) will gradually work it up and out. Not sure if I used soft jaws in the vice).

Then in the bottom of the pump you will find several roller bearing impellers (used to pull the fuel through the pump). One might well be jammed, can be freed and pump is put back together and works fine.

I have wedged fuel line between the plastic mount and the pump. Just cut a slot into the side of the short length of fuel line to key into the lip on the inside of the plastic mount. Took three lengths of approx 100 mm. Temp solution only.

good luck

Guy

If I'm not mistaken, some of the inmates here have successfully run their bricks with inexpensive(cheap doesn't sound good in reference to an important part like a fuel pump) ChiCom fuel pumps.  I believe Martin is one of them, and he may soon add some further information.

I myself, have one of these $15 pumps in the top case of my touring bike.  I carry it on the theory that it prevents the pump in the tank from failing.  So far, it has performed perfectly in over 40,000 miles of riding.

I found all sorts of crap in my tank when I first got my bike with only 12000 miles on it.She hadn't been run for almost 15 years and everything in there rusted.I pulled it all out,washed the inside of the tank with heavy duty floor washing detergent then put in some muriatic acid .In 3 seconds the inside of the tank shined like new ! Then I washed it out again with detergent and rinsed a few times with water and I had a like new tank.Don't get the acid on the paint and wear protection on your eyes and your hands  and wear a good respirator!  PROTECTION IS IMPORTANT ! I then bought the middle of the road (price wise) stuff from https://www.euromotoelectrics.com/category-s/1639.htm and for just about 300 dollars totally rebuilt my fuel delivery system from the gas tank down to the injectors with the exception of the actual injectors which I cleaned and are fine. All new hoses , clamps,pressure regulator pump filter,submersible lines and so on. Start fresh like this and it will be a real reliable bike for a real long time

I have just ordered a full aftermarket in tank fuel pump kit for the trike. When this is installed, can I just pull out the injectors on the rail and check if they are clear by turning the engine over. I am hoping any blockages will be obvious.

My $37.00 Au Aliexpress pump has been whirling away without missing a beat for nearly 2 years. I ran it as a experiment while keeping my OEM cleaned and preserved  in the tail as a backup. I did as much research as possible and went with a manufacturer. http://www.motobrick.com/index.php/topic,10054.msg86054.html#msg86054
Some Chinese parts are probably not up to scratch, but some are, and they are improving. You'd be surprised how many car and bike parts are actually made in China.I'm currently running a Chinese rear master cylinder $13.00 Au a Chinese motorcycle GPS $100.00 Au and a Chinese twin port USB handle bar mount $5.00 Au. The only problems encountered have been the GPS power supply ( No backup) and that the map updates are dearer than buying a whole new GPS. I did have trouble with a temperature sensor but it was for the later K100 so I gave it to a mate. 
Regards Martin.

@stevenh wrote:When this is installed, can I just pull out the injectors on the rail and check if they are clear by turning the engine over.

You could do that, or you could just try starting the engine to determine how well it runs. If you test the injectors on the rail by activating the starter, be aware that could become a method of igniting the moto by accidental misdirection of fuel spray.

Well I have now replaced the components of  the in tank fuel system, pump filters lines etc. while I had the tank off I checked and cleaned all the electrical terminals I could find. Including the CDI, Fuel injection manager, relays etc etc. 

The motor seemed to be running sweet. I took the trike out for a run of about 50km. All seemed well untill the last 10km of the trip, when the missfire started to return, and I only just made it home. So I am back to where I started. I still have a feeling it's a fuel issue, so the next move is to remove the fuel rail and injectors. Is there any common issues with the fuel rail or injectors ??

I haven't checked for vacuum leaks yet could this be the problem even though the motor was running ok for a short time.

Any more suggestions would be appreciated

Cheers
Steve

Assuming that you're running a two-valve engine then yes; an expensive one I'm afraid. If the inlet manifolds (the rubber bits above the throttle bodies) and the inlet stubs (the rubber bits between the throttle bodies and the crankcase) still have the oertiker clamps on (funny looking metal rings that crimp together - I'm going for a record number of sets of brackets in one sentence, in case you hadn't realised) then you can almost guarantee that most (if not all) of them are split (five sets of brackets, dammit. I was hoping for more ). If it's a four-valve engine then the inlet stubs are still suspect.

