1973 Z1 Maui

wrote:

In the photo, piece 62 is listed as overflow clamp. It’s a rubber bungee with a round end and an oblong end. Does anyone know how it mounts? The parts book doesn’t really illustrate it location. 
 

On the KZ650, one end of the rubber bungee goes around the negative (-) wire from the battery to the engine, and the 4 overflow tubes from the carbs route through the other end of the bungee.

Initially, the engine started right up…..on 1-4, that’s when I found that the 2-3 points were bad. I fixed that and was able to determine all 4 wires got spark and cranked with plugs out using a timing light to see that spark timing was right. From then I started to get my short starts and stall with the engine itself being difficult to turn over with the kick starter or the 17mm nut at the points. After carefully coaxing it with the wrench the motor would free up and turn with the wrench, kick starter or electric starter A restart attempt resulted in firing right up but stalling. It’s hard to duplicate the condition without starting it.
what I think is happening is I did something wrong at assembly and something in the drive train before the transmission ( in neutral this whole time) is shifting and binding. There is no noise or weird sound.
I removed the exhaust, valve cover and oil pan and oil pump. Did not find anything, no metal or foreign material.
my plan is to continue checking, something must have left a mark in all of this. 

I will check (until I find something)
valve timing
remove the clutch
ill remove the cams and check the valves and tappets
remove the kick starter
check electric start clutch equipment
if necessary:
Remove the head
remove cylinders
remove engine to split the cases and look at the primary drive train

somewhere along the way I hope I find something that looks like a wear point. 
This is a mystery, it did not do this when I ran it before tear down so it’s likely something I’ve missed upon assembly.

 

I once had to tear down the engine and split the cases five times before I found a problem that occurred at startup.  But I eventually found it.  I only point this out to emphasize that patience is a virtue!

So you know that the bike starts and runs.  That likely means spark and carburetion are OK.  You also know the oil pump is providing pressure.

Some things I would check before pulling the head off.

Timing - are the cams set properly?
Oil getting into the head?  For kicks and giggles you can leave the valve cover off and crank the engine.  Be ready for a little mess though.
Cam chain tensioner on the back of the cylinders - I once had it slip off the chain on startup.  No idea how it happened but it screwed up timing and I bent two valves.
Cam chain running through the top idler correctly
Cam bearing caps properly torqued to about 75 to 90 INCH pounds?  (Note that the book has an incorrect torque spec)
Are the cam bearings all in place?
Are the cam bearing caps in their correct positions?  (They are numbered and must go back to their original position)
Valve clearances correct
Cam chain correctly mounted on the crank sprocket
Tach drive gear set into the exhaust cam correctly.

Edited to add that most of these are things that come to mind when I ask myself why the engine would be "tight" after turning over a few times.  

 

I am curious to know why you think there might be a problem in the clutch?  If it is in neutral and stays there without dropping into gear I wouldn't be too concerned about that.  Without being able to hear what is going on this is a tough one.  I can only assume if this was my bike I would try to check compression to see what it is across the board if you can.  Running for a few seconds and stalling points to a fuel supply issue many times.  Just thinking out loud, if something is physically dragging on the engine to cause it to stall after a few seconds it might be related to piston clearance or a lubrication issue.  The clue I am using there is that the engine is difficult to turn over after running for a bit, but gets easier after a cool down.  A bore scope would be great to look into the cylinders with at this point.   In any event MauiZ1 you have a mystery on your hands that will take some effort on your part to sort out.  From past accounts it is not unusual to have valve timing issues with a new build crop up and result in many problems.  Good luck with this!!
Rick H.

 

After carefully coaxing it with the wrench the motor would free up and turn with the wrench, kick starter or electric starter A restart attempt resulted in firing right up but stalling. It’s hard to duplicate the condition without starting it.
What I think is happening is I did something wrong at assembly and something in the drive train before the transmission.

Something is wrong.
You have to find what is wrong and fix it.
We can only guess.
Check the cam tensioner plunger moves freely when bolt is loosened.
The plunger and housing can rust and the plunger can stick, have seen this with CB750 and Z1.

