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Discussion Starter · #1 ·
I have noticed, consistently, that when I start my Z125 when it is already "hot" from being run (like when filling up at the gas station), it turns over very little before it fires - pretty fast starts. But, when it is cold (like has sat overnight in the garage), it takes several seconds of cranking before it fires up.

I am wondering if there is perhaps a subtle "leak" in the fuel injection system that is too small to cause a significant loss of psi during a short stop (like gassing up), but is enough to depressurize the fuel system overnight.

Is anyone else experiencing anything like this?

I searched the forum but saw only references to the sometimes iffy behaviour of the kill switch, and I knwo that is not the issue on mine because I never use the kill switch. I always shut off the ignition with the key.

I really notice this issue because my other current bike, a Yamaha R3, fires instantly, hot or cold, virtually every time.

Jim G
 

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Yeah, ours does it too. New 2018 purchased end of Aug. Don't know mfr date off hand.

I don't like the behavior (particularly considering how tiny the starter motor is) but I'm used to my BMW that eats batteries and sometimes requires choke in the summer so I've sorta just accepted it.
 

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Discussion Starter · #5 ·
Usually on the 3 time at about 4 second cranks @ 60 Degree's or so. never tried any colder than that.
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Heres some posts on it
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https://www.z125owners.com/forum/ka...-anyone-else-have-engine-starting-issues.html
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https://www.z125owners.com/forum/engines-discussions/4569-cold-start-up-issue.html
Thanks for these links! They were very helpful, especially the first one, which contains this:

"Mine would do this when stock. Without the added parts. I would cycle the key and let the fuel pump cycle a few times to prime fuel. It would start everytime by doing this."

A couple other comments mentioned that adjusting the throttle posiiton sensor ("TPS") setting to make the mixture richer helps. Other comments talked about how a Power Commander or Bazazz can make it worse or better, and I suspect that is because they do indeed make adjustments to the TPS system.

This all supports my theory that this is because the engine simply does not get enough fuel at starting, and the quote I included above from the first thread might be the simplest remedy if it works for ALL Z125s. I'll try it.

Thanks again for the links.

Jim G
 

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2018 Grom fires instantly, 2017 Z cranks for several seconds.

Immediately after starting AFR is like 10. I don't think it is too lean.

I think there is not enough timing advance.
 

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Discussion Starter · #7 ·
2018 Grom fires instantly, 2017 Z cranks for several seconds.

Immediately after starting AFR is like 10. I don't think it is too lean.

I think there is not enough timing advance.
YES, that is very interesting! BUT, this is important to note:

You are talking about a 2017 Z125. I assume it got the new ECU during the ECU recall then? If so, note that one of the big changes in that ECU recall was that Kawasaki retarded the timing at idle from 10 degrees advance to ZERO advance!

So, your comment about "not enough timing advance" might indeed be valid. Kawasaki needed a quick fix to the stalling problem on rapid deceleration, and evidently retarding timing was the poor but quick and cheap fix kawasaki adopted.

BUT, while optimal timing advance for optimal combustion pressure IS important for getting the MOST power, why would retarded (non-optimal) timing utterly prevent firing at all? If you've got a combustible mixture of air and fuel, and you introduce a spark, it SHOULD at least fire. In fact, remember that Kawasaki was trying to keep the engine running at a closed throttle setting, and retarding timing evidently HELPED them do that.

So, I THINK the underlying problem might actually be simply too little fuel during startup, making ignition difficult to achieve. This MIGHT be why opening the throttle slightly during startup can help. Yes, that actually adds more AIR, but evidently it also perhaps adds PROPORTIONATELY more fuel?

Jim G
 

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Mine did the same thing with a Hoedar ECU. Talked to Chris about it, he made some tweaks and now it fires up right away hot or cold. However, when it's sub 40F, the bike will die 1x then start right away on the 2nd try and stay running. That can be handled by giving the bike some gas.


TL;DR. Seems like a fueling issue with the ECU.
 

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2018 Z125
In 60* garage several seconds before fires
After riding with a short break fires instantly
After sitting in parking lot all day and 40*F took about twice as long as in 60* garage

When I got home put it on trickle charger due to long and slow turn over and charger went straight to storage mode.
 

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Discussion Starter · #10 ·
2018 Z125

. . .

When I got home put it on trickle charger due to long and slow turn over and charger went straight to storage mode.
That tells me that the battery is definitely not the issue.

But speaking of batteries, a Lithium battery MIGHT be a solution. I just ordered the WPS (Western Power Sports) HJTZ7S-FP-IL Lithium Ion battery. This battery is the same physical size as the OEM battery (4 7/16" Length 2 3/4" Width 3 3/8" Height), offers 105 cold cranking amps, and the approx. weight = only 0.9 lbs!

This saves 2.21 lb over the OEM battery, and that weight is from (a) one of the highest points on the bike, and (b) over the rear axle (A stock Z125 is tail heavy). And unlike a lead acid battery, a Lithium battery actually gets "stronger" as it cranks because of the higher temperature cranking instantly creates. After I installed a similar battery (just a different brand) in my Yamaha R3, it began to start "instantly" most of the time, whereas the lead acid battery had always taken a second or 2. I suspect the lithium battery might make the same difference on the Z125.

In The U.S. you can get the WPS battery from Hardracing for $79US plus shipping or Amazon.com for about $100US shipped.

Jim G
 

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Discussion Starter · #11 ·
Sorry, I did not say that well. What I meant is that tbswope's posting tells us that his battery is not weak, nor does the Z125 run a battery down overnight for some reason. But, a Lithium battery MIGHT solve the problem, simply because a Lithium battery actually gets stronger as it cranks because it heats up a bit, unlike a lead acid battery that gets weaker as it cranks and heats. So, A Lithium battery might crank for a fraction of a second and then fire the engine, whereas the lead acid battery starts to fade as soon as it starts to crank.

