TOPIC:

1977 kz750 twin. I couldnt get the bike to start after tear down paint and reassembly. I determend something was wrong with the points so i swapped them for the ECI from an 82 kz750 twin. After some finageling with the carbs an. Three or four kicks and it starts beautifully. I shut it off then in two kicks it starts. Shut it down for that and came back the next day; two light kicks and it starts, so now its time for the test run. I turned it off so i could get all the lighting right, kicked it once and fired, so now im riding. Its running good and strong but idling to high so i pull over shut it down to look over the carbs, i do what i need to do but now it wont start. It just back fires really loud, sometimes it blows my breathers off. After gettin it home i noticed that the neg wire from ECI had disconnected from the harness

Questions: can it be 180deg outta time?
Which cylinder is number 1 and which is number 2?
Any help would be great. I know its gettin spark, its strong. I put a lil gas thru the carb past the butterfly valve and directly into the cylinder head, get nothin but back fire.

It is possible for a KZ750 twin to be 180 out of time, but it can't happen spontaneously, so if it ran ok, and the advancer rotor was not touched, then it can't be 180 out. More likely would be that the timing plate has moved, or a wire is intermittently shorting, or the power wire to the coils is not getting full power, or that the igniter is going bad, or that the pickup wiring is intermittent, or the pickup is failing when hot. There are, unfortunately, many possibilities.

If you had the rotor off since then, it may be on 180 out.

I hate to ask, but is there a chance you ran out of gas? A motor will usually idle slightly higher just before it runs out.

You will need a multimeter to really go through everything.

The left cylinder is #1 when sitting on the bike.
You can probably figure out which one is #2.

You can build a replacement ignitor, which you can also use for coil testing on a bench. It's very cheap and easy to build. The details for the twin is at the bottom of the page.
home.comcast.net/~loudgpz/GPZweb/Ignition/GPZgmHEImod.html

Thanks i been lookin for proper cylinder location for about two months. But i swapped the points system out for a CDI from an 82 kz750 twin. It ran good for two days, on the third day i took it for a test spin. I pulled over and turned the engine off. I couldnt get it started again. When i got it home i found that the ground wire from the CDI box came loose( thought i was home free). Reconnected the ground wire, still nothin. All i get is a back fire every once and while.

Hopefully this pic comes thru. I know every body loves the Honda CBs, but they sleepin on Kawaski.

Looks like a fun ride!

Is there a way to test the coil, the CDI box, and the pick up? I have a decent multi meter.

Yeah she is a great ride. I had no troubles from her before I took her apart. I feel like the bike has a good amount of power, speed, and good handling characteristics.

You can ohm out the pickup to get an idea if it's working. But all of those things need to be under stress (voltage and/or heat) to confirm they are good. BTW, it's not actually a CDI, even though many sources call it that. It's really transistorized-kettering.

If you look on the HEI link, it shows a way to bench test the coil and pickup using an HEI igniter.

Another way to test for spark is to just tap the pickup center with a screw driver. That should make the plugs spark.

Be aware, you must check for both sparks at the same time so make sure both plugs have a path to the engine or you can damage the coil or igniter.

Ok, thanks again. I'll try it out and get back to you.

If the ground wire from the igniter was not connected, then it's amazing it was even backfiring.

Have you tried connecting teh ground wire again and starting it?

If you replaced the points plate with the electronic ignition p/u, then you already kno that there is no adjustment for it.

Im not trained mechanic, im just mechnically inclined. I tinker on cars and motorcycles, take em apart and try and put them back together again. Im learning as i go; so while the lil bit of information i find that say there is no way it can be 180deg out, the problems just remind me so much of a car 180deg out.

I reconnected the neg wire the day after i got my self stranded. It still wont run. I'm want to figure out if the cdi box got messed up some kinda way. The curious thing is that im gettin spark outta both plugs, strong spark too, thats why i was so hung up on it being 180deg out but i guess i need to check the carbs again. One question is there any way the timing coulda jumped a tooth?

Pretty tough to jump a tooth when it's the end of the crankshaft, no chain, gears or rubber belt needed.

It "can" be 180 out, but you have to remove the ignition cam lobe from the advancer, then re-install it 180 out. Then it backfires through the carbs. Most of us twin owners have done it.

The twin fires both plugs at once, if yours are sparking then the igniter is good, and so is the rest of the ignition.

Hackworth wrote: 1977 kz750 twin. I couldnt get the bike to start after tear down paint and reassembly. I determend something was wrong with the points so i swapped them for the ECI from an 82 kz750 twin. After some finageling with the carbs an. Three or four kicks and it starts beautifully. I shut it off then in two kicks it starts. Shut it down for that and came back the next day; two light kicks and it starts, so now its time for the test run. I turned it off so i could get all the lighting right, kicked it once and fired, so now im riding. Its running good and strong but idling to high so i pull over shut it down to look over the carbs, i do what i need to do but now it wont start. .

It sounds like carbs/fuel problem or maybe a vacuum leak (high idle is vacuum leak symptom).

The tank and petcock should be drained/cleaned and inline filters installed. Carbs need to be cleaned and fuel levels set with clear tube. If the carbs and carb holders were removed, they might be leaking air.