TOPIC:

I had a post going in the engine forum but it appears to have died off and I am now assuming my issue is regarding wiring/electrical/timing advancer so I am going to attempt to start a new topic in this part of the forum.

My bike was running fine but it suddenly is hard to start and when it does start, it dies on even a minimal amt of throttle.

I was told to look at the advancer - checks the springs, movement etc, but on my bike there are no springs and there doesn't appear to be any movement whatsoever.



I've seen reference on the forum to electronic ignition on the 83 and later models. Is that the ignitor box behind the battery or something else?

Any advice would be appreciated.

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Background: Bike was running fine. Parked it for two hours, then couldn't start it and had to tow it home.
- Hard to start, idles rough and very low, dies when throttle applied.
- I have spark
- have tested the power into the coils and that seems ok.
- I have gas and it is getting to the carburators
- I have 150 compression on all cylinders (so should be no stuck valves or major engine trauma)
- I checked for plugged exhaust and all is clear.
- I checked for exhaust leaks in and out of the carbs and it all looks good.

Post a pic of the center.

steell wrote: Post a pic of the center.

That is a CDI ignition, no mechanical advancer. It is all electronic.
Check for spark, pull your plugs and lay them out against the head, and crank the starter with key/ kill switch on. Your plugs should have a nice blue sharp spark. Start there.

Spark seems fine. Aside from no power (won't turn faster than about 1000 rpm) the issues include backfires through the air cleaner and right tailpipe including the occasional flame out the pipe, so I am assuming there is a timing issue. Since the compression is strong on all four cylinders, I want to look at the timing advance. Does the CDI control that and if so, where do I find it and how do I test it?

Or am I looking in the wrong direction altogether?

I would love to get back on the bike as two months of rain here in Vancouver has just broken into sunshine!

John

Do you own a service manual for your bike? if so use it to check the ignition system. the manual will tell you what to check.Sounds like a timing or electronic issue to me. Just hard to believe its out of time since you said it was interment. If it was out of time then it would act up all the time. but it probally couldnt hurt to pull the valve cover and look. but i would start with the electronic side of the ignition. something is probally going bad or went bad. some simple test with your manual and a good multi meter will help you alot.

are you sure you dont have sparkplug wires mixed? just saying

I thought maybe someone had messed with my spark plug wires (since I was parked at the beach when the issue started) but they are all marked for the cylinder that they go to and each one really only reaches comfortably the correct cylinder anyway.

I have a manual for the kz750, not the 700 and the 750 has a mechanical advancer. I agree that it sounds like timing but would likely be an electronic issue. But what electronically controls the timing on this bike? The CDI? And where do I find the CDI unit - this site has a schematic for the kz750 which doesn't show the CDI.

Ok, I just found the CDI unit on ebay and it is the same thing as the ignitor. Any idea how to test this so that I don't go out and pay $100+ for something I don't need?

It's not a CDI, a CDI is a totally different animal.

Looks like the same setup used by the 83-85 GPZ750, and yes the igniter controls the timing advance. I suspect any of the 83-85 GPz igniters will work, GPz600/750/900/1100.
some have rpm limiters (and at different rpms) and timing curves may be different.

The 81- 650 and 80- 750 ignition advancer/pickups/igniter will bolt right on, won't directly plug in though.