Rattle at 40

I was riding my bike (Honda Sabre 1100) today and heard at around 40 mph in
third and fourth gears some kind of rattling. I stopped to check it out,
but couldn't find a single loose part. If I rev the engine while stopped,
there is nothing making noise either...

It probably happens at higher speeds, but I do not notice it with the wind.

Any ideas?

TIA,
Sabre

 

Yes -- you need earplugs.

 

Try this.
Go out on a long straight stretch with little or no traffic.
Take it up to 40+ until you hear the rattle, pull in clutch and let engine
drop to idle and coast for a bit.
Rev and let clutch out go back to 40+, pull in clutch, leave in gear and
kill engine, coast.
Restart.Go back to 40+, pull in clutch, shift to neutral and kill engine,
coast a bit.
Restart, regear and your done.
Post and let us know if and when the rattle disappeared or changed.
PQ

x

 

How does one clean the carbon out of the combustion chambers?

 

The traditional way to blast carbon out of an engine was to go out and
ride hard for a few miles. If somebody asked why I was riding full
throttle in 3rd gear at 100mph, I'd explain that I was "just blowing
'er out". You can easily ride 100 mph in 3rd on a literbike.
Nowadays there are literbikes that will go 100 in 2nd gear...

There are commercial preparations that will loosen up carbon so it goes
out the exhaust pipe under normal engine operation. You usually add a
few ounces to a tank of gas and go riding. Look on the chemicals shelf
at Walmart or Pep Boys for those chemicals. They usually contain oily
solvents...

Riding on a damp day when there is a lot of moisture in the air will
blow carbon out of an engine, just like steaming it out...

Here is the steam procedure. Do this at your own risk. Very carefully
spray a fine mist of water into the carb mouths while the engine is
running in neutral at a high speed, say 5K or 6K...

The water is supposed to turn into steam, making high pressure in the
combustion chambers and this loosens the carbon so it blows out the
pipe. You'll see lots of black soot blowing out the tailpipes...

Don't breathe the soot...

The hazard of steaming out the carbon is when you get too much liquid
water in the combustion chamber on the compression stroke. You can bend
a rod if the piston hydraulically locks, even momentarily...

 

1st, even. ;-)

 

I just got rid of a whole bunch of alarming noises by remounting
and damping the aluminum bash plate that protects my oil pan.
The bash plate was a large flat aluminum surface acting just
like a sounding board and picking up all kinds of funny
harmonic vibrations at different RPMs. With a little bit of
rubber damping on this one spot, the engine sounds 100% OK.

Take a look at the tank, muffler and other possible sources
of harmonic vibrations. Also, does it come and go at given
RPMs, or as the tank gets empty ? Any big flat surface is
a suspect, especially if it's sheet metal.

Just for laughs too, you might try some techron in the tank
in the hope it might smooth out the engine.

If you've got a timing chain, they can also make some funny noises
if they're worn or not tensioned right, though I'd expect
you'd hear that when stopped.

 

Thanks for all those clues.

I haven't resolved the fouling problem in my left cylinder (waiting for
delivery of carb overhaul kits). I was somewhat worried about getting
the engine too carboned up during my test drives. I take it that
getting rid of carbon isn't all that hard ... I'm thinking that I'd
better watch out for pinging though ...

 

Heavy carbon buildup can restrict intake and exhaust flow and it can
cause pinging when it glows red hot and ignites the fuel/air mixture
before the
spark plug ever fires...

You can cool off the combustion process by wasting fuel from very rich
jetting, or you can fall back on an old trick that isn't seen very
often anymore. You can inject water into the intake tract...

Pinging and detonation were studied in the 1920's by an investigator
named Ricardo. Gasoline octane was so low in those days, the engine
designers didn't dare use more than about 4:1 compression ratio, which
reduced the "air standard efficiency" of the engine...

Air standard efficiency is the theoretical percentage of heat converted
to work, and it assumes that the cylinder is filled with dry air and
heat is added. It ignores silly things like the fact that the air
contains X percentage of moisture and maybe 15 percent fuel by weight
and it ignores the fact the evaporating gasoline cools the process...

But, anyway, if an engine has an ASE of 47.5% at 5:1 compression, it
will have 60.2% ASE at 10:1 compression. The 27% increase in efficiency
was worthy of being found, somehow...

Of course, modern gasoline isn't the low octane stuff that Ricardo had
to work with, nowadays a procedure called "reforming" cracks the
pentane ring
in low octane gas and re-arranges the molecules to make them burn
slower and be more resitsant to pinging...

But Ricardo had to work with what he had. One of the interesting things
he found was that engines pinged under heavy load if they weren't
turning fast enough and they pinged under light load, too. The pinging
phenomenon seemed to be related to combustion pressure in the cylinder.
Under heavy combustion pressure, the engine wouldn't ping until the
operator reduced throttle...

As I recall, Ricardo worked with water injection, too.

Water doesn't burn, why inject it? When you heat a pound of water to
raise the temperature 1 degree, it takes an amount of heat called a
British Thermal Unit to raise the temperature 1 degree F. But if you
instantly turn the water into *steam* in the combustion chamber, that
same pound of water absorbs 944 BTU's changing phase.

So a tiny amount of water introduced into a combustion chamber absorbs
a lot of heat and cools the combustion process, while at the same time,
the water is expanding into steam that occupies about 2700 times the
space that the water took up.

So the water raises the combustion pressure, which forces the spark at
the plug to occur later than it would if there was wasn't as much
pressure in the cylinder...

The injected water does three things: it cools the combustion chamber,
raises the combustion pressure and retards the spark, and it blasts the
carbon buildup out of the top end of the engine...

Back in the 1940's and 1950's, hot rodders who'd found out about
water/alcohol injection used on WW2 airplane engines jumped to the
conclusion that the alcohol was in the mix to raise horsepower.
Actually the alcohol was there as an antifreeze agent...

Nowadays, only oldtimers seem to remember anything about decarbonizing
an engine with steam...

 

Sorry I wasn't able to respond sooner, but I have had some computer
problems. Anyway, thank you all for your input. I Just got back from a
ride, and took her to about 90 in 3rd. Was there only for a moment before
shifting. No change.

Although now it will make the noise while revving it.

On my way to the highway I stopped by the local auto part store to get a
spark plug socket, as none of mine fit. But they didn't have one for me
either. I wanted to see if there is any carbon build up on the plugs.

Thank you for all of the ideas.

Someone thought it might be the timing linkage... I will investigate that
next.

I will be on vacation and will not have internet access for the next week,
so don't expect any replies from me.

Thank you all!

PS
What's the difference between a Honda Sabre and a Honda Shadow Sabre?

 

snip

Heh. Put 8500 miles on mine and sold it for what I paid for it new
($3000).

Had a co-worker tell me it was a POS, his buddy had one and it "would
barely do 100".

Can't be any help on the tech-end, other than routine maintenance,
only problem I had with mine was after doing a squid-drop in the
gravel the LH mirror head would tuck in a little at about 110 mph.

Poor mirror spent better than half it's life tucked in.

Another co-worker once took it for a spin and utterly and totally
dropped the hammer in 2nd while swerving to the left to pass a
pick-up. He didn't have a lot of street experience, but his dirt
knowledge paid off as he did a power-slide on dry pavement all the way
around the pick-up (didn't let up).

He thought I would be pissed (I saw the whole thing), I was jealous
that I didn't have the cojones to try it.

I guess I would be a recovering V-65 Sabre former owner also.

Sigh.

TC