Please help a fresh back solider get his bike to run.

[drewj]

ok, i just got back from afghanistan, long year.  All i want to do is ride my cb (76 cb750k).  I got it out of the garage changed all the fluids and made sure the battery had a charge. ran great. the next day i go out and it will only run on the number 3 cylinder. my buddy and i check everything and come down to the point we decide it needs new coils/wires since it still had the originals. there was no/weak spark at best at the other wires.  Get the new coils in from vintage 750 and now it wont stop blowing the main fuse?! even if i run a jumper wire from the coils black/white to a separate 15-30 amp fuse holder straight to the battery with all the fuses in the block pulled, it still pops the fuse? any idea? this has been three days in a row testing and trying things out and all i want to do is ride this damn thing. thanks for all the help.

[TOOLS1]

drew
First, welcome to the forum, and I thank you, for your service. My stepson did two tours, and I can understand how much you want to ride. His motorcycle was a big help in readjusting to life back here in the real world.
Now, for your bike. The Honda's are notorious, for wiring problems. One of the worst is the connections on the fuse block. they are weak, and cause overheating of the fuses. I replace the fuse block's with the wire in blade type fuse holders.
Now to try to diagnose. You are having a dead short somewhere. have you tried tracing the wires? Checked the connections?
What coils did you get? Some of them will blow if you crank the engine without having the wires connected, and the plugs grounded.
And now the bad new's. I do not think you had an ignition problem to start with. The Honda's do not have a very powerful ignition system, and always seem to have a weak spark (iridium spark plugs are a great. and cheap improvement.)  It would be improbable that both coils would just go out, and when coils do go out. they will not fire on only one wire. Also one cylinder firing will not have enough power to keep the engine running. I think you have a fuel/carb problem. It would not be uncommon for the bike to suck in some gunk after sitting. i would try cleaning the carbs.
Hope this helps.
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[drewj]

i've gone through and cleaned the carbs. the bike was running on one while i would feed it throttle with the choke on. Three cylinder would be cold with one hot one. the coils i got were the stock replacement ones from vintage750.com. i think the main reason the fuse keeps popping is cause i think the (new) coil is grounding to the frame through to mounts some how, if i connect one of the old coil not bolted to the bike it doesn't pop the fuse but yet there is still no spark when grounding the plug to the block even the (-) post on the battery even when running a jumper wire from the battery to the black coil +'s. i did just notice that when i started working on it the points would spark a little when i opened them but now there dead and no sound/visual of a spark. i am getting ~12v at the +connector for the coils but i just can't figure out why it wouldnt spark.

[Re-run]

Tools gives a lot of good ideas. Get the manual from here if you can, it is the honda shop manual.
I would say that if the bike ran one day and then not the next, if the bike started, then it is most likely fual related and after sitting, crap can build up if the tank was not cleaned and that gunk blocks up the carbs.

The blade fuses are a good change but they are not causing your popping. You may have something grounding. Check out the wiring diagram and trace your wires.
Just fyi, #1&4 are on the same coil/point and #2&3 are on the other coil/point.
When sitting on the bike, it starts from left, 1,2,3,4. Make sure your plug wires are in the right order.

[TOOLS1]

If you are seeing sparks at the points it means that the condenser is bad, and this will burn the points up in just a few seconds.
Are you sure it wasn't running good on one cylinder, and hit, and miss on the others. Causing the pipes to be cooler on those? I have seen clean carburetors still run rough. It does not take much to plug up the tiny little holes in those things.
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[drewj]

the carbs were running great when i rode it and it has a clean tank and an inline filter so i really don't think its fuel or carbs.  the thing that disturbs me is there is absolutely no spark anymore at the plugs. i didnt so much see the spark at the point but i could hear them crackle when i opened them. but thats not even there anymore. and if the condensers did go out wouldn't that make a big arch? also i cleaned the points very carefully and theres still no spark anywhere in the system. like the coil wont spark since theres no open/close signal form the points.

[TOOLS1]

I am not going to swear to it as your problem, but if I only had a nickle, for every time I heard "it was running perfect yesterday." hell it happened to me last week. Rode the Toolmatic to the store, and as I was about to pull into the parking lot it started to run rough at idle. ran great when i would rev it up, so went home, and rebuilt the carbs. They also looked pretty clean when I took them apart.
The way the points work is, when they are closed they complete a circuit that allows the coil to charge. When they open the coil will discharge it's stored energy to the spark plug. Also when the points open, the condenser will absorb any extra energy, so that the points will not arc. If the condenser is bad the points may as well be an arc welder.
Also when the points are open you will get 12 volts at them. When they are closed you will not get any reading. It will seem as if it went dead.
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[drewj]

so if i have power to the coils at the connection, the coils test out good, what would be the proper way to check the points to figure out why the coils wouldn't be discharging on the secondary side. I thank you for stressing to make sure the carbs are clean but i know for a fact there was no spark and that is the pressing issue. ( i found this out originally when i pulled the plugs trying to figure out why the three other cylinders werent running and the plugs where all gas soaked and my timing light wouldn't pick up any wire pulse on those three cylinders. I've very familiar with ICM but sadly not points ignition, this is my first.

