Hard starting KZ305 and kz400

Both bikes do this on first start of the day.
Crank the engine and get a pop or 2, but woun"t start.
Crank the engine again, engine starts and runs for a second then dies.
Crank again, starts and dies after 2 seconds.
Crank again, starts and dies after 4 second.
Crank again, and maybe can get it to keeps running, without more attempts.
Do not have this problem when bike is restarted after it is warm.
Fuel level checks good with clear tubes.Tried different choke positions. I installed an ignition coil relay and iriditrum plugs on the 305.
What are some tips on getting a bike to start and keep running without going through this dance?

My 305 has almost always acted that way.  Doesn't the 400 have the same CV-32 carbs? Some people think those carbs just suck and are beyond help, and have switched to Mikunis with good results. I'm not willing to pay that much for carbs so I'll never know...

Are you twisting the throttle when attempting to start?  If so, try keeping the throttle closed.  The choke linkage cracks open the throttle automatically, with Keihin carbs.  Also, verify the choke butterflies are closed fully on a cold start.  The butterflies often hang open, which inhibits good choke action.

When are you doing the fuel level checks: after the bike has been running for a while or before you try to start it?

It sounds like you have a reluctant vacuum-operated petcock. If the engine is not running, there won't be vacuum and fuel won't flow. As it runs a little bit, more gas goes to the carbs and it stays running.

If the float bowls are empty or low before the first start of the day, the clear tube test should show it.

Nessism wrote:

Are you twisting the throttle when attempting to start?  If so, try keeping the throttle closed.  The choke linkage cracks open the throttle automatically, with Keihin carbs.  Also, verify the choke butterflies are closed fully on a cold start.  The butterflies often hang open, which inhibits good choke action.

 

I leave the throttle closed. Sometimes I'll crack it open a hair in an attempt to keep it running once started.
Yes the choke plates fully close. Although I find the bikes start better 7/8 closed.
This morning I had the clear tubes connected to the bowls of the 305. fuel level was 3mm below the bowl gasket. Using a 10cc syringe I injected about 8cc of fuel into the carb bowls through the clear tubes, this brought fuel level to 3mm above the bowl gasket. The bike started immediately when start button was hit, and kept running. I'll repeat this test tomorrow morning.
Unfortunaly, I only get one shot at troubleshooting this per day, as the bike starts fine after the initial start.

Nerdy wrote:

When are you doing the fuel level checks: after the bike has been running for a while or before you try to start it?

It sounds like you have a reluctant vacuum-operated petcock. If the engine is not running, there won't be vacuum and fuel won't flow. As it runs a little bit, more gas goes to the carbs and it stays running.

If the float bowls are empty or low before the first start of the day, the clear tube test should show it.

I have clear tubes on both bikes now, and monitor fuel level before and after starting. the 305 has a manual petcock. the 400 has a vacuum petcock that I put to PRI before starting.

Over the past 4 days, I have now cold started the kz305 in the mornings with the fuel hight 3mm above the float bowl gasket and it started and idled great. Almost no cranking, just hit the starter button, and it fired right up.
Now for a permanent solution: 
The float tabs are persently set to keep fuel level at 3mm below the carb bowl gasket. This is center of the spec of 2 - 4mm. I could just adjust the float tabs for a higher, (out of spec) fuel level. Is this likely to make me too rich while riding?
Or, would a larger pilot jet have the same effect as a higher fuel level but not effect mid to high speed riding? 
Any other thoughts? Thanks.
 

Okay, it sounds like there is progress - excellent!

IIRC the pilot jet is usually used from off-idle through about one-quarter throttle, so going up on the pilot shouldn't have a huge effect on normal riding. However, that's just my opinion and I am frequently wrong, so maybe one of the knowledgeable people here can corroborate.

I never seen this.
You have spring loaded doors in your choke plate.
Double check they are closing after they are pushed open.

 

Also be sure that the relief flaps open easily, and that one or more of them have not come loose and gotten sucked into the engine.

ckahleer wrote:

Over the past 4 days, I have now cold started the kz305 in the mornings with the fuel hight 3mm above the float bowl gasket and it started and idled great. Almost no cranking, just hit the starter button, and it fired right up.
Now for a permanent solution: 
The float tabs are persently set to keep fuel level at 3mm below the carb bowl gasket. This is center of the spec of 2 - 4mm. I could just adjust the float tabs for a higher, (out of spec) fuel level. Is this likely to make me too rich while riding?
Or, would a larger pilot jet have the same effect as a higher fuel level but not effect mid to high speed riding? 
Any other thoughts? Thanks.

 

Running the float level 6mm too high is obviously compensating for something else (must be close to flooding) I suspect you have air leak issues (hardened boots etc) when the choke flaps are closed and the air speed is reduced the engine relies in vacum to create a "negative depression" and pull fuel out of the carbs. Any vacum leak would reduce the bikes ability to draw fuel. Once the choke is open the increased air speed draws the fuel out of the carbs (negligable vacum with an open throttle)