V4 woes

Hi to all!
Was on here many years back around 2008 while located in Perth WA. Had an 85 model 1000f then…and now just got hold of a 87 model. And now I recall a few less desirable traits of what a belligerent V4 is like.
Anyway…I write firstly to enquire if there are any other VF1000f (not interceptor) owners reasonably local to chepstow? I’ll explain below…

This current VF will not run on pots 1 and 3, it has but briefly and tries now and then but fails with occasional backfiring thru pipes. Ive had carbs off, cleaned and reset, had new plugs, checked spark, multimetered the pulse generator (hot), coils and checked charge system. Ive looked for bare/dodgy looking wiring but all tells me they’re good although the rev counter has started doing strange things. The battery is new. It therefore points to the CDI unit but I’m not convinced. The other one I had was in an awful state, cosmetically and mechanucally with a blown No1 big end. I rebuilt that motor and had a similarly frustrating time tryinh to get that going. It did in the end but I was never sure what it was that gave me so much grief. I know they can be a reet royal bstard on the electrical front so hence my apprehension.

So, fellow VFers…does anyone live around the Bristol/chepstow/glos/cheltenham/worcester areas who would be willing to let me try their CDI unit? Travel is not an issue as I need to get the better of this one!!


your pulse coils should read 480 ohms each ±10% cold
i had this problem
my one broke when hot

Gday windysolar,
Thks for the reply. I didnt mention that I also have a spare pulse generator that I know is good. Made no difference when swopped. I’m having a few days off it now for a regroup.


Goning to rename my self Snowysolar
this week looking out my window in Norfolk

reading your main writing you mention the speedo doing strange things
this is definately ignition problems my baby did the same thing
all you can do then is start at the pulse coils and work backwards
then its the fuel system
hope its warm where the bike stays

Yes…I’m in Forest of Dean Gloucestershire just off River Severn and now confined to the garage due to snow! Integral garage with boiler and thermal store in it so that helps.
Just looking at your post…the rev counter is inconsistent and only goes to 1500rpm now, after which it reverses and then dies when it feels like it. The longer this goes on and with the tacho taken off 1-3 coil I’m going to have to bite it and get anothet cdi unit. Ive had another go today, left 2&4 leads off and used easy start direct into 1&3 carb venturis. That stuff starts anything but not this. Had a bit of attempted firing during attempts with an unhealthy amount of backfiring thru carbs and in exhaust. It looks like the CDI is the issue after this easy start session.

When i finally find the issue I’ll post on here. This is a really good site and glad to see this bike still has a sound following.

Hi mort.

Are you any good with a soldering iron? Quite often the problem is dry joints on the circuit board caused by vibration and can be fixed by re soldering the back of circuit board, concentrate on the joints for the cables. Your problem would definitely point to this being the problem. You can send me cdi if you dont fancy doing it, no guarantees though! Pm if you want me to try can have it back to you within a few days. May save a couple of quid instead of buying a second hand one that may develop same fault.


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Hi Gary,
Many thanks for this advice, much appreciated and “yes” I’m ok with a soldering iron so I’ll give that a go today.
As an aside…as mentioned above when in ozz I searched out a place in Belgium that could test the CDI unit and sent it for examination. It came back as no fault found and I thought no more about it. The bike started very soon after this but not straight off. Hence I say I was never quite sure what was the culprit. I had opened the cdi unit and had a look at the obvious contact areas of the wires but made no attempts to resolder.

I’ll get on it later.

Good luck, let us know how you get on. The pic from vf100fe above is spot on. If you have the equipment de solder the connection then resolder to make sure any oxidation under the solder has gone, just melting the original solder will not get rid of it.


I’ve never cleaned the connection first, just ReFlow’d the solder.
But extra cleaning can’t hurt, right graby?

While you’re at it, why not pull the connectors out of the plastic block and solder there too?

Maybe even solder the crimp connectors at the coils.
Get at ALL the possible issues.
I use an Acid Core Solder, so it cleans the copper at the same time (then brush off with solvent).

All the connectors that carry power (heavier gauge wires) have been Solder’d on my bikes.
They will corrode (specially after 30 years) and cause problems.

Note that the Spade is fine, its the Crimp that fail’d.

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great pictures, who are you using to host your pics. i’m using Dropbox and they don’t seem to work anymore on the forum or i’m doing it wrong!


Thanks chaps for the advice. I didnt get to the soldering yday as the wife got in the way but it’s on my plans. I did open the CDI unit case and can say that the PCB doesn’t look like the photo but never mind…I’ll go through the process of resoldering. Will get back to you…

Hope you drained the engine oil to replace both the pulse coils and remove the right bottom engine casing for access unscrew both coils and remove the wiring loom up to the connector block

Hi Mort,just checking which model you have,FE or FF?
I have spare units for both,PM me details and I will get one down for you to try
Regards Bif

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Hi Mort,
I read your woes about the #1 & #3 not firing. I had the same issue with my '86. Intermittent firing when cold but lost spark when warm. Your problem is in the pick up (signal generators). As there are two of these, the one that controls the signal for 1 & 3 is out of resistance and shorting out. Since these signal generators are very hard to come by and are a common problem as they age, finding a good set of these is difficult. The signal generators from the VF1100 Sabre or Magna are nearly identical and with minor mods on the wiring pigtail will adapt to the VF1000. There are plenty of VF1100s out there which makes this part easy to acquire.


I concure the last comment happend to me made up my own harness of good pulse coils

So you are all aware too, the VFR750 coils have the same impedance, and if you can make a bracket to fit will also fire successfully. I have not done this as yet, but with 9 V4s in my stable it’s only a matter of time.

I’ll keep you all updated if i have to do this.


I host my own stuff.
My ISP gives me (and everybody here) 100Mb of free Web Space on their server.
I upload the data, using WS_FTP95.
Then just point to it when I want.
A Perk for a yearly signup.

I don’t understand this Ritual of using a 3rd party, who always says “Trust Me!”.
What do you guys get in the UK?
… A free Sheep with every yearly Subscription? (maybe I shouldn’t ask)
… A BeerCan HashPipe to hang around your neck?
… Free Time & Space?

It would seem I need to look closer. And it looks like both sets of pickups I have are unserviceable. Thanks for you feedback on this. Will let you know when something positive occurs.

Hi to all,
Just a line to thank all the participants who gave their time/advice on this thread regarding my trauma with my VF.
It turned out to be a failing CDI unit causing all the trauma. I guess the peculiar reversing tacho was a sign it would appear. I also found that my spare pickups are also knackered.
Anyway, it’s on all 4 now so hopefully get to ride it in the near future.

Thanks again

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