Startup crank bang noise - SE comp vs Comp release
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Road Warrior
Joined: Jun 2009
Posts: 1,943
Likes: 3
From: NYC
Startup crank bang noise - SE comp vs Comp release
just wanted to put this out into the general knowledge bank. Im one of those guys that had the startup crank bang problem. I did buy the SE comp but never got around to install it. I did some motor work which included add compression release. Using the compression release's I never had the startup crank bang noise. I'll get around to installing the SE comp at some point. Also found out that these is a spring pack kit 83936-09 that some folks think will upgrade a standard compensator to a better compensator but not quite as good as the SE compensator.
Road Warrior
Joined: Jul 2006
Posts: 1,532
Likes: 7
From: Rochester N.Y.
My understanding of the stock comp is that the comp gets bottomed "forward" when cranking and get bottomed "backwards" when it lights off.
The compression releases would soften this action and get rid of the bang on start.
The stock comp under load rides nearly at max which kinda negates it's purpose.
I installed a SE comp after my stock comp bolt loosened on a trip.
After the stock comp was tightened to spec , it still made noise anyway.
The SE comp is so much heavier and the springs stronger than stock , that I have to think it never bottoms in either direction anymore.
The SE comp completely eliminated my starter bang and most of the weird primary noise that I had.
The freaky thing is that the bike is "much" smoother going uphill , two up under a heavy load.
I have to think that the SE comp does the job properly that it was intended to do.
This was one of my first mods , and one of the better end results that I've had.
Mine is an early version SE comp which has a stinker of a thrust washer that you can crack on install ( I did ) but it's been quiet for about 12,000 miles so far.
Mick
The compression releases would soften this action and get rid of the bang on start.
The stock comp under load rides nearly at max which kinda negates it's purpose.
I installed a SE comp after my stock comp bolt loosened on a trip.
After the stock comp was tightened to spec , it still made noise anyway.
The SE comp is so much heavier and the springs stronger than stock , that I have to think it never bottoms in either direction anymore.
The SE comp completely eliminated my starter bang and most of the weird primary noise that I had.
The freaky thing is that the bike is "much" smoother going uphill , two up under a heavy load.
I have to think that the SE comp does the job properly that it was intended to do.
This was one of my first mods , and one of the better end results that I've had.
Mine is an early version SE comp which has a stinker of a thrust washer that you can crack on install ( I did ) but it's been quiet for about 12,000 miles so far.
Mick
Road Warrior
Joined: May 2009
Posts: 1,945
Likes: 4
From: Victoria, Australia
My 09 BargeGlide banged on startup and I put up with it for a few thousand miles, then changed to the SE comp. No more start bang after that --zero.
Since then I've replaced the cams with S&S 551 EZ starts so especially no more bang. The starter loves me for the cam change as well.
Since then I've replaced the cams with S&S 551 EZ starts so especially no more bang. The starter loves me for the cam change as well.
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Road Warrior
Joined: Jun 2009
Posts: 1,943
Likes: 3
From: NYC
My understanding of the stock comp is that the comp gets bottomed "forward" when cranking and get bottomed "backwards" when it lights off.
so now on your harley. as the miles accumalate, carbon builds up in the pistons, this results in higher compression. When you shut your bike off, in most cases, the engine will stop turning right before top dead center due to the compression which acts like a brake. if you try to start your bike while the compression build up is still there....the engine will kick back and grind the starter teeth. where does the compensator fit into all this....a good compensator will transfer axial energy into a horizontal one and due to the spring action put that energy back into rotational energy in the correct direction. If you wait a while for the compression build up to dissipate....the engine will not crank bank. If you bump your bike forward while in a high gear, its the same as feathering the lawn mower start cord and the bike will not crank bang either.
so root cuase is carbon build up leading to increase compression which results in a pressure build up .
Grand HDF Member
Joined: Jan 2012
Posts: 4,459
Likes: 2,896
From: Oklahoma
Your theory is fine except for those who share my experience. Mine had the bang from day one and the factory standard 3 or 4 miles on the odometer. For 2 years I thought it was heavy spark knock because the cylinder has more air in it at rest than it will ever have while running. When I got on the forum and began reading about the weak compensator, I finally broke down and got the SE unit. Installed at 15,000 miles and no more starter bang, even at the present 45,000 there is still no bang. The only explanation I can come up with is that some of the original comps worked at or above engineering specks, some below due to manufacturing tolerances.
