TOPIC:

There is a tl'dr version at the end.

I picked this bike up about a year ago from the (third?) owner as a project, who had been riding said bike the previous summer but left it sitting for a while. The bike, at the time, was stock with the exception of pods. I got the bike home and cleaned the carbs, got a new battery, and after kicking it over for at least half an hour finally got it started. At this time it ran okay, though it smoked which I assumed was due to all the dirt and grime on the head. It also had a hanging and increasing idle problem, which I will explain later.

After measuring the compression of the bike, I found that it was quite low and after throwing a spoonful of oil into the spark plug sockets and trying again deduced that it was the piston rings. So I pulled the engine apart with a mechanic as a mentor and replaced the rings. He took it upon himself to call in a favor with a buddy who has a machine shop and got the valves ground, so he re-lapped them and we put everything back together (there was a few month time gap here due to us both being busy and on completely different schedules). During this time, I also rebuilt the carbs with carb rebuild kits from PartsNMore (I live in Canada, and their prices are very reasonable).

About a month to a month and a half ago I put the motor back in the bike, spent another 40 minutes trying to start it and bam, it started. BUT, it had almost zero power, along with the hanging idle problem. At idle, after letting it run for a few minutes and on about 3/4 choke, revving it up (eventually to 300-4000 rpm) and letting out the clutch would just cause it to stall trying to head back up the driveway into the shop (though the driveway has a slight grade to it, it wouldn't by any stretch of the imagination qualify as a steep one). I also noticed while the bike was sitting that one carb was overflowing so I pulled the carbs apart, measured the float height which was fine, and gave them a brief clean which seemed to solve the problem then.

At this point I started cruising forums and saw it mentioned that incorrect valve clearance could cause a lack of power, so I took apart the cylinder head and measured the valve clearances, ordered new shims, and installed them. I also ordered a Dyna S ignition system with 3 ohm coils along with the ignition system which I then installed with the shims and adjusted the timing. When I measured the clearances, they were way off. I triple checked my math, and it was right, so somehow I must have measured the clearances on an angle and got incorrect readings. I figured I would try to start it anyway and see what happens (probably because I was pissed off at the time, not entirely sure).

Of course, it wouldn't start. With ether I could get slight ignition, but no catching. I pulled the valve cover off again and put the old shims back in, and rebuilt the petcock, removing the small screen which was gunked to shit and clogging everything, and replacing and lubricating the O rings. I also noticed when removing and draining the carbs that two carbs weren't even filled which I found weird, so I pulled the carbs apart, blew out every passage with compressed air, then cleaned it with carb cleaner and blew it out again.

Yesterday I put everything back together and tried to start it up which ended up being a no go (no surprise). It would start and hold a brief idle using quick start (ether) but wouldn't stay started, or start at all without it.

So now I'm here, asking what to do next. There are probably a few things I forgot to add here that I've done as well. Any reply would be appreciated.

tl'dr Bike won't start, the following is a timeline of stuff done to it

- Came stock except has pods, no breather filter though
- Cleaned carbs and it started, but had hanging & increasing idle problem (carb flooding maybe)
- Low compression, determined it was rings. Put new rings in, ground and re-lapped valves, and put everything together again with new gaskets, and rebuilt carbs.
- Got it back and started, had no power and very rough idle (though could have just been choke. I couldn't idle it without the choke.).
- Put Dyna S in and 3 ohm dyna coils (7mm supression plug wires), rebuilt petcock.
- Carbs were flooding, so measured float height which was fine and cleaned carbs, seemed to have solved problem.
- Figured lack of power could be valve clearances, so measured, calculated, and ordered new shims.
- Put shims in, re-measured clearances, and got wrong measurements. Figured I measured at an angle one of the two times and was completely off.
- Tried to start the bike anyway (because I'm stupid) and didn't start
- Put old shims back in, bike wouldn't start. Noticed that the outermost carbs weren't getting gas, so blew every passage out of carbs, cleaned with carb cleaner, and blew passages out again.
- Will start briefly with ether, but won't even catch without it.

If you got all the way to here, I commend you. Any insight anyone can offer would be much appreciated. Thanks! (also didnt proofread this so there are probably a lot of errors, but it's late. And I work tomorrow.)

If when you bought it the bike ran ok but smoked and had hanging idle, and now it doesn't run, you have created problems where they did not previously exist. Please consider this - if the changes you made were needed, and if those needed changes were done properly, each change should have improved the way the engine ran instead of making it run worse.

You have introduced so many variables that diagnosing the problems may prove difficult. You have changed rings (without properly determining if they were bad - the spoonful of oil will raise compression in every engine because is displaces air and cannot be compressed), ground valves (what does that mean and why), replaced the ignition system, fiddled with valve shims, rebuilt the petcock (??? there's nothing in a '77 KZ650 petcock to rebuild); rebuilt the carbs (why - the metal parts don't wear out and unlike the original Mikuni parts rebuild kits often have crappy parts); etc. and now the engine doesn't run. The bike has pods, but you don't mention any rejetting attempts. The idle was hanging when the engine ran, but you don't mention testing the carb holders for leaks. Your compression was low, but you don't mention performing a leakdown test to isolate the problem.

