Very little compression

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bearholt
Posts: 3
Joined: Sun Mar 28, 2004 7:03 pm
Bikes: '54 FLE; '40 & other years trike, '43 flat track racer; 2003 FLHSTC
Location: Edmonton, Alberta, Canada

Very little compression

#1

Post by bearholt » Mon Jun 28, 2010 9:49 pm

I was just wondering if anyone out there could suggest why I suddenly have very little compression in my '54. I rode it into the shop (heated) last fall just fine. This spring I went to kick it over and could get no compression. I've checked the pushrods (twice, and left them looser than I normally like just to be sure they're closed) (solid lifters) and have visually watched all the valves moving and have looked at them with a borescope too. The top rings at least look fine (again with a borescope) and I've put oil into them 3 times now. After the last time I got one conpression kick but then it went away again, so then LOTS of oil the last time. I've left it for 2 weeks now to soak in good. Also I had a quart leak down from the tank during the winter but drained all of that from the cases. I can't figure this out. It's too coincidental to have happened to both cylinders. I took a compression reading and got an equal 30 lb. from both. The engine was a very tight rebuild but I've put on over 1000 miles on it since.
Thanks

Bear



NightShift
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Re: Very little compression

#2

Post by NightShift » Mon Jun 28, 2010 10:14 pm

Dear Bear,
That IS diabolical! Can you put air pressure through the sparkplug holes and listen everywhere like the timing plug?

Sounds like a genuine X-files case to me,

steve_wood
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Location: Belleville, Ontario, Canada

Re: Very little compression

#3

Post by steve_wood » Mon Jun 28, 2010 10:22 pm

Maybe the head bolts came loose??

PanPal
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Re: Very little compression

#4

Post by PanPal » Mon Jun 28, 2010 11:33 pm

Clutch could be slipping too. You sure the motor is turning all the way over when your kicking.

john HD
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Re: Very little compression

#5

Post by john HD » Mon Jun 28, 2010 11:39 pm

what kind of rings did you use?

john

bearholt
Posts: 3
Joined: Sun Mar 28, 2004 7:03 pm
Bikes: '54 FLE; '40 & other years trike, '43 flat track racer; 2003 FLHSTC
Location: Edmonton, Alberta, Canada

Re: Very little compression

#6

Post by bearholt » Tue Jun 29, 2010 3:13 am

Hi to all that answered my post. I had considered doing a full leakdown test next but then John, you peeked my curiosity and I thought I'd check my clutch. The engine was turning over OK but maybe slipping. I figured I try something and disconnected the clutch rod from the lever. Behold!! Compression and a start on the 5th kick! A little smoky from the oil I put in the cylinders but that was all. The 54 purrs again. Perhaps a clutch adjustment is in order...
Thanks to everyone that answered. Should have come to the forum 3 months ago :-) Cheers
Bear

bearholt
Posts: 3
Joined: Sun Mar 28, 2004 7:03 pm
Bikes: '54 FLE; '40 & other years trike, '43 flat track racer; 2003 FLHSTC
Location: Edmonton, Alberta, Canada

Re: Very little compression

#7

Post by bearholt » Tue Jun 29, 2010 3:14 am

Sorry that was PanPal that had the clutch idea. Thanks

PanPal
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Re: Very little compression

#8

Post by PanPal » Tue Jun 29, 2010 9:18 pm

Sorry that was PanPal that had the clutch idea. Thanks
Well my name is John anyway. Good to hear you got it going!

john HD
Moderator
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Re: Very little compression

#9

Post by john HD » Tue Jun 29, 2010 10:13 pm

my father in law (who was named john) once said

"all the good guys are named john"

john :D

Henrik_K
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XLH '65
Location: Copenhagen

Re: Very little compression

#10

Post by Henrik_K » Sun Jul 25, 2010 9:00 pm

I'm in the same situation as you - with very little compression.

How would you know if the clutch is slipping? If I can see the main sprocket rotate when kicked - everything (in that department) must ok, or??

Thanks, Henrik

john HD
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Re: Very little compression

#11

Post by john HD » Sun Jul 25, 2010 10:13 pm

How would you know if the clutch is slipping?
easy, remove the primary cover. then place a chalk mark on the pressure plate and one on the clutch shell. make the marks so they line up. then kick the bike over about 5 times. if the marks remain lined up the clutch is holding and will probably handle top gear under acceleration.

if they do not remain lined up try one half turn on each of the nuts on the pressure plate and try again.

john

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