78 KZ650 missing on idle

I picked up my KZ650 last week for a very decent price. The motor ran strong and all it needed was some tlc. Well I started to hear a slight tapping/knocking sound at idle. After reading the shop manual I decided the cam chain tension needed adjusting. I adjusted it and voila noise goes away. Out on my test ride the bike performs terribly, slow accel, popping hesitation. Then about 10 mins in it smooths out and rides like a dream, then it popped some more but not as baddly then smoothed out. Really got on her and was IMPRESSED with the accel. So I decided my tension may have been a tad off. Readjusted and was super confident. Took it out and it was HORRIBLE. Popping, almost dying. If I accellerated slowly it would do ok, but if I really hit it boom, bogged down, I mean crawling and popping all over. Then about ten minutes in again (could this be the warmup time she needs) it smoothed out. Running like a champ! Accel was enough to push me back in the saddle, and it was a thrill to ride. Well I park it, and now its missing on idle. Maybe every 5-10 seconds or so. Other than that the idle sounds good. Even tone no knocking or noise other than the missing. Any ideas? I am pretty new to motorcycles (this is my first) but am a helicopter engine mechanic and am very competent/confident in wrenching, just looking for a little guidance from the more seasoned bike guys.

Some idea's:

1.Fresh, properly gapped sparkplugs.

2.Replace the sparkplug caps(they unscrew from the sparkplug wires/high tension leads).Contact www.z1enterprises.com for new caps.

3.Try running either Seafoam or Berryman's B-12 in the gas. Both are sold at Wal-Mart in the U.S. Seafoam can also be bought at most boating supply stores.

4.After removing the sparkplug caps, cut about 1/4" off and screw the new caps on.

5.Check the mechanical ignition advancer for proper operation. It's behind a CD sized cover on usually the right side of the engine. Give it a twist and see if it returns to where it was. If it sticks, remove,clean and relubricate it with some light oil like 3-in-one or sewing machine oil.

You say you adjusted the tensioner... I take it this is a manual model.

They are required to be adjusted with the engine in the TDC position.
Turned in only hand tight, then turned back about 1/8th turn, then locked in place.

The berrymans/seafoam is good advise and can help to eliminate alot of junk in the carbs. Helps things run nice and smooth.

GL!

Don't forget your coils are 32 years old...... whenever I hear of an intermittent miss, that's what I think of.

Thanks for the prompt response all. I am currently running a fuel system cleaner through (this is the first tank of gas since purchase) not sure of the brand, picked it up at walmart, will check tomorrow. I am about 50 miles in on this tank, so still quite a bit yet left till she's all the way through. Both spark caps and coils sound plausible to me. I checked the number 4 plug while I was changing the oil and it looked great. Good gap and all. Will check the other 3 tomorrow.

Tek. Not sure what you speak of, I did the procedure where you remove the ignition cover and rotate the shaft 2 revolutions and then line the corner by the 2/3 up with the timing mark at 12 oclock. Then loosened the locknut and bolt aft of the case in the center. What procedure are you referring to?

Mfolks, I am guessing you are referring to the ignition cover. Now what am I turning? When tensioning the cam chain I turned the shaft with the 11mm wrench. That did not return to it's original position, but I wasn't under the impression it should since you need to adjust it to line up with the timing mark.

Hi Dave, These bikes are just great when they run right and a bitch when not. The wiring is over thirty years old and the thing I recommend is to clean all the electrical connections on the bike. It may take a few hours , but is is worth the time invested. One of the guys here or on KZ 650.info told about using bent pipe cleaners with chrome polish to clean the inside of the female bullet connectors. and a piece of Scotch bright or steel wool on the outside. Make sure you have a good fuel filter also. You can spend a lot of time cleaning the carbs, and screw them up soon as you put the petcock on prime. Another asset is a good manual to assist in trouble shooting, maintenance, and repair of your bike. I'm sure you don't tear into a helicopter engine unless you have a manual to assist you. Good luck, Bob