Pulse generators?

I'm at my wits end with my 83!

Rode it last Saturday and Sunday without issue. Monday morning I went to fire her up and it turned over beautiful, sounded like it was about to catch and then just continued cranking over. Repeated this and got a fairly loud backfire, about an 8 inch flame followed by a sound something like Darth Vader sparking up a light sabre, I assume that was the flame being sucked back in.

I then noticed my tach was not acting like it usually does. Usually jumps up to about 3 or 4 grand while turning over, it was doing nothing. I suspected the CDI box, I encountered this once before and thanks to this Board resolved it. I swapped the boxes around to see if the tach would at least jump and nothing. Turned over and would eventually backfire.

Swapped CDI's back and the tach started jumping like usual but it still won't fire. Would pulse generators be the root of this?

 

I just had a situation where my wiring harness ground was disconnected (cross brace under the seat where the breather bottle thingy mounts) and my tach jumped all over and it wouldn't start. I also had a back fire from hell (hurt my ears actually). Once I got that hooked up in fired right up.

 

Thanks Hank. I checked that ground and it seemed solid. I even took it off and cleaned it up a bit but it still didn't fire up.

I cleaned the carbs a few weeks back, I'm going to pull the plugs and see what they say and then see what the carbs look like. Cold and damp out there lately...

 

Okay...Pulled the carbs and they seem fine. Jets are clear, bowls were full of gas. Pulled plugs, checked for spark, nice solid spark. Checked and cleaned grounds again. Turns over fine and eventually will backfire but just won't start. What am I missing?

 

Maybe measure resistance between the ground connectors at various points in the harness just to see if there is a break. Seem unlikely though.

I had spark with my ground issues too, but it wouldn't run.

 

I need to follow this thread, this is exactly what my bike is doing. 84 vf700 interceptor. Ran it, came home to put on warmer gear, then nothing. tried the next day, tach did nothing, then it bounced a bunch and BOOM! huge backfire, scared the c**p outta me.

 

Ground..Ground..Ground..it all sounds like a ground problem. Check for chaffed wires and see if a Hot wire is touching a ground. Also theres a little wire in your switch housing coming from your start button which is known to cause issues. Check your fuses..even if they look good they may fall apart in your hand..

 

Okay, thanks again guys. I'll start pulling the harness apart and look for bare spots.

 

Make sure to check the plug wires as well. Mine was a PITA to start and I chased that around for about 4 hours one night before I found out that that was the problem.

To check the pulse generators, you can take a multimeter that does RPM up to the leads of each and crank the bike. They should generate an RPM signal if they are functioning.

 

I have never owned, used or played with a multimeter. There's a multimeter that measures rpm or am I measuring the leads that go to the tach?

 

All you have to do for the pulse generators is just test them to see if the circuit is complete..make sure theres not a broke wire..pulse generators are just magnets and rare that they go bad..ive seen them have a bunch of metal shavings stuck to them and not wanna work right but its rare thats the problem...just unplug it from the wiring harness and test it to see if the if the circuit is complete..should be 4 pins i think..2 for each one..

The plug wires do have resistors in them that can get corroded but hard to imagine all 4 would go bad at the same time...the one thing i learned is you have to consider is whats wrong effecting the whole bike or just 1 or 2 cylinders...that will definately narrow things down...

A multimeter is your best friend when it comes to working on a bike..it tells you this..put a lead on one end of a wire and one lead on the other end and see if current will flow thru it..if not the wire or what its connected to is bad..think of your electrical system as a sprinkler system in your yard..the battery is the water spicket and it has to flow from there..if you have a break in a pipe water will be spraying out from it..well the multimeter will find that leak...test and make sure you're getting 12v to everything...test your couplers to make sure the circuit is complete across them...test your ground to make sure its not hot...

again its a chain so trace everything down..start at the battery positive are you getting 12v to the relay? come out of the relay are you getting 12v to the CDIs? come out of the CDIs are you getting 12v to the Coils? and so on....turn the key on with the kill switch on and crank the bike..test at the coils it should be Zero volts...flip the kill switch off and crank the bike you should have 12v to the coils....you just eliminated the kill switch being the problem

heres what happened to me and it was a dumb mistake...my bike would crank and crank but no spark..when i let off the start switch i would get a spark and the bike would cough and spit like it wanted to hit...i tested everything and was getting 12v to eveything like i should...but when i hit the start switch the volts would drop to zero..well what had happened was my neighbor who was helping me had hooked the main ground connection that mounts under the seat to the starter relay..with the rubber flap over it it went un-noticed...well that was making my ground hot when you hit the start switch...i put it back to where it was suppose to be and the bike fired right up...took me forever to figure that out and it was so simple...

just play detective and start eliminating suspects...work your way from the battery to the ignition switch...follow the chain and find the broken link...

Oh yeah..go on youtube and watch a video on using a multimeter and you'll be a pro in minutes...

 

Once you get your meter, the first thing I would do:
At the various connectors around the harness, measure from the green wire to the frame. You should not have any resistance, or voltage with the key on or off.
That was my biggest clue when I had my problem. With the key on I had 12V between the green wire and the frame, which told me they weren't connected, and they should be.

 

Thought it was spigot :smile: Spic-it kinda made me laugh though. Anyway, bravo with that fine Anal-oh-gee, Multimeters are kewel but dont cheap out and buy a harbor freight one. Fluke is kinda like the Figidare or Kleenex of meters, its so good the brand name took over the generic name. So excuse me, me needs to go to my refrigerator and get a tissue. I like using a test light too, just more tools, oh boy. Can you ever have too many? NOPE

 

Thanks Dutch and Hank.

I picked up a multimeter and I'll start going over things when I get home tonight, starting at that ground under the seat. I have been having issues with my front left turn signal. At the beginning of the season it just stopped working as well as the left rear. I checked out the front left and found that the piece of fiber board that the wire lugs are attached to had cracked and was allowing the lugs to touch and ground out that bulb. I managed to find a similar replacement socket at the local automotive and put it in there, is it possible that light would be the culprit?

 

While my buddy was over last weekend we pulled the rear two spark plugs and laid them on the frame and the bike really wanted to kick over and just on the front two cylinders.

 

Have you checked your kill switch? The start/kill switch unit does go bad on those years. Check the switch itself and the harness connector behind the head light.

 

U sure the proper wires are hooked to the appropriate sparkplugs??

It's not too hard to mix wires up on some bikes, either the low voltage coil wires or the high-tension leads.

 

Hey Squirell. I'm completely positive the leads on the sparkplugs are correct. I was out on the bike a couple of days prior to it not starting and it was running great. I didn't do any maintenance to it in that time period either.

I parked it, sat for 2 days. Pulled it out into the driveway and it wouldn't start. Turns over, loads up on fuel, grumbles a couple of times like it's going to catch will suddenly and hellaciously go boom and then back to turning over.

 

Maybe try a well-charged jumper battery hooked in parallel with the battery you have cuz it's possible to have a battery that's sufficiently energized to crank the starter but not enough power left over for the needs of the ignition system at the same time...........

 

Feels like I'm shooting you down Squirrel...I tried jumping it with my battery charger and ultimately my truck battery. It would definately spin faster, which led to the backfire a little sooner.

I'm almost done work for the day, I'll try the multimeter and see.