TOPIC:

80 kz750 LTD

I was tooling down the road about 60mph and heard a loud snap and the engine stalled. Pulled the clutch and rolled to a stop. I tried starting but the engine wouldn't turn over. I decided to push her home "wasn't far" and had a hard time shifting to neutral, felt stiff. Once I got it home I removed the valve cover and plugs, the cam chain seems loose but what concerns me the most is that I can only turn the engine over with a rachet about one rotation and it stops. Do you think my primary chain broke or cam chain jumped teeth? I'm on a limited cash flow and don't want to tare into something I should just call the junk man for.

drop the oilpan and see if theres timing chain parts laying in there,maybe it jumped time when the chain got loose and bent some valves.

Timing chain? Is the same as the Primary chain. Which is not the Cam chain right? I will pull the pan. If the parts are in there is it a total loss? Can valves be replaced? Or would I be best to find another head?

pull the pan 1st and see whats in there.

Thanks wireman, I'll do that. I could use some of your patients. I'm just completely insane over the fact that my riding season is already over. Thanks for your response I'm sure I'll be posting again!

Post edited by: rm3sweet, at: 2006/07/10 00:45

hows the oil look?

When you say that you heard a loud snap and the engine stalled, are you saying that the motor locked up, in gear, at 60 mph??

Or just that you lost power, like turning the key off?

Since you mentioned nothing about a crash, then I'm guessing that you heard a loud snap, followed by the rear tire giving a brief chirp, then you pulled in the clutch. Is that the way it went?

Timing chain = cam chain.
The 750 fours have a cam chain guide mounted in the top of the cam cover on the inside that pushes down on the cam chain, so when you remove the cover the cam chain appears to be loose.

If you don't have a manual then go HERE and download it.

If you remove the gas tank and the spark plugs you can use a penlight and look down inside the cylinders to see if there are any shiny marks on top of the pistons, or if there is anything in there that should not be.

Post edited by: steell, at: 2006/07/10 01:30

steell,
Thankfully no chirp of the tire or skid. I heard a what sounded like metal breaking and then the engine died. What followed sounded normal....forced compression but no egnition coming from exhaust. This is when I pulled the clutch and coasted to a stop. Will be dropping the oil pan and searching for shiny marks on the piston tomorrow. Haven't been able to remove number 3 sparkplug. Seems cross threaded but I know better because I installed it and was very careful not to do just that. The plug moves but extremely hard, and once out I'm already assuming I'll be installing a hellacoil. Does anyone know if something in the clutch assembly could suddenly break and prevent the engine from turning over even when disengaged? I have a bad feeling in my gut that it is gearbox related not engine but I'm trying not to jump to conclusions and take it one step at a time. Which is what I think wireman would suggest.

You can determine which cylinder pair is preventing the motor from turning over by removing the right side timing cover (the round one) and turning the motor clockwise (from your position on the right side of the bike looking at the motor) with a wrench on the head of the large hex nut behind the small hex bolt head on the end of the crank, and watching the timing marks to see which one is nearing the pointer when it stops.
It will either be 1/4 or 2/3 if it is cylinder/piston related (and I'd almost bet it is), as in dropped/bent valves.

Since you have the cam cover off, look and see if you have lots of clearance between the cam and the bucket on any of the valves.

If it is anything other than piston related (including the valves), then chances are there will either be a bulge or a hole in the case somewhere.

Sounds like you may have dropped a valve in #3 and hammered the spark plug.

I had a motor lock up on me at 70 mph, I have quick reflexes but was still sideways before I could hit the clutch

Post edited by: steell, at: 2006/07/10 03:15

take it from the guy on his second pacemaker,take it apart and do an autopsy before ya get too excited! hahaha

wireman wrote:

take it from the guy on his second pacemaker,take it apart and do an autopsy before ya get too excited! hahaha

Probably not going to be to expensive to fix either way, worst case is ~$250 for another motor.

And wireman you had better quit working those pacemakers to death

I'm at work right now but my head is still in my "head". I don't recall seeing any gap between the lobes and buckets but will inspect closer tonight. Crap it's not even lunch time yet!