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Discussion Starter #1
Hey guys, I recently picked up a 2017 Z125. It only has 1200 miles on the clock. The engine and electronics are 100% stock other than a zoom exhaust. I am having multiple problems.

1.When the bike sits overnight it is very hard to cold start. I live in Ohio so it’s 30-40* but I have to crank it multiple times to get it to fire. Once it’s warm it fires no problem.

2. It has a cel code 51 for a bad coil. I have replaced the coil and added a ngk plug wire. Still had to start and cel still on after multiple rides.

3. The bike over heats and goes into limp mode really easily. I do a lot of slow speed wheelies but being 40* out it seems to get hot way faster than it should. If I stop and idle for more than a minute after some wheelies it will go into limp mode and only rev to 3k. If you shut it off for 5 minutes it’s back to normal.

I’ve searched and watched videos but I can’t really find anything to fix any of these problems. Do you guys/girls have any advice or experience with these problems? The bike is a ton of fun but it’s quirks are getting annoying fast.
 

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They are normally harder to start when its cold out, I find that turning the key on without cranking it for a few seconds and then back off and then back on for a few seconds will prime the fuel rail and allow for faster starting after sitting, as for your overheating, how do you know its actually overheating?
 

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Discussion Starter #3
They are normally harder to start when its cold out, I find that turning the key on without cranking it for a few seconds and then back off and then back on for a few seconds will prime the fuel rail and allow for faster starting after sitting, as for your overheating, how do you know its actually overheating?
I don’t know exactly what the temp is, but it is definitely hot. I could take an infrared thermometer with me and see how hot the head is when it happens. I think the slow speed wheelies and revs hanging at 7-8k just heat soaks the engine good
 

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im at redline or close to at the track for laps at a time. Something is wrong here. Did you change the oil since you've gotten it? I recommend semi or full synthetic for this bike. Is there an o2 sensor connected to the exhaust?

And how long are you moving at slow speeds for when wheeling?
 

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Discussion Starter #5
im at redline or close to at the track for laps at a time. Something is wrong here. Did you change the oil since you've gotten it? I recommend semi or full synthetic for this bike. Is there an o2 sensor connected to the exhaust?

And how long are you moving at slow speeds for when wheeling?
Yes the oil is full and fresh. 02 sensor is still there. I do wheelies up and down the road, maybe 15-20 minutes at a time. I probably just need to make a cool down lap more often to get some air moving over the thing.
 

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Discussion Starter #7
If you just ride do you overheat?
No, it seems ok if you keep moving in the higher gears. I thought about adding an oil cooler to help dissipate some heat during the slow stuff and add oil capacity. Still seems weird to me that it overheats when I see guys on YouTube in Arizona doing wheelies and circles and no mention of overheating.
 

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Depends on their setup. What are they using for fuel, do they have an oil cooler. and how long are they wheeling for. These engines are aircooled and can get hot pretty quick if they arent moving. I turn mine on every few weeks for about 15 minutes idle during the winter when the track is closed and thats as long as I let it sit for.
 

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Discussion Starter #9
Depends on their setup. What are they using for fuel, do they have an oil cooler. and how long are they wheeling for. These engines are aircooled and can get hot pretty quick if they arent moving. I turn mine on every few weeks for about 15 minutes idle during the winter when the track is closed and thats as long as I let it sit for.
I just rode it for a bit and it did the limp mode thing. I checked the temp of the cylinder with a infrared thermometer and it was only 205* F. I’m wondering if I need to do a tps reset because I did bump the idle up just a little the other day. With the stock idle it would randomly stall when pulling in the clutch coming to a stop
 

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Any signs of carbon around the head? Just wondering if you have a head gasket leak. Hard to start might be from running lean, this might be from a defective o2 or other condition causing it to go lean. Could be a defective temp sensor too. Going to need to sit down with a service manual and go through several diagnostic trees.
 

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Discussion Starter #11
I don’t think it is actually overheating. I turned the idle back down and it quit going into limp mode. It’s still a pain to start sometimes, and the cel for the coil is still on even after replacing the coil but it runs fine otherwise.
 

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How to clear the CEL instructions attached. If it works and the light stays off you won. If the light comes back on or stays on you still have a problem. At that point pull the codes again and let us know what you have.
CEL ERASING.jpg
 

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How to clear the CEL instructions attached. If it works and the light stays off you won. If the light comes back on or stays on you still have a problem. At that point pull the codes again and let us know what you have. View attachment 26186
I’ve done many rides since replacing the coil and the same code is always there. 51 if I remember right. Whichever code is for coil. The light will not shut itself off. I’m over it at this point. It runs fine once it’s fired up so I’m just going to live with the light and continue beating this thing like it owes me money.
 
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