KZ650 engines are extremely tough, but any engine can be made not to run. Not trying to bust your chops, but it really sounds like you made changes all over the place in a shotgun approach rather than diagnosing and correcting problems in a logical fashion and ensuring that each step improved the engine's performance. I believe your best bet at this point is to take it to a professional mechanic and have him sort it out. Ed

I agree there are a lot of variables here. I will try to prioritize them.

Correct valve clearances are vital to these engines. Make sure you're not confusing standard and metric measurement. the shims are labeled in decimal millimeters but your feeler gauges may be dimensioned in thousandths of an inch.

Did this mechanic also hone the cylinders when he replaced the rings? If not, it will drastically reduce the wear life on the bore and the rings.

By re ground I hope you mean he lapped the valves in.

Hanging and hunting idle is indicative of a lean condition either from air leak, under jetting or poorly adjusted idle air screw. If these are cv carbs, they will not enjoy pod filters and unless you're an experienced mechanic and tuner (which I assume you are not) you had best find a stock air box.

Most of the time the pilot jets are clogged. I use a guitar string the clear them. One thing at a time then move on.
Steve
kzrider.com/forum/11-projects/598262-kz-...-will-it-live#672882

650ed wrote: If when you bought it the bike ran ok but smoked and had hanging idle, and now it doesn't run, you have created problems where they did not previously exist. Please consider this - if the changes you made were needed, and if those needed changes were done properly, each change should have improved the way the engine ran instead of making it run worse.

You have introduced so many variables that diagnosing the problems may prove difficult. You have changed rings (without properly determining if they were bad - the spoonful of oil will raise compression in every engine because is displaces air and cannot be compressed), ground valves (what does that mean and why), replaced the ignition system, fiddled with valve shims, rebuilt the petcock (??? there's nothing in a '77 KZ650 petcock to rebuild); rebuilt the carbs (why - the metal parts don't wear out and unlike the original Mikuni parts rebuild kits often have crappy parts); etc. and now the engine doesn't run. The bike has pods, but you don't mention any rejetting attempts. The idle was hanging when the engine ran, but you don't mention testing the carb holders for leaks. Your compression was low, but you don't mention performing a leakdown test to isolate the problem.

KZ650 engines are extremely tough, but any engine can be made not to run. Not trying to bust your chops, but it really sounds like you made changes all over the place in a shotgun approach rather than diagnosing and correcting problems in a logical fashion and ensuring that each step improved the engine's performance. I believe your best bet at this point is to take it to a professional mechanic and have him sort it out. Ed

New rings and doing the valves improved compression to spec, and one cylinder had a broken ring. Cylinder was rehoned.

By valve grinding I assume he meant correcting the seat angle and using coarse compound in addition to fine? but honestly he did it without telling me, so thats what I got from it anyway. Honestly the majority of the decisions including the rings were after inspection by him and he decided to go forward.

Rebuilding was the wrong term. I took apart the petcock, fixed one constriction which was the clogged filter and gunked up pathways and Then put it back together. Blowing through the petcock a large difference in air flow was noticed.

Tested the carb holders for leaks to no avail. Ether and carb cleaner around the boots produced no change in idle.

No rejetting attempts but that would have been a better solution at an earlier point. Plugs seem to be reading as rich ( black carbon deposits ) to my understanding, but could be from excess idling?

With all due respect, im aware that the changes I made could have and probably did cause problems, but Im not going to pay money to someone to fix my fuck up if I can do it myself, regardless of how long it takes.

Ill try to find a stock airbox somewhere as a starting point to fix all this. In addition Ill measure clearances again a couple times to see if I can get a definitive measurement.

1) Install stock airbox and verify the jet numbers match those from the factory Kawasaki service manual (not some aftermarket manual like a Clymer/Haynes).

2) Make sure the carbs are CLEAN. This involves a lot more than just changing jets. All passages need to be verified as clear including the pilot and choke circuits.

3) Adjust the valves properly and verify proper clearances.

4) Check petcock function and make sure the tank is clean.

5) Verify proper spark.

Until you do all these things I wouldn't even bother trying to start the bike again. Work up from the bottom through proper maintenance and then troubleshoot afterwards, as necessary (although you most likely won't have to).

Also, 3 ohm coils will kill your battery. They're a marketing ploy, like organic or gluten free. The only way to run 3 ohm coils and not overwhelm the charging system is to run resistor caps on the plugs which nets the same end result as running 5 ohm coils.

That depends on the charging system. I have Dyna 3 OHM coils and a Dyna S. Yeah they take more power and I have a good dependable HOT spark. Went HID and LED's to make up for the increase in draw. Running lights and marker's too.
Steve

Well I'm talking with stock lights etc. My built Honda 750 has dyna s ignition and stock 5 ohm coils and it sparks just fine. Never found a real reason to go to 3 ohm coils, they don't have any effect on power, and if your motor isn't running reliably, I doubt stock resistance ignition coils are the problem.

The old Honda's have a different kind of coils. They produce a "fatter" spark.
Mine runs reliably and the 3 OHM do produce a hotter spark. I'm also running VM 33's so I need all the spark I can get to burn all that juice.
Steve