[TOOLS1]

When the points are closed. there should not be any reading at the coils. they should be absorbing the charge, so if you are getting a reading with them closed. It would mean they are not making contact. Another thing that might seem far fetched would be engine ground. Both the coils, and engine should have a good ground.
When you say the plugs were covered in gas, did you try checking, for spark with new dry plugs?
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[drewj]

ok, been running stuff down with the multimeter.
i have 12v all the way down to the + side of the points reading with them open.
i have continuity from the - side of the points to the block/frame/-bat terminal.
continuity from point to point when closed.
I can see/hear small spark at the points when they are opened.
double checked point gap to .014.

heres what boggles me.
I'm not getting any spark from the coil to the plug when i open the points. this has been done visually watching the spark plug grounded to the block and mainly with the plug in the cylinder with wire connected and my timing light hooked to both 4 and 3 to check both coils. since all checks out between the + side of the coil down to the - side of the points, that leaves me to believe some how the points aren't tripping the coils (brand new and also verified with the old ((working)) coils) into discharging the spark to the plug on the secondary side. I've double checked the boots to wire connections as well.

main thought: if the primary side of the coil all checks out from the + lead to the points, when i open the points (either) by hand, my timing light should flash if it reads the spark.

i just want to roll this thing into the road and run it over with the powerstroke (or hurry up and finish the xs650 bobber).

[drewj]

ok, just read your post after writing mine as i was doing it. noticed that when the points are closed i was still picking up 12v from the + side to the frame. checking the coils right now.....yes, still reading 12v on the + coil lead to the block with the corresponding point closed. also my multimeter lead slipped and tripped the points and i heard one of the cylinders fire.

does this just mean i need new points or to clean them?
i still dont under stand when i was tripping them by hand and seeing a spark why the timing light wouldn't flash.

going to go try to jump the points with a piece of wire and see if i cant make that timing light dance.

[drewj]

ok, used a jumper wire from the + point to the engine mount, held it for a second that broke it and the timing light flashed, so im guessing that just means the points are shot?!

(did this to the 2-3 point and it flashed on the #4 wire but i must just have the yellow/blue crossed.)

could i just resolve this never happening again by paying a $110 and getting the pamco ignition since i have to prob get new points anyway (more than likely)?

[drewj]

ok, runs like a charm now. used the dremel to take down the top .002 of the points and now she runs great. the every now and then miss is gone too.

one last problem, i'd like to use the replacement coils ive got from vintage750.com but they keep popping fuses every time the touch metal. and by touch metal i mean i got them mounted to the two off set t bars with the factory screws that held the factory ones and they keep grounding out. what am i doing wrong compared to the factory ones that they would be doing this?

[drewj]

was there some trick to the factory ones not grounding out that i didn't notice when i took them out? i didn't think a coil could ground out.

[TOOLS1]

Glad to hear you found the problem, and have it running. I do not know about the new coils. I have only used stock ones on my two Honda CB 750s. I would try calling vintage, and asking them about the coil's, or contacting the manufacture. Maybe try insulating the mounts with rubber, or plastic. I have thought about switching the Toolmatic to a Pamco, but I am afraid of being somewhere far from home, and having it go out. I know I can get points, and condensers all most anywhere, and they are easy to install/repair. I like things simple, and easy.
XS 650 bobber? Sounds cool. How about some pictures, and info on the build?
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[drewj]

1978 Yamaha xs650, tc bros weld on hardtail, sportster tank, buell cyclone fender, clubman bars kick only (with hidden starter button underneath), and every thing else is something i welded up in the garage.

[URL=http://imageshack.us/photo/my-images/850/22356970474016822933807.jpg/][IMG]http://img850.imageshack.us/img850/6295/22356970474016822933807.jpg[/IMG][/URL]

[TOOLS1]

looks like you are off to a great start. I like the stance.
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[drewj]

switched back over to the factory coils and now there shorting out the main fuse when there bolted to the frame, any one have a picture of how the stock coils mount?

[drewj]

is there any sort of insulation that keeps the coils not grounded?
it runs fine haning from the bike but once it grounds, you see the fuse burn up.

[TOOLS1]

Sorry it took, so long. I had to take the bike apart to get pictures



I would bet that you have a wire being pinched some where. When you tighten the coil down
TOOLS