Very poor acceleration.

I am very new to the motorcycle mechanics world so please forgive my lack of knowledge.

I was recently handed a 1980 KZ750 Standard-4 that sat for about 5 years in a shed. Luckily the carbs were completely drained and dried before storage so after putting some gas in it, it started easily. But now at idle when I pull the throttle back (almost WOT) it dies or almost does then revs slowly. When riding it, no matter what RPMs I'm at it is very slow to accelerate at WOT. As far as I know it was working fine before it was stored.

I've read ALOT of pages on this forum and many others about rejetting and carb syncs. I just checked the diaphragms today for anything but they look fine. And today I saw something on a forum about an accelerator pump. I'm not very knowledgable on these things but I'm eager to learn.

I know you guys are the best. Been surfing this forum for weeks straight. Any opinions?

Welcome to KZR
Start with the simple stuff first.
Tell us a bit more.
Is there an airbox on the bike asnd are the carbs connected ? Is there an air filter? Clean ?
Is the exhaust stock 4 into 2 or has it been modified ?

Is it firing on all 4 cyclinder ? When you get er started use a spray bottle or spit on the exhaust pipes near where they are connected to the cylinder head. If the liquid sizzles right off then that cylinder is firing. If slow evaporation then cylinder not firing.

If cylinder or cylinders are not firing then remove the spark plugs, leave them attached to the plug cap on the end of the lead, lay then on the engine so the thread part of the plug is in contact with the metal of the cylinfer and hit the start button. You should see spark across the top of plug.

If the carbs are the stock Keihin carbs then there was never an accelerator pump fitted

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Welcome aboard. Despite what the previous owner did or told you he did it still sounds like the carbs need cleaning. Ed

Don't forget to check your ignition advancer. Could be sticking.

Ok guys. Got a chance to get out and try the things you said.

I tried the spit test. (When sitting on the bike) the 2 left cylinders sizzled and were noticeabley much hotter to the touch than the 2 on the right. The 2 right cylinders I could touch with no problem and the spit was not affected.
I then did the spark plug test and all sparked (and even gave me a jolt).
And the carbs are in fact Keihin.

To answer JR's additional questions: Has individual pods and everything is hooked up tight. And I did notice yesterday that the tank has tiny pinholes where it looks as though rust under the paint ate through. They're by the gas cap but I didn't even notice until it was dark and I shined a light in the tank. Could those holes affect something?

Also forgot to add that we did go through and clean the carbs.

And im not sure what an ignition advancer is

TheJoshManKZ wrote: ..........I tried the spit test. (When sitting on the bike) the 2 left cylinders sizzled and were noticeabley much hotter to the touch than the 2 on the right. The 2 right cylinders I could touch with no problem and the spit was not affected.
I then did the spark plug test and all sparked (and even gave me a jolt).
..........................

OK
so it's only firing on 2 cylinders which would explain the very poor accleration. You have spark - the plugs are sparking so if it wont run on cylinders 3 and 4 then you have either poor compression or the cylinders are not getting fuel.
Like Ed said you probably need to go through the carbs again. It took me at least 4 tries before I got it right. Also, given the rust you will find that unless you have a fuel filter then small rust particles will make their way into the smallest carb passageways.

Put the spark plugs back in. try to start. take them out again - are they wet with fuel or dry?

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Well guys. I appreciate the time you took to post and I am glad to report that the problem has been solved. The 2 plug wires on the cylinders that were giving me trouble were switched. Now it runs like a champ. I feel dumb for it being that simple but I did learn some things that could be helpful in the future. Thanks again. And I'm sure you'll be seeing me again.

Ignition Coil Primary And Secondary Wiring( a general description of ignition coil wiring, read carefully as several models are listed)

Ignition coils on the 80’s Kz1000,Kz1100’s and Gpz1100’s are wired the same, that is as you sit on the bike, the LEFT ignition coil primary(small wires) are two wires, RED and BLACK. The secondary (or sparkplug wires) go to #1 and #4 sparkplugs(your primary wiring may be different).

The 550’s, 650’s, 700’s & 750’s are backwards to what is listed for the bigger 4’s.

The cylinders are numbered left to right as you sit on the seat; #1,#2,#3, and #4.

For the RIGHT ignition coil, the primary wires, again are two wires, RED and GREEN, with the secondary going to #2 and #3.

The RED wire gets it’s voltage from the run/stop switch on the right handlebar switch pod. Your primary wiring may have a different color.

The BLACK and GREEN wires connect to the IC Igniter(if the bike has the Kawasaki supplied electronic ignition) it actually gives the coils their grounds to fire the sparkplugs.

Primary(small wires) side of the coils will read between 1.8 to 3.0 ohms.

Secondary(sparkplug wire ports)side of the coil will read between 10.4K to 15.6K ohms. These ports are wired together, so it makes no difference which is used, as long as the correct coil to sparkplug configuration is followed.

The sparkplug caps should read 5K OHMS(5000), any higher, or a reading of infinity means new caps should be ordered. When re-installing the old or new sparkplug caps, cut about ¼” off the sparkplug wires for a new un-corroded connection.

To stress the ignition coils, take a hair dryer, heat the coils and see if the ohm readings change from cold to hot . If they do, it’s time to buy new coils.

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Keep in mind, the wiring is reversed for the 550’s, 650‘s,700’s, and 750‘s, that is the RIGHT coil primary will be two wires, RED and BLACK with the secondary(sparkplugs) going to #1 and #4.

The LEFT coils primary wiring would be again two wires, RED and GREEN, with the secondary(sparkplugs) going to #2 and #3.

An indication of black and sooty sparkplugs may not mean a carb or carbs are in need of cleaning, but may mean the input voltage is low.

When checking the input voltage to the ignition coils, first have a fully charged battery, and the using a multimeter, set it up to measure VDC(Volts, Direct Current), range of 20.

Put the RED probe from the multimeter on the same terminal that either a RED wire or ones that’s RED with YELLOW stripe, and the BLACK probe on either a good frame/Earth ground or the battery Negative(-) terminal/post.

Depending on the motorcycles current draw( lighting, and other high amp needs) the reading might be 10 volts or more, but if the reading is down around 8 volts or less, this indicates a corrosion or wiring problem needs correcting to improve input voltage to the coils.

These engines have what is known as a “Wasted Spark” that is, a sparkplug will fire during an exhaust stroke. It does no damage and many other motorcycle engines have this design.