Won't start and backfiring through exhaust and carbs

I have tried searching for this but couldn't find anything that helped.

I have a 1978 KZ650C that I just put new intake valves in and now am having this problem. This bike has been sitting for like 6 months since I tore it down. I got her all together this morning and charged the battery and it won't start. I kick it a few times and it'll either backfire through a carb or exhaust. I have checked the coils and they are wired right. I've checked cam timing and it is correct. I've checked plugs and it has a blue spark... it's kinda skinny ( don't know if that matters ) and they are splitfire plugs. This is really killing me because I've waited all this time to get it running and now it won't start Any help is greatly appreciated.

Thank you,
Jordan

Still sounds like your cam timing is off. There used to be stories of having the cams 180 degrees off. Don't quote me on this, it's not my idea, but you notice it takes 2 complete revolutions of the crank to equal 1 rotation of the cam. So when you have your 1-4 timing marks aligned, you can turn the crank 1 complete revolution and the cams have turned 180 degrees. Guys have told me they then unbolted the cams and realigned them positioned with the marks from that point and the engine ran essentially turning the cams 180 degrees. Now this never made any logical sense to me, but it was a story I've heard more than once.

Sounds like something I will have to try. Thank you.

I had a post before though where someone posted a picture of the timing for my bike. I'm supposed to line up the t on the timing advancer then like the exhaust cam level with the head and count back and the intake goes between teeth 35 and 36. I did that and the lobes face opposite of each other.. I don't know if thats how it's supposed to be. Atleast I'm not bending valves like I was lol.

I will try what you said tomorrow and I'll check the timing again. It does seem to have nice compression though.

if you put the cams in exactly 180 off, cant you just switch the coil wires from the 1/4 coil to the 2/3 coil and essentially put it back in time?

Seems to me that having a cam 180 degrees out would immediately mean bent valves.

KZCSI

sounds like the coils and or wires are backwards, if the cams are that far off you will bend valves and have no compression, check the coil wiring and also run a compression check, also did you recheck the valve clearance

I'm with Ron, 180 degrees out don't make sense to me either. If the cams were 180 degrees out and you rotated the engine one revolution then the cams would be in time.

Post edited by: steell, at: 2008/02/15 08:25

I went out there and looked at the timing and I'm not sure how to tell if it's right or not. I turned it over once and it was good, turned it over again and it wasn't so I set the cams there. I tried starting it but it still does the same thing except less now. I'm thinking now they're out of time. It still won't start though I've kicked it over atleast 100 times trying to get it to sputter even for a second but nothing. Any more help guys?

If both cams are exactly 180 out relative to the cam sprockets, #4 will be firing instead of #1, but because the ignition is set up to fire both 1 and 4 plugs simultaneously, it will run the same and you won't be able to detect the error. Likewise, 2 and 3 swap firing positions, but would be undetectable. The difference is only relative to the markings on the cam sprockets (which you don't see while running unless you want to spray oil everywhere).

One cam 180 out won't run, but still no bent valves. You won't get much compression since the valve timing will be severly overlapped.

When #1 piston is at TDC at the beginning of the fire stroke, the #1 exhaust cam lobe will point forward, and the #1 intake cam lobe will be pointing backward. In other words, they will both point away from the spark plug (approximately).

(Conversely, when the piston is at TDC at the beginning of the intake stroke they point toward the plug. I'm saying #1 because that's what you use to set the cam timing, but this general rule applies to the other cylinders as well.)

The starter is not strong enough to turn the motor if the valves severly interfere with the pistons (a buddy of mine found this out the hard way). Maybe if it's only off by a tooth and the piston just barely touches the valve, the starter might be able to turn it over.

There are many other things that could be wrong, like using the wrong mounting holes for the cam sprockets. The manual can be wrong on valve timing (I've seen more wrong manuals than correct manuals for the 550's, that'll make you hit something with a ballpeen). The ignition points-cam may be 180 degrees out. The coil primary wires may be swapped. The plug wires can be on the wrong plugs. I'm sure there are more.

Post edited by: loudhvx, at: 2008/02/15 13:49

I got a little progress I think. I was reading through old posts and found one where a guy was having similar problems to mine except he had a 1000. Someone posted a reply telling him to check the timing advancer to make sure it was on properly. My Dyna S does go on backward ( I don't know if stock one can or not ) and I think it was. I flipped it around and now I kick it a few times and it'll make a loud bang out the exhaust instead of a small puff. Maybe now the timing is out? I have to go fix my aunts computer then I'll be back a read anything you guys post then head back out to the garage and try the cam timing along with whatever else you guys may have posted while I'm gone. Thank you all for the help given so far.

I'm just posting this for future reference.

Well, I went out and did some work on the kz. I whipped out the compression gauge and found it like this...

#1 120psi
#2 0 psi
#3 80PSI
#4 120PSI

I also forgot about breaking off on of the studs right by the number 2 cylinder. Do you think it is the head gasket leaking because of the missing stud? and would that also cause the low psi in the #3 cylinder as well? I'm going to run down the the storage unit tomorrow and grab a stud so hopefully I'll be able to get it back together tomorrow.

I was also thinking about putting some gas in the #2 cylinder and turn it over without cams because then it'd shoot gas out of where ever it is leaking air. That should help me narrow things down fairly quickly.