Snapped Crank !

Yes have manual and have it popping but unable to get running ! now the working week is here again.

We seem to have lost a couple of posts here, probably when KZQ was repairing the site. So the following is a repeat of what I had originally posted

If you time the pulse coil housing at the "T" mark when the crankshaft is at the "T" mark lined up with the half joint of the crankcase, that will set your basic timing +- 2-3 degrees from where it needs to be and that should get you running.

You can confirm the crankshaft  "T" mark at the half joint is top dead center #1 and #6 by pulling out the sparkplug of #6 and then placing a screwdriver down in the cylinder and feel the piston while rotating the crankshaft. the piston should be at top dead center when the crank "T" mark is at the half joint.

(Ideally, this would be done with a dial gauge but not everyone has this type of indicating measuring tools. When you do this check with a dial indicator, you need to mark the rotor at .050" before top dead center and then .050" after top dead center, then split the difference. The reason for doing that is that there's a flat spot at top dead center of anywhere from 3 to 8 degrees where it seems like there's no movement of the piston. This is dependent upon the length of the connecting rod to the stroke of the crank. Basic engine blueprinting)

Just as a side note- The relationship of the "T" marks between the pulser coil and the crankshaft will change with the growth of the primary chain and the growth of the water pump / pulser coil drive chain which will retard the timing. If the pulser coil housing is not periodically checked for proper timing to the crankshaft, then any strobe light checks of the timing which is done at the pulser coil will be falsely indicated. It's a system that I REALLY don't like but understanding this phenomenon is important to getting the correct basic timing. This only relates to the 1979, 1980 and 1981 model years which use the pulser coils in the housing on the back side of the engine.  When they moved the pulser coils to the crankshaft in 1982, the timing check is done through a window looking at the timing mark on the crankshaft, which is a more definitive indication not affected by any chain growth.

So still no fire up of the donor lump , been through the timing dozens of times , walked away a couple of times !!
The best I get is coughing but not all the time , I have all the ingredients but no cake.
Annoying but it will be my victory at some point , maybe

Simon South Wales 11 wrote:

So still no fire up of the donor lump , been through the timing dozens of times , walked away a couple of times !!
The best I get is coughing but not all the time , I have all the ingredients but no cake.
Annoying but it will be my victory at some point , maybe

When I struggle with a problem like this, I like to pull out my WD40 spray bottle with gasoline in it. The WD40 bottles have o rings in the sprayer that work with hydrocarbon fluids so the o rings don't fail. I use the spray bottle to mist the carburetor throats while cranking to see if the bike will fire. If it still coughs and sputters, then I go after the spark problem. Sometimes it's as stupid as a fresh set of sparkplugs to remedy the issue.

So just a quick update I have discovered the valve timing is out and removing the cover and checking alignments of the timing dots it's out ! T mark on rotor equals dots on exhaust and valve cam not aligning with the mating surface ! 

Simon South Wales 11 wrote:

So just a quick update I have discovered the valve timing is out and removing the cover and checking alignments of the timing dots it's out ! T mark on rotor equals dots on exhaust and valve cam not aligning with the mating surface ! 

If it's out less than 1 tooth on the camshaft sprocket, that would be the stretch in the camshaft chain + the stretch in the secondary drive chain.

If it's out more than 1 tooth, then you have some investigating to do to find out why the camshaft chain got enough slack in it to allow the timing to jump.

Things to check-
Cam chain  tensioning roller - chunks have been known to break off. Remember they are rubber immersed in oil and now 40 years old. It would be on my list of things to replace when acquiring a used bike regardless of the mileage on the bike at the time of purchase.

Cam chain tensioner- Known to have a weak locking mechanism on the spring loaded plunger. There are 3 possible fixes. Replace with a ZX11 tensioner, or replace with a manually adjusted tensioner, or modify the stock tensioner to fit a locking bolt on the end of the tensioner. You can find info on all of these using the search tab and setting the time span to "any date"

Last but not least, once you have the timing corrected, you need to do either a leakdown test (preferred) or a compression test to determine if you bent a valve. These are interference engines and skipping a tooth on the camshaft usually bends a  valve(s).

Keep us in the loop and I hope all turns out well.

KB