Hey guys, I've been plugging away at my VF, and I've got it to fire every once in a while but it won't run. I've tested coils, pickups, cleaned plugs. I still have a thin, weak spark that really can't fire on the compression stroke. This is giving me a fair bit of after fire. I'm currently thinking it is the Ignition modules in front of the tail light that are causing the problem. Does anyone know any basic tests I can do to them? Or does anyone have a pair they are willing to sell? -A2
Maybe a low battery ? Weak battery won't supply enuff juice to both starter and ignition system while cranking so weak spark.
Fouled plugs have carbon on them, if you remove the carbon with methods that do not damage the plug, the plug will generally work fine unless there is another problem with it. Either way, I have plenty of spark plugs. I'm sure I have the right ones somewhere I can try. I was running the bike on a car battery hooked up to the charger, I had 12v at the coil. I will say that I was checking spark between the coil and the wire due to how easy it is. Is the spark normally long and weak there? -A2
Alright, I tried new plugs, Voltage is good, I tried a couple of different spark boxes. Still, nothing. I'm starting to wonder about the pulse generators. Spec is ~480, mine measured about 460. I'm wondering if thats too low and not sending enough signal to the boxes. Anyone more familiar with these want to weigh in?
That resistance reading is fine, not too low. If it was reading 50 that would be too low, or if 5000 too high. Are you getting weak spark or no spark at all? Start at the plugs and work back till you find it. Check the plugs wires. Check the coil resistance, check that the 12 volt control lines to the coils are pulsing between 12 and ground when cranking, etc.
weak spark. man if I have to bust out the o-scope I'm gonna be a little peeved. Ah, one other thing I noticed from lots of googling this site, my Tach does not move when I'm cranking and others say it should. I think this points to the ignitor boxes but I've swapped them and no real change.
It sounds like it is almost there but just not enough current flowing to make a good spark. Check for high resistance in the power lines, e.g. corrosion on lugs/terminals on frame or battery, igniter box ground, etc. If you have a clamp-on ammeter check current on control lines into coils. Probably will need the scope. Then you can check the pulser output also--maybe the gap is too large. If the bike has ever been wrecked there could be wiring harness damage, have to check it over and look for patches and pinches.
Ok, that sounds pretty good to me. Any idea what waveform/voltage I am looking for from the pulse generators? I'm a noob to this particular bike but I have been thinking that if I'm getting low voltage from the pulse gen maybe it can't properly switch a transistor or energize a coil or something along those lines. I haven't put it down myself but there is evidence of it falling over a few times and going down while moving slowly at least once. That kinda thing just happens as bike gets old, too much time too many chances. I also think the last rider was a wheelie popping squid from the burned up clutch plates and missing turn signals :smug:
alright, no O-scope for a bit. Cannot find probes. Ebay ones on order. gonna go over the main wiring looking for excssive resitance, voltage drops, corrosion, etc on Sunday. I will update you guys on Monday or Sunday night.
Ok, got the probes, and my dad to help me work the O-scope. He knows about the scope, I know about engines, it works out. Was barely getting a waver at the coils (low V), was barely getting a tremble from the pulse generators. Turn signals made a decent square wave, so the scope is fine, the pulse generators are just not putting out signal. Since the pulse gens have good resistance, and I bought the bike with the side cover off I'm betting something was fiddled with. I'm going to take the cover off and check gap before ordering anything.
Ok, I adjusted the gap on the pulse generators from .033 to .012. This made a decent change in that the Tach actually moves now, it will jump up to 2k sometimes. It usually just sits just off the post and twitches while cranking now. I still cannot get this thing to start up. I'll check it with the O-scope again but I'm running out of ideas. Anyone know of a VF guru in the south east MI area?
Get ready for a necro post, I finally got the bike running! The PO must have rebuilt the starter clutch/signal wheel. I found it to be 120 degrees retarded. Made for very poor timing! -Arrmon
Excellent, always so hard when somebody has had a fiddle and you don't know what they have done. Closing up the pulse gap to .010 on my CB Supersport, improved things dramatically, got rid of the clutch rattle and improved starting and got rid of the misfire at 100kph and smoothed it out at idle, almost feels like a new bike
cool that you figured that one out! You know, in this day and age of phones having cameras on them, there is really no excuse to bollocks things up like that. I deal with lay-out dye and wittness marks for your original alignement on rotor/shafts/gears. Can use this dye for doing cylinder heads too and a bunch of other things. Cheers :vtr2:
i recently replaced the entire clutch assembly due to severe grooves in the clutch basket.. i had to remove the stater clutch gears in order to remove the clutch gear.. manual doesnt mention anything about specific timing when reassembling.. yet i dont have any spark at any cyclinder. bike just ran and idled nicely just the other day.. the little pick up points are within the gap spec.. but im lost because the gear only goes back on the way it was how could i messed with the timing??? any advice?
