Bike won't start after rebuild

Hi all,

I just finished rebuilding my '79 KZ650, new rings, used head assembly, and gaskets but now I can't get it to start. The engine timing seems to be 180 degrees out of rotation, and I'm getting a backblow through the carbs (backfire, but no explosion). I followed the Clymer manual closely while doing the rebuild. I made sure that the 1 and 4 cylinders were at TCD, installed the cams making sure the "T" marks were pointing to the top surfaces of the cylinder head, and counted the chain pins per the manual. At this point i'm just looking for some advice on what I can do to get it running. Any suggestions?

Is your advancer 180 out by any chance?

It might be, I took it off prior to the rebuild. I thought that after I reinstalled it the bike would run bad until I adjusted the ignition. How would I go about finding that out?

Flip it 180.
I personally detest clymer manuals, get a real one, it's worth it:)

It looks like it can only go on one way, with the wire being at 7 o'clock and the hole in the case matching it. I'll have to take another look at it I guess.

nebx wrote:

It looks like it can only go on one way, with the wire being at 7 o'clock and the hole in the case matching it. I'll have to take another look at it I guess.

I think you can get it 180 out if the coil wires to the points are reversed or if the cam on the crankshaft is reversed.. I believe one set of points fires the 1-4 and the other fires the 2-3 cylinders?

Make sure your valves are adjusted if you haven't already. Some 25 years ago after I had my KZ400 head rebuilt, the damn thing refused to start. Dad said, "Did you adjust the valves?" Duh. Fired right up after that.

Based on your description, it's likely not the valves, but worth a check if everything else seems correct.

Good luck.

nebx; You might verify ignition timing by bringing #1 up to TDC on the compression stroke with the ignition on and the spark plug held against the engine. Remove the other plugs before doing this. I'm guessing you'll find that the plug fires on the exhaust stroke. If so, remove the cam sleeve from the advancer unit and index 180 degrees and your home free. You'll know it's on the compression stroke because the camshaft followers will rotate and the cam lobes will point away from the head. It's also worth measuring compression on all cylinders. My .02 worth. Ride safe, Steve

The only way your advancer could be out 180,is if you took it apart,because yes,they DO only go on one way as a unit.
If you took it apart to clean it,you might have put the lobed section of it back on 180 out.

This doesn't mean that someone ELSE before you,didn't take it apart though.(never assume).

I didn't take it apart though, all I did was pull the contact breaker plate (leaving the pigtail attached) put it in a bag and stored it under the seat until it was time to put the engine back in. I never messed with the timing advancer. And, the timing was fine prior to the rebuild.

EDIT::

I'll have to get the shop manual. Also, since I didn't actually remove the advancer would you guys still suggest rotating it?

No I haven't adjusted the valves yet. I'll read up on how to do it.

Quick idea for what I have done before: swap the coil power wires. Spent a while on that one. I remember saying "the wires automatically lay this way, so it must be right...."

I can testify that it doesn't hurt anything but pride.

If not already done, would assure the plug wires are routed so that one coil fires both outside plugs, and the other coil fires both inside plugs.

Looking under the points cover, the lefthand points or module signals whichever coil is firing both outside plugs, and the righthand points or module signals the other coil firing both inside plugs.

Good Luck!