Starter grinding when hot!
Road Warrior
Joined: Jun 2008
Posts: 1,343
Likes: 173
From: Watertown, CT
I had the same problem and as Bates said waiting for fuel pressure to build should only be done when the bike is cold. When hot I start the bike immediately and don't have any trouble now.
Because when you shut off a hot engine like for a fuel stop, the engine goes through a heat soak which means it's even hotter than it would be while riding down the highway. Once you turn the ignition on to restart it, 90% of the people will wait for the check engine light to go off before trying to start it. When you do this the fuel being sprayed into the hot cylinder turns to vapor which equals automatic pressure inside the cylinder. Here's some food for thought, most everyone drives a fuel injected vehicle nowadays. Do you wait to start it like most people do on their bikes? Most everyone I know puts the key in and immediately starts the car. We wait on our bikes because "somebody" said this was the way to do it because our bikes are different. Pure BS. If you'll make it a habit to crank your bike as soon as you turn the ignition on, especially when it's hot, this issue will likely never occur. I'd still use the releases though. They're there to protect your starter.
Literally, as soon as I hit the run switch, I immediately hit start. Starts on one revolution. The longer I wait, the longer the bike takes to start. Also, this is less wear and tear on the starter and battery.
Seasoned HDF Member
Joined: Aug 2011
Posts: 11,814
Likes: 5,120
From: SW Ohio
It's an air cooled engine. Compression is higher on a hot engine because the pistons/rings have effectively increased in size forming a better seal.
Last edited by Campy Roadie; Jun 23, 2016 at 05:49 AM.
Seasoned HDF Member
Joined: Mar 2009
Posts: 24,653
Likes: 9,114
From: Snow Hill, NC
While I had my 96" on the 07 it would grind when hot, SE compensator, high output starter and 1 comp release installed....the comp was the last piece of the puzzle that was installed and finally fixed my problem...now with the new 103HO in the 07 it hasn't done it yet....My battery tender cable isn't good so my battery us a bit weak and acting up....changing the cable this weekend.
Tourer
Joined: Jan 2014
Posts: 353
Likes: 32
From: New Brunswick Canada
Because when you shut off a hot engine like for a fuel stop, the engine goes through a heat soak which means it's even hotter than it would be while riding down the highway. Once you turn the ignition on to restart it, 90% of the people will wait for the check engine light to go off before trying to start it. When you do this the fuel being sprayed into the hot cylinder turns to vapor which equals automatic pressure inside the cylinder. Here's some food for thought, most everyone drives a fuel injected vehicle nowadays. Do you wait to start it like most people do on their bikes? Most everyone I know puts the key in and immediately starts the car. We wait on our bikes because "somebody" said this was the way to do it because our bikes are different. Pure BS. If you'll make it a habit to crank your bike as soon as you turn the ignition on, especially when it's hot, this issue will likely never occur. I'd still use the releases though. They're there to protect your starter.
I'm no expert but what makes you think fuel is being sprayed into the cylinder while you wait for the CEL to go out? If that were the case I think bad things would happen when you hit the start button, not to mention that the fuel would wash the cylinders creating a dry start and a very serious wear problem.
The fuel injection on these bikes I believe is a throttle body, fuel is not injected directly into the cylinders but into the throttle body where it mixes with air feeding the intake to each cylinder. When the motor is not running there is no fuel being delivered, when you hit the start button the injectors start spraying fuel to mix with the air to feed the intake valve. No fuel delivered until you hit the button!
I'd have to agree with Nomadmax, when the engine is hot the compression is higher making it a bit harder to turn over. Any weaknesses in the starting system are gonna show up at that point. A bad compensator will exaggerate the problem as well or so it seems.
Maybe I'm wrong but this is what I think I know.
Seasoned HDF Member
Joined: Aug 2011
Posts: 11,814
Likes: 5,120
From: SW Ohio
I'm no expert but what makes you think fuel is being sprayed into the cylinder while you wait for the CEL to go out? If that were the case I think bad things would happen when you hit the start button, not to mention that the fuel would wash the cylinders creating a dry start and a very serious wear problem.
The fuel injection on these bikes I believe is a throttle body, fuel is not injected directly into the cylinders but into the throttle body where it mixes with air feeding the intake to each cylinder. When the motor is not running there is no fuel being delivered, when you hit the start button the injectors start spraying fuel to mix with the air to feed the intake valve. No fuel delivered until you hit the button!
I'd have to agree with Nomadmax, when the engine is hot the compression is higher making it a bit harder to turn over. Any weaknesses in the starting system are gonna show up at that point. A bad compensator will exaggerate the problem as well or so it seems.
