Hi one and all..... just having a problem cranking the bike over and getting her to fire....

Battery is a good one and holding it's charge but as soon as i turn the ignition on and press start the starter motor turns for about 3 secs then acts as if there is to low a voltage....
Puff of smoke and that's it i know that the starter motor has burnt itself out and the starter relay has arched... ignition off no change have to grab a screwdriver to disconnect the battery....

Any ideas where to look? what is going to be the likely cause of the probable current drain? I think that the spare starter motor i have here i can repair her but know it will also need a new brush set soon....

I also know that the spark plugs are sparking so that is one thing.....

can someone confirm which cylinders are fired off which o/p of the coils... when looking at the straight on fitted to the bike.... many thanks

walking away now as i want to scream....

hi twincarb

the spark system is a "wasted spark system " that is when number 1 fires (off the first coil ) it also fires number 4

but because number 1 is on the compression stroke it will fire ...number 4 being part the way between exhaust and inlet cycles does nothing .

it is important that you have the right leads connected to the right plugs so the first coil back from the throttle bodies is 1 and 4 the second being 2 and 3 ....it doesnt matter the location either front of back of the coil packs that they are wired to...just the importance of clean ignition path ...ie no losses in the system cabling connectors etc ....

about the low voltage ....the biggest issue seems to be main earth wire to the frame ...its resistance ...and the cleanlyness of the connections to both the battery and the lug at the gearbox connection .....but we have seen that the earth connection from the starter body to the gearbox being an issue ,,,,recently we saw a mod of another cable lug connected to one of the starter longitudinal assembly bolts which then connects to the negative of the battery a really decent sized cable would be an advantage .((possibility that there is corrosion between the engine and mounts of the starter or the bolts at least )

similarly the same applies to the main positive wire to the starter solenoid /relay ...cleanliness and cable security of lugs etc is a high importance .
also the cable from the relay to the starter ...corrosion in the connectors or lug on the actuall starter ?


but sounds like there is some restriction in the start process ....high load of the crank ? rings siezed in bore ? main bearing dry ? how long since oil was passing through ? might pay to spray some oily stuff in the cylinders ?

the brushes in the starter , their reach , spring tension and acuracy of the brush to comutator sectors is all important ...(if a brush colapses .skews sideways or is not tensioned correctly ) high arcing and currents would quickly make a motsa of the armature /comutator ...as it sounds like has happened

in low voltage situation the current under start conditions becomes excessive ...example ...the starter might draw 700 watts for a few seconds at 12 volts that a big current 700/12=58 amps but at 10.5 that would be in excess of 69 amps witch would exceed the contac ratings of the starter solinoid /relay ....the contacts heat ...and often weld closed

nothing for it ,,,replace the starter relay ...repair swap the starter ...and get a new battery ? but make sure that the load to the starter isnt too excessive (crankshaft turns freely etc ) use short bursts durring start 2 seconds at a time max ...make sure the battery is fully charged whilst attempting first start ......if it discharges ...stop then charge it up again before trying again ...,,,gett a bigger battery (out of the car ?) and big jumper leads to assist the whole thing (in parallel with the bike battery )

you might be able to unweld the starter relay contacts ...but will only be a short term fix as the contacts will stuff up in time

hope that helps ...

sad to hear of the issue mate ,,,got my fingers crossed for you

Thanks for the reply, everything you said is backing up what's on my mind... As you say once the battery voltage drops the current increases, I didn't think about putting the car battery on, which would ensure that the voltage is stable and prevent the current overdraw.
I have replaced the cables to the starter, starter relay, battery (well sistered the originals) I now have 16 and 10mm cables which means they don't even get warm... The only part that does is the poor positive connector on the starter....(I know its not a true positive but good description for now)
The starter relay had fused but nothing serious compared to the one I just replaced! I know in my mind that I should replace it! The start brushes hmmm not going to mention they are brand new.... Probably dead but that's just an annoyance! I had only just cleaned the inside of the starter motor up this morning! Hence why I sounded a bit peeed lol!

The engine hasn't run since its rebuild, I did oil all well on reassembly mind, its had oil in the engine for the last couple of weeks and I have cranked it over which should have allowed some oil to circulate....

