Stock bike won’t start - fouled plugs?

[RaYzerman]

I've had it happen on 4 of the last 5 bikes I've owned (2 FJR;s, Honda CBF, Kawi V1K), ..... note, it is not 100% that it happens EVERY time it's just you have very high odds it was the cause if it did not start the next time... FJR's in particular are notorious for the issue, others less so IMHO. 

Edited November 30, 2023 by RaYzerman

[skipperT]

4 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.

 

 

No it doesn’t. You just got lucky, is all. 
-Skip. 

[skipperT]

You CAN ABSOLUTELY foul plugs on modern motorcycles.

You need to remember that the Fi systems on bikes are NOT the same as FI systems on cars. For discussion purposes they perform the same functions, yes but cars are mapped differently than bikes. 

Early FI bikes were notorious for this, especially sport bikes from the mid 2000’s as FI was just entering the scene and the manufacturers hadn’t figured out how to map them well enough yet to prevent this problem. Honda F4i’s, GSX R’s, and even Yamaha and Honda dirt bikes.  Part of the issue was early open-loop Fi where the ECM doesn’t adjust the fueling based on o2 feedback during startup - which is what cars do. Only more modern FI bikes go into closed-loop with o2 feedback correcting the fuel mixture during warmup. 
 

@duckie the other thing you need to remember is that immediately restarted your bike several times in quick succession. Letting it sit for a week like the OP said they did is worse - because all that unburned/extra fuel sits on top of the piston and gradually dries out the oil film in the top compression ring where it seats to the cylinder wall.

This causes a compression loss, creating a harder start with more unburned fuel entering the combustion chamber on the intake stroke that accelerates fouling of the plugs and further compression loss. Snowball, meet hill.

It’s a combination of all these factors, along with a lack of air that creates the hard start. Sometimes cracking the throttle fixes it, sometimes not.

In extreme cases I’ve had to put oil down the cylinder of some engines after letting them air out overnight To get the compression back up, before they will finally start. 

-Skip

[theog]

On 11/30/2023 at 10:30 AM, kilo3 said:

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?

I’ve had mostly good success with Antigravity on my bikes. I’ve used them on my last 7-8 bikes and only experienced one issue, which they took care of. In most cases, I use them because I don’t have to leave them on a tender over winter. Although I ride year round, there’s typically a month or so where the roads are just too salt caked for my liking. The longest I’ve let a bike sit was a 6 months and it fired up without issue. No charger. And, best part, the oil was changed right before storage with the same procedure I used last week. 
 

Anyway, hope you northerners aren’t having an early onset of Parked Motorcycle Syndrome!

[duckie]

So, waited a few days…….went to start it up why WOT on the first try…..did not start…….hmmmm maybe the injectors were turned off…..or just too cold…

Did a about three cold starts with about 15 secs run time each.

Then did a WOT start………it started and headed to full RPM

so, if the injectors are turned off at WOT…..it should not have started.