help - no compression
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Stage I
Joined: Jun 2010
Posts: 1
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help - no compression
Please help. I am trying to help a friend's sister out by getting her old bike up and running. It is a 1979 Shovelhead with only 37,000 miles. I had a friend bring over his compression tester and we got 125 psi in the front cylinder and zip in the rear. We squirted some oil in the cylinder and still nothing. Obviously, there is a problem. Any suggestions? Also, I am in north Atlanta. Any recommendations on who might work on it. I have heard that most dealerships wont work on a bike this old. I am just trying to help out and it is getting worse everyday. Thanks in advance for your help.
Elite HDF Member
Joined: Dec 2009
Posts: 4,598
Likes: 14
From: navarre ohio
start by pulling the head, gonna need a valvejob at least.. it probaly has the rings stuck in the piston, it realy isnt that hard or expensive to make it rite.. get a manuel, it is probaly going to need the cyl,honed,new rings, the piston cleaned up.. autozone loans all the tools you would need. you would probaly have less then $200 in rings,gaskets, and a head job..get the head done first, they will be able to tell you if there is a bad valve or if it was stuck open enought to cause that, bolt the head back on, no need for the pushrods rocker box carb, exhaust yet, recheck the compression, if it was good, put back togeather.. if not rings are stuck(unless you see a quarter inch gouge in the cylinder walls or a hole in the piston or somthing)the head gasket can be reused after checking if it wasnt started.....
Last edited by j1mmy; Jun 9, 2010 at 11:14 PM.
Cruiser
Joined: Jan 2009
Posts: 143
Likes: 0
From: New Mexico
Pull both spark plugs out and run compressed air into the rear cylinder with the piston at top dead center on the compresion stroke and the cylinder should hold compression if it does not hold listen at the exhaust pipe to see if the air is comming out there and listen at the carb and seeif it is comming out there. With the bike in gear and on the ground and at top dead center the cylinder should hold most of the compressed air but since you are experencing NO compression it will likely leak from one or the other.
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