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1986 VN750
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3,255 Posts
AGM stands for Absorbed Glass Mat. It's a newer battery technology that is sometimes referred to as a sealed battery.

I have a wiki page with a bunch of compatible batteries.

http://wiki.vulcan750.net/index.php?title=Batteries

Just a note, make sure your bike is charging properly. You want to use a multimeter to check dc voltage at the battery terminals. You should see upwards to 14-14.5v @ 4000RPM. You will see little charging at idle with the stock system (12-13v).
 

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2014 KLR 650!
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3,361 Posts
Well I think if I can understand the part about the 8" wire then this should be fairly easy and I'm sure, easier than the other mods I was going to do for hot starting issues. So in order of ease I guess, I'm going to:

Ignition coil mod
Pickup coil mod
Rebuild Starter

Hopefully this will fix my starting problem. FYI the ACCT to MCCT was a delightful mod. The engine is more responsive for sure. I was also able to then do a carb synch and have the idle remain at a reasonable level.

Oh, and ordered the $55 rectifier from Amazon to place outside the frame. Can't be any worse than the corroded dinosaur under me now.
 

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Premium Member
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4,054 Posts
Discussion Starter #44
okay so I read about AGM, but those are designed for heavy-load newer vehicles... people adding tons of extras like HID and fog lights etc... my bike is stock when it comes to the load on the battery - is there another reason to use that style battery?
Most of us feel like the OEM battery on this bike is a little underpowered for its size. Add to that the liquid that is going to eventually bubble up and splatter all over your bikes guts, eating parts that you'd probably rather not have eaten. The AGM's usually have more CCA's and seem to start your bike better cold or hot. Couple that with this coil relay mod and you will probably see a huge improvement. I saw a drastic improvement on mine and it already had an AGM battery.

I appreciate all the kind words from everyone on this mod but I didn't come up with it but borrowed it from KZrider.com. Just FYI :beerchug:
 

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2014 KLR 650!
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3,361 Posts
Most of us feel like the OEM battery on this bike is a little underpowered for its size. Add to that the liquid that is going to eventually bubble up and splatter all over your bikes guts, eating parts that you'd probably rather not have eaten. The AGM's usually have more CCA's and seem to start your bike better cold or hot. Couple that with this coil relay mod and you will probably see a huge improvement. I saw a drastic improvement on mine and it already had an AGM battery.

I appreciate all the kind words from everyone on this mod but I didn't come up with it but borrowed it from KZrider.com. Just FYI :beerchug:
Mod was easy once I re-read and figured out that the switch power was coming from the red wire to the rear coil. This didn't fix my hot starting issue. Rebuilding the starter fixed it. My bike is running like a mad man. If I can figure out what is rattling when I hit the vibration range of 3-4k, it will be so quiet and powerful with all the mods I've done that it's like a whole new bike.
 

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R/R = Relocated Redneck
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628 Posts
Mod was easy once I re-read and figured out that the switch power was coming from the red wire to the rear coil. This didn't fix my hot starting issue. Rebuilding the starter fixed it. My bike is running like a mad man. If I can figure out what is rattling when I hit the vibration range of 3-4k, it will be so quiet and powerful with all the mods I've done that it's like a whole new bike.
It could be any number of things. Items to check: heat shields on exhaust, cable routing, wiring routing. (and convert your other ACCT...)
 

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this helped me do this project

I didn't have any problems that I could tell with coils but did have a small coil voltage drop so did this just to be safe. Used the rear coil wire to pull in the relay which I may not have thought of on my own. That way kill switch still works normally. Used battery tender cable with fuse for power.
 

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ok did this mod in conjunction with the ear shave. the bike will not start. new gel battery. new ngk iridium plugs. 89 octane ethanol free gas. ran it first with the rear coil power for the trigger ,no result inefficient or not in time spark. i am getting spark just no start or run. an occasional backfire every now and then. not even with starting fluid. switched the trigger wire to the yellow red wire from the kill switch ( spliced in on the line from the fuse box to the starter relay area) same result as above, getting spark but no start, not even with starting fluid. in the diagram above it implies both cylinders fire at the same time is that correct? with plugs removed it appears that the front and rear cylinders ARE firing at the same time. ANY ideas???
 

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This seems pretty straight forward, but I have one question. Instead of the 3 way splice between the relay and the coils, couldn't you go from relay to back coil to front, with there being hot in and out together in the spade to the rear coil? Or bring both front and rear to the relay and make the junction in that spade instead? It seems the three way joint is an unnecessary point of potential failure.
 

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Note- if you are having firing issues or hard starting issues after a while after doing the mod, check your connection points. I found corrosion on my positive terminal that stopped my bike from cranking. It would turn over but wouldn't crank.
 

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I have a question here. If the wire for the original rear coil is being used to trigger the relay, wouldn?t that mean that all of the plugs are only getting spark when the ignitor box is sending signal for the rear coil to fire?
 

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I have a question here. If the wire for the original rear coil is being used to trigger the relay, wouldn?t that mean that all of the plugs are only getting spark when the ignitor box is sending signal for the rear coil to fire?
This mod does not cause the new relay to turn on/off each time a coil fires, but rather provides a more direct path from the battery to the coils. You're cutting the wire from the killswitch to the coils and using that old voltage (weak because it passes through ignition and kill switch) and using it to switch strong voltage to the coils from the battery. The coils have two inputs. One solid voltage (now from the relay) on red wire, and one pulsed input (from the ignitor box, controlling the timing of the spark, untouched by this mod) on dark green and black wires, one for each coil.
 

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This mod does not cause the new relay to turn on/off each time a coil fires, but rather provides a more direct path from the battery to the coils. You're cutting the wire from the killswitch to the coils and using that old voltage (weak because it passes through ignition and kill switch) and using it to switch strong voltage to the coils from the battery. The coils have two inputs. One solid voltage (now from the relay) on red wire, and one pulsed input (from the ignitor box, controlling the timing of the spark, untouched by this mod) on dark green and black wires, one for each coil.
Awesome! Thank you very much. I could not shake that thought. One last question about this then: which leads on each coil get which wire?
 

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Ok, figured out that it doesn't matter which wire you put on which post of the coil.

I did mine a little differently by using a five pin relay and connecting each coil to its own pin of the relay (both pins 87 on the relay) and seems to work great. Spark is incredibly improved on the front cylinder, unfortunately didn't resolve my rear cylinder no spark issue like I had hoped it would. Problem is that it isn't geting the signal voltage to the other connector on the coil. It's unrelated to this mod, but I've gotta track down the issue either between the pickup and igniter box, or between the igniter box and the ignition coil. Or it IS the igniter box. Here we go again.....
 

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I think these machines run on whats called a wasted spark so the plugs will spark on every stroke hence( wasted spark) mean compression and exhaust stroke
 
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