Look what my neighbor gave me (not a KZ)......

DiamondSkyBlue1000 wrote: I had one of those Yams when I was a kid, my first street legal bike. Seeing that brings back alot of good memories. Man, I could go anywhere on that thing!

Do you have any idea what they cost when new? Just curious if there is anything comparable being sold today.

I ride with a guy that has a '78 KZ650, he is about 20 yrs older than me. I called him yesterday when I got the bikes over to my house. He came right over and was talkng about having those same bikes when he was a kid too. He sat on them and had a grin ear to ear. He talked about riding on the beach with his. Sounds really fun! I gotta get 'em going!

I was just doing some searching and found some threads about law mowers and golf carts having the same spark plug issue.

Spark when out of the engine and no spark when in and under compression. Change the plug and all is good. Hopefully it ends up being that simple!

Very cool, I love messing around with these little old bikes makes a nice break from serious wrenching on the Z's. You can do anything to/with them :laugh:
Ke 100 Before:

After:


F11 250 Before:

After:


Good luck with them and have fun!

Still messing with the Yamaha no spark with plug in engine issue.

Put in new plug, same result, spark when not in hole, no spark when in hole.

Put on a known good coil I had, (Yamaha, same # coil) same result.

Tried putting old plug in the hole and the new plug attached to the coil and grounded to the head thinking maybe the problem will repeat with a load on the starter (compression). Same result.

Tried powering the coil straight off the battery...same result.

Tried running a new ground wire from the battery neg. to the engine....same result.

Tried bypassing the key switch thinking maybe loosing power there....same result.

So I decided to check the timing, was way late and gap a touch to small, regapped point to .014 and set timing.

I'm using the timing light to know if I am getting spark or not with plug in engine. Somewhere during all this I noticed I would get a flicker here and there with plug in engine.

After resetting the point gap and timing it started to flicker more and more. Now every time I crank it, it seems to be getting a little better.

I also noticed a little sparking inside the dynamo behind the point plate. So now I'm betting the magnets and pickups are dirty and the more I crank it the better it gets. The rotating is cleaning itself I'm thinking. I might just have to pull it all apart and check it out. There was water in this section of the motor when I pulled the side cover off. Bike has been outside laying on its left side for 10+ years with water in it. I sprayed some of that electro cleaner in there thru gaps in the timing plate but thats only going to do so much.

This is a pic of what I am up against.....anyone ever had one of these apart?



I just messed with it a little more....sprayed some more electro cleaner thru the gaps and onto the brushes....started sparking really well....even started for a second. But now nothing again.

Looks like I'm going to start tearing into it....hopefully I can get it back together!

Perhaps a tenuous connection between the spark plug cap and plug wire is conducting when the plug isn't installed, but isn't conducting when the plug is installed.
Could check the attachment of cap to wire, and possibly snip off a bit of the wire to allow a better connection to the cap.

Also possible that the old plug wire is shorting against the head when attached to the installed spark plug, but not shorting when the uninstalled plug is being held against the head.

Just guessing.

Good Fortune!

How is the plug wire attached to the ignition coil?
Thinking maybe it pulls away form the coil when the wire is connected to the installed plug.

A new plug wire might resolve the issue.

Good Fortune!

Patton wrote: How is the plug wire attached to the ignition coil?
Thinking maybe it pulls away form the coil when the wire is connected to the installed plug.

A new plug wire might resolve the issue.

Good Fortune!

The plug wire slides into the coil then has a kinda jam nut thing but rubber. The few old Yamahas I have worked on had the same style coil.

Its not the coil or wire, I tried a known good unit and same result. Its in the dynamo but it seems to be much better now. Its getting a good spark with the plug in the head now.

I will probably still take the unit apart and clean it out...I'm betting those pickups/sensors...whatever they're called are dirty/corroded. I've had to do that on boat motors that had been sitting for years, a little steel wool fixes it right up.

I did actually get it to run just now, but only for a couple seconds at a time. And only after a little shot of starting fluid, which I do not like doing so I only did it a few times. I went thru the carb but I think I set the float level too low so there isnt enough fuel in the bowl. I'll pull it back off tomorrow and adjust it and see if it makes a difference. I need to get a larger clear hose to fit the dain plug on it, much larger than on our KZ carbs.

So it seems like I'm getting close to the Yamaha running now. For the Suzuki I think its going to take a new coil.

I got a NOS coil for the Suzuki on the way.

The Yamaha is put to the side for now. I did get a good spark and its running now but...it runs at wide open even with the carb slide/throttle closed.

It takes a shot of starter fluid to get it to fire (choke/start plunger on) and then it runs rough ans sputters while it climbs up until about 5K and then it takes off like a rocket. It will rev right thru redline almost instantly! I have to hit the kill switch to stop or push in the choke/start plunger to kill it. I can even hold my hand over the carb throat and it will still run wide open like that!

I have been thru the carb 4 times and made sure every passage is completely clear.

I've done some searching and found that an air leak can cause this. Crank seals being very common on these bikes. They go bad and suck in air and or crank oil and make it run super lean causing it to race for the moon. I do have oil dripping from behind the dynamo/flywheel after running it. It drips out from inside right under the timing mark plate in the pic I posted.

I read the gasket at the bottom of the jug where it seals to the crankcase can also cause reving out of control if it sucks air. I probably need to do a leak down test and see exactly where all its leaking from.

So looks like I will eventually be pulling the jug to replace the bottom and head gaskets. The crank seals can be replaced without splitting the case so thats good.

I'll post when I get the Suzuki coil and, fingers crossed, have it running!

I will be watching, I have a 1974 DT 125 that needs crank seals too! Has been sitting for a few years but this is reviving my interest in it!
Wayne

kzz1king wrote: I will be watching, I have a 1974 DT 125 that needs crank seals too! Has been sitting for a few years but this is reviving my interest in it!
Wayne

Was yours doing the same thing? Reving out of control like that? I dont exactly understand how oil can get in thru the crank seals and make it into the combustion chamber? But from what I have read it does happen.

I'm kinda figuring its more likely the bottom cylinder gasket causing the runaway from sucking air in. But its not going to hurt to change my crank seals along with it. Heck....I could just change the cylinder gasket first and see what happens.

I dont know if I am going to be working on this right away but I will put my results here when I do it. But it really wouldnt take much time to pull the cylinder so I may go ahead and do that sooner than later. Then I could take a look at the rings and cylinder walls and see if it worth going further. I dont know the history of this bike so there is no telling.

No, mine would only run if sprayed in the cylinder or carb. It leaks so much there is no draw on the carb. At least I think it is crank seals.
Wayne

Did you replace the capacitor (condensor) with a new one? Over time those things will develop internal problems, often a short, and will short the spark energy to ground when the points open rather than reinforce it as it's supposed to do.

Bad points that don't make good contact cause their own set of problems...