Question NC700X won't turn over...?

[bigbird]

heisenbigbird uncertainty principle

Didn't know that attaching a multimeter to a cranking motorcycle electrical system involved quantum mechanics.

 

[lootzyan]

...A car battery pushes a lot more power through the system. That can backfire...

Battery doesn't work like that. It can't "push power". It is an electrical device for storing energy. The battery provides as much energy on demand as its capacity allows. Something like a water tank.

 

[670cc]

The car battery being swapped in may have created further issues. A car battery pushes a lot more power through the system. That can backfire.

Battery doesn't work like that. It can't "push power". It is an electrical device for storing energy. The battery provides as much energy on demand as its capacity allows. Something like a water tank.

I agree with lootzyan. The car battery could only "push" more power if it's output voltage was higher, but in this situation the car battery is at the same voltage as the motorcycle battery. One could get into details comparing the internal resistance or current delivery capability of the car vs the motorcycle batteries, but those differences are not going to result in "a lot more power" to the starter motor. The resistance of the starter and the supplied voltage largely determines the current flow in the circuit, and thus the power (E times I).

 

[spark82]

I think I give in and order a replacement starter motor. Today I disassembled the starter motor again and checked the magnet positions (the Yamaha guys gave me an idea, they experienced some magnets moving due to bad gluing, some types use similar starter motors) I couldn't exactly remember checking them the last time, but they seem OK, no movement or position shift at all. I tried the motor again by directly hooking it to multiple batteries (tried the kid's quad battery as well) it works but somehow it feels a little lazy to me. Also a bit suspicious that even with no load it reduces the battery voltage to around 10,3V while spinning (after that the battery recovers to 12,6-7 normally in a few seconds). That seems a little excessive pull for such a small motor without load. Maybe there are shorted windings in there but I have no means to check that, so I'll go with a replacement. While I was at that, I checked the starter clutch again as far as it can be checked without disassembling the engine, it seems OK (only grabs one direction, other direction freewheeling is OK, no axial movement, tried to rotate the engine with the nut under the left side engine cover cap, engine seems OK, there is compression where it is expected, other than that it rotates without any strange noises, I can rotate it with a short socket wrench handle, the torque feels OK compared to my kickstart bikes)

I only hope that the new motor will solve my problem.

 

[670cc]

I think I give in and order a replacement starter motor. Today I disassembled the starter motor again and checked the magnet positions (the Yamaha guys gave me an idea, they experienced some magnets moving due to bad gluing, some types use similar starter motors) I couldn't exactly remember checking them the last time, but they seem OK, no movement or position shift at all. I tried the motor again by directly hooking it to multiple batteries (tried the kid's quad battery as well) it works but somehow it feels a little lazy to me. Also a bit suspicious that even with no load it reduces the battery voltage to around 10,3V while spinning (after that the battery recovers to 12,6-7 normally in a few seconds). That seems a little excessive pull for such a small motor without load. Maybe there are shorted windings in there but I have no means to check that, so I'll go with a replacement. While I was at that, I checked the starter clutch again as far as it can be checked without disassembling the engine, it seems OK (only grabs one direction, other direction freewheeling is OK, no axial movement, tried to rotate the engine with the nut under the left side engine cover cap, engine seems OK, there is compression where it is expected, other than that it rotates without any strange noises, I can rotate it with a short socket wrench handle, the torque feels OK compared to my kickstart bikes)

I only hope that the new motor will solve my problem.

Your troubleshooting is very thorough. Good luck with the new starter motor, and let us know the results.

 

[TheIronWarrior]

Battery doesn't work like that. It can't "push power". It is an electrical device for storing energy. The battery provides as much energy on demand as its capacity allows. Something like a water tank.

To elaborate, a battery is effectively (though not always perfectly) a constant voltage source (plus a small internal resistance). The chemical reaction in each cell produces a certain amount of voltage, and all cells taken together output about 12.4V.
Knowing V=IR, the voltage output is (effectively) constant, and the resistance in the circuit is constant, the current flow through the system is also constant.
The problem with jumping a bike off a car is not the battery, but the car alternator. The car alternator is so much bigger that that in the bike so it's likely to fry the R/R and possibly other things in the system.

 

[TheIronWarrior]

I think I give in and order a replacement starter motor. Today I disassembled the starter motor again and checked the magnet positions (the Yamaha guys gave me an idea, they experienced some magnets moving due to bad gluing, some types use similar starter motors) I couldn't exactly remember checking them the last time, but they seem OK, no movement or position shift at all. I tried the motor again by directly hooking it to multiple batteries (tried the kid's quad battery as well) it works but somehow it feels a little lazy to me. Also a bit suspicious that even with no load it reduces the battery voltage to around 10,3V while spinning (after that the battery recovers to 12,6-7 normally in a few seconds). That seems a little excessive pull for such a small motor without load. Maybe there are shorted windings in there but I have no means to check that, so I'll go with a replacement. While I was at that, I checked the starter clutch again as far as it can be checked without disassembling the engine, it seems OK (only grabs one direction, other direction freewheeling is OK, no axial movement, tried to rotate the engine with the nut under the left side engine cover cap, engine seems OK, there is compression where it is expected, other than that it rotates without any strange noises, I can rotate it with a short socket wrench handle, the torque feels OK compared to my kickstart bikes)

I only hope that the new motor will solve my problem.

Definitely sounding like a bad start motor to me. Best of luck with the replacement!

 

[bigbird]

The problem with jumping a bike off a car is not the battery, but the car alternator. The car alternator is so much bigger that that in the bike so it's likely to fry the R/R and possibly other things in the system.

