Well, there you go! After 22 years of 1100 ownership and never having need to go looking for that connector, I learned another tidbit about the machine!
Compression Test & the Starter Motor
- Thread starter glen
- Start date
why are you doing a compression test??? Is there a cylinder misfiring?? If is running good a compression test will tell you nothing. if one cylinder is 7 lbs lower than the others what does that mean? What are you going to do to correct the problem or is it a problem. A better indicator might be a running compression test. All this other bs about grounding coil wires and burning out modules is in theory only. I have done hundreds of compression tests and only be necessity unplugged coils. If you have fuel injection the fuel pump needs to be disabled, the fuel pumping into the cylinders can cause an inaccurate reading. If it has a dead cylinder then a compression test could help pin point the cause follower up by a leak down test. Now we use a pressure sensor for compression tests. It gives me a graph of cylinder pressures on each one of the four strokes. You can tell if the valve adjustment is an issue by comparing suction of each cylinder. So what is it you are trying to solve???
I suggest you read the first post.
I think it's a hoot 
that with all of the high mileage ST1100 we have in this group very few folks have actually done a
compression test. Mother Honda must have done a very large number of thing correctly with they made these bikes!
that with all of the high mileage ST1100 we have in this group very few folks have actually done a compression test. Mother Honda must have done a very large number of thing correctly with they made these bikes!
YIKES!!!! guess it's not a good time to ask questions glen. Shut up, nobody knows what they are doing. EVERY BODY SHUT UP!!!
Slydynbye
Will ride for Pie
Sounds like you've been there.
Where is this Maintenance cover and what does it look like? What needs to be removed to get to it?
That's the piece of tupperware (one on each side) that fits in the space where the engine's heads stick out. Held by two socket head bolts.
I changed out the coils and plug wires about a month ago so I had to unplug that connector
Slydynbye
Will ride for Pie
OK found the connector, it's tucked up behind the left pocket. You can see it by looking in and up past the valve cover looking forward from the rear after removing the maintenance cover. I think that is probably the best and safest way to disable the ignition.
Hey folks, sorry for the delay. Life attacked and I had to put this one on the backburner. I see y'all have been busy here in my absence! And I appreciate all the info. Truth is, there's nothing wrong with my bike that I know of (except for that random clicking noise). I'm just working through the manual in order to learn as much as I can about the machine. Also, when I finally got time to try it again, the parts store no longer had a compression gauge for rent. So, I'll keep you posted after I find another one.
Nice to know !! Now I can add cleaning those connections to my yearly list of PM chores to accomplish !!
Sorry, I'm a little late chiming in here ......
To really understