Sensitive Choke

I'm about to my wit's end with my '78 KZ650C2. I had been having problems with the bike idling, so I pulled the carbs and did a very thorough cleaning of all the circuits, with particular attention to the pilot circuit (where I suspected my idle problems were coming from). I soaked the pilot and main jets in carb cleaner, blasted them out with compressed air, the works. They're so clean I'd eat my dinner off of them.

The previous owner of the bike added pod filters and a 4-1 exhaust, and she's running with 110 mains and 17.5 pilots with the needle on the 3rd clip.

Once I finished my obsessive-compulsive run-through of the carbs, I put everything back on the bike, including an in-line fuel filter to keep those jets clean in the future. I topped off my battery's charge and kicked her over (reg/rec is fried, anyone have an old one for sale? ). She roared right to life fully choked, as normal. Once she was nice and warm, I held my breath and began to take her off choke, which is when the problems previously occurred. To my horror, as soon as I moved the choke lever down the tiniest bit, it was like a replay of what was going on before my invasion of the carbs. Idle shot up from a nice steady 1k up to anywhere between 4-6k, and once I passed a certain point, the idle dropped steadily until she finally died. She revs fine choked, but if I try to give any throttle while un-choking, she dies.

My thoughts now are the carb boots. I can see some VERY slight cracking on the outside of the boots, but the insides still look fine. I didn't have any WD-40 on hand to spray on at idle to test this, but they appear to be in decent condition.

Can any of you KZ650 gurus offer any insight to a 21 year old college kid trying to get his first bike resurrected? It's been great to have a project to work on, but I just feel like I'm banging my head against a wall with this one!

jehymel wrote:

Can any of you KZ650 gurus offer any insight to a 21 year old college kid trying to get his first bike resurrected? It's been great to have a project to work on, but I just feel like I'm banging my head against a wall with this one!

I feel the same way :S

When i first got my 650, the exact same thing happened until I cleaned the carbs at least another 2 or 3 times. Chances are that even though you think your carbs are clean, they probably aren't. Could be something else, but i say carbs. The third time i cleaned my carbs, i found some crud hiding in some very hard to clean/see places. Also, check your ignition points/condensers if you still run the original setup. Good luck.

Pods :laugh:

I know! Believe me, I would rather have the stock airbox setup, but the pods were on there when I bought the bike. I've been keeping an eye out on Ebay for a stock box, but haven't come across anything that looks like it's worth buying yet.

That being said, a quick search turned up a few on Ebay from early 80's KZs, would these be compatible with my '78 C2?

edit: Ignition points have been cleaned and set to their proper clearances, so I'm pretty sure that's not the problem

chances are the airboxes from other kz's wont fit. Even though so many parts from these bikes look almost identical, most are only slightly different, but enough to prevent you from being able to use them. Sometimes you get lucky, but i haven't yet. Hold out until you find the right part. Keep checking ebay.

According to Kawasaki.com the air filter assembly, part #11010-1078, fits the following models:

KZ650-C1 (Custom) (1977)
KZ650-C2 (Custom) (1978)
KZ650-C3 (Custom) (1979)
KZ650-D1 (SR) (1978)
KZ650-D1A (SR) (1978)
KZ650-D2 (SR) (1979)
KZ650-E1 (LTD) (1980)
KZ650-F1 (1980)

and air filter assembly, part #11010-1002, fits the following models:

KZ650-B1 (1977)
KZ650-B2 (1978)
KZ650-B2A (1978)
KZ650-B3 (1979)

This seems very strange to my as I thought the "B" series and "C" series would take the same.

Maybe someone else with hands on experience with both models can chime in. Ed

Ed, thanks for that information on the airboxes; now it just looks like it will be even harder to find one that will work.

That being said, I know there are plenty of people that run pods with no problems. Is a super sensitive choke a common problem that comes up with a pod/4-1 setup?

Great news! My problems have been alleviated (for the time being). Yesterday, I got some parts in, so I got to work on the 650 for a while. I did a lot of stuff to the bike, so it's hard to say exactly what my problem was, but I'll share what all I did, in case people are having similar problems.

First of all, my spark plugs were fouled. I found this odd, since I was sure if anything, I was running lean with 4-1 exhaust and pods. A closer look at the plugs showed them less sooty and more oily.

I figured it was as good of a time as any for an oil change, so I started to drain the oil into an old milk jug. I figured it would fill the jug up and maybe a little more, so I brought a 2 liter as well. Milk jug filled, so I plugged the hole and went to drain the rest in the 2 liter, not expecting much more. Well, the two liter filled up as well, and it was still flowing strong! I scrambled to plug the hole, and in my scurry, dropped the drains screw into the bottle. Great. Luckily my roommate heard my pleas for help and brought another two liter out, which filled up almost halfway. Turns out the previous owner had put about 6 liters of oil in her! I guess that explains my fouled plugs then!

I bought some new carb boots off of ebay, so when I removed the carbs to put them on, I figured I'd go ahead and bench synch. Turns out, one carb was wayyyy off, so I'm glad I got that fixed. The carbs went on no problem with the new boots.

I also got my new reg/rec unit from www.oregonmotorcycleparts.com in the mail, so that went on along with a fresh glass mat battery from ebay. Turns out, a reg/rec is pretty worthless, and will destroy a battery's charge when the output voltage to charge the battery is shorted out to ground!

Once everything was all put together, I got her all primed and choked and hit the electric start. What a great sound to hear after days of kicking with the old battery! To my utter joy, she roared right to life!

Now came the most anticipated part of my work, where my problem was occurring before. Once she was warmed up, I slowly backed off the choke. Amazingly, the idle didn't shoot through the roof! Once the idle screw was adjusted, she stayed at a steady 1200, and was very responsive. All my hard work had finally paid off!

Now that everything is in running order, I can finally get to working on the cosmetics. First things first, getting rid of the hideous King/Queen seat!

WOOOHOOOO!!!!

:woohoo: :woohoo: :woohoo:

That's great news. Pat yourself on the back and pour yourself a large glass of your favorite beverage, you've earned it.