Re: Harley Compression

 
:90-95 psi rear, and 95 psi front.  I next ran to my brand new repair
:manual to find the acceptable range, but it seems Harley doesn't care
:about compression, as not only can I not find the allowable compression, I
:can't find a How To, either.  I was reminded while searching the web that
:I should have help the throttle open while cranking to ensure adequate
:airflow.  Ah well, perhaps I'll repeat for tomorrow.  Since it snowed 6
:inches today, I won't be riding, so I'll have time.
:
:Anyone know what's normal compression for a stock 1997 80 CID
:ElectraGlide?
:

Don't quote me, but I'm pretty certain that it is well above the
readings you are getting. I seem to recall 150 and up for most Evo
motors, depending on the cams, pistons and heads. 190-220 wouldn't
be out of the norm for many motors.

Make sure you have the throttle wide open when you run the test. By
the condition of your spark plugs, I suspect problems.


---
Typical White Person

 

I suspect problems with his compression tester!!

--
PoorUB
'05 Ultra Classic

 

I think it's his methodology rather than the tester.  It could be anything,
I'd guess valve timing being off (which would explain the plug colors).

 

Thanks Steve,
I didn't mention some words of wisdom my dad had given me about autos
because I don't trust my crappy memory, but your number fits right in
there.  As I recall, he said a V8, which often had 8 or 9 to 1 compression
ratio in those days, should run something around 130 or 150, and that 70
was about as low as compression could get before you in effect had a dead
cylinder.  I think my bike has something like 8.5 to 1 compression ratio,
so I was thinking I should have been in the 100s anyway.  It's been 30+
years since my dad taught me about engines so I might have it wrong.  At
least the two numbers were within 5% of each other.

Robert

 

Did you do the compression test with the throttle wide open? You always
should, because that's the reading you want, and it varies considerably
from a reading with the throttle closed.

It's just that of all the things that could be wrong with a five
year-old Harley, I'd put compression fairly low on the list.



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