The engine does rotate when rotating it from the fingy me jig where the timing doofa lives.... (sorry having a brain name moment)

For some reason I didn't even think it was a wasted spark system! Think I was looking for where to problem could be rather than apply logic as to what will be ok.....
I am happy the spark plug leads are on the right coils... So that def rules that out.... So my plan ahead now will be (once I have a working starter)

Jump start the bike off the car I am guessing that positive to the battery negative to the engine? Car engine running to hold the voltage up and that should allow me to crank the bike in 2-3 second bursts potentially with only 5 second gap between each attempt... Net result should be that the starter will lossen anything that's sticking and allow oil to circulate till it fires on its own accord....

Any tips on anything to squirt into the cylinders just to ensure the rings are lubed

How long was the engine apart, or more specifically the injectors off/dry? I had this exact same problem on the RS. While I had all apart for several weeks, the injectors dried out and the fuel varnish sealed them up for all eternity. So I had spark, fuel pressure, and the injectors were testing for power, but they were not opening. Even if you just pulled out the plugs and sprayed a little carb cleaner in each hole, you should at least get a pop when you put them back in and try a starting. If you do, you'll know it's injector issues.

Regarding lubing the rings, you can get a 'fogging oil' for engines that you spray through the spark plug holes.

Injectors are all good, one wasn't working so I got 3 off eBay I tested them all and fuel passes through them.

That was one of my thoughts before but am happy all is good with them.

I will google the fogging oil now, I take it it will still work despite our engines being on there side?

Just read your post about boosting from the car battery. NONONO. It is positive to positive, negative to negative when you just booster cables. Also, I would not recommend having the car running, as it could overwhelm your bike charging system. You just want to do 2 second starter bursts, rather than prolonged cranking. Prolonged cranking overheats the starter and can melt the solder right out of the armature (ask me how I know).

I think I described it very poorly! Positive from car positive to bike positive negative from car battery to bike engine case.... Which would rule out the battery negative problems, mind you with my uprated negative cable it shouldn't be a problem.
I know what you mean about melting the solder on the starter I am hoping that's what's happened to me, when I get home in the morning I will get the starter out and see what damage was caused when the smoke came out!

The starter plays a critical role in grounding your circuits. If it is messed up via heat/smoke, it is going to give you all kinds of grief trying to troubleshoot. Speaking of that, have you meticulously followed the troubleshooting guide posted by Crazy Frog?

Here is an example of fogging oil available in the UK: Click Here

I need to go back through the fault diagnosis, but I did and ruled out most bits more because of the feeling that its possibly mechanical ie not seized engine but stiff if that makes sense.... I may borrow the big boy current tester from work to see what sort of current is being drawn. My meter at home only works to 10 amps but one at work is a lot beefier

ok so the engine has been apart ? or more specific has the oil pump been apart ?

it will take some time for the oil to suck up from the sump . usually overnight ...what ever, the oil backs up some and keeps some in the gears area of the pump ...but if its been dry for a while ...it will take a fair while to suck up

maybe just some light oil squrited in the cylinders from something like a vapour sprayer -squirt gun to the pistons in the down position

regarding the start process ....2-3 seconds on ....10 seconds off ....repeat twice ....then 2-3 seconds on then 20 - 30 seconds off

ouch about the starter ...just replaced the brushes !...

your battery might still be ok ....but in a low state of charge ? by using the car battery you might have a good chance to get a firing happening ...if you notice the starter drop off in revs ..check the cables again

yeah the oil pump has been off the bike and rebuilt as well, I have spent a couple of hours with the car hooked up to the bike to ensure there is sufficent voltage and current.... There are signs of life in so far as the starter is spinning and engaging the engine which in turn is turning.... it's been so close to firing a dozen or so times....

The spark plugs are wet with fuel confirming that fuel is getting through and the fuel pump can be heard....I feel like I have checked and rechecked all the connections. I have got a new set of spark plugs coming (waiting for a call to say they are there to be picked up in the morning) I am thinking about replacing the HT leads to be on the safe side.

Before I do that I think i will have a look at the readings that are being sent to the EFI jetronic unit to see how they compare to Berts guide....

The quest continues...

Just done some quick measurements on the EFI computer plug.... apparently the temp here is in excess of 70 degrees C that coupled with the readings below...

pin 7-5 93 Ohms..... OK
pin 7-8 180 Ohms ..... Suspicious
pin 8-9 126 Ohms ..... Very Suspicious

but to add to it..... pins 2 & 3 don't show any voltage.... ok 0.03V kind of level

Will have a closer look tomorrow unless someone can see off the top of there heads what I may have done wrong...

