1984 VF1000 has me stumped........................

Hello
I have a new to me 1984 Vf1000F with 48k kms that ive been resurrecting. It was all dirty forgotten about and needed rescuing. It was only running on a couple of cyls, given the smell of the gas and time standing its a miracle it ran at all.

The carbs where a mess, they where stripped cleaned with lacquer thinners, and compressed air. New main, pilots jets (Honda) , throttle valves, bowl gaskets, pilot screw o rings (aftermarket) . Assembled correctly with the correct mains, springs and needle jets in correct places. New intake manifolds, clean air filter. Carbs synced with Manometer.

The problem;

The bike fires right up, and revs ok on the stand. When riding it will cruise along at highway speeds ok, but if you lean on the throttle it takes off in fits and starts. I have tried this in all low gears opening the throttle full, it will surge and falter at different points. Or if you will there is no constant point in the rpm range that this will happen...............the only time when it seems to pull almost right constantly is at hi rpms in 4th.......maybe 5th, but space is a issue to check 5th properly. If you roll on the throttle gently the same thing will happen...............it feels like its running on 3 and a bit most of the time, with it feeling like old school turbo kicking in when it runs correctly. There is a slight missfire, popping on the decel when the bike is running on the stand

All spark plugs are equal colour and ok (a tad rich) accept for the rear left #1 cyl which is moist and sooty. All four cyls will steam a wet rag at the top of the exhaust.

Valves done, clearances adjusted

New plugs , swapped around

Float height set

Compression 150psi give or take 2psi on all 4 cyls

New battery

Clean tank, lines in tank blown through with air, new fuel lines, filter and CBR pump that works, module thingamagig bypassed. Tank breathing Ok. No kinks in fuel line route, proper fuel pipe used.

91 oct fresh fuel

Coils swapped over, also wires swapped over

Carbs cleaned again, checked setup again.

Equal pulses from both exhausts

Cleaned checked earths



Please, before you say carbs, i have 27 bikes, including a CBX and KZ1300s, these carbs are a walk in the park compared to KZ1300 carbs, (i may come to regret that i know its not a ultimate qualification, but i spent the best part of a day cleaning them, so while its a possibility its carbs , im thinking its electrical, bad carbs have more consistent bad areas in the rpm range when they are a problem if you knwo what i mean .

lm at best a smart monkey when it comes to electictrickery. So im open to any and all suggestions , cos im stumped.

......................what have i missed?

Cheers AOI

 

Sounds like mild fuel starvation, check fuel lines and inline fuel filter by fuel pump, also check rubber boots for carbs, make sure no leaks & all clamps are tight.

Sorry, missed where you said new line & filter. Float levels?

Also check running voltage, could be a tad weak and not effect spark until under load. I see new battery, but corrosion on a guilty contact/connector can pass voltage but not current.

I had problems with the connectors to the coils on my 83, check wires just beyond crimp for broken strands and corrosion on contacts.

 

Thanks for the input Allyance.

................... float height set, intake mainifolds are new and fitted correctly.

Also, if it where a starvation, i dont think the plug would be damp, not sopping wet, but sooty and damp

 

......................how do i check the running voltage, electrical dumbass here?

Will double check coil wires, i cleaned all that up when i swapped the coils etc around.

 

Check the other end of the ground cable from the battery for possible corrosion. Low voltage systems are very prone to voltage drops across corroded contacts due to the resistance of the corrosion. Do you have a good meter? You measure voltage from various + (hot points) you can find to ground. Current is very difficult because meter has to heavy duty and measured in series with device. Check connections from the stator to the R/R (Rectifier/Regulator). Stator puts out AC voltage and varies with RPM. Output of R/R puts out DC voltage in the range of 13.5 to 15 volts (may be off a little). What ever your problem is, it is subtle and hard to find.

 

you know the emulsion tubes are different front/back cylinders ?

 

Sorry I can't be more legitimately helpful...

 

yes, as are the springs

 

Thanks for your help Allyance, i will get at it over the weekend and get back to you

 

Might be Spark Failure.
I would ReSolder all the Crimp Connectors in the Ignition Circuits;


The CDI boxes are old and the Circuit Board Pins develop hair-line cracks (use a magnifier).


Resolder the Connector Pins AND the FET pins.
I had the occasional misfire issues, and they went away after the soldering.
Went from a wimpy orange spark to a Fat Blue Spark.
Running with Hair Line Cracks will eventually damage the FET.

Heat the plastic CDI box with a hair dryer and use pliers on the Heat Sink to CAREFULLY extract circuit board (glue).
Reseat ALL connectors in the Spark Circuits.

Putting more fuel into a Cylinder increases the mixture Density, harder for a Spark to cross the gap.
Might not be this, but it fits.

 

To double check for slight starvation, you can pull on the manual choke while testing bike, if that clears it up, then definitely the carbs, but keep all the comments about electrical gremlins because of it's age.

 

Thanks, done that (two stroke guy at heart

 

Thanks, that is very helpful, im going to solder the joints.................................not sure that i will get into the CDIs, will check pulsar coils etc first

 

So some follow up on the VF saga. We have seasonal riding here and i needed the arseometer for testing on this so ive only just got back to it. lts turned out to be poor/crapped out pulser coils ( ones on the right hand side). l swapped them out for a good pair. The carbs also got cleaned again due to the purchase of a ultrasonic cleaner over the winter, as well as electrical connections cleaned by scraping and cleaner spray. There is now a massive improvement, rode it for 120kms today, it pulls cleanly through the gears to near the red line, well up until 3rd as i like my licence. lt does not pull away in top from say 80kmph in top as clean as i would like, but i have yet to sync the carbs properly properly with the manomter and solder the ign wires as advised here yet, but im being ultra picky, i think its in the tuning due to being able to 'ride round the issue' by slowly opening the throttle rather than cracking it wide open, Anyways. Thank you for all your help, job well done, well almost, its classic bike ownership, is it ever done

 

carb synch has no real affect at 80 mph, so it must be something else.

 

Have you checked the plug caps and hit leads. It could be one breaking down.

 

Really, now isnt that something. lts not, actually that is arguably the most idiotic mechanical ''information'' ive heard to date. Off course it matters!!! lf they are not synced they are not pulling together.


..............if you need conformation that you are wrong, having synced the carbs today, it now runs perfectly.

lf this is what passes for good advice im out

 

Thanks yes, trimming back leads was done at the beginning.

 

bad carb synch has most affect at and around idle speed and up to about 3.5K rpms, not much above that no matter what you experienced.

 

Whatever. if i thought you were a fool before you have now confirmed it. You are a classic example of why these types of forums are dying. You actually equate high post count with knowledge, then you blatantly ignore actual results in the face of your deluded ideas, Pathetic............................carb sync doesn't matter over xxx. lm going to dine out on that for a while.