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Discussion Starter #1
So, I have an 07 ZX-10R with 16k miles on it and it is starting to become rather hard to start when warm, which is what is throwing me off here. The battery was replaced last year, but it was a cheap one so it is possible it is that. But I do keep it on a battery tender. Anyways after riding for a few minutes, if I cut the bike off and try to start it back up, it bogs pretty bad and then fires up. Although, somewhat rarely it grinds like the starter gear disengaged mid cranking (like a torque activated clutch didn't fully engaged, if we even have one). I haven't had the time or money to go diagnosing yet and I'm afraid of what I might find. It's also starting to sound like I need a valve adjustment, but just barely. I don't know if this is the starter, battery, or the engine.

Any ideas?
 

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So, I have an 07 ZX-10R with 16k miles on it and it is starting to become rather hard to start when warm, which is what is throwing me off here. The battery was replaced last year, but it was a cheap one so it is possible it is that. But I do keep it on a battery tender. Anyways after riding for a few minutes, if I cut the bike off and try to start it back up, it bogs pretty bad and then fires up. Although, somewhat rarely it grinds like the starter gear disengaged mid cranking (like a torque activated clutch didn't fully engaged, if we even have one). I haven't had the time or money to go diagnosing yet and I'm afraid of what I might find. It's also starting to sound like I need a valve adjustment, but just barely. I don't know if this is the starter, battery, or the engine.

Any ideas?
A weak battery would be indicative of weak cranking on the starter motor. And a weak starter or weak battery would really have no effect on the bogging of the engine once it's actually running. If the starter cranks strong, then your battery is OK. If it's not cranking fast, then the battery should be replaced.

And I'm not sure how you would "hear" if it needed a valve job or not. :dontknow: That's done on specific mileage intervals. The valves wear slightly and sink deeper into the head which tightens the clearances. In extreme cases, the valves ride the cam lobes all the time and never get a chance to fully shut. This leads to poor running due to a drop in compression, but they get quieter because the lobes stopping "tapping" the valve shim buckets. If you're hearing noise, it's likely from the timing chain loosening up.

This sounds like a fueling issue primarily (as most hot-starting issues are). You should try draining the fuel tank COMPLETELY and refill with fresh fuel. And I mean removing the fuel pump and draining it that way, not just running it out of gas or tipping it upside down. This will eliminate any residual water and debris from the bottom of your tank. Next would be to try and disassemble and clean the fuel filter as best you can. Unfortunately the fuel filter is integral to the pump and not replaceable on it's own. The entire fuel pump assembly must be replaced as a unit if the filter is clogged at all. But some people have had good luck disassembling and cleaning the filter assembly themselves if they're careful and take their time doing it. Next would be to clean the fuel injectors.

If the fuel isn't atomizing properly when the engine is warm, it will be hard to start. There's typically too much raw fuel in the cylinders to get a good start. To help with this. you may try cracking the throttle open slightly while hitting the starter button to see if this helps eliminate the bogging.

And yes, the starter actuates through the starter clutch. If that's not disconnecting properly it may cause the motor to back-drive the starter and make noise on start up.
 

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Discussion Starter #3
I always thought that as the valvetrain wore in, the clearance between the cam and the "bucket" became larger and created the tapping noise thus needed a larger shim under the bucket? As for the bike, it runs perfectly fine once started, I'm probably going to bite the bullet and just buy yet another battery. Anyone have good luck with the lithium power-sport batteries? Also the engine is not back-driving the starter, what I am talking about happens at it's worst bog down moment and I have to let off the starter and try again. Like it didn't have enough torque to keep the starter clutch fully engage so it slipped off the gear.
 

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I always thought that as the valvetrain wore in, the clearance between the cam and the "bucket" became larger and created the tapping noise thus needed a larger shim under the bucket? As for the bike, it runs perfectly fine once started, I'm probably going to bite the bullet and just buy yet another battery. Anyone have good luck with the lithium power-sport batteries? Also the engine is not back-driving the starter, what I am talking about happens at it's worst bog down moment and I have to let off the starter and try again. Like it didn't have enough torque to keep the starter clutch fully engage so it slipped off the gear.
Typically the valve clearances tighten over time, not increase. They get tighter because the valve face and valve seat wear from the closing of the valve. This makes the clearances tighter in most cases.

I have a Shorai lithium battery. It's works good for me, but lithium ones do require more attention and are helped by the special balance chargers to equalize the individual cells within the main battery case. They are lightweight and provide more starting voltage. But they cannot be allowed to fully discharge or they will be forever damaged.

The starter gear mechanism is constant mesh. There's no gears that can grind together. The starter clutch is one way. One side is always connected to the starter and the other end is always connected to the flywheel. When the motor is running, the clutch is is freewheel mode and spinning faster than the starter. When the starter is engaged, the clutch locks up and the starter can turn over the crankshaft.
 

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Discussion Starter #5
Typically the valve clearances tighten over time, not increase. They get tighter because the valve face and valve seat wear from the closing of the valve. This makes the clearances tighter in most cases.

I have a Shorai lithium battery. It's works good for me, but lithium ones do require more attention and are helped by the special balance chargers to equalize the individual cells within the main battery case. They are lightweight and provide more starting voltage. But they cannot be allowed to fully discharge or they will be forever damaged.

The starter gear mechanism is constant mesh. There's no gears that can grind together. The starter clutch is one way. One side is always connected to the starter and the other end is always connected to the flywheel. When the motor is running, the clutch is is freewheel mode and spinning faster than the starter. When the starter is engaged, the clutch locks up and the starter can turn over the crankshaft.
So, I'm probably either missing a tooth or have some jacked up teeth. Does the starter cover have a gasket or am I good to just remove it?
 

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So, I'm probably either missing a tooth or have some jacked up teeth. Does the starter cover have a gasket or am I good to just remove it?
If your teeth are screwed up, you'll be the only one in the world with that problem. And you'll have bigger issues because the missing tooth would fall into the crankcase. :headshake: I can't fathom how you'd mess up the gear teeth in a constant mesh arrangement. You're likely hearing the starter clutch slipping or starter backspinning when the motor is bogging and can't complete a revolution and goes backwards slightly from the cylinder compression when it stalls.

The starter clutch is behind the timing cover which uses a gasket to seal it. It's a paper gasket that's likely to rip unless you're extra specially careful removing the cover. But it's always a good idea to replace it.

But all of this is secondary. If the motor would start properly and keep running (not bog down and stall), then this noise you hear would be irrelevant and a non-issue. Fix the source of the problem. This is a symptom of that bigger issue, not the cause of it or anything to be worrying about now IMO.
 
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