TOPIC:

I inherited a 1979 kz650 custom last year that didn't run. Took it to a shop who cleaned and adjusted the carbs, as well as replaced some fuel lines. Since then, I have put on 1200 miles. Lately it idles terribly. I have to play with the choke to keep it from dying at every stop sign (or any time the clutch is pulled in for 3 seconds). Does anyone have any ideas where the problem might be? And any resources for me to learn how to solve the problem? I know my way around tools, but other than sparks and oil, engines are uncharted territory for me. Thank you. Bonus, the bike came with a shop manual!

Is there an inline fuel filter? If not, there is a good chance that some dirt or rust from the tank has made its way into one or more carbs, clogging up some of the tiny fuel passageways for low speed operation. You can drain each carb into a clean glass container to see if any trash that settled in the float bowl is visible. If this is the case, you will most likely need to remove the carbs in order to clear the passages.

No, there isn't a fuel filter inline. Good idea about draining the carbs individually. Nice to begin troubleshooting without removing the carbs from the bike!

Do you have a factory Kawasaki manual for your bike? If not I'd get one and then start doing maintenance. Valve adjustment, clean and adjust the points, clean airfilter, and of course check for debris in the tank like TexasKZ suggests. It's very difficult to diagnose running problems on a bike where the maintenance is not all up to date. If the problem doesn't go away while performing maintenance at least you know what the problem is not.

Yes, it is a Kawasaki manual that was purchased with the bike, new in 79. Would this influence the mpg? I am getting about 30 on a good day.

They are really sensitive to the carbs being synced, and the points are only good for about 500 miles between fiddlings. Some may dissagree of course, but that was my experience brand new back 40yrs ago, and things have not improved in those two critical areas.

RonKZ650 wrote: They are really sensitive to the carbs being synced, and the points are only good for about 500 miles between fiddlings. Some may disagree of course, but that was my experience brand new back 40yrs ago, and things have not improved in those two critical areas.

No offense intended, but I would be first one to disagree since my experience over the past 40 years has been completely different. I'm very surprised that the points on your KZ650 were so problematic; my experience is just the opposite. I've never felt like I needed to adjust or clean mine until they had about 5,000 miles on them, and I've been keeping pretty good records of maintenance. As an example - I very recently (June, 2017) replaced the points and condenser on my KZ650-C1; the bike had 60,047 miles. The bike was running fine, but I felt I should replace the points and condenser as part of normal maintenance since I have a number of new sets in my parts cabinet and it had been nearly 4 years since I had touched them. Prior to June 2017 the last time I touched them was at 54,638 miles in 2013 and that was only to clean, lube, and adjust them - not replace them. The last time I actually replaced them was at 50,118 miles and that was in May, 2011. So for me points easily last about 10,000 miles with a lube and cleaning performed at roughly 5,000 mile intervals. Considering it takes me only a few minutes to do that seems to me like pretty trivial maintenance.

Certainly touching the points every 500 miles would indicate to me a very serious problem, otherwise the KZ650 would have been labeled a lemon and very few would have been sold. Even the Kawasaki Service Manual shows a 5,000 km interval for checking the points and setting them if necessary. To my knowledge the basic points technology used on the KZ650 was no different than that used on other KZ models of the era, so if the technology had an inherent problem it would have been a very widespread problem. Ed

When my "so clean I could eat off em carbs" did this a few weeks back (1st 10 miles perfect then all of a sudden rough) I drained em each with a clean bowl and found a fair amount of lint, hair? and junk in #2 and very little in #3 and 4. and none in #1....... so I really went over #2 and the other 3 a little less so but still good...... the carbon on the #2 plug and clean 1-3-4 plugs seconded the finding too and after a tank rinse and running the fuel through a new Golan fuel filter that I finally broke down and bought.... also cleaned the APE pods again and rinsed them twice and oiled em up thinking some of the lint was coming off them .........problem solved.........

And although I never really had any problems for the first 4 years with the points 80 to 84 or so...... and for several more when in 04 my 1st Dyna S went out on one side I sure do like em..... set it once and forget it.

I am beginning to wrap my head around the task of cleaning out the carbs. Since this is far enough outside of my wheel-house it's a bit intimidating. Looking at the Golan fuel filter, is that a throw-away item in the future? The pictures on revzilla don't show a disposable component.
First step is figuring out how to drain the carbs while they're still on the bike

There are drain screws on the bottom of the carb bowls. If you still have the tubes on the bottom of them routed down the rear of the engine. You can pull them out and put them and put them in a drain pan. Then open the screws near the bottom of the fuel bowls. If you don't have the drain hoses, just put a butter tub under the nipple on the bottom of each carb and then open the drain screw.

Regarding a rebuild it looks worse than it is. I would suggest you get containers numbered 1 through 4 for each carb. Carbs like parts to go back in the units from which they came. I would leave one of the carbs assembled for reference your first time through. After you have done the first three you will 1) remember and 2) have three carbs sitting there for reference. I like to spread out a hand towel so any small parts dropped don't get away from you. I recommend getting a rebuild kit as the o-rings and carb bowl gaskets are almost certainly shot.

Read the manual before you even start. Keep it with you on the bench. With the Kawi service manual and the guys on this site you can't fail.

The Golan filters are washable, so you will not likely need to throw it away in this lifetime.

Golan filters definitely are NOT throw-aways. Just clean the little screen inside the filter if you find it has trapped crud from the tank. The Golan filter is made in such a way it should last forever. Ed