Cam timing problem? Air and gas being spit out of carbs

[odl777]

the bike is akz 650 but i also have a gs 750. Anyway the bike has a fresh topend and i am currenlty having problems starting the beast. I was trying to pull start the bike becasue i have it kick only when i put my hand over the carbs and notice my hand was full of gas. I milled the head a month ago or so so i am wondering if i degreed my cams wrong. any help or knowledge is greatly appreciated. Also is the intake valve open at topdeadcenter or does the exaust or does the intake open when piston is at bottom of stroke. thanks

[rphillips]

The intake will open before top center & close after bottom center, on every other revolution of the crank. The ex. will open before bottom center & close after top center on every other revolution. I think there are 2 top center marks on your ign plate, one for cyl 1&3, the other for 2&4. Be sure to set the cams with ign. 1 & 3 mark.

[Steve]

Does your service manual not have instructions for how to set the cam timing?

The marks on a KZ will likely be a bit different, but should be similar in concept to setting cam timing on a GS. With the cams out of the head, rotate the crank a couple of turns while holding the cam chain taut enough to ensure there are no kinks in it. Align the TDC marks on the crank, set the exhaust cam in making sure it's timing mark lines up with th edge of the head. Count the proper number of links from the exhaust cam to the intake cam, install the intake cam. Install the tensioner, rotate the engine carefully to make sure nothing gets closer than it should (valve/piston clearance).

.

[odl777]

I have degreed the cams so in order to do this i had to slot the cam sprockets I am just wondering also if the cam timing is a little off if it would cause the bike to do this. Thanks

[rphillips]

Shouldn't, unless you went way overbotrd with the slots. Shouldn't need more than 1/4" both ways from centerline of orig holes.

[chef1366]

If your cams were this far off you possibly would be tapping valves. You might have the cam chain on the crank 180 degrees off.

[odl777]

could it possibly be valve clearences? The clearences would be too tight if anything right? thanks

[robertbarr]

Check compression. If it's OK, you can't be too far off (if at all) on the cams. At least you'll have some idea.

[mike-s]

At the very least do check cam clearances and the cam timing, if nor no other reason than to rule them out as a cause. The numbnuts who owned my bike before me obviously found this an exceptionally difficult task and the thing managed to burn out one of the exhaust valves as well as have zero clearance on all seven other valves. At $70au each, im fortunate only the one died from abuse

[odl777]

I should have good compression because i have new pistons and rings with fresh bore. It is hard to check compreesion because i think the air is escaping out of the intake ports. I am going to check clearences tomorrow but i thought they would be fine because i chnaged them while the motor was out. i hope valve clearences are my only problem. The intake valve clearence would have to be too tight for my hypothesis to be correct correct?

[jed.only]

im betting your compression will be ****-poor because it sounds like your valve timing is WAY off. your pistons are pushing what would be your compression charge out the intake valves and through your carbs.

[Steve]

It is hard to check compreesion because i think the air is escaping out of the intake ports.

If air is escaping out the intake ports, something is definitely wrong.

Could be as simple as valve adjustment (too tight) or could be cam timing. If valve adjustment doesn't do it, check the timing.
Heck, while you have the valve cover off to check the clearance, check the timing anyway.

.

[Flyboy]

I should have good compression because i have new pistons and rings with fresh bore. It is hard to check compreesion because i think the air is escaping out of the intake ports. I am going to check clearences tomorrow but i thought they would be fine because i chnaged them while the motor was out. i hope valve clearences are my only problem. The intake valve clearence would have to be too tight for my hypothesis to be correct correct?

No, this is the whole reason for the compresion test, the new pistons, rings and bore mean nothing if the compresion is escaping through valves that are not sealing, the test is not to check the bottom end, but whether or no the valves are sealing.

If the clearences are too tight, it will prevent the valve from returning properly onto it's seat, thus leaving a small gap, and no compresion.
If you have air escaping out of the intakes, then this would be a sign of an intake valve that is not seating.
The valve timing would also show up on a compresion test, as the valves are not seating when they should, for instance, if you have air being pumped back through the intake, then the intake valve may be slightly open, when the piston is on it's way up the bore.

Hope this makes sense.

[silverhorse47]

Well a compression test would check rings for sealing, and in a roundabout way it would check for valve timing and also bent or bad valves.
But to check valve sealing specifically you might want to do a leakdown test. That will tell you if a valve, ring or gasket is leaking when it should not be.
Do you have spark? Does your crank appear to have more oil in it than you put in? Have you checked to see if there is a pulse at the muffler as well as the carb?
If this were my problem I would take the valve cover off and check the valve timing and valve clearances. If you are not certain that either are correct, people here will be able to help you. A digital camera for pictures will help.
If all is well with the cam timing and clearances, you should do a leakdown test. There is info on the forum about how to make an inexpensive tool by reaming out a spark plug and attaching a hose to the guts, unless you already have the real deal tool.
Did you turn the engine over by hand before you tried the starter or push start thing? Were there any bad noises?
Good luck.
S.