very VERY hard starting -- out of ideas

Alright, I've had lots of trouble getting my KZ750 spectre to start reliably. Here's the checklists I've gone through.
-Battery is fully charged
-Hitting starter rotates crankshaft "fast enough" (limited experience, but seems good)
-Timing is good on a four cylinders (checked once bike was running with inductive lamp)
-Carbs have been recently professionally cleaned
-Compression strong on all cylinders (>150 on all four, if memory serves from a week ago)

If I hold the starter in many sets of bouts, after the 10th or 11th 10 second hold I'll get a sputter pop. Three more times I'll get two pops. Continue this growth until battery almost dead and engine kicks itself over and runs. Same thing happens with push starting -- after about the 20 or 30th push start it goes on its own.

When it gets going it takes a VERY long time to warm up. I have to slowly back off the choke in fractions of a degree to prevent either super fast idle or stalling. After about 10-15 miles I can work down the choke all the way, but i still have a bit of a roaming idle.

I'm completely out of ideas.

del

I'll try to be thorough:
-Carbs cleaned by wiredgeorge with stock jetting

-Fuel level in each carb within spec

++Will sync carbs tonight

-Air screws set as correctly as I know ~2 turns out. The idle is so rough I can tell how to check mixture. I can try the kill/coast/read plug method, but I fear I don't have the experience necessary to read them right

-New B8ES plugs (correct) and gapped to .7mm

-Coils checked, both primary and secondary resistance correctly in spec and sparks fire big and blue when out against cylinder head

-Timing advancer clean and lubed. Timing correct at idle and advances correctly with rpm increase

-6mon old airfilter. Could replace, but the airbox and air intake seem good.

-Very good fuel flow. I've had this problem with many tanks of good gas. Has inline fuel filter since before carbs were cleaned so I know fuel is not spitting rust or the like.

-15,000 miles on bike: Did a valve check one week ago reshiming one intake and one exhaust to be in spec. Has had not made it easier to start

-Stock exhaust, stock airbox, stock jetting.

--->Leaves one very frustrated rider.

Are your fuel screws on the bottom of the carb or on the side?

If you shoot a burst of wd-40 into the airbox, will the bike fire right up, or have you tried that yet?

Don't use starting fluid for this test.

By fuel screw, I assume you mean idle adjustment screws? Please correct me if I'm not talking about the right thing. They are on the top, right before the intake manifolds. For reference, the carbs are Keihin CVK34

I have tried the WD-40 and it didn't start any easier. Still lots of cranking

Idle mixture screws, yes?

I don't know the first thing about those carbs, sorry. But maybe if you get it started, you can check for vacuum leaks.

It seems you have hit all the other possibilities.

After many many pushes where my heart is about to explore, it will start. When it is running, and I spray WD40 around the intake manifold and vacuum tubes, no change in rpm, thus I believe no vacuum leak.

Seriously, it's driving me crazy trying to find this elusive demon.

Can you post some history on the bike?

How many miles are on it?

How long have you owned it? How many miles have you put on it?

Has it always been really hard to start?

Why did you send the carburetors out to a professional to go through?

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Do the mixture screws have the springs and I think there is a washer on Keihins as well.

On that carb., do the screws control air or fuel?

I'll do my best.

I bought it used on craigslist a year ago. With 14,000 miles on it (speedo cable broken though, so it may well be higher in reality). I've riden a bit under 1,500 miles on it. Once it goes, it goes alright, except for a rough idle. Above 2.5K, it runs beatifully. It has always been hard to start. First I thought it was bad battery (was bad), replaced it. After a summer of riding with having to push start constantly, I sent the carbs away because I didn't know their history and I was willing to make sure i could check it off the list of possible problems. I've replaced the starter brushes once, as all the starter wear wore them down -- I have a feeling it's close to needing to be done again now.

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The mixture screws do have springs and washers (supposed to) -- I can check to make sure they are acutally there, but I really don't want to mess up the idle mixture if I don't have to. It is my belief that the air is constant, and the screw adjusts fuel.

This sounds so similar to what I was dealing with when I got my current bike at 12k miles.

It wouldn't start without lots of cranking. I think I about burned up my starter clutch and starter. Wore out my leg trying to kick the freak out of it. Finally figured it out.

The fuel screws were in too far. That and Kawasaki put out a technical service bulletin regarding the choke pickup tube on the carb on my bike. The tube was to be drilled out to 1mm or 1/32 or 1/64 or something. The drilling out didn't help. I still have the bitty drill bit I used. Sure glad that thing didn't break off in a choke well.

Maybe what has happened with your bike is that the mixture springs are wrong. They are allowing the needle in too far. Two turns out isn't enough, even though it is numerically correct. That is what I found out was wrong with my machine. In my case, springs were missing entirely, so 1 & 1/8 turn from bottom was too close, because the spring was missing or too short or something. If the springs were wrong before the carbs were sent out, they may still be wrong. That part usually isn't part of rebuilding.

So get the bike running, and try turning a fuel screw out a little at a time, and see if the engine speed starts picking up and smoothing out. Keep doing that on one carb until the engine speed doesn't go up any more. Leave it at this point for now. You might have to adjust your idle speed (not mixture) a couple times to bring it back down. Move on to the next carb.

I hate that you have to push the bike. Maybe if this is the problem, you won't have to anymore.

Post edited by: KaZooCruiser, at: 2007/05/07 16:42

Adjusting the idle mixture on two of the carbs caused the idle RPM to up significantly. I guess two weren't firing, or wren't firing well at idle. For the rest of the night, it fired up nicely with minimal starter. My adjustments were rather coarse though. I have a colortune on the way to make it more precise and a carb sync is totally in order.

Thank you so much for suggesting enriching the idle mixture. I'm really, REALLY hoping this puts an end to the push-start workout.