Totally agree.
I think anyone would be foolish to jump start a motorcycle battery with a car that is running.
In fact, every car owner's manual that I have ever seen states that the donor vehicle engine should be turned off when boosting a dead battery.
Once the dead vehicle starts, don't start the donor engine, just disconnect the booster cables, then start the donor engine.

 

[TheIronWarrior]

I am not going to debate power pushing and pulling. That is just goofy. And yes. Whatever you test you also change. That is part
of the uncertainty principle. That is also not up for debate. But. By hooking a giant battery up to a device designed for a wee battery fries it. Motors, circuits. All of it. Part of learning basic engineering is burning the begeesus out of stuff. And learning that current draw and the potential for it are as simple as… hmmm. “Let me hook up this gigantic power source to it and see if I can force it to spin.“

And I did a lot of that. My father discovered the LED that way. So it runs in the family. So. Getting a new motor now is the best bet. It may have been overheated internally. Good job! And. The details of coming and going won’t solve problems. Knowing when you are frying something does.

If you hooked up a 28V battery, you'd fry it.
If you hooked up a large 12V battery, it will operate just the same as if you hook up the proper sized 12V battery.
If you connected 1,000,000 gigantic 12V batteries in parallel, you would still only output 12V. V=IR, V constant, R constant, therefore I constant. Nothing gets fried.
If you hooked up 1,000,000 gigantic 12V batteries in series, you'd output 12,000,000V and fry just about anything you touched with it.

I've let the smoke out of plenty of electronics by increasing the input voltage, because in that case V increase, R constant, therefore I increase.
Hooking up a 12V starter motor to any "size" of 12V battery will NOT fry it, it is simply impossible.

 

[670cc]

Fortunately, the thread originator has a good understanding of electrical and mechanical devices and won't be swayed off course by the misinformation and misguidance that is beginning to appear in this thread. I say we wait until the starter motor is replaced, see the results, and if the repair is successful, we close the thread.

 

[spark82]

Well, folks, at least I know now that it wasn't the starter motor. With the new one the symptoms are the same.
I tried something tho, that I haven't done before. Removed the generator cover, and tried to crank the engine with spark plugs first, then without spark plugs to see what happens. After several attempts without the spark plugs (engine rotating happily) the engine spit out a small cylinder shaped thingy, which I reckon to be some kind of a breather (? not sure tho, a cylinder about 5 mm in diameter, 8 mm long, with a hole of 0,2 mm in the middle, I saw a similar thing in a Stihl saw, the oil tank has a breather like that). Also oil started to drip out, cannot really see where it came from, have to remove the flywheel to see it (will do that tomorrow maybe). Not much, I put a small pan under the bike, it starts to drip when I crank the engine, stops a few seconds after. I thought maybe that changed things so I put the spark plugs back - nothing changed. But I heard something while trying, and tried to find the source while rotating the main shaft with a wrench. A very low hissing noise while turning the shaft. Can be the compressed air making its way past the piston rings, I cannot really tell.
Now I have to find where the small cylinder came from and where the oil comes from.
Cannot really wrap my head around the problem. The bike worked fine the last time I used it and now all this fuss. Well, that's how it goes this year it seems (a lot of things went south on me the last few weeks. I hope it stops soon...)

 

[spark82]

Scratch the cylinder thingie, found it in the service manual, it's supposed to come out with the cover removed, and the oil comes from its place as well.
While I was at that, I checked the cyliders with a small USB endoscope camera. They look clean, piston tops also look clean a healthy.

Damn I hate riddles.

 

[lootzyan]

...Damn I hate riddles.

Who can like this kind of riddles? But, no offense, from my point of view (I'm getting slower to comprehend things) you only add more to the guess what you are doing with your description of your activities. It would be more helpful, maybe if you at least included a few photos to help describe what you are doing.

 

[spark82]

Who can like this kind of riddles? But, no offense, from my point of view (I'm getting slower to comprehend things) you only add more to the guess what you are doing with your description of your activities. It would be more helpful, maybe if you at least included a few photos to help describe what you are doing.

True.
I'm going to take a few pictures and maybe a small video recording.

 

[lootzyan]

I'm not sure this question was asked.
In testing, did you connect a larger capacity battery directly to the engine starter motor?

 

[spark82]

I'm not sure this question was asked.
In testing, did you connect a larger capacity battery directly to the engine starter motor?

Yeah, tried that. Two different car batteries, both working good. Same result.

 

[lootzyan]

Long shot question: did you check the clearance of the exhaust valves? I know that it is not very probable, but one of the reasons for the resistance of the cylinder stroke would be that the exhaust valves would not open, e.g. due to a timing error (the chain could skip).
It is easy for me to come up with crazy theories when I am not seeing the patient.

 

[TNHoosier]

I was thinking something similar but I am grasping at straws at the moment. It could explain the hissing sound when hand cranked.

I really want to know what the issue is when this is solved.

 

[670cc]

A timing chain jump can be ruled out by looking at the marks in the camshaft and crankshaft inpection ports. The directions are part of the valve adjustment procedure. This possibility was never discussed because it was reported that at the onset of the slow cranking issue, the engine supposedly ran normally once started. Even when the engine had to be bump started, if I remember correctly, it then ran normally.

 

[lootzyan]

... Even when the engine had to be bump started, if I remember correctly, it then ran normally.

We can say that you are right. There is also a starter clutch between the engine starter motor and the engine, but it can be concluded from the design of the clutch that this is not a problem.
So he must go back to retest the battery and connections to the engine starter motor.
This is somewhat frustrating as it should be resolved relatively easily.