Bike hard to start when it’s hot???

[bobrebos]

If I ride my 2013 Stelvio for a while and it gets hot and I shut it off, when I return like 45 minutes later it turns over and over and over without starting.  Then I stop trying to start it, wait a few more minutes, try again and it starts.  Starts fine in the morning when it’s been sitting/cold.  Electrical problem somewhere when hot like a coil failing or something???  Any ideas before I bring it to a shop somewhere. 

[Wayne Orwig]

I would reset the TPS and do a throttle body sync. It sounds like it is just a touch lean (or rich) at that temperature.
It may also be a sticking idle stepper motor.

Also, double check the spark plug gap. Everything may be struggling in those conditions and a bit too much gap may just be enough to prevent it from firing.

[bobrebos]

I would reset the TPS and do a throttle body sync. It sounds like it is just a touch lean (or rich) at that temperature.
It may also be a sticking idle stepper motor.

Also, double check the stark plug gap. Everything may be struggling in those conditions and a bit too much gap may just be enough to prevent it from firing.

Thank you

[Mayor_of_BBQ]

Set the valves and change the plugs, that would be the first stop for me, then proceed as wayne says above if you a a guzzidiag person

[bobrebos]

These plugs on my 2013 Stelvio (Ngk CR8EKB) are dual tab type plugs so I don’t think I can adjust change the gap??  Maybe I should order some single tab (NGK PMR8B) which are also recommended for the Stelvio.  Single tab would be able to set gap. 

[Caffeineo]

May/may not apply.....but I have noticed occasional hard starting on my new V85 when hot. I have opened the gas cap and noticed the whoosh of air. Immediately after that the bike runs better. Easy to check and see if that is your problem. Also seems to have a greater effect when the gas tank is closer to empty?????

[John A]

Another cause can be a slight vapor lock. The hot engine heats up the fuel lines. If you cycle the kill switch it does two things, it ( I’m told)  sets the ecu to start and it runs the fuel pump which should push fuel past any vapor that may be there.

[guzzisteve]

These plugs on my 2013 Stelvio (Ngk CR8EKB) are dual tab type plugs so I don’t think I can adjust change the gap??  Maybe I should order some single tab (NGK PMR8B) which are also recommended for the Stelvio.  Single tab would be able to set gap. 

Double electrodes are throw away, more expensive single trode is reusable & cost less in long run.

[bobrebos]

Double electrodes are throw away, more expensive single trode is reusable & cost less in long run.

 

[guzzisteve]

Got software Bob?

[rschrum]

Bring a spare plug with you. When it won't check for spark. That will narrow it down.

[Lee Bruns]

Checked valve lash lately? Not wanting to start when hot is a sign of tight valves.

[Chatmanx]

I am assuming that this is maybe a new bike to you are a bike behaving oddly under under new circumstances. It is carbureted right? Sounds like you're evaporating the fuel while shut down and it takes a couple tries to fill the bowls and start the engine. If that is right then there isn't much to do about it.

If it is fuel injected, then the increase in fuel pressure a startup should prevent that problem. Let me know.

[Chatmanx]

And to follow up on fuel injected, a test would be to put a fuel pressure garage inline and make sure that  the fuel pump it is working.

Or doo you hear a hum when you turn the key on and before starting? A simple test is to turn the key to power on and loosen a fuel supply line. Gas should spray everywhere and you know that you have fuel at pressure.

[lucian]

Checked valve lash lately? Not wanting to start when hot is a sign of tight valves.

  ^^^^^ this

[bobrebos]

Got software Bob?

No.  I’m an idiot when it comes to these newer bikes.  Give me a carbureted 1970 Honda and Il be happy!!!  I’m going to keep an eye on it and see if it stops doing it but I doubt it.  I ram it for a short 15 minute ride, let it sit for 45 minutes and it started fine.  I don’t know what’s going on but Il keep watching it I guess or I got a Stelvio boat anchor!!!!

[pressureangle]

Dual electrode plugs have a purpose, and if the factory put them in rest assured they had a reason. Usually it has to do with guaranteeing fire with a very lean mixture, as a stock motor must have these days.

If these bikes are prone to tank vacuum, as suggested check that first. I'm not sure how it can affect an EFI system, but it will kill carbureted engines until the pressure equalizes. It usually looks like this;

Runs fine, fuel circulating
Park, engine off
Hot fuel cools, creates vacuum
No start
Pressure equalizes over time through pressure valve or cap leaks
Good to go.

