KZ650 VM24 - Carb not spraying fuel?

My friend gave me a KZ650 and I have been tinkering with it for quite a while trying to get it running. It has a VM24 carb, we replaced the battery, plugs, put on a dyna ignition and bought a carb from a junkyard off of a "running bike" supposedly.

We keep turning it over, and it backfires and fires occasionally, it has good spark, but it won't start. I'll turn it over for 30 seconds or so, and the plugs don't smell like gas.

We either hooked up the carb wrong or the carb is bad. We put the carb on last fall and let it sit since then. Is there some magic screw or vacuum line that we should check? We know it is getting some fuel because of the backfires. Also, the airbox is sitting slightly off the carbs if that makes a huge difference.

Thanks so much for your help! I'm dying to get this bike running!

You did a lot of stuff and something other than the carbs could be the issue. First check compression. If you have no compression, you will not get the bike to start. Then, check the ignition. The rotor on the mechanical ignition advance can go on two ways and if you put it on backwards, the black and green ignition wires reverse function and the bike will NEVER start... only sit there and chug and backfire... which sounds like your bike. Recheck the install instructions. Last, open a drain screw on one of the carbs and see if there is fuel in the bowl. Carbs DO NOT spit gas... engine vacuum draws gas from them via the carb venturi. If the carbs are dry, they won't have gas to be drawn through. You can sort of "test" the carbs by giving the combustion chambers a shot of starter fluid... be careful, it is flamable. If the bike starts briefly on starting fluid, the carbs might be suspect.

Thanks WG, we spent ~6 hours on it yesterday.(i'm sure you could have fixed it in 10 mintutes)

UPDATE
There was a vacuum line that wasn't hooked up on the carbs that was keeping the fuel from being sucked down. We ran a vacuum line from the ports that sit on 2&4. I have no idea if that is how it is suppsoed to be hooked up, but it sucked fuel down out of the tank much better now. Is that wrong?

There was a wiring problem that was causing very weak spark (it was okay sometimes), so we ran a new wire from the battery to the +12v souce to the coils and it sparked MUCH better.

It is running on two cylinder right now (1&4). 2 & 3 are sparking good, but they aren't getting fuel or there is a stuck valve. it's running though (on 2). Let me know if you have any ideas why it wont run on 2&3... but it should be pretty straightforward to troubleshoot.

We cleaned bottom half of the carbs twice, cylinder #4 keeps overflowing. maybe it just needs to be rebuilt a third time? Our biggest concern is why it isn't running on 4 cylinders...

Thanks again for the help WG (and anyone else reading this).

I should mention that I put 5w30 in it after I got it running because that's all I had. Let me know if I need 10w40.

Post edited by: Cyphear2, at: 2007/06/17 16:20

#1 Get a manual and learn how your engine is suppose to operate.
#2 The engine does not get fuel by vacumn. It gets fuel by gravity flow thru a valve that is, most likely, actuated by vacumn.

Cyphear2 wrote:

...running on two cylinder right now (1&4). 2 & 3 are sparking good, but they aren't getting fuel or there is a stuck valve. it's running though (on 2). Let me know if you have any ideas why it wont run on 2&3...cylinder #4 keeps overflowing...put 5w30 in....

#4 overflow might be caused by float needle not fully closing against seat because of crud in seat orifice. Or possibly a hairline crack in overflow tube.

Lack of fuel reaching cyl 2/3 might be obstruction in pilot circuit.

What was result of the starter fluid test earlier suggested?

5W30 is a little light. When get it running, would change to 10w40 or 20w50.

Am not very familar with 650's but believe there may be a shop manual available somewhere on this site.

did you run a compression check as ststed before?

also did you set the float level?

how did you check the timing after you put the dyna on?