1984 VF700 Ignition Problem Please Help

I have a 1984 Interceptor VF700..1 owner bike in great original condition with 7k miles..the bike has been sitting for 14yrs..i plan to restore the bike but need to get it running to see if its worth it..ive had the carbs cleaned with new seals and float needles, new plugs, battery, oil change...i used a test meter and checked the resistance for all the wires and everything checked out fine...the bike turns over fine...its getting fuel to the cylinders...my problem is its not firing right...i tested a plug to see if it is firing and what it does is while cranking no spark..let off the switch you get one spark...so i hook up the tank...crank it to start it and it just turns over...let off the switch and it hits one lick..it coughs, backfires from the spark when you let off the start switch....has anyone had this problem? is it the coils, cdi box, pulse generators??? please any help would be very much appreciated...

 

I ordered a needle volt meter so im gonna check the voltage at the coils like you suggested...im with you in I cant imagine a dual system acting the same so its got to be something that controls both...i will update with what I find...thank you TWStuff!!

 

voltage regulators can be funky once in a while check it again
did you check for spark on each side right 1 left 1 could be cdi unit/s
there is no test for these either there good or they are not.

 

Check the resistance on the coils- should spec out with the manual. Primary should be aroung 5 Ohms, seconadry should be around 15K ohms.

 

Ok i had time to work on the bike today and here is what all ive done and what its doing....
ive used a digital meter and an analog meter and have checked everything...when i say everything i mean everything...resistance checked out on all switches, coils, pulse generators, nuetral safety switch, cdi boxes, run/stop switch, etc....i checked all the fuses and even rewired a 30a ATC fuse link in place of the stock fuse...
now heres what the bike is doing....
we took a plug, stuck it in the plug wire and ground it to the body..crank the motor..no spark until you let off the start switch then you get 1 spark..we checked all 4 and they all did the same thing...
we tested to see if we were getting 12v to the coils and we were not...the coils were not grounded...so we ran a jumper from the ground on the battery and we had 12v to the coils...we tested both leads on the coils...12v when cranking and when you hit the kill switch no voltage so it was working like its suppose to...
so now we are getting 12v to the coils with the run switch on while cranking....
so we did the plug test again....its still doing the same thing...engine cranks with no spark and when you let off the start switch you get one spark..
I tested the resistance on the coils and they tested right main and sub circuit...
i unplugged the cdi boxes and tested all the tabs and they tested fine for resistance...
we have 12v coming from the battery..im only using the bike battery but it is new and fully charged...
run/stop switch works cause the circuit resistance opens and closes as you flip the switch...
I Dont Know....please...ask any questions, suggest any thing to try....its driving me nuts

 

Okay.

First question is your rpm meter jumping up and down (crazy) when you crank and is the fuel pump turning also.CDI box 1&3 controls rpm meter and CDI box 2&4 controls the fuel pump.Have you ever disconnected the coils if you put the wire in the wrong place you will get this trouble.Here is a website to help you.

http://users.rcn.com/kochc/moto/spark/ig_repair.html

Best regards

Gunnar

 

Maybe try hooking up an additional battery ( car battery) in parallel with bike battery .......maybe not enuf power for both starter and CDI.

 

Squirrelman, Gunner thanks for the reply....im going to work on the bike today and im gonna hook up another battery so i will let you know on that...

Gunner...the tach is NOT acting crazy...when I first started working on it I was getting nothing from the fuel relay..we tried to hard wire the fuel pump and it was locked...i ordered a used fuel relay and pump off ebay...we hard wired the ebay pump and it worked but didnt sound too healthy..i did have the carbs off to be cleaned so the coils were disconnected..i'll double check and make sure they are wired correctly..when we put the carbs back on the fuel pump worked for just a few seconds then it crapped out...we hard wired it and it was dead...so now i have it hooked up for gravity feed....i will double check everything tomorrow, try the things suggested in the link and I will let you know what i find out...

thanks for the help....we gonna figure this thing out...i cant wait to start my restoration thread..

 

The cdi box w/red plug in controls fuel pump and spark on left side of motor
you can see if those are good by putting small wire in connector and touch it
to a battery and you will hear it work if you short them out and hook it up you will
blow a fuse don't forget to check your wires off the fuse box and corrosion on connector
plugs .

 

ok had more time to work on the bike....

first off can anyone tell me if I eliminate the fuel pump what do i do with the wires? do i leave the fuel relay hooked up and pump plugged in? do i remove them and jump a wire on any of the connectors and if so which wires do i jump?

ok first off i hooked a 12v jump starter battery to the bike to give it more juice and its still doing the same thing..crank it, let off the starter switch you get one spark...

ok i took my time and checked resistance on everything..all fuses, coils, plugs wires, cdi boxes, pulse generators, R/R, switches, wires running to everywhere i could find lol...everything checked out...

i ran a test on the coils..i unplugged the wire leading from the cdi box to the coil..put the POS meter lead on the wire and NEG meter lead on the ground...nothing...turned key on...nothing...flipped switch to run...nothing...hit start switch i get 12v let off nothing hit start 12v...

i ran a test on Blk/w wire on the other post of coil it gets constant 12v with run switch on....

i put the POS meter lead on the battery POS and the NEG meter lead on the cdi box Bu wire going to the coil..hit the start button...nothing til i let off the start switch then the needle bounced a tiny bit....

im thinking maybe its the pulse generators..the bike has sat for almost 15yrs...im gonna pull the side cover and check them for corrosion...even though they checkout fine for resistance im thinking maybe the pickups are bad...

please tell me what you think?? anyone heard of any of these problems or experienced bad pulse generators??

thanks for all the help guys.....

 

Calling Dizzy .............

 

The connectors on these old bikes corrode, build up resistance and then fry from the heat. Look at all your high current connectors, particularly the ones between stator and regulator, and between regulator and battery, and anything between battery and ignition circuit. Best to replace these with solder joints if you can.

I believe the reason you are getting one spark when you let off the cranking is that the starter motor sucks a lot of current. When you let off, that stops. If there is any resistance in the path between battery and ignition the voltage may be getting too low when cranking is going on. In fact if you have a tired battery it may be good enough to crank but the voltage may drop too low to run the ignition (that is, there is resistance within the battery itself). Make sure you have a fresh battery. Monitor the voltage at the ignition with the motor cranking. If it drops too much, trace it back to the point where it drops. My money is on the tired battery.

 

It is very possible that a wire could've been chewed by a pesky rodent. But DO double checked all of the wires connectors. They can be a real b%^*# to clean but they can throw readings off, cause intermittent disconnects, etc. They are usually easy to spot because the connectors can be a lil brown and toasted. I had similar issues on an old GS750 and had to solder all of the connections just to get a safe and secure ride out of it. It was cutting out irregularly and the headlight would shut off mid-ride on dark nights. Not something I want to do again, ever. Finishing the ride home on your turn signal is nerve racking.

Also, when you said that you would crank the engine and get no spark while cranking and get one spark when you stop it does point a finger directly at the coils not getting the 'signal' from the pulse generators. Coils, as I understand, work by receiving voltage and when that voltage drops their fields collapse sending the voltage stored to the plugs. Its seems to me that perhaps when you stop cranking the voltage drops and it gives that one spark. I am just saying that its a possibility. Electical issues are usually some of the hardest to track down.