Loosing rear cylinders

Hi boys and girls.
Took my vf1000fe to get mot a couple of days ago.
After about 3 miles the rear cylinders went off, no spark, then after a slow ride back with a full mot the the cylinders sprang back to life. This happened again the next day ( same thing exactly)
I limped back home checked for loose wires ( not found) changed rear plugs and ht leads and fitted new caps, same thing again on ride out.
So do I have a bad igniter box or bad pickups or something else.
Everything is pricey for no guaranteed second hand parts so would appreciate some wisdom from your experience please. I will get a new tester to see what the readings are for the generators. also , when they go off I loose the tachometer.

well what can I say.
just took the seat off and removed tail unit and what did I find?
One of the cdi units ( throttle side) had its plug flopping in the socket with the lock tab not engaged , I touched it when started and it immediately jumped on 2 cylinders and immediately 4 when touched again do its now plugged in tight and firing and reving like a new bike. I will be going for a test run after lunch and will report back
fingers crossed this is the problem but it looks pretty good from here.

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Fast forward to the ride and i can now report that……. it didn’t work!
Back to the garage and pull the tank seat and side panels ready for further investigation.
I will look at the fuel supply ( not likely as it just drops the rear cylinders)
get the pickups checked ( the verdict could be the clincher ) then if not them I might be looking at cdi replacements!
Please chime in if you can send me to a possible check point before i start buying second hand components please.
Thanks chaps.

Hi intruder,
I would check the wireing where it leaves the cdi units, they have a tendancy to break there due to the sharp bend in the wires.

From my own experience when pick ups fail intermittently, the bike needs to stop and cool down before they come back in again…

You could swap the cdis over, go for a ride and see if the same fault occurs, if it does its not the cdis… if you loose fuel pump that would point to a faulty cdi.

Hi thanks for the input.
I swapped the cdi units and took it out, after a 5 mile run it went to 2 pots.
I then headed for home but on the way it kicked back to 4! so I carried on with the ride. 3 miles later i stopped for a chat with a mate for 20 mins. Jumped back on and all was good for another 5 miles , it then went off completely and wouldn’t restart!
I was nearly home so i pushed the ship home.
1 hour later and a full lunch down i went to the garage and pushed the button, it started right up on 4 ???
so this surely states that when hot it cuts out and restarts when cooled. coils or pulse gen pickups ?? Or is it a cdi as this time it shut right off meaning that the bad one dropped 2 pots before but struggled home and this time stopped 4 pots meaning did it shut off the fuel supply pump as well (this time the cdi boxes were swapped around)
When i was trying to start it the pump was giving a kick so looked like it was pumping on the start button.
What do you guys think?

just been at bike with new multimeter.
bike was sat for 2 hours so cooling down, i unplugged the coil pickups and between yellow and white then blue and white I got a reading of 557/558 on both.
Started bike till hot and it went down to 2 cylinders! then took same test.
The blue and white had a reading of 558/570
the yellow and white read 1.
I let the bike cool for 15 mins and the yellow and white read 578
I am guessing this means one pickup is failing when hot and a new set are needed.
thank you for your wise replies please.

Just tested a stone cold motor and the values are both 478
then hot and cylinders drop out it’s back to 1 for the rear cylinders going off.
so time for pickups.

Hi intruder, looks like youve nailed it down to the pulse generators… as you say, they are no longer available “nos”,but as bif says, all the vf1000 are the same, so it looks like ebay will be your best option, :+1:

Thanks vf- pete.
Very pricey goods for second hand and no idea of how long they will last.
looking forward to a longer ride than 5 miles before limping home.
I have noticed that the oil is smelling a little fuely i guess because of the rear cylinders not firing so will give it an oil change.
thanks buddy.

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