She is now fireing and chugging away for short periods of time.... She will then stall, or there is a loud metal on metal screech which doesn't sound too good... Can't work out where it is coming from my thoughts at the moment are the alternator or final drive.

hmm ...about the stalling ...vacuume leaks me thinks

you have checked that the breather pipe (plenum to crankcase ) is good and free from holes or cracks ?

could be the alternator drive twincarb ....those old monkey nuts (dampers) do suffer over time

its almost as if it's strugging to get/keep going she is starting with the choke just open, not even to the first on setting, I was wondering about the air fuel mix..... Vacuum leak.... spraying carb cleaner around possible area's would be one way of proving that....

The breather pipe is a new one so that's in a great shape...

Would the alternator cause that sort of noise? I was thinking about taking the alternator off and running the bike attached to the car which would of course prevent the battery from flattening so quickly.

hard to know what the noise is ...but its not an uncommon issue

\yes the throttle bodies do leak/crack over time ....but have you checked the rubber hats that sit over the tb take off points, usually 3 off ....number 4 goes to the fuel presure regulator ....check it also ... if any ar split, replace .

think it's a job for tomorrow morning to try and rule out the metal noise first. as don't want to cause more problmes on the poor girl... and then to sort out the running problems....

I had to replace one of the rubber tubes from the TB to the engine. the others all looked good... The TB has been through the ultrasonic cleaner but was carefull not to adjust any of the settings... I may need to adjust the idle i guess....

forgot to mention the oil filler cap is on and sealed twincarb

hehe yeah... I checked that one... as it's one of the silly things that can get missed! I even released it to make sure that it was seated just right!

Not sure what you mean by your post. Is the screech as the engine stops or is it what happens before it stops or do you think that it is what makes it stop.
If it happens as it stops it very well may be that the engine comes up to compression on one cylinder and that stops the engine turning futher and then the engine turns backward because of the compression and that engages the sprag clutch and spins the starter backwards.
It is very common on the K75s but not so common on a K100 but does happen. Most engines will stop in the same place most times and if yours likes stopping in that place then it will do it most times.

Back to square one again... Battery is fully charged but when the engine turns over, she doesn't run.

Whats good... I/P to the EFI comp
Spark is good on all 4 cylinders
fuel is being pumped out of the injectors.

I suppose I can summerise there is no ignition of the fuel... This could be to much/to little air/fuel

going to have a look in the clymer and see if there is a setup for the throttle bodies from where it can then start to allow enough air to kick off...

Is it hard to keep running or hard to start and keep running. It sounds to me like it could be a bit lean and not making it rich to enable starting.
When it does sort of run try pressing the starter button, the starter should not engage when its running but it will send a signal to ECU to make it rich. If it runs better then that will mean its lean at start and could signal a sensor fault making the ECU think the engine is warm or hot and not give the correct mixture.

The choke does nothing more than make it idle fast, it does not make a rich mixture for starting the ECU will or should do that. I think BMW called it a choke because they couldnt fit FAST IDLE on the cap.

Thanks Rick,

It is very hard to start running (not even running now) and when it did run yesterday it was really struggling.

Will try again now, the clymer says to start it with the "choke" at the first stop position unless hot. If i can get her to fire I will try pressing the starter and see if she picks up when she is given a larger amount of fuel.

Apart from the air sensor are there any others that are taken into consideration?

The coolant temp sensor which is behind the throttle bodies and behind the radiator you get to it by taking the air filter boxout.
Iys a 2 function sensor. ie 2 sensors in 1 housing. There are 2 wires to it and each sensor works from one of those wires to earth or ground. First sensor is for engine temp for the ECU the other is to switch the fan on (103 deg C) and to turn the temp light on (111 deg C)
Bert has quite a good bit about testing it in the downloads and portal.

Just checked the compression.... Bearing in mind that the engine is cold my reading are...

Cyl 1 100 psi
Cyl 2 120 psi
Cyl 3 0 psi
Cyl 4 0 psi

not tried to put any oil in the cylinders to see if it will increase them, as a reading that low says something major... top end strip down now see if my valves are Foobarred....

oops that's just put this thread into the wrong section hehe