Checking Compression
Thread Starter
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Elite HDF Member
Joined: Mar 2006
Posts: 4,722
Likes: 5
From: Biddeford, Maine
Checking Compression
I want to check the compression on my bike, and I'm looking for the proper procedure to do this.
I'm guessing with an EFI bike, I should disconnect the fuel pump fuse, remove both plugs and ground them out, put the compression gauge into a sparkplug hole, and crank the motor over 4-5 times. Then repeat on the other cylinder.
Does that sound right?
Steve
I'm guessing with an EFI bike, I should disconnect the fuel pump fuse, remove both plugs and ground them out, put the compression gauge into a sparkplug hole, and crank the motor over 4-5 times. Then repeat on the other cylinder.
Does that sound right?
Steve
Road Warrior
Joined: Nov 2006
Posts: 1,439
Likes: 2
From: Lancaster, PA
RE: Checking Compression
Sounds dead on to me. Pull the fuse or take off the seat and unplug the fuel pump (that's what my manual says to do for my bike, YMMV), whichever is easiest for you. 
Road Warrior
Joined: Nov 2006
Posts: 1,439
Likes: 2
From: Lancaster, PA
RE: Checking Compression
Touching metal. Just make sure they are up against the heads, fins not against the black krinkle finish. I grounded my plugs out and cranked the motor over till i had oil pressure before firing up the motor on my recent cam swap. Wanted to make sure the new lifters were pumped up.
ORIGINAL: twoseas
What's the proper way to ground the plugs ???
Ray
What's the proper way to ground the plugs ???
Ray
Seasoned HDF Member
Joined: Apr 2006
Posts: 10,675
Likes: 95
From: Billings,Mt.
RE: Checking Compression
ORIGINAL: Bryan TTM
gotta hold the TB wide open also...
gotta hold the TB wide open also...
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4th Gear
Joined: Sep 2006
Posts: 8
Likes: 0
RE: Checking Compression
What I did to make this all easier was I made a cord with a push button on one end and a clamp and starter plug on the other. Put the clamp on the hot nut on top of the starter and the white plug into the starter solinoid socket. Now I spin the motor over with the power to the bike turned off. Plugs don't have to be grounded, fuel pump is not running, and headlight is not burning. Made it for less than 10.00. Just used it on a buddy's bike the other day while he was changing cams. Spun the motor over with the outer cam chain off to make sure the oil pump was pulling oil before he assembled the whole thing back up and find out later it's not. Been there done that.
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Thread Starter
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Elite HDF Member
Joined: Mar 2006
Posts: 4,722
Likes: 5
From: Biddeford, Maine
RE: Checking Compression
Does the motor have to hot or cold in order to get a compression reading?
What does holding the throttle wide open do for a EFI bike?
I thought you had to ground out the plugs to protect the ignition coil or components?
Steve
What does holding the throttle wide open do for a EFI bike?
I thought you had to ground out the plugs to protect the ignition coil or components?
Steve