I once had to tear down the engine and split the cases five times before I found a problem that occurred at startup.  But I eventually found it.  I only point this out to emphasize that patience is a virtue!

Patience is more then a virtue.
You have to have it to work on old bikes, things will go wrong, it takes time to find them, without patience the result is anger and misery.
When I assemble engines every part has to be perfect.
All sorts of things have gone wrong in the past, I do everything I can to get it right the first time, I few bikes have come back to life with minimal problems, lots more fun, I know things can still go wrong.
 

Hi Maui
with regards the electrical circuit for the starter, the fault finding guide I posted in "FAQ" goes into detail ref checking the starter circuit. However what you are describing appears to be a mechanical issue. There are a couple of things I would suggest (only my opinion) when rotating manually ensure the plugs are removed ( you will get a better feel for what is happening if you are not trying to overcome compression)

1. When it tightens, if you rotate backwards does in loosen straight away (if you are coming up against a mechanical lock such as valve timing issues, backing it away from the interference should allow it loosen immediately)
2. I have had similar issues with a "spun" crank bearing. I know your Z has roller crank bearings but I believe the "cam bearings"are shells. What can happen is the cam picks up on the bearing and rotates the bearing in the head. Because the bearing has a locating lug when it is out of place there is extra bearing material between the cam and the head causing the tightness. In this instance normally rotating the crank backwards will loosen things, if you continue to rotate backwards approx half a turn the pistons etc will be well away from valves. If you now rotate forwards again and things begin to tighten it would be worth checking that one of the cam bearing shells hasn't rotated in the head (bear in mind a cam locking with the engine running could break the timing chain)

Be lucky 

wrote:

 A little careful turning with the 17mm nut by the points and it loosens up. find.

Be VERY gentle turning the motor over with the nut at the advancer!  That nut loads the timing pin that's pressed into the end of the crank.  It's fairly easy to snap it off using the advancer nut.  Pull all the plugs so you're not working against compression.  We almost always use the kick start lever to turn the motor forward, and the rear wheel with 2nd. gear engaged to turn it backward.

May be a long shot, but check the dyno rotor for a loose magnet leaving a mark on the inside of the dyno hoop.  May be centrifugal force moving a magnet.

Good Ridin'
slmjim & Z1BEBE

I second slmjim's advice.  I know from experience!

It pains me to report that my problem is a spun cam bearing. I’ve removed the head to check everything and now I need to try and figure out why the bearing spun. Good news is there appears to be no other damage. I’m going to get two
new head gaskets  and base gaskets so I can assemble the head and do some flow checks before any valve gear goes in. The parts were very clean and blown out so I’m not sure what I’ll find.
my oil pump raises pressure very quickly so the problem is above the pump. 
good thing I’m not in a hurry.

Hi Maui
that is unfortunate as this isn't a common fault (I've been working on cars and bikes for over 40 years and have only seen it once with a TL1000 crank bearing!) but on the up side it would have cost a lot more to do a full engine strip and possibly not find anything conclusive. Possible causes are

1. you where unlucky and got a faulty bearing with a poorly formed lug or the bearings are not the correct ones for your engine 
2. there is no oil getting to the head
3. there was oil on the back of the bearing (should be dry)
4. the cam was rotated before the caps were fully torqued down
5. the assembly oil had drained out of the bearing so the cam was dry on the bearing (how long was it between build and first start up)
6. the assembly lubricant was too thick and stopped the cam from seating correctly

Good hunting 
 

I’m pretty sure I had insufficient oil delivery upon closer inspection. I’ll be taking the cylinders off and doing a lot of checking to figure out why. The cam is toast but I have another hollow cam. Lots of checking to do now.
 

That’s messy, don’t forget when the bearing spun it would have blocked the oil supply to that bearing (the hole in the bearing would be out of line) is it only the spun bearing that has burned up ?
still worth checking all possibilities