Stock bike won’t start - fouled plugs?

[theog]

Strangest thing happened today…my completely stock Yamaha wouldn’t start!

Changed the oil last week on the 2017 @10k miles. Ran the bike for somewhere around 15-30 seconds (idled, no throttle) to circulate oil. Let oil settle overnight and topped off in morning. As I’ve done on every bike I’ve owned for almost 20 years. Let it sit for a week due to holiday and kiddos school break. 
 

Fast forward to today, no start. 13v on the LiFePo battery, cranks and crank, and cranks. All electrical systems and switches work. Sure enough, I can smell fuel. 
 

Looks like I’m going to have to check the plugs. Anyone else run into this issue?  Totally odd that it worked fine before parking. I’d be shocked if the plugs fouled like this, but all signs point this way…

[RaYzerman]

If you don't let FI bikes warm up, they think they need to stay in enrichment mode.... ECU is feeding it fuel for a cold start longer than it should....... hold throttle wide open while cranking and that shuts the injectors off.  May have to repeat, don't do extended cranks more than 30 seconds and give it a rest.  Once it starts, be ready to let off.....

[betoney]

I was going to suggest the exact same as @RaYzerman   Key on, hold throttle open, crank for about 10-15 seconds, repeat if necessary.  When it finally turns over, let the bike run until it completely warms up.

[theog]

Unfortunately, that trick didn't work.  But it was the first thing I tried when it failed to start, so at least brilliant minds think alike!  No amount of throttle opening or cranking duration changed the results.

Although you're correct that the ECU enriches the A/F at start up, stock bikes designed in this century seldom, if ever, run rich enough to foul plugs if the bike isn't fully warmed up.  If these are fouled, they'll be the first on my watch!

So it looks like I'll have to disassemble the bike when I can find the time to see what's up.  The ease at which it cranks and the lack of sound are interesting...almost reminds me of a low compression scenario.  But I'm getting ahead of myself (I hope).

Still, keep the ideas flowing.  

[kilo3]

What's the voltage on the lipo when it cranks? These ecu's super sensitive to drops.

[miweber929]

2 hours ago, theog said:

Although you're correct that the ECU enriches the A/F at start up, stock bikes designed in this century seldom, if ever, run rich enough to foul plugs if the bike isn't fully warmed up.  If these are fouled, they'll be the first on my watch!

Gotta disagree with your statement. It’s VERY common to flood a modern FI bike by only running it 15-30 seconds and shutting it off. Search, you’ll see, as @RaYzerman said they literally dump gas into the motor to get it to fire straight up, unless it’s burnt off it will foul plugs. 
 

I’d be pulling the plugs and drying them off, or simply replacing them, if it were my bike. 

Edited November 30, 2023 by miweber929

[theog]

2 hours ago, kilo3 said:

What's the voltage on the lipo when it cranks? These ecu's super sensitive to drops.

I can't say what the cranking voltage was on the initial non-start.  However, the resting voltage was 13.1 volts.  After a few more tries at starting over the last two days, the resting voltage dropped to 12.75 and cranking voltage to 11.8 volts.

I had a freshly charged Yuasa on the shelf, so your question prompted me to try it out.  Initially, it gave the same results.  However, it had an ever so slight 'bump' in the exhaust note which gave hope.  After 4-5 more tries on the starter using all sorts of throttle openings, it roared to life.

After it warmed up, I swapped in the lithium battery to see what would happen.  To my surprise, it started up *almost* like normal, even if the first crank was a little slower (which I'll attribute to the state of charge from all the cranking).

Going to give it another go tomorrow AM and see if it'll take me to work.  I'll be bringing along a portable jump pack just in case it fails me again.  We'll see.

24 minutes ago, miweber929 said:

Gotta disagree with your statement. It’s VERY common to flood a modern FI bike by only running it 15-30 seconds and shutting it off. Search, you’ll see, as @RaYzerman said they literally dump gas into the motor to get it to fire straight up, unless it’s burnt off it will foul plugs. 
 

I’d be pulling the plugs and drying them off, or simply replacing them, if it were my bike. 

You're free to check the fueling, timing, and enrichment maps for yourself, but can assure you that they there is no "literal dumping of gas".  This is a good bit of urban legend that stems from days of manual chokes and carbs...which still aren't as sensitive as we're discussing here.  Properly fueled with proper heat range plugs (as most bikes are delivered), they don't foul plugs if the bike is turned off within the first 15 seconds.

If you want proof, go to any dealer, moto mechanic, or auto shop...not every bike is fully warmed up when the engine is started.  That's just not feasible for many maintenance operations.

In either case, I agree that it's always preferable to let an engine warm up to temp after starting for a plethora of reasons.  On that we won't disagree.  

 

So anyway, good looking out @kilo3...looks like the battery and ECU were at odds with one another.  Will update this thread if the problem returns.