A Lithium battery speeded up my Yamaha R3's starting notably. It always starts instantly now, even after sitting several days in cold weather.

Jim G
 

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We've also been seeing 3-4 seconds of cranking time too when cold... to the extent that it ever gets 'cold' here in California. I assumed this was a battery, so I followed the recommendation of others here and have an Antigravity AG-801 lithium battery on order. Which might not be as cool as a Lithium LI-801 antigravity battery would be, but hey :) If it makes a difference, I'll let you all know.
 

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Mornings (starting bike in garage) are starting in the 30's but afternoons (starting bike outside) are getting in the 60's so I haven't had any more excessively long turn over since the one time it was about 40 in the afternoon. Just a thought feel free to correct any wrong thinking. Some guys have said after exhaust swap slight backfire for the first 20 miles but seems ecu self corrected. Is it possible once the ecu learns the colder temps I am riding in that start up will be richer and the long turnover will go away?
 

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Same here

I ride till the rock salt gets thrown around... on a day where it’s 50* or colder it takes a few second to start.... otherwise it’s normally pretty quick to fire..... the coldest I have had to start it was 28*.... I have a programmer, YOSHI pipe, and intake from MNNTHBX.... my bike is a 2018 z125pro.... bought it in September...... I now have 1200 miles on the clock... I commute on her and ride pretty much 5 days a week...
 

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We put the lithium battery in this morning. It makes a huge difference. Bike starts up much faster.
 

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Discussion Starter · #16 ·
We put the lithium battery in this morning. It makes a huge difference. Bike starts up much faster.
Good to hear, as I just last night installed a WPS (Western Power Sports) HJTZ7S-FP-IL Lithium "Featherweight" battery, hoping that it would have this effect! The WPS HJTZ7S-FP-IL is exactly the same size as the OEM lead acid battery, but supposedly produces 150 cold cranking amps versus the OEM's under-100 cold cranking amps. It also weighs 1.19 lb (actual on my digital scale) versus the OEM 3.12 lb (actual on my digital scale), so is also a big weight saving off of a point that is very high on the bike.

It is cold and rainy here on Vancouver Island right now, so I have not been able to do a test "start", but will do so at first opportunity!

IF this really does shorten the cranking time, that will:

- Conserve battery power in an already small battery

- Extend the life of the starter motor a LOT

- Make cold weather starts much easier on both the battery and the starter

My Yamaha R3 (320cc engine) has a Shorai Lithium battery, and starts INSTANTLY, regardless of how long it has sat unridden and how cold the ambient temperature is at the time.

Jim G
 

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According to their website, the Antigravity AG801 is a whopping 240 cranking amps. I don't know whether this is true or not, but the first time I tried it, my thought was, "Why bother with the engine? With this baby, I could drive around using just the starter motor!"


I'm glad we didn't get one of the their 12- or 16-cell units. Those would probably vaporize the entire bike...
 

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Discussion Starter · #18 · (Edited)
According to their website, the Antigravity AG801 is a whopping 240 cranking amps. I don't know whether this is true or not, but the first time I tried it, my thought was, "Why bother with the engine? With this baby, I could drive around using just the starter motor!"


I'm glad we didn't get one of the their 12- or 16-cell units. Those would probably vaporize the entire bike...
That battery IS very powerful (and very expensive). But how did you get the height to FIT? It is about 7/16" taller than the OEM battery in the Z125, and the oEM battery seems to be a pretty snug fit in the comaprtment that Kawasaki built for it. Did you have to cut out the plastic supports at the bottom of the comaprtment? or?

I just the found the weight of it. It is 1.56 lb, which is still a saving of 1.56 lb versus OEM, and that cranking power is awesome.

How much cranking time does it need to start the Z125 engine?

Jim G
 

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That battery IS very powerful (and very expensive). But how did you get the height to FIT? It is about 7/16" taller than the OEM battery in the Z125, and the oEM battery seems to be a pretty snug fit in the comaprtment that Kawasaki built for it. Did you have to cut out the plastic supports at the bottom of the comaprtment? or?

I just the found the weight of it. It is 1.56 lb, which is still a saving of 1.56 lb versus OEM, and that cranking power is awesome.

How much cranking time does it need to start the Z125 engine?

Jim G
A fair question that, and one that had me puzzled for several long minutes :) I ended up mounting it on its side. You get to do that with lithium batteries, since there isn't acid to leak out (Bubble... HISS... "Aargh!" et cetera). . The new unit slots in nicely because its height -- or what would be the height if it was standing upright -- is the same as the width of the OEM battery. I did have to spend several more minutes slowly bending the terminals on the cables to match the shape of the ones on the battery. This must be done with care, lest one suffer the dread "Oops, I just stress fractured the darn thing dammit," experience. Rerouting the cables also involved a bit of head scratching. I took a photo of the install if you're curious.
 

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Discussion Starter · #20 ·
A fair question that, and one that had me puzzled for several long minutes :) I ended up mounting it on its side. You get to do that with lithium batteries, since there isn't acid to leak out (Bubble... HISS... "Aargh!" et cetera). . The new unit slots in nicely because its height -- or what would be the height if it was standing upright -- is the same as the width of the OEM battery. I did have to spend several more minutes slowly bending the terminals on the cables to match the shape of the ones on the battery. This must be done with care, lest one suffer the dread "Oops, I just stress fractured the darn thing dammit," experience. Rerouting the cables also involved a bit of head scratching. I took a photo of the install if you're curious.
A photo would be helpful to others who want to duplicate your solution! How long does it need to crank the Z125 engine before it starts?

Jim G
 
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