Also, do the throttle bodies have a full set of unperished vacuum caps on them? On no.4 cylinder there's a small hose that runs from the vacuum takeoff to the fuel pressure regulator on the back of the throttle bodies - is that intact? Finally - if it's a two-valve engine - my current money is on the crankcase breather hose between the plenum chamber and the crankcase because they split for a pastime. Anyone got a pointer to the RealOEM part? I can never find it.

And make sure that the oil filler cap has a good o-ring on it. The engine relies on the crankcase being pressurised.

It would also help if you could put the year and type of your donor bike in your signature because that that will help us troubleshoot it.

It seems to me that by your description, you started with a machine that was unrideable but now you have a machine that was rideable then failed after 40 kilometers. You should determine whether that condition is repeatable or whether you truly are back where you started.

Troubleshooting should be an orderly process. It's tempting to theorize then start throwing more parts at the engine to effect repair. If the condition is intermittent, more patience is needed to find its source. There is a troubleshooting guide for 2V engines in the Portal's Tech section that has helped many owners.

Right now, does the engine start easily and rev smoothly when not moving? Does its running condition now differ from the description in your first post that described the engine as misfiring?

@Dai wrote:Assuming that you're running a two-valve engine then yes; an expensive one I'm afraid. If the inlet manifolds (the rubber bits above the throttle bodies) and the inlet stubs (the rubber bits between the throttle bodies and the crankcase) still have the oertiker clamps on (funny looking metal rings that crimp together - I'm going for a record number of sets of brackets in one sentence, in case you hadn't realised) then you can almost guarantee that most (if not all) of them are split (five sets of brackets, dammit. I was hoping for more ). If it's a four-valve engine then the inlet stubs are still suspect.

Also, do the throttle bodies have a full set of unperished vacuum caps on them? On no.4 cylinder there's a small hose that runs from the vacuum takeoff to the fuel pressure regulator on the back of the throttle bodies - is that intact? Finally - if it's a two-valve engine - my current money is on the crankcase breather hose between the plenum chamber and the crankcase because they split for a pastime. Anyone got a pointer to the RealOEM part? I can never find it.

And make sure that the oil filler cap has a good o-ring on it. The engine relies on the crankcase being pressurised.

It would also help if you could put the year and type of your donor bike in your signature because that that will help us troubleshoot it.

Thanks Dai, this is good info I will have a good look over the weekend. So if I spray inlet stubs with some easy start this should tell me what I need to know, right ?

I will update the info on the Trike. However it is a 1987 k100 LT, 2 valve

Thanks 
Steve

Easystart - yes. Now I know it's a 2-valve engine then my money is definately on the crankcase breather hose as the primary source of the problem.

Got the wee skitter:-

https://www.realoem.com/bmw/enUS/showparts?id=0516-USA-02-1987-K589-BMW-K_100_LT_87_0506,0516_&diagId=11_4676

Item 10.

https://www.motorworks.co.uk/vlive/Shop/Parts.php?T=5&NU=15&M=40&Ct=BA&SbCt=BA_15_40_BA_25

I'd treat the inlets as suspect too; mine were screwed after the bike sat unused for four years (not me!).

+1 on Dai’s response(s) (2 brackets so far). At a very much beginner level, what I have learnt (K wise (4)) is the closed nature of the air system. 

If the MAF doesn’t know about the air, it doesn’t get figured into the air/fuel mix calculation. 

My bike stood outside/uncovered for 10 years before I bought her. I’ve replaced everything ‘rubber like’: airbox to plenum hose; plenum to throttle bodies; TBs to inlets; injector rings and caps; S breather from crankcase; rubber caps. Every refresh brought noticeable improvements in: starting, tickover, throttle response, rattly background noise and backfire reduction transforming the bike from an ok old nail to a credible long distance tourer. (The TB to inlet port rubbers were pricey enough to go for a used Motorworks set, which were spot on (6)).

Dai, I’ve totally (and shamelessly ( 8 ) blagged the bracket count). Would be very smug if I had a back brake that worked.

Most (but not all) of the hiccups, in my experience to date, boil down to the rubber bits and the electrical connections.  Replace as much of the rubber as you can if you don't know its actual age or condition.  Go over all the electrical connections with abrasive, Deoxit and dialectric grease.  Sometimes they can still be giving you grief even if you have already serviced them (more than once or more than twice even -DAMHIKT).  Do not give up hope