kz650 rebuilt motor with mild head work

I am finally done with the bike and am currently trying to start the thing. I milled the head about 25 thous and put gpz cams and slotted and degreed cam sprockets. I also put gpz carbs. It seems like the motor is not getting any gas but has gas in carbs. I forgot to mention the bike is kick start only. Do any of you think in order to get the bike to run i will need to pull start it?

You should certainly not have to pull it. Are you sure the plugs are dry? If so, that's a carburetor problem. Are you dead sure the cams are timed out and the ignition is firing? All valve clearances in spec? Can your timing advancer be 180 out like mine? That makes it REALLY hard to start.....:dry:

Have you installed an airbox or pods yet?

I just finished putting together an old GS550 with my son and initially it was a bitch to start. I hadn't put the airbox back on yet (expected to need to pull the carbs off again so took a shortcut) and the bike didn't want to start. Interestingly, when I placed my hand over the intake of one of the carbs, the bike picked up its gas and started right up. Tried a couple more times and the same thing.

Clearly, with no resistance on the intake there wasn't enough vacuum to draw fuel through the jets. Once the bike started, an increase in RPM seemed to result in enough vacuum to make it work. As an aside, the bike has the same carbs as my old KZ650 used to have.

Just a thought

A little more info on the bike. I have a dyna s ignition with dyna coils ( can i still have it a 180 degrees out of time or no?) I also have new pistons one over and rngs. i do not have any air filters or air box. THe plugs are sparking blue as lightning.

It appeard to me since i put the gpz carbs on the bike and it has no el;ectric starter i am having trouble getting gas to the plugs I have primed the bike and kicked it over for a long tme and gave her plenty of gas but to my suprise no fouled plugs or any sort of look that makes them look like their getting gas.

The carbs are getting fuel checked the bowls it just seems like you said earlier not enough vacume. Thanks for any help that i can get

Little story:

83 GPz750, 170 psi compression in all cylinders, Accel coils, new plugs, etc, but no air filters (bike didn't come with any, bought as a non-runner). The only way that sucker would start was if I laid my forearm across all four carb intakes to manually choke the carbs. Put the stock airbox on it and the problem was fixed.

I had the advantage of electric start, good luck trying to kick start it with no filters

I dont want to use an air box any suggestions? i was planning on using velocity stacks any suggestions just to get the bike going to see if she works. Thanks

odl666 wrote:

I dont want to use an air box any suggestions? i was planning on using velocity stacks any suggestions just to get the bike going to see if she works. Thanks

As known, where the choke is actually an enrichener circuit (as opposed to the old fashion air intake blocker), it's designed for maximum function with the throttle completely closed.

Upon initial crank-up of a cold engine, pull the choke lever fully ON, and don't touch the throttle. This also applies when kick starting.

By the numbers:
Transmission in neutral;
Choke on (lever up);
Ignition ON;
Keep throttle fully closed -- Don't touch it.
Kick start.

If that fails, may resort to this:
Transmission in neutral;
Choke on (lever up);
Ignition ON;
Throttle held wide open;
Squirt some starter fluid in each carb intake;
Close throttle (Don't touch it. Let it stay completely closed);
Kick start.

Whenever seeing anyone furiously working the throttle while attempting to crank a stubborn engine, it's likely some abortive misguided effort to prime or pump some fuel. It doesn't work that way. Neither does "cracking" the throttle just a little, which actually disables the enrichener circuit.

Good Luck!

with dyna s ignitions the rotor can be installed 180 out depending on what set of cylinders you have at top dead center when you install the rotor set it to tdc on number 1 and install the rotor on to the advancer so that the magnet is to the left side that should get you close enough to fire it once it is running then you can set the timing with a light if that is properand it still wont run try switching ether your plug leads 1-4 for 2-3 or switchthe leads coming out of the ignition plate. that should get you going. there is really no other place that ignition can go wrong

steell wrote:

Little story:

83 GPz750, 170 psi compression in all cylinders, Accel coils, new plugs, etc, but no air filters (bike didn't come with any, bought as a non-runner). The only way that sucker would start was if I laid my forearm across all four carb intakes to manually choke the carbs. Put the stock airbox on it and the problem was fixed.

I had the advantage of electric start, good luck trying to kick start it with no filters

Let's see.... he has to get in the saddle and kick it but at the same time use a body part to block the carb intakes.

That would take a REAL man.....

bountyhunter wrote:

steell wrote:

I had the advantage of electric start, good luck trying to kick start it with no filters

Let's see.... he has to get in the saddle and kick it but at the same time use a body part to block the carb intakes.

That would take a REAL man.....

I'm glad someone got it


Velocity stacks huh, on the street? Do a compression check after a year of riding on the street with velocity stacks and see how much compression is left.

I've seen all the filtration studies, and I've read the research, and it all supports my thoughts regarding people that run a motor without air filtration.

Rather than rant I'll just ease on out of here, there are plenty of other folks here to help you.

Thanks for the help every one i'm gonna try and adjust my ignition i think that may be my problem along with the no filter on the carbs. Steel i hear you on the stack I was gonna try rigging up sme sort of thin filter to help with dirt and stuff especially becasue i live in new mexico. Thanks again!

Why would you do all this work then run your engine without filters....IN MEXICO!
you want to do another rebuild 5 months from now dont you.?
Get your self a good air box and at least a set of pods.