I wonder if anybody has experienced this. Start bike up. Runs perfect, all dash lights correct, after about 20 seconds stops. Does not cough, splutter or give any indication, just stops, dash lights come on. Checked plugs, no spark. Starter turns over fine.

Cleaned and lubed all connectors and earths. Removed instruments and checked all diodes I could find o.k.

Went to bed got up next morning, big fat spark, started, ran perfect for 20 secs then stopped.

Threw spanners about, got grumpy, went to pub.

Next day same again, started,ran fine then stopped.



What do I do next:?:



Any suggestions:?:



(other than the pub, or anything to do with matches)



Martin

hmmmm.....hey martin ....i think we need more information .

is the fuel pump running still when this happens ?


do you have enough fuel for it to run when when sitting on the bike ?


cause it kinda sounds like that its out of or not getting fuel to me.



try starting the bike with at least the headlights on also , this could be the clue for the f1 relay working correctly ..if they go out durring the start sequence and dont come back on , you might concider the starter motor brushes are "dusty"



3rd thought ...check the connectors to the fuel rail injectors and the under seat brain (efi computer )

hope this helps

Hi Charlie,

thanks for the help.

fuel pump is running and can see return flow in tank, which is nearly full. Tried with the headlamp on, goes out when you press the starter, bike starts, let go of starter and the lights come back on. I thought fuel, BUT, engine stopping immediately, no missing just dead stop.Plugs are damp after stop. Injectors and efi connections checked.In my 'umble (probably misguided) opinion, something appears to be breaking down under load. Hoping someone has had a similar experience to save me swapping all sorts of expensive bits.

Martin

only thing i can think of this morning is the hall sensor to loom connections martin .....maybe the 4 pin connector under the tank is corroded somewhat .....might be worth a look and a deoxIT treatment ,

whilst your there check the ignition box in there for solid connections also

This sounds very electrical to me. Replace all your fuses with new ones. My immediate thoughts are that there is an electrical connection somewhere that is heating and going open circuit and cutting the connection and fuses are an easy place to start.

If you turn the ign on and not start do the lights go out after the 20 seconds and how long before they come back on, do you need to turn the key off and back on to get it to work or does it just come back on without any intervention. I am thinking temp relay because they have a failsafe where if the engine gets far too hot the whole system closes down till the temp goes down to normal range.

Check out those and let us know how you go Martin.

Hi Martin, may be of no use, but i had a similar problem, spent the whole day doing all the checks, only to discover right at the very end of the day that the big multi plug on the efi computer had come loose........one click and all was fine again.............hate that. cheers Andyb

Thanks everybody, checked efi plug, tank off and everything seems fine under there. Going to try the test on the lights today. Which is the temp. relay?Bearing in mind this happens with a cold engine the relay could be faulty. Is this relay inter-changeable with the others on the block?This a later model 88 with abs and has a clutch of 4 small relays together, the drawing showing the relay tray shows only 2 in the same space.



Martin. (now clutching at straws)

martin the temp relay get its sence from the dual temp sensor at the stubb of the water riser tube at the back of the radiator .



its a dual unit with only 2 connections visable ...the third connection is the earth/body of the riser tube itself ...that could be the issue i guess ..

but im still thinking something is interupting the spark , as you have noticed ...and i missed in the first post .

is there a chance that something has crushed or is now shorting to the frame along the ignition (electrical) path , once you start the motor the vibrations are causing the fault to occur .....please follow the hall sensor cable ...and then the feed to the ignition coils down the other side ..take each connector apart and clean clean clean .



the primary of the ignition coils should measure 2.2 ohms



oh just another thought... the frame earth under tank at the frame connection might need cleaning also ..whilst under the tank check connections for loosness etc in the relay box cabling (fuse cabling and all the rest )....its an odd behaviour you have there .



....just thinking aloud

Thanks Charlie,
latest update, cleaned and replaced everthing, checked ht leads and coils.
Started bike up, revs freely to red-line, so discounted ht. Ran for 2mins then stopped again. Checked water level and it was low so maybe got an airlock in the engine block causing temp sensor to operate when engine temp rises? Have refilled system and will try again later..

Martin

Since there has been a change in the symptoms, I think you've actually touched the problem. "Cleaned and replaced everything" is quite a statement. What is "everything"?

During the rebuild of the Honda I had trouble starting and running to a die situation. I checked the complete ignition replacing the coils and condensors, I had already fitted new recommended plugs so getting the same conditions I went for the plug caps. removing these I got a fat blue spark twix the solid lead and the plug top...problem solved I thought but No...so I went for the kill switch.Still I got the same effects. A pint and a curse and a long look at it....it can only now be the plugs. \changed these for champions and bingo..sweet as a nut. Change your plugs mate.

NGK plugs from the internet e-bay are probably fake ones from China.



By the way, suppressor caps are not needed with digital TV...they do not interfere with Digital TV only analogue.

Worth a try Martin.

Had trouble with internet plugs myself, these are 'proper' ngk's and when the bike starts it revs to the red line without fault. All connectors have been cleaned and lubed. Coils checked, jetronic unit exchanged,relays swapped around, something is switching the ignition off, but I don't know what.



Martin

Check the ignition switch wires on the handlebars. Mine recently cut out and i posted a small piece on it. A slight pull on the wires stopped the engine dead, and because of where it is its full of dirt. Just a thought. http://k100rt.aforumfree.com/t2391-ignition-switch#18780

Update,
Removed and cleaned temp sensor and changed temp control relay,bike ran for 15 mins until I turned it off:D . Fan or temp warning light did not come on so not sure if I'm 100% there yet. Although it was only idling in a cool garage.

Good to hear martin!

Martin, which temp sensor are yo utalking about? the one on the pump or the one responsible for ingnition mapping behind the radiator?

great news martin ...looks like your onto it

congrats buddie

Hi pajonk,

the one behind the radiator..

Martin

Update. Ordered a temp relay which took 2 weeks to arrive. Managed to get the bike put back together last week and only had time for a short run , but all seemed fine.



Been for a longer ride today, about 130mls with a few stops and starts, faultless:cheers:



Thanks for all the help, info and encouragement.



Martin