Won't start after rebuild

It certainly behaves like that, but I've checked and rechecked cam timing: cams installed with notches to right side of engine, at #1TDC (piston and timing rotor mark) I have the 'IN' mark aligned with the cyl head on the intake cam and the <can't remember the designation right now but it's the right one according the the Kaw shop manual> mark aligned with the cyl head on the exhaust cam. The marks are the proper number of gear teeth apart.

It's driving me nuts.

Are your plugs wet with gas after trying to start the motor? Have you checked your valve clearance? Are you using the choke? Every KZ I have owned would never start cold without using the choke.....chris3

frankenchopper wrote:

... If the supply voltage/current to the IC Igniter is low or the pulse voltage from the pickup coils is low, won't that reduce the output voltage to the primary side of the ignition coils, and thus make a reduced energy soark that may still have enough of a pulse to fire the timing light? Any ideas how to measure the voltage pulses?

Can't specifically answer the questions

But -- has a plug been removed and held against the engine while cranking with ignition turned on, to see whether there's apparent decent spark at the business end? (Fat blue spark would be good)

compression is too low. Something is wrong here. And is it cold outside where and when u try to start this thing? If it has cv carbs and the the throttle butterfly is open too far it's gonna have a hard time getting gas with the the low pressure situation. Just a tad open on that butterfly, alittle choke, and NO fouled plugs, and that's the way they like to start. U should not have compression at 90. yes i know the rings aren't seated yet but still that's not only low but it's about where u started from. And that is raising suspicions. Id be counting pins on the timing chain instead of just looking. And are u !*) that is 180 out. back fires are lean misfire, incorrect timing ign/valve, over fueling. just remember... BOOM!

I forgot to mention ONE BIG VAC LEAK

It's getting plenty of gas - the plugs are wet when I pull them after trying to start it. The spark is pretty weak. I have replaced every part of the ignition system that makes the spark plugs fire with tested parts except the wiring harness itself, and I am going to bypass the wiring on that next. That's why I mentioned a possible bad power lead to the IC Igniter.

The emissions systems were removed long ago and all the vacuum taps are plugged except the one from the #2 carb, which operates the fuel petcock. The carb boots are in good condition.

I'm in Florida - it doesn't get cold here.

Keep the ideas coming - I'm trying everything.

Your going to have to measure the spark energy. Should be blue, orange tiny spark is no good. Is the spark equal strength on each coil? When it misfires are you talking BLAM or PUFF? Put some oil in the cylinders and compression should bump up considerably. If not you have valve problems. Does every cyl. have equally wet plugs? If all you have is a tiny orange spark its ignition related. Are u using the tiny original wire that carrys batt. voltage to the coils? They have to flow enough current as well as the 12volts. Does the igniter have a gap that is large enough? Are the wires inside the kill switch tight? Do the coils have a clean tight ground connection?

How strong is your battery? When my battery is reaching the end of it's life and gets weak, the bike gets hard to start, aka weak spark. Is your ground wire to the engine tight? chris3

Try some fresh fuel.The fuel the sell these day can go bad in a very short time

Spent a few hours today with the DMM, the wiring diagram, and a spare wiring harness I've removed all the tape from and ziptied back together. Makes it easy to trace wires on the actual bike. No corrosion/high resistance in the wires or connectors.

I'm using fresh gas and the battery is new a couple months ago.

Spark energy is low - orangeish to no spark and all four the same. I measured the spark plug wire resistance - 27Kohms on #4. AHA! 28Kohms on #3, 25Kohms on #1, 4Kohms on #2. AHA! Clipped the ends off the wires and remeasured - all four at 4Kohms. I'm buying new low-Z copper core plug wires this afternoon and will try them tomorrow.

Hope hope hope.

frankenchopper wrote:

... Spark energy is low - orangeish to no spark and all four the same. I measured the spark plug wire resistance - 27Kohms on #4. AHA! 28Kohms on #3, 25Kohms on #1, 4Kohms on #2. AHA! Clipped the ends off the wires and remeasured - all four at 4Kohms. I'm buying new low-Z copper core plug wires this afternoon and will try them tomorrow. Hope hope hope.

Might also be a problem with the plug caps.

Ohm testing the original sparkplug caps on my 1976 KZ900 gave sporatic readings and all different. Purposefully smashed one apart to see how it was made. Found a small inline chip of what seemed like carbon, so assumed it was the resistor which gave the ohm reading. Anyhow, when replacing stock coils with Dyna green 3 ohm style, also installed new Dyna solid core plug wires which came already equipped with plug caps pre-installed. I believe the pre-installed Dyna plug caps are straight through with no resistance. Obtained the Dyna coils and plug wires from Z1E and couldn't be happier with the performance. I don't use resistor type plugs either, so am running with no resistance between coils and plug tips. Only downside is radio interference if that matters. Was a pleasure not having to goof around with threading plug caps onto the plug wires.

Would suggest again checking for fat blue spark after installing the new plug wires. If spark remains weak orange, would address the plug caps.

And don't bet the farm on a battery just because it's relatively new. :laugh:

Good luck!

This is killing me.

I put on new plug wires - copper core stranded, measured at 0.8 - 1.1 ohm resistance. I removed and replaced the plug caps (screw-on ends) and measured their resistance - less than 1 ohm. Same problem, slightly improved. Spark is better but still not strong. With the improved spark the bike will run with the throttle open, but it's occasionally firing through the carbs (no the plug wires aren't reversed, yes I previously looked at the valve timing and it appears correct).

Any other ideas,anyone? If I can't get it this week I'm going to an aftermarket ignition system. I am running out of patience with this bike.