Maybe I'm wrong but this is what I think I know.
The fuel injection on these bikes I believe is a throttle body, fuel is not injected directly into the cylinders but into the throttle body where it mixes with air feeding the intake to each cylinder. When the motor is not running there is no fuel being delivered, when you hit the start button the injectors start spraying fuel to mix with the air to feed the intake valve. No fuel delivered until you hit the button!
I'd have to agree with Nomadmax, when the engine is hot the compression is higher making it a bit harder to turn over. Any weaknesses in the starting system are gonna show up at that point. A bad compensator will exaggerate the problem as well or so it seems.
Maybe I'm wrong but this is what I think I know.
You're right, it doesn't have anything to do with fuel injection. It's the same for a carbed bike as well for the reason I stated. But, who am I to tell another man that Bigfoot doesn't exist ?
Seasoned HDF Member
Joined: Mar 2010
Posts: 38,309
Likes: 6,328
From: Honah Lee
When you say grind do you mean a starter sound without the engine turning over? Mine does a lot of silliness when hot and let set a few minutes. Seams that no mater what I do, the cables to battery get loose after 4-6K of miles, the injector drips a little and until the engine turns over one turn, I sometimes get a bang from kick back or an actual grunt as the starter slows down from the load till it clears the charge in the cylinder (what your compression release is doing) and then it cranks freely.
There is a youtube showing the starter solenoid failing to throw out the starter. However, the starter clutch is a sprag clutch that drives against a shoulder. Only until the gas motor start, does it outrun the electric starter and the drive pins run up the ramp and disconnect the clutch. Someone said the pins can get flats or maybe the grease get hard and caked jamming it opened .
The compensatory cannot slip. Just bang with a broken spring.
There is a youtube showing the starter solenoid failing to throw out the starter. However, the starter clutch is a sprag clutch that drives against a shoulder. Only until the gas motor start, does it outrun the electric starter and the drive pins run up the ramp and disconnect the clutch. Someone said the pins can get flats or maybe the grease get hard and caked jamming it opened .
The compensatory cannot slip. Just bang with a broken spring.
Last edited by Jackie Paper; Sep 14, 2018 at 10:20 AM.
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
8 Best Harley-Davidson Motorcycles Ever
Pouria Savadkouei
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
10 Things Harley-Davidson Needs to Fix in 2026
Verdad Gallardo
Southpaw Super Glide: A Left-Hand-Drive 1979 Harley FXE Built to Fit the Rider
Verdad Gallardo
Seasoned HDF Member
Joined: Jan 2013
Posts: 10,637
Likes: 1,246
From: Lake, Ms
I'm no expert but what makes you think fuel is being sprayed into the cylinder while you wait for the CEL to go out? If that were the case I think bad things would happen when you hit the start button, not to mention that the fuel would wash the cylinders creating a dry start and a very serious wear problem. The fuel injection on these bikes I believe is a throttle body, fuel is not injected directly into the cylinders but into the throttle body where it mixes with air feeding the intake to each cylinder. When the motor is not running there is no fuel being delivered, when you hit the start button the injectors start spraying fuel to mix with the air to feed the intake valve. No fuel delivered until you hit the button! I'd have to agree with Nomadmax, when the engine is hot the compression is higher making it a bit harder to turn over. Any weaknesses in the starting system are gonna show up at that point. A bad compensator will exaggerate the problem as well or so it seems. Maybe I'm wrong but this is what I think I know.
Tourer
Joined: Jan 2014
Posts: 353
Likes: 32
From: New Brunswick Canada
I think we are going to have to agree to disagree on this one, I still say the injectors are only injecting when the motor is turning timed of course by the computer to inject prior to the intake valve opening.
As for pulling the fuel pump fuse, the fuel pump only runs up till the fuel rail is pressurized then it stops again only until the start button is pushed which would indicate to me that the rail pressure has dropped enough to bring the pump back on. The reason the fuel pressure has dropped is because the injectors have now started spraying fuel due to the motor being cranked.
The higher compression when hot is the same reason HD went to ACRs in the new bikes, so they start easier when they're hot.
Again, this is what I think I know.
As for pulling the fuel pump fuse, the fuel pump only runs up till the fuel rail is pressurized then it stops again only until the start button is pushed which would indicate to me that the rail pressure has dropped enough to bring the pump back on. The reason the fuel pressure has dropped is because the injectors have now started spraying fuel due to the motor being cranked.
The higher compression when hot is the same reason HD went to ACRs in the new bikes, so they start easier when they're hot.
Again, this is what I think I know.
