Another Cold Hard Start...

old1959

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#1
Bike is a 2017 non ES model and resides in the Texas hill country area.

First time the bike didn't start was on a cold day, approximately 50 degrees F. Bike had almost 24k miles with receiving only oil and filter changes. I pushed the starter button a few times and heard it fire but wouldn't fire continuously. Afterwards, I opened the throttle wide open, WOT, and it immediately started and idled fine. I smelled a hint of fuel or richness. I didn't think much of this since this was the first time and bike was due for maintenance.

A few weeks ago at approximately 25k miles I checked the valves (all within spec), replaced spark plugs, along with air filter. Also, changed oil filter plus sync'd throttle bodies. Note: When doing the throttle bodies I opened left cylinder, white painted air screw, a quarter of a turn (was fully closed) and adjusted right air screw to achieve balance. All good.

Last week I took a trip to the Big Bend area and twice the bike wouldn't start in the morning and exhibited same conditions as before with a few fires and then starting with WOT. And, afterwards, a slight smell of fuel. Both mornings were cold, or at least cold for me, with temperatures in the 50's. Nighttime temperatures were colder.

Bike runs great and starts fine with warm engine and or temperatures. I used the Yamaha shop manual to do all the work along with checking for error codes; found none. Obviously, the fuel air mixture is rich when cold as each time a no start has occurred I smell fuel. Plus going WOT is allowing more air for the mixture. Personally, I can live this but the situation bugs me as the bike should start without throttle when cold. Also, to complicate matters further I don't think I'll have cold weather at home for several months to do further troubleshooting.

My question: What sensors are being used to determine air fuel mixture for startup? Bike runs fine the rest of the time so I don't suspect something like an O2 sensor. Instead, maybe a sensor such as the coolant temp sensor? My thoughts are to remove such sensor, put in frig or freezer, and take resistance readings at different temperatures. However, I don't really want to remove several sensors to do this little science experiment. Thoughts...
 

EricV

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#2
What spark plugs are you using? At my last service I changed to Irridiums and the bike starts noticeably easier/faster.
(NGK (5258) CR8EIB-9 Iridium IX Spark Plug)

The air intake temp sensor, coolant sensor and possibly one more likely control the cold start routine. I don't think the O2 sensor is in play right at start up. It starts looking for stoichiometric once the system reaches closed loop. I don't think it's in play during cold start/open loop mode.

And actually, no, it's not obvious that the fuel/air mixture is rich. That becomes part of the problem when you crank it at length w/o it starting. If you read the earlier threads on this issue you will learn that there is a bit more in play. Cylinder wash down impacts compression and is part of the hard start issue. While I have experienced mild hard starts like you describe in cold conditions, (50F is not cold), it was low 20s with the bike left outside all night and following an accidental engine stall, (my fault), and a 36F pouring rain after a similar stall. The only time I've had a classic hard start in the garage is after I washed the bike, fired it up to move it, then shut it down w/o allowing it to fully warm up to 140-160 coolant temp.

The short run followed by an overnight sitting period is the single most common pre-curser to a hard start. The short description of the issue is that the choke system is engaged and still engaged when the bike is shut off. The excess fuel runs down the cylinder walls washing off the oil residue on them, then the next start, still in choke mode, adds a big shot of fuel before oil pressure can build up and coat the cylinder walls well enough to get good compression again. Repeated cranking w/o WFO only makes this worse.

The question I have for you is did you fire up the bike the night before and shut it down before it fully warmed up? If so, stop doing that. If not, not all of the issue is classic hard start. In 140k miles I've had a few times I needed to use throttle to get the bike started too, but by and large it starts fine w/o throttle.

Battery voltage is another part of the equation. I run a larger battery than stock with more CCAs. The stock 12S battery is a known poor performer, though does fine under most conditions. Not knowing how you store your bike at home, if you use a battery maintenance tender or not, what battery you have, etc, I have no way of knowing if the battery is a factor on the cold starts you've experienced.
 