Edited November 30, 2023 by theog

[miweber929]

12 hours ago, theog said:

You're free to check the fueling, timing, and enrichment maps for yourself, but can assure you that they there is no "literal dumping of gas".  This is a good bit of urban legend that stems from days of manual chokes and carbs...which still aren't as sensitive as we're discussing here.  Properly fueled with proper heat range plugs (as most bikes are delivered), they don't foul plugs if the bike is turned off within the first 15 seconds.

If you want proof, go to any dealer, moto mechanic, or auto shop...not every bike is fully warmed up when the engine is started.  That's just not feasible for many maintenance operations.

In either case, I agree that it's always preferable to let an engine warm up to temp after starting for a plethora of reasons.  On that we won't disagree.  

I can tell you from personal experience, talking to mechanics at various brand dealerships and repair shops, and being a mod on several forums, that fouling plugs on modern FI bikes after being started and shut off for short durations can, and will, happen on modern bikes. And is easy, and common, to do.
 

I may have oversimplified my explanation by saying “literal dumping of gas” but by that I mean the FI systems will send a larger than “normal” amount fuel for the first cranks and first few seconds of running to aid in the start and initial revolutions of a cold motor. This allows the ECU to read parameters and decide the correct map with the fuel it needs to stay running. This process is used in lieu of a choke of carbureted and “high idle” knob on early FI systems and why it’s not abnormal to foul plugs.
 

If it wasn’t possible, there wouldn’t need to be a procedure in the manual on how to do start a bike with fuel soaked plugs, right?

There’s a strong chance your original battery that was marginally charged and didn’t spin the motor enough to combat the fuel soaked plugs. Once the fresh battery was installed, it did crank fast enough, then it burned off the excess fuel and made it able to start back on the old battery. Or not. But it is easy to still foul plugs whether you choose to believe it or not. 

Edited November 30, 2023 by miweber929

[RaYzerman]

Sorry, I should have advised you to start with a freshly charged battery, FI bikes need enough oomph in the battery...... cranking with part throttle just exacerbates the problem, you have to use WOT to shut the injectors off.  Anyway, you got there, all good.  Now you know for next time.

[kilo3]

Added note, not a lot of people talk about it but those lipos do/should/prefer a full charge outside what the bike can deliver voltage wise now and again.  IIRC some even suggest keeping it on a charger full time but I've seen some get away with not doing it at all so maybe it's just vehicle dependent?

[duckie]

So, got a 19 GT…its 46 degrees….been sitting awhile…

I just went out, started it up, let it idle for 20 sec, didnt give any throttle input…..turned it off…

Waited about 10-15 sec…..tried to start it up……guess what…..it started right up….

Did this same routine two more times……started right up….it never got warm.

The only thing happen was the TCS light flicked until I applied rear brake.

Just food for thought……

[miweber929]

19 minutes ago, duckie said:

So, got a 19 GT…its 46 degrees….been sitting awhile…

I just went out, started it up, let it idle for 20 sec, didnt give any throttle input…..turned it off…

Waited about 10-15 sec…..tried to start it up……guess what…..it started right up….

Did this same routine two more times……started right up….it never got warm.

The only thing happen was the TCS light flicked until I applied rear brake.

Just food for thought……

Great, what does that prove? I completely submerged an XR250R many years back, pulled it out, started it up and ran it another 10 years without doing anything. Doesn't mean that submerging a bike is good for it or that it can't, at times, cause an issue.

 

My point was/is simply this: fouling plugs, or having your bike be hard to start after running a short time is not uncommon nor is it that unusual. Common thought would be it's a fuel injected modern ECU controlled bike, it should next to impossible to do. It's not. I personally have experienced it on 2 different bikes, one cleared up after using the flooded bike procedure, one needed fresh plugs. And on several forums I visit and some I am a mod, others have had the issue as well; replacing plugs or flooded procedure got the bike to start again. 

Literally the title of the OP's post is "Bike won't start- fouled plugs?" and is arguing it can't possibly happen. So.............

[duckie]

It disproves the bullshit about a FI needs to come up to operating temp and the ECU dumping extra gas into the engine….

And a battery needs to be fully charged

And that lots of people really dont know what they are talking about.

 

 

[betoney]

30 minutes ago, miweber929 said:

Great, what does that prove?

Literally the title of the OP's post is "Bike won't start- fouled plugs?" and is arguing it can't possibly happen. So.............

 

16 minutes ago, duckie said:

It disproves the bullshit about a FI needs to come up to operating temp and the ECU dumping extra gas into the engine….

And a battery needs to be fully charged

And that lots of people really dont know what they are talking about.

In fairness it simply proves that it didn't happen to you in your attempt to recreate the scenario, not that it can't happen or that others offering advice don't know what they are talking about.  Who is to say that someone else couldn't have an issue when trying the same starting procedure?

[miweber929]

2 hours ago, duckie said:

It disproves the bullshit about a FI needs to come up to operating temp and the ECU dumping extra gas into the engine….

And a battery needs to be fully charged

And that lots of people really dont know what they are talking about.

 

 

As @betoneysaid it only proves it didn't happen to you, doesn't mean it can't happen.

You are jumping to a LOT of conclusions on things that were not said or even implied. Except by you.