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Hey guys as most of you no i had a starting problem after the engine rebuild. It turns out the timing was off. So timing has been adjusted to a T. Carbs cleaned, plenty of fuel. Plenty of spark. Battery fully charged even tried jumping it off a freshly charged car battery and still wont start. All connections checked and rechecked. All grounds sand shiney and tightened. Still nothing. It wont even fire with starter fluid. Its cranks and cranks but just wont catch. Anyone on here got any ideas on what could cause this. Everything is working as it should. Im at breaking point with this and im close to parting it out.
 

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Are you sure about the spark? it might be good in open air but it is it good under pressure in the chamber? Do you have a way to check ignition timing?
 

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Was it the cam timing?

Agree about the spark and pressure. What color is the spark?

Maybe a compression check? Seems that with everything there, you should get at least a nice ka-boom once in a while.

No rats nest, or air filter foam, blocking the air intake?
 

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Discussion Starter #4
Are you sure about the spark? it might be good in open air but it is it good under pressure in the chamber? Do you have a way to check ignition timing?
Was it the cam timing?

Maybe a compression check? Seems that with everything there, you should get at least a nice ka-boom once in a while.

No rats nest, or air filter foam, blocking the air intake?
i havo no way of checking ignition timing at all. There is only 19000 original miles on the bike and from what i can gather without a guage there is compression there. The timing is spot on 305* degrees on the rear as instructed by the service manual. How would i go about checking the ignition timing. And if all else fails i think a rebore is the last option on this.
 

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Discussion Starter #5
Was it the cam timing?

Agree about the spark and pressure. What color is the spark?

Maybe a compression check? Seems that with everything there, you should get at least a nice ka-boom once in a while.

No rats nest, or air filter foam, blocking the air intake?
also there is a nice strong blue spark from all plugs.
 

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i havo no way of checking ignition timing at all. There is only 19000 original miles on the bike and from what i can gather without a guage there is compression there. The timing is spot on 305* degrees on the rear as instructed by the service manual. How would i go about checking the ignition timing. And if all else fails i think a rebore is the last option on this.
Do the thumb check on the two shallow spark plugs, put your thumb in the hole and crank it. Would be a good idea to unplug the other spark plug wire, in case it decides to fire with your thumb in there. You should see enough compression to blow your thumb off the hole, if you get nothing, or it's really weak, you'll know that's a problem.

Need a timing light to check ign. timing, but I'm not seeing many ways that could be off. A sheared key on the rotor maybe. Although .... Any chance the pickup coils are mixed up? That would definitely screw up ign. timing.

edit: Another check of the ign timing - With the shallow plug connected and grounded, put your thumb in the hole, crank it. Watch the spark plug for spark to occur at about the same time as the compression on your thumb. If this happens a long time apart, good chance the pickup coils are reversed.
 

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Discussion Starter #7
i havo no way of checking ignition timing at all. There is only 19000 original miles on the bike and from what i can gather without a guage there is compression there. The timing is spot on 305* degrees on the rear as instructed by the service manual. How would i go about checking the ignition timing. And if all else fails i think a rebore is the last option on this.
Do the thumb check on the two shallow spark plugs, put your thumb in the hole and crank it. Would be a good idea to unplug the other spark plug wire, in case it decides to fire with your thumb in there. You should see enough compression to blow your thumb off the hole, if you get nothing, or it's really weak, you'll know that's a problem.

Need a timing light to check ign. timing, but I'm not seeing many ways that could be off. A sheared key on the rotor maybe. Although .... Any chance the pickup coils are mixed up? That would definitely screw up ign. timing.

edit: Another check of the ign timing - With the shallow plug connected and grounded, put your thumb in the hole, crank it. Watch the spark plug for spark to occur at about the same time as the compression on your thumb. If this happens a long time apart, good chance the pickup coils are reversed.
i will definatly try the compression and spark in a few mins as i have the starter apart to check that. It all looks good so i can rule that out. As for ignition coils beeing reversed. Highly unlikely as i havent taken them off the bike at all. I will report back once i have the starter on it. Also the bike had the ear shave done. Could this have something to do with it.
 

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i will definatly try the compression and spark in a few mins as i have the starter apart to check that. It all looks good so i can rule that out. As for ignition coils beeing reversed. Highly unlikely as i havent taken them off the bike at all. I will report back once i have the starter on it. Also the bike had the ear shave done. Could this have something to do with it.
Not the ignition coils, but the pickup coils at the rotor/stator. Could be swapped positions or the maybe the wires mixed up. You had the engine all apart for rebuild, right? If you didn't take the two pickup coils out of the stator case, that just leaves the wires, if they can be mixed up. It's happened before, I'm just not sure in what way they were mixed up.

Earshave shouldn't be the problem, it should at least fire.
 

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Discussion Starter #9
i will definatly try the compression and spark in a few mins as i have the starter apart to check that. It all looks good so i can rule that out. As for ignition coils beeing reversed. Highly unlikely as i havent taken them off the bike at all. I will report back once i have the starter on it. Also the bike had the ear shave done. Could this have something to do with it.
Not the ignition coils, but the pickup coils at the rotor/stator. Could be swapped positions or the maybe the wires mixed up. You had the engine all apart for rebuild, right? If you didn't take the two pickup coils out of the stator case, that just leaves the wires, if they can be mixed up. It's happened before, I'm just not sure in what way they were mixed up.