Jlq1969

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#3
. I don't think the O2 sensor is in play right at start up. It starts looking for stoichiometric once the system reaches closed loop. I don't think it's in play during cold start/open loop mode.
It is a doubt that I have. supposedly the 4-wire CO sensors are heated. I put the key to ON for a minute, I touched them and they did not feel hot, but I do not know if they would be inside, they would have to check it
 

EricV

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#4
A heated O2 sensor is only heating the small element in the sensor. You would not be able to feel any heat from the outside by just turning the key on. The four wires are two ground, one power to the "heater" and one sensor. The heater helps it be more accurate, and possibly reach closed loop sooner, but the bike still starts in open loop using maps for cold start routines. When we interrupt that cold start routine, something doesn't re-set and we end up with a hard start. This bike doesn't have a wax choke, so it's apparently all software in the ECU.
 

old1959

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#6
EricV, I installed stock NGK spark plugs. I store the bike in my garage, except for trips, and all hard start issues were after riding all day. No short startups and then shut down. No battery tender since I ride the bike almost daily and, such as my recent trip, all day long.

Normally, bike fires up quickly. Consequently, when it doesn't catch I immediately stop cranking. Then I wait almost a minute and try once more. If doesn't start, then I stop, WOT, and in about 30 seconds press starter button again. I only hold starter button down for a few seconds at a time.

Regarding sensors, I agree with the air intake temperature and coolant sensors being in play. However, I've noticed the dash readout for ambient temperature is rather accurate and coolant temperature readings seem normal. I'm assuming ECU is providing this data from these same sensors.

Battery? If it cranked slow, sure... But not the case. Plus I have a voltmeter and the lowest voltage seen has been 11.4.
 

old1959

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#8
Oh, and stock original battery. Bought bike new March 1st, 2018. Thank you all for your comments.
 

Madhatter

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#10
it seems to me at times on my bike (a WOT start is not common ) in trying to start bike I have let my finger slip off start button mid start and that seems to confuse the bike . I push the button and I hold it down at least 20 seconds or so , it usually starts before that time . if your only giving it a few seconds and in that time it doesn't start you might be confusing the bike. I also rock my bike back in fourth to make sure the lousy alcohol infused gasoline is mixed well. Old 1959 what part of Texas do you reside ?
 

old1959

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#11
Cycledude, regarding popping sounds while slowing down, I would say no or nothing unusual.

Mad hatter, I’m in New Braunfels. We should meetup sometime. Twenty seconds would seem like eternity to hold the starter button. The bike typically starts within a few seconds.
 

Fennellg

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#12
I had a similar situation. Mine would crank pretty good, but would not catch. Experimented, hooked the battery to my charger. I had depleted the battery pretty good. After a some time on the charger, it started fine. Ordered up a new battery and put it in. Hard start gone now for a couple of years now. Conclusion reached by reading in the Forum and first hand experience, our bikes need a good battery’s to run. Ok battles won’t cut it. The bikes will bump start on a weakened battery though. If you are in a jam good thing to know.
 

Cycledude

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#13
Cycledude, regarding popping sounds while slowing down, I would say no or nothing unusual.

Mad hatter, I’m in New Braunfels. We should meetup sometime. Twenty seconds would seem like eternity to hold the starter button. The bike typically starts within a few seconds.
Old1959 thanks for your reply.
I was mostly just curious because my 2018 seems to have quite a bit of popping from the exhaust when slowing down and I don’t remember my previous 2013 doing that, other than the popping exhaust while slowing down it seems to start and run fine. I suspect it might need some kind of fuel adjustment.

As far as no start so far in 6,000 miles my 2018 has never had that issue, in fact I believe it actually starts better than my 2013 ever did, last month on a trip a couple mornings when we left the motel it was below freezing and it started just fine. I only experienced the no start issue with the 2013 twice in 50,000 miles and fortunately it happened at home in my garage both times.
 
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