Cracking open the throttle makes the ECU mix in the lowest throttle section of the PowerTuner mapping with the CO-setting "map".
If your engine won't start with the throttle closed but does start with throttle cracked
that is proof, that your CO setting is set to a start-unfriendly value.
Cracking the throttle open has nothing to do with the co (fuel mixture) it does affect the cylinder pressure in a BIG way when the decompressor is active.
This is why the bike is not starting!
If the co setting was off the bike would not idle because the co setting only changes the fuel mixture at idle. It is exactly the same thing as turning the pilot mixture screw on a carb bike.
Cracking the throttle just allows more air into the cylinder to restore some compression which would otherwise be really low with the throttle closed.
sensor in the intake manifold along with the air intake sensor determines the air density and adds fuel according to the map
that was programmed into the ecu.
Yes the co level at idle can be changed with the tool. But without an o2
sensor all your doing is screwing up an otherwise correct fuel setting.
The reason changing this value to a richer setting has helped some but not eliminated the problem is because your adding fuel which makes the mixture a little cooler and a little more dense and may help a hot engine light off easier by the root cause of the issue is the decompressor.
Ask anyone who has had a Honda
with premature valve wear. This condition causes the bike to be hard to start when hot because the valve faces are worn and when the valves are hot, the stems get longer as a result the valve lash is at 0 because the faces are worn and all the valve lash is lost so they essentially end up zeroed out. which causes them to open just a little too far to maintain enough compression when hot.
The same issue exists here but for a different reason. The decompressor pin is too tall from the factory. They needed to lower the compression enough so the starter could turn the engine over. Any more compression and you risk damaging the starter if the engine can't turn over. Too little and it won't start.
The problem gets worse at high altitude like where I live at 6500 feet we have less dense air up here so a bike with already marginal compression up here has even less cylinder pressure than at sea level.
My mechanic finds that grinding a small amount off the decompressor pin resolves the starting issue. It causes the exhaust
valve to close slightly more with the decompressor active. This increases compression on start up. It totally eliminates the starting issue.
Now you guys know the truth! Believe what you like with your hocus pocus adjusting of the co setting! It's your bike and if it makes you feel all warm and fuzzy thinking you've somehow solved the mystery here. But every time your bike doesn't start I want you to remember that bass mechanic said your decompressor is over decompressing the cylinder.
You'll find that if you crack the throttle slightly, restore some of the compression that's already to low, or if your ballsy enough to modify the decompressor pin and actually fix the root cause of the problem. Then you can continue to struggle with starting your bike.
It's your bike, not mine! mine starts easily every time. If you would like I am sure for a fee my mechanic would be happy to modify your cam for a fee if you would like to ship it to him.
If my bike starts as easy at high altitude as it does those of you who live at lower elevations should have even easier time starting at your elevation.
For ANY OF YOU WHO DOUBT THIS INFORMATION do this experiment..
Start your bike, hold the throttle at between 2300-2500 rpm and hold it there. With your left hand kill the engine without moving your hand on the throttle.
Now while holding the throttle in the exact same position hit the starter. I bet you 100 bucks it starts every time on the first try!
Now after you've started the bike a couple times and convinced yourself that I'm not full of crap, release the throttle keeping note of how much throttle you were using to start the bike. When I say "crack the throttle" this is exactly how small cracked I'm talking about. The bike is supposed to idle at 2100 rpm stock (I run mine at 1700-1800) now keep in mind how tiny of amount it takes to raise it 300-500 rpm from idle!
You'll discover just what I mean while doing this experiment.
Now after you complete this experiment and see for yourself that I am right about the hard to start nature of the bike I want you to report back to this thread with your findings so everyone else will start to see that this is a simple fix.
On a side note, I suspect that if you know how to do a valve adjustment with the shims I an confident that if you shim it on the "loose" side of in spec it will solve most of your starting issues. So for those of you who still have issues I recommend you do a valve adjustment and in particular set the exhaust valve with the decompressor pin a little on the loose side while still being in spec.
I believe this is where the variance between bikes is and how hard or easy they are to start resides.
So there you have it. If your totally bored on New Year's Day and are looking for something to tinker with on your bike give this test a try!
Ive already seen at least a dozen people who have tried this on their totally stock bike either pm me or post in threads where I've shared this info that they no longer have starting problems.
Sorry for the long post but this is really getting ridiculous and all these posts about hard to start makes this bike look bad.
Edited by Bass Mechanic, January 01, 2016 - 06:13 AM.