If this is the case, as suggested above open the gas cap next time it won't restart hot and verify.

[Mayor_of_BBQ]

I will say again cause it seems like others are agreeing with me...
Any time I have had issues losing idle when hot or getting no start when the bike was hot (but I knew the carb jetting/ecu tune was correct), the culprit was tight valves. I have never had a 8v bike, but seems like this is a simple and quick check that costs zero dollars

[pressureangle]

I will say again cause it seems like others are agreeing with me...
Any time I have had issues losing idle when hot or getting no start when the bike was hot (but I knew the carb jetting/ecu tune was correct), the culprit was tight valves. I have never had a 8v bike, but seems like this is a simple and quick check that costs zero dollars

You're not wrong.

[bobrebos]

I will say again cause it seems like others are agreeing with me...
Any time I have had issues losing idle when hot or getting no start when the bike was hot (but I knew the carb jetting/ecu tune was correct), the culprit was tight valves. I have never had a 8v bike, but seems like this is a simple and quick check that costs zero dollars

 

[Huzo]

Could you have a malfunctioning engine temp sensor that is commanding an inappropriate mixture for the fuel injection ?
What does Guzzidiag say ?

[PJPR01]

As has been stated several times and recommended by numerous folks, when it’s hot you’re likely to be getting some level of vapor lock.  Open the gas cap and let it vent a few seconds and try again…

Certainly check the valves too but if it was running fine Until the day you rode it on a hot day, then it’s unlikely to be the valves…

Highly recommend learning Guzzidiag also as well as getting a quality throttle body equalizer (Carbtune or Twinmax).

[bobrebos]

As has been stated several times and recommended by numerous folks, when it’s hot you’re likely to be getting some level of vapor lock.  Open the gas cap and let it vent a few seconds and try again…

Certainly check the valves too but if it was running fine Until the day you rode it on a hot day, then it’s unlikely to be the valves…

Highly recommend learning Guzzidiag also as well as getting a quality throttle body equalizer (Carbtune or Twinmax).

Looks like I have some learning to complete!  Thanks for the info!

[balvenie]

Plug leads and/or coils are breaking down.

[Jack Straw]

I encountered hard hot start problems on a few bikes.  Every time it's been coils, and, every time the problem coils checked out OK with basic multi meter testing. Go figure, eh.

[bobrebos]

I encountered hard hot start problems on a few bikes.  Every time it's been coils, and, every time the problem coils checked out OK with basic multi meter testing. Go figure, eh.

 

[Chuck in Indiana]

I encountered hard hot start problems on a few bikes.  Every time it's been coils, and, every time the problem coils checked out OK with basic multi meter testing. Go figure, eh.

You need to put the coils in the oven and warm them up.. then check with a multi meter.
A bad plug can mimic a failing coil.. don't ask me how I know. 

[Wayne Orwig]

As has been stated several times and recommended by numerous folks, when it’s hot you’re likely to be getting some level of vapor lock.  Open the gas cap and let it vent a few seconds and try again…

Very unlikely. That fuel pump is submerged under liquid fuel. That pressurizes the entire system down stream from there. Even if the tank does not vent properly, the pump will typically keep pushing out fuel. Very difficult to get a vapor condition in a system with a submerged pump. Now in the systems with the external pump sucking on the lines, that is very common.

[pressureangle]

Unless the sparkplugs have 150,000 miles on them or were fouled by poor fuel or oil burning they are not the problem. Modern sparkplugs are not the crappy AC Delco's of the 1970's. They last a looooooooog time. If they are iridium you'll get tired of the bike before they are worm to the point of needed replaced.

There's a clear misuse of terms in this thread.

Vapor lock is when the fuel boils within the system, and displaces liquid fuel at the engine entry point.

Tank vacuum is when the pressure in the tank becomes too low to feed the carbs or pump. Seems unlikely in an EFI system, but still to be verified.

[PJPR01]

Very unlikely. That fuel pump is submerged under liquid fuel. That pressurizes the entire system down stream from there. Even if the tank does not vent properly, the pump will typically keep pushing out fuel. Very difficult to get a vapor condition in a system with a submerged pump. Now in the systems with the external pump sucking on the lines, that is very common.

From personal experience on my 08 Norge, it's behaving exactly as I've described - I understand the above statement, however opening the gas cap, relieving the pressure  and the bike runs fine again immediately, so....This only occurs on extremely hot days, and not very often.  Which sounds like what Bob is experiencing.  Either way, it's one alternative for him to explore...hopefully he finds the root cause.