Earshave shouldn't be the problem, it should at least fire.
oh right i get you now. This i will definatly try as i had the wires removed during the rebuild. So currently i have a new starter rebuild kit ordered ( same thing when its apart ). And also because of pure frustration with the whole thing i ended up braking the plastic fuel elbow on the carb. Not a biggy as i will just replace them with solid brass ones. Im ordering a carb repair kit also with new jets etc. So after all said and done if it still wont start the only other thing i can think of is compression. Even tho a rebore is easy to get done i am finding to hard to get the pistons here in ireland. I cant get them in the uk either for some reason. Im hoping compression is not the issue as new oversized pistions and rings from the states is coming in at close to 300 euro (350$) for the 2. I will keep this thread updated as i go as it might help someone else in future if i ever get the demon started.
 

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I know it sounds crazy but, I have a 19hp B&S engine on my wood splitter it was running fine. I welded something on it and when I tried to start it, I got nothing. I changed everything I could think of. I remembered I didn't change the spark plugs. put new plugs in and bingo!!! You might try a set of plugs.
 

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I know it sounds crazy but, I have a 19hp B&S engine on my wood splitter it was running fine. I welded something on it and when I tried to start it, I got nothing. I changed everything I could think of. I remembered I didn't change the spark plugs. put new plugs in and bingo!!! You might try a set of plugs.
Sound advice however the plugs i have are brand new. They were the first thing i could rule out. There is only 4 things left i can try. Starter rebuild, new carb rebuild kit, switch pickup coils like spokster said and a rebore. After that i am out of options as everything else checks out..
 

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Discussion Starter #12
Ok lads upon taking spockters advice i checked the pickup coils. Right, from what i gather on other threads i have them in the wrong location and should be switched the other way. Can anyone confirm this. Not sure why the pic is sidways tho. The left side is the top
 

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Ok lads upon taking spockters advice i checked the pickup coils. Right, from what i gather on other threads i have them in the wrong location and should be switched the other way. Can anyone confirm this. Not sure why the pic is sidways tho. The left side is the top
Yes, they look reversed. A bit hard to see the colors in the pic, but I can tell the black/yellow wire is in the wrong place.

According to the repair manual: VN750_Vulcan_Service_Manual_Parts_Catalogue

Rear cylinder wire colors: black/white and black/red at the top position (rear cyl)

Front cylinder wire colors: black/yellow and black at the bottom position (front cyl)

Swap them around and it's gonna start right up! :)
 

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Discussion Starter #14
Lets hope so. I have them swapped so i will hopefully start it today. How i never thought of checking them in the first place is beyond me. Its always the small things aint it. I will keep you posted.
 

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Ok lads upon taking spockters advice i checked the pickup coils. Right, from what i gather on other threads i have them in the wrong location and should be switched the other way. Can anyone confirm this. Not sure why the pic is sidways tho. The left side is the top
Yes, they look reversed. A bit hard to see the colors in the pic, but I can tell the black/yellow wire is in the wrong place.

According to the repair manual: VN750_Vulcan_Service_Manual_Parts_Catalogue

Rear cylinder wire colors: black/white and black/red at the top position (rear cyl)

Front cylinder wire colors: black/yellow and black at the bottom position (front cyl)

Swap them around and it's gonna start right up! /forum/images/smilies/smile.gif
ok so i went to start it up today. Never started only backfires really loudly. Near damn popped my ear drum. Lol. However it did run for a second while i held the start button but as soon as i let it go it cut out again. Its really close but not close enough. I tried starter flued also with the same results.
 

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Discussion Starter #17
You getting the “thump thump BANG!!!”? All these attempts can be eating away the battery
yes. Its a brand new battery. Bit puzzled as to why its not starting. Even more puzzled the fact that it started while holding the start button but as soon as i let it go the bike died.
 

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Do you have a voltmeter to read the battery voltage? It could be weak by now if hasn't been charged at all.

Is there any chance the cam timing is still off?

How long did it run while holding the start button? Would it rev up, or just fired a bit more? How well was it running? The start button has a wire connected to the CDI box, consensus here is that it alters the ignition timing during starts. (could be the reason for backfire on low voltage starts)
 

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Discussion Starter #19
Do you have a voltmeter to read the battery voltage? It could be weak by now if hasn't been charged at all.

Is there any chance the cam timing is still off?

How long did it run while holding the start button? Would it rev up, or just fired a bit more? How well was it running? The start button has a wire connected to the CDI box, consensus here is that it alters the ignition timing during starts. (could be the reason for backfire on low voltage starts)
No i dont have a voltmeter. However the battery was not fully charged but i did connect to a car battery. As for cam timing, i set it exactly to the instructions in the downloadable manual. It only ran for a few seconds as i didnt want to keep the start button pressed to long and damage the motor. It would not rev at all. Do you think it could be to do with the cdi box?. I will fully charge the battery today and see was that the problem. So plan today is clean plugs, drain carbs (just incase), fully charge battery, recheck all connections and im also trying to locate a gauge to measure compression. Fingers crossed.
 

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Can't rule out the cdi yet. Not sure what tests there are for it, check the manual.

You have decent spark, but is it at the correct time.

Something about the start button, it means something, but on this system I'm not sure what. That symptom has been mentioned here before, but I'm not sure if anyone ever posted their fix. Never hurts to try the forum search.

Sometimes on old points ign systems, running only in the start position, meant a defective ballast resistor. But the ballast resistor on those old systems was there to keep the points from getting more than 9v, to reduce burning of the contacts. Could be something similar happening in the CDI, because there is that white/red wire between the start button and the CDI. The ignition timing could be going numb when you release the start button.
 
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