Extreme HDF Member
Joined: Jun 2011
Posts: 10,216
Likes: 224
From: Glendale AZ
not to disagree...but a different perspective. Think about starting a gas lawn mower. Anyone who has used one for any given time will pull the crank cord out a little and get a feel for where the pistons are at. If you feel the psitons are just before top dead center...you do not want to crank that cord...why...becuase the engine will yank you back. SO you pull the cord a little and bump the pistons past TDC.
so now on your harley. as the miles accumalate, carbon builds up in the pistons, this results in higher compression. When you shut your bike off, in most cases, the engine will stop turning right before top dead center due to the compression which acts like a brake. if you try to start your bike while the compression build up is still there....the engine will kick back and grind the starter teeth. where does the compensator fit into all this....a good compensator will transfer axial energy into a horizontal one and due to the spring action put that energy back into rotational energy in the correct direction. If you wait a while for the compression build up to dissipate....the engine will not crank bank. If you bump your bike forward while in a high gear, its the same as feathering the lawn mower start cord and the bike will not crank bang either.
so root cuase is carbon build up leading to increase compression which results in a pressure build up .
so now on your harley. as the miles accumalate, carbon builds up in the pistons, this results in higher compression. When you shut your bike off, in most cases, the engine will stop turning right before top dead center due to the compression which acts like a brake. if you try to start your bike while the compression build up is still there....the engine will kick back and grind the starter teeth. where does the compensator fit into all this....a good compensator will transfer axial energy into a horizontal one and due to the spring action put that energy back into rotational energy in the correct direction. If you wait a while for the compression build up to dissipate....the engine will not crank bank. If you bump your bike forward while in a high gear, its the same as feathering the lawn mower start cord and the bike will not crank bang either.
so root cuase is carbon build up leading to increase compression which results in a pressure build up .
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Stage IV
Joined: Apr 2012
Posts: 4
Likes: 0
From: Canal Winchester
I thought my starter might be going bad, but this theory makes sense. Reason being, I only notice it after I start the bike up soon after shutting it down. Thanks speaker fritz
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not to disagree...but a different perspective. Think about starting a gas lawn mower. Anyone who has used one for any given time will pull the crank cord out a little and get a feel for where the pistons are at. If you feel the psitons are just before top dead center...you do not want to crank that cord...why...becuase the engine will yank you back. SO you pull the cord a little and bump the pistons past TDC.
so now on your harley. as the miles accumalate, carbon builds up in the pistons, this results in higher compression. When you shut your bike off, in most cases, the engine will stop turning right before top dead center due to the compression which acts like a brake. if you try to start your bike while the compression build up is still there....the engine will kick back and grind the starter teeth. where does the compensator fit into all this....a good compensator will transfer axial energy into a horizontal one and due to the spring action put that energy back into rotational energy in the correct direction. If you wait a while for the compression build up to dissipate....the engine will not crank bank. If you bump your bike forward while in a high gear, its the same as feathering the lawn mower start cord and the bike will not crank bang either.
so root cuase is carbon build up leading to increase compression which results in a pressure build up .
so now on your harley. as the miles accumalate, carbon builds up in the pistons, this results in higher compression. When you shut your bike off, in most cases, the engine will stop turning right before top dead center due to the compression which acts like a brake. if you try to start your bike while the compression build up is still there....the engine will kick back and grind the starter teeth. where does the compensator fit into all this....a good compensator will transfer axial energy into a horizontal one and due to the spring action put that energy back into rotational energy in the correct direction. If you wait a while for the compression build up to dissipate....the engine will not crank bank. If you bump your bike forward while in a high gear, its the same as feathering the lawn mower start cord and the bike will not crank bang either.
so root cuase is carbon build up leading to increase compression which results in a pressure build up .
Mike
Club Member
Joined: Aug 2008
Posts: 479
Likes: 1
From: In the flatlands!
just wanted to put this out into the general knowledge bank. Im one of those guys that had the startup crank bang problem. I did buy the SE comp but never got around to install it. I did some motor work which included add compression release. Using the compression release's I never had the startup crank bang noise. I'll get around to installing the SE comp at some point. Also found out that these is a spring pack kit 83936-09 that some folks think will upgrade a standard compensator to a better compensator but not quite as good as the SE compensator.
I had the startup, crank bang noise when hot (say right after fueling up) so I replaced the comp with the SE. First stop the next day I still had the startup crank bang noise. I immediately replaced the battery and now no more problems until after @2-3k miles on the SE comp the darn thing started making noise to no end. Was reading about some with the SE comp going south. I reinstalled my original comp...no problems since! But, I'll have to say, some are having good luck with the SE replacement.