1981 KZ750 E2 will not accelerate past 70 mph

Crank case oil level not over-filled?

Throttle butterflies fully opening?

Good Fortune!

Oil Level not overserviced, I keep it filled so that sight glass is 2/3 full with bike on centerstand. Throttle plates open and close completely. I too wonder about cleaning the carbs again, however, they have been off and cleaned at least three times this year alone. The most recent cleaning was an ultrasonic bath. Every jet was inspected with a 10X magnifying glass for obstructions, none found. No fuel has been run through unless a fuel filter was installed. When the fuel valve is in the prime position fuel flows easily from the filter. Fuel tank has been pressure washed, oiled, purged with fuel and inspection for corrosion, none found. I plan on checking compression again later this week with a different gauge. When the headlight was pulled no corrosion was found on any of the wire connectors.
I have never put so much effort into a motorcycle project without it yielding a positive outcome, this one has me stumped!

Thanks again for all of the input, I will continue to work this problem until it is resolved.

Here's a shot in the dark. I know you said you cleaned and lubed the ignition advancer. But are you sure it isn't hung up on anything? My points plate was all bent to hell due to it being dumped by a PO. Didn't notice it until I had taken it out to lube the advancer. Hammered it back straight. Was also missing one of the eclips on one of the advancer posts. Mine wasn't hanging due to the damage, but anything is possible. They could have replaced one points (module in your case) with a screw that's too long and effecting the advancer. Not sure if that is even possible.

SoDak52 wrote: ...Compression is 130 psi common to all four cylindersngine....

SoDak52 wrote: ...Borrowed compression tester form local auto parts store, 30 psi indicated on all four cylinders, either it is a leaking gauge or I have a big problem. I will try another gauge....

Compression history is inconsistent.
Any particular change in circumstances that prompted the second test?

Perhaps valve clearance adjustments were attempted prior to your acquiring the bike, entailing removal and replacement of the cam shafts, and the cam timing has since been incorrect.
If not already done, would double-check the cam timing.

But for expressed certainty about proper functioning of the timing advancer, would have suspected it was stuck in the idle position and not advancing properly with increased rpm, which usually produces the reported lack of power under load.

Good Fortune!

SoDak52 wrote: I am a new member to the KZR site with an old problem. I purchased a 1981 KZ 750 E2 three years ago and have been fighting with it continously since then. It will not accelerate beyond 70 mph, indicated RPM will not exceed 6000. The following parts have been inspected or changed:

Carbs cleaned
New idle jets
Carbs Synched
New Carb Holders
New Airbox Boots
New Air Filter
Rebuilt Fuel Valve
New Fuel Lines
New Vacuum Lines
In-line fuel filter
Dyno-Jet Stage 1 Carb Kit Installed
Dyna-Tec 3.0 Ohm Coils
New Spark Plugs, 7mm non-supression, copper core
New Spark Plug Wires
New 5000 Ohm Spark Plug Caps
Cleaned and Lubed Ignition Advancer
New Battery
Dyna S Pick-up Coils
Compression is 130 psi common to all four cylinders
Valves clearances are with-in specs
Cam chain tensioner cleaned and inspected
Disconnected every wire, applied di-electric grease, re-connected
Removed, cleaned, inspected exhaust system, no obstructions or corrosion
Cleaned, inspected fuel tank vent system
Checked resistance of all wire bundles
Verified 12 volts is available at required locations:
Battery
Coils
Starter Switch
Kill Switch
20 Amp Fuse

Bike starts easily and will settle into a smooth 1000 rpm idle. At rest the bike will reach 9000 rpm instantly when throttle is snapped open.

The bike will pull red-line in the first three gears, however, it does not do so quickly. Once 4th gear is selected RPM's will not go beyond 6000 and the top speed stalls at 70 mph. At 70 mph if the clutch is pull in the engine will accelerate to 9000 easily when the throttle is snapped open. The problem I am having only shows up when a load is felt by the engine; the weight of the bike, rider weight, wind resistance, friction, etc......

Have review hundreds of on-line forums, at this point I am out of ideas.

Bike is in excellent condition and I would like for it to run as good as it looks.

Thanks for any input that may help me fix this bike

The Dyno Jet Kit, why? Also maybe the Main Jet is to Small. Best to Verify Fuel Level in the bowls with a clear piece of tubing before any jetting.
Previous post stated compression Good at 130psi.
If the compression is Not 130, and you have checked valve clearance, did you verify camshaft timing?

Dyno Jet Stage One kit installed on the advice of local motorcycle mechanic. He stated that this era Kawasaki suffered from lean carb settings to satisfy EPA regs. The idle screw is currently turned out 3 1/2 turns per Dyno Jet instructions. I installed the recommended jets at the time of the modification. It may indeed be too small. I have not tried changing it.

Carb float level was carefully set during one of the carb cleaning exercises. Used clear plastic tube to set level flush with carb bowl mating surface.

When valve clearances were check it was in the middle of winter, stupid cold, all clearances were within specs. Before the valve cover was installed I verified there were 45 1/2 links from the Z7EX line on the exhaust cam to the "IN" line on the intake cam. Also cleaned and inspected the Cross Wedge Cam Tensioner, it was in serviceable condition. I suspect the Cam Tensioner was not original to the bike. The Cross Wedge was installed on late run 1981 bikes. The reason I think that is the Clutch Release is the old style Spiral Gear type with the 11 ball bearings. This part was used on first run 1981 KZ 750 E2 bikes.

When compression was checked it was also winter time. Stone cold engine, however, it pumped up to 120/130 on all cylinders. When I rechecked it last week the borrowed gauge indicated 30 psi across all the cylinders. I am thinking faulty gauge. I will recheck it this weekend.

Another thing I have not tried is raising the clip on the carb slides. The slides move easily at this time. Would it be worth moving the clip so that the Needle Jet could let in just a bit more fuel?

Thanks to all for the ideas, I am confident we can get this bike running correctly!

Ignition advance was cleaned and inspected. Found to be in serviceable condition. When engine accelerates you can observe the advance move with the timing light. I suspected this component strongly for a time, however, I now believe the problem is not related to the Ignition advance.

Thanks for sharing your insight to this problem.

It will take some time but we will find the problem, it can not hide forever!

45 1/2 links? What manual are you using? I've never seen a 1/2 link count. It is always a whole number, like 46 or something. I don't have the 750 4 cyl manual.

Can one of the Members please post the 750 Cam chain timing procedure, along with the picture of the cams, and the Pin count?

set the crank timing mark on T, then put the exhaust cam on the z7ex parallel to the head, then count 45 pins and set the IN mark on the intake cam between the 45 and 46 pin. if memory serves or even better

Your memory has served you well, this is the method I used to check cam timing when the valve cover was off.

I spoke with the the guys at Z1 Enterprises yesterday. I may have problem with excessively rich fuel mixture at WOT. If weather permits I will do some additional troubleshooting today.

Thanks for the cam timing post.

His is a 4 cyl, not a twin. I hope you haven't used the twin timing instructions to set up your 4 cyl bike. :blink: :S

If you need the correct Kawasaki Service Manual for your bike, download here;
www.google.com/url?sa=t&rct=j&q=free%20k..._ETR5yNjhfhg&cad=rja

It is a pdf file so you will need acrobat reader to view; get.adobe.com/reader/

This is from that manual

Atraeu wrote: set the crank timing mark on T, then put the exhaust cam on the z7ex parallel to the head, then count 45 pins and set the IN mark on the intake cam between the 45 and 46 pin. if memory serves or even better

Attachment ZX750camtiming.jpg not found

TWIN NOT 4 CYL!