Not at all, one of my co-workers has one with over 36K and it runs fine. I
don't pay much attention to cold motors behavior since that's only a temporary
situation. The determining factor is always how much care it had on the way to
it's present state. Almost any motor will puff a bit cold. Just lay a light on
the floor so that the exhaust is between you and it. Does it use any oil ? Do
you have to add often ? Frequent oil changes will prolong a motor's life for
years. Lot's of early Wings smoked like mad on start-up and they still run fine
at over 100K.
--- On Mon, 11/3/08, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
From: [EMAIL PROTECTED] <[EMAIL PROTECTED]>
Subject: [Nighthawk Lovers] Re: Compression Testing
To: nighthawk_lovers@googlegroups.com
Date: Monday, November 3, 2008, 6:01 AM
You mention that 23K is high but not excessive and I have been wondering what
that figure might for other nighthawk models. My 84 650 has about 26K (Ihave
had it only one season) is beginning to show a little blue smoke at startup
after sitting all day but over runs very well. Is the end near? Thanks
On 11/2/08, Dennis Hammerl <[EMAIL PROTECTED]> wrote:
Your intentions are good but your methods need a little refining. Testing on a
warm motor is preferred. Your measurements are all quite low and that tells me
some about your situation. First off, both plugs out to reduce effort of
starter. Check and adjust valve clearance before checking compression. 23K is
considered high mileage for one of those but not excessive. When taking a
compression reading, open the throttle completely and have the choke open as
well. (if you can't get air into the engine, there is nothing to compress.)
This alone should result in a higher reading. I would be quite happy with about
150lbs each. A Honda engine will run OK at as low as 100lbs. Below that figure,
expect poor running. The difference between cylinders is important. That should
be no more than 10~20lbs.
FYI: compression tests are cumulative (longer you crank, the higher it gets up
to a point) They are considered to be a rough indication of condition. A
leak-down test tells far more and diagnoses problems. Operate the starter for
no more than 5 seconds. That's more than enough to get results.
Your running problems are indicative of carb problems more than engine. You
didn't say what year 450 you have, earlier ones (80's) have drivability issues
from lean carburation.
Happy wrenching
--- On Sun, 11/2/08, Redtail <[EMAIL PROTECTED]> wrote:
From: Redtail <[EMAIL PROTECTED]>
Subject: [Nighthawk Lovers] Compression Testing
To: "Nighthawk Motorcycle Lovers!" <nighthawk_lovers@googlegroups.com>
Date: Sunday, November 2, 2008, 4:23 PM
I bought my first bike, a used CB450SC back in the summer and have
been riding it ever since. It has 23000 miles on
it. The engine
coughs and spits and backfires sometimes, but starts and runs every
time. I had a quick look at the carbs and gave them a quick clean at
the time but plan on going at them again as soon as I quit riding for
the winter, (which will be soon.) I borrowed a compression tester
from a friend to check it out in case I have to perform a little
engine work. I'm not necessarily good at diagnosing a problem, but
once I know what is wrong, I can fix just about anything.
A couple of questions:
1) Should the test be performed with the engine cold, warm or both?
2) What should a normal reading be?
3) Should both spark plugs be out at the time or does it matter?
So far I have only checked it with a cold engine. The left cylinder
tested about 80 to 85 each time, whereas the right one was down about
55 at first, but increased to 100 after checking it the forth time.
(I used a spare boat battery
so as not to wear down the bike battery
and I let the starter cool for 10 minutes in between tests.)
My thinking is that the oil was being circulated and coating the
cylinder walls and increasing the pressure in the right cylinder, but
what about the left one? Is there a problem with the rings in that
one?
Also, I read somewhere once that if one cylinder is low and you squirt
some oil into it and then check the compression again, if the numbers
increase the rings are worn, and if they stay the same, the valves are
leaking. Is my thinking correct?
Any help would be greatly appreciated.
Paul B.
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