Vulcan VN1500 Fi Hard to Start When Warm

rebeltaz · Renault 5 Driver Joined: 02 Jul 2005 Karma :

I'm not experience in fuel injected engines. My bikes have always been carbureted. This fuel injected VN1500 starts perfectly when cold - pull the choke, spin it over a couple of times and voom. Once I let it warms up, though - after riding it for a while - I can let it sit anywhere from a few minutes to a hour or more and it will spin over for thirty seconds or more before it will finally catch. Throttle open or closed doesn't matter. Once it hits, it's fine.

Could anyone point me in the right direction?
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Derek Tombrello
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jaffa90 · World Chat Champion Joined: 06 Apr 2016 Karma :

Can you here a suction noise when releasing the fuel tank cap?

Have you tried the choke (near home) to see if it improves warm starting?

What`s the mileage?

When were the valve clearances last checked?

Robby · Dirty Old Man Joined: 16 May 2002 Karma :

What's a fuel injected bike doing with a choke? Has someone stuck a carb on it?

Grubscrew · Scooby Slapper Joined: 23 Dec 2018 Karma :

I had a car do that to me, turned out the valve clearances had closed up once warmed up effectively altering the position at which the valves opened ie too soon.
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FJR1300/CBR1000F

rebeltaz · Renault 5 Driver Joined: 02 Jul 2005 Karma :

Easy-X · Super Spammer Joined: 08 Mar 2019 Karma :

Yes, we had this discussion about "EFI chokes" with the Himalayan. Sort of a manual override or enrichment booster if you will.
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Islander · World Chat Champion Joined: 05 Aug 2012 Karma :

jaffa90 · World Chat Champion Joined: 06 Apr 2016 Karma :

Robby · Dirty Old Man Joined: 16 May 2002 Karma :

This is a tricky one.

My usual answer for hot starting trouble is that the valve clearances are too tight, which holds the valves slightly open and doesn't let you develop any compression. Somehow it starts working after a bit of cranking, I presume the air and fuel hitting the valves cools them down enough to start working.

But this one has hydraulic tappets.

Slightly grasping at straws, but wrong oil grade could be the reason. If its too thick then hydraulic tappets can misbehave. Less of a problem on cold starts because you have no/low oil pressure for the first couple of revolutions of the engine.

So if someone has put 20W50 oil in there, which is quite possible because Harleys use it and Silkolene sell a 20W50 oil for V twin cruisers, that could be the problem. That's assuming it's standard fill is 10W40 or 10W30.

rebeltaz · Renault 5 Driver Joined: 02 Jul 2005 Karma :

When I got this bike, I had to replace a gasket on the front bevel gear case. Then I had to replace the clutches. When they started slipping again, I had to go back in, with yet another oil change. So that's three times that I have personally replaced that oil - each time with Kawasaki 10w40 oil.

Looking in the service manual again just now, though, - just to make sure I used the right oil for this bike - it shows that this thing is pretty adaptable. For recommended oil type it calls for (SAE10W-40, 10W-50, SAE10W-40 20W-40, or 20W-50).

I'm glad to see that I'm not the only one that this has stumped Confused

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Derek Tombrello
www.ShelbyCycle.com (for profit)
www.RobotsAndComputers.com (just for fun)

Hong Kong Phooey · World Chat Champion Joined: 30 Apr 2016 Karma :

Sounds electrical to me, air intake/engine temperature sensor or crank position sensor would be my bet.

I don't gamble much though so I'd be checking them with a multimeter and making sure it's all in spec. rather then throwing parts at it.
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~~'81 CG125, '97 FZS600~~ : '99 CBR600F4, '09 KTM RC8

rebeltaz · Renault 5 Driver Joined: 02 Jul 2005 Karma :

jaffa90 · World Chat Champion Joined: 06 Apr 2016 Karma :

Another test when warm, ignition key on for 10 sec then switch off and then back on for another 10 sec. ???????????????????

someone · Two Stroke Sniffer Joined: 26 Jul 2019 Karma :

if its an older bike , you should check fuel pressue and the injector/s
check the spark plug with a chart to see if its running lean or not
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EJ6 FOREVER AND FOREVER A HUNDRED YEARS EJ6.

Hong Kong Phooey · World Chat Champion Joined: 30 Apr 2016 Karma :

rebeltaz · Renault 5 Driver Joined: 02 Jul 2005 Karma :

someone · Two Stroke Sniffer Joined: 26 Jul 2019 Karma :

while at it , check the engine with a vacuum gauge , its around 30 usd new and very good for troubleshooting it also doubles as a fuel pressure gauge , and since its an efi the dail should spin more than the gauge can read .

https://ae01.alicdn.com/kf/HTB1sHCaSpXXXXaZapXXq6xXFXXX9/Motorcycle-Universal-Gauge-4-Carb-Carburetor-Synchronizer-Set-kit-Vacuum-Hoses-Extensions-4-GL-1100-1200.jpg
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EJ6 FOREVER AND FOREVER A HUNDRED YEARS EJ6.

sickpup · Old Timer Joined: 21 Apr 2004 Karma :

As its FI have you checked for fault codes?

rebeltaz · Renault 5 Driver Joined: 02 Jul 2005 Karma :

rebeltaz · Renault 5 Driver Joined: 02 Jul 2005 Karma :

So... no fault codes. Also, the plugs are all running about right - a tad tan, no black or white residue...
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Derek Tombrello
www.ShelbyCycle.com (for profit)
www.RobotsAndComputers.com (just for fun)