Looking for some guidance

I have a 1978 KZ1000A2 that I purchased new. It has about 14,000 miles on her and is in very good shape. I repainted it black years ago and will eventually put it back to the original (or close to) luminous green. The only modifications are a Kerker pipe and a K&N replacement air filter. So, all other components are original…..chain, coils, shocks, etc. When I purchased the Kerker it was a “no rejetting needed” version, so I never did rejet, even after installing the K&N. The bike does run fairly well, but seems to sputter around 5000 rpm and up. It is also difficult to start after it has been setting for a while and needs to be kicked several times as the electric start won’t start it on its own. Is this likely due to a jetting issue? I am running the original coils and plug wires, but the points have been changed long ago. What would you recommend? I don’t want to put a fortune into this, but if there are some obvious upgrades that would improve the overall performance, I’d like to hear about them.
Thanks!

Its likely that your filter lets more air through, making your jetting too lean.

Easy way to check is to pull the filter, run it and see if it is better or worse. If worse, buy a larger main jet, install them and your filter, run and check again. You can do it a jet size at a time to try and fix the problem or just send it to someone like Wired George, pay some money, and get it back pretty darned close if not right on.

What is your current jetting? Also, will your bike start with the choke on full and throttle all the way closed?

Check your coil voltage. It's possible you're not getting full power to the coils. Also possible that something in the original ignition (coils or wires) isn't functioning properly. If you have a full 12v at the coils I'd check out the wires. If you have removable plug boots pull them off and snip a little bit off the end before threading the caps back on. Your symptom could be jetting related, but could also be insufficient spark.

give it a good tuneup 1st before you start throwing a lot of money at other things and see if it helps.

Thanks guys,

Unfortunately, I don't do any wrenching anymore and I don't have any meters to check the voltage. So I need to either take it to a mechanic, which I am most likely going to do, or just buy new coils and plug wires. If I recall, I did have the air filter out once (accidentally) and it did run worse. When I change the jetting, will that increase the possibility of plug fouling?

Kerker had a no re-jet version? Thats a new one on me but still with the K&N I would guess it's a lean situation and a re-jet is now needed. If you really think it's a voltage problem you can get a meter at any Hardware store for cheap. Mechanix cost big bucks if you can even find one to work on these dino's.

That bike came with super lean jetting. Someone will correct me if i'm wrong but i believe 105 on the main jet.

You need to go up one or two jet sizes on the idle and i usally run 112 to 115 on the main. Roy

I would simply replace the original air filter and see if that makes a difference (and if by luck you have the original exhaust, I'd put that back on until I found the problem). If the bike exhibits the same symptoms with the original type air filter, I would leave it on and work from there trying to find the problem. Rejetting a bike that has other issues just compounds the number of variables that must be considered in trying to find the root cause of the problem. In other words, if for example you have an ignition system problem, you can rejet until the cows come home and not correct the problem.

As far as upgrades, forget it until you've done a complete tuneup - i.e. points, plugs, condensors, clean carbs, synch carbs, check valve clearances, lube points cam, etc. (If you can't say for sure the last time these things were done - it's been too long.) If you start making changes before a complete tune-up you won't know if problems are related to normal maintenance items or the "improvements." If you can get this bike running as it did when new, then you can determine what improvements in performance,if any, you may want to make and you will have a baseline from which to work. These bikes had plenty of power and no sputtering when new; getting back to that performance level should be your first goal. Ed

I like the idea of getting the bike tuned up first. It's running pretty well so I hadn't really thought of doing that. I also like the idea of trying the stock air filter before I start any jetting. Z1 Enterprises has one for about $9.00. Is this genuine Kaw or is it an aftermarket piece? I saw another site that had the same filter for $25.00!

At $9 it's probably aftermarket, but that may work ok. According to Ma Kaw the air cleaner for the KZ1000-A2 is part #11013-063. Z1E can get them as they are still active, but they will probably be about $25 + shipping. You may find one on eBay for less, but be careful they don't sell you an aftermarket item that they claim to be original. Ed

OK, this might help a bit. I have been racking my brain trying to remember some of the things that I had done to the bike. Regarding the "no jetting required" Kerker.....well, I just remembered that the original baffle rusted out and the bike shop didn't have a replacement in stock so they re-packed it with bulk fiberglass from Ace. So, I guess the "no jet" Kerker was possibly a "yes jet" at that point. That with the K&N is leading me to believe that my mix is indeed lean. Does this make sense? BTW, and I'm embarrassed to say, I checked my records and my last valve adjustment was in 1994......only 2000 miles ago!

i whould definitly rejet and try what roy said that would be a good start 112 or 115 mains for sure i have put quite a few kerkers and k&n filter combo's on over the years and i have never seen one that you don't have to rejet for i would also lower the clip on the needle at least one notch maybe two from stock as well.