Questions for you old KZ Pros

Hey there y'all. I'm the new guy. I have an '82 KZ750 with 25k miles, stock everything (except it has air pods, and the airbox is long gone), and, as you may have guessed, a characteristic half-gallon sized dent in the right side of the gas tank!

My bike was a Craigslist special that I got for $750 from a retiree who rescued it out of a field where it had languished for years. He did what was necessary to get it running and presentable, but it understandably has its issues-- it's a good bike, but far from excellent.

Well, enough of all that, here's the meat and potatoes: The bike seems pretty slow (especially compared to my '97 Intruder 800) and gets about 28MPG. It needs a lot of choke to get warm. Since I have owned it I have fouled out two sets of plugs. The internal exhaust baffles have a 1/2" hole drilled in them. The bike will sometimes die when idling on uneven ground, or after a sudden stop. I have found that running with the petcock on "prime" gives me the most reliable idle.

Obviously, what I would like is to a) restore power (if there's more to be had) to the bike, b) stop fouling out spark plugs, c) develop a steady, reliable idle that does not die randomly and d) improve the bike's fuel economy.

My mechanical experience is limited, but I am a good learner. I have the original tool kit for the bike, and I just yesterday took off the carbs, opened one up, then put it all back together with no problems. That's a good illustration of how much I can do-- not much, but maybe a good starting point.

So, all you KZ veterans out there, if you are still reading after all this, what do you suggest? Any good ideas, good starting points, or tips? I would appreciate the help because I do not want to get rid of this bike.

First off, welcome to KZr HGD!

The problems you're describing sound like it's running lean to me, and I would highly recommend not riding it again until you address that issue so you don't burn a valve(s) or piston(s) = BIG $$$! ::ohmy:

My guess is that whoever replaced the OEM airbox with pod filters and drilled the exhaust baffles didn't re-jet the carbs to compensate for the increased air flow and slightly better breathing exhaust, which pretty much covers all of the issues you stated.

If the intake manifolds between the carbs and cylinder head aren't bolted securely to the head or clamped properly to the carbs, or if they have any cracks/weathering (even hairline cracks) to them they will cause a vacuum leak.
Also be certain that the vacuum lines are connected properly, and that the required brass "nipples" on the manifolds or carbs have the little black rubber caps on them.

id say start with a good tuneup and start fixing other things as ya go;)

First off, you need to provide a little more info about the bike

Is it a two cylinder or a four cylinder? Kawasaki made both as 750's in 1982 (and 1980 and 1983).

As usual, make sure the ignition is right before you mess with the carbs.

Welcome halfgallondent,

I agree that we need to know which model KZ750 you have. I can tell you that the 4 cylinder models, when running right, have tremendous power all along the range up to over 100 mph. Mine get about 40-45 mpg riding aggressively on my daily commute.

I would also start with the basics in addressing your problems.

First, fuel: make sure the tank is reasonable clean, remove and clean your petcock filter, be sure your petcock is opening (it is vacuum operated, except when on "prime" -- you may have a vacuum leak somewhere, or a leaky vacuum diaphram in your petcock), install an in-line fuel filter (to keep the crud out of your carbs), and consider a carb teardown and cleaning. Be sure to set your carb float height per the manual (if you don't have one get one. Someone has posted a digital version for the 4 cylinder 750s somewhere on this site, I think).

Ignition: Assuming you have the stock electronic ignition system, check all wires and grounds -- cleaning and tighening as necessary. Also, consider the "wiredgeorge coil mod" which you will find on this site. Double check your plug wiring is correct (1 & 4 goes to one coil, and 2 & 3 goes to the other). Check for spark at each cylinder by pulling the plug, laying it against the block with the plug wire attached, and cranking the engine. You should hear and see a blue spark.

If the above does not cure lack of power problem, then you should do a compression test. If that turns out well, then you should start adjusting the carbs. (You might try trading in a stock airbox and filter, to see if that corrects the problem.) If the compression is poor, then you may need to simply adjust the valves (not real simple, but doable by anyone that can follow directions). If it is not the valves, then you may need to replace the piston rings. With your low mileage, that does not seem likely.

Hey, you guys are full of good advice, and I thank you very much for the time you put into your responses.

My bike is a 4 cylinder. It backfires a lot--just little pops-- when I'm riding it. I can't think of any other pertinent information at this time.

Today I took off the gas tank, took off the carbs, unhooked the lines and hoses, etc. I did this just to familiarize myself with the guts of the fuel system, and I cleaned things up a little while I was at it. I sealed the airpods (which were a little loose) and hopefully this gives me good results.

Thanks again and keep the advice coming! It feels great to get my hands dirty and tear apart a motorcycle like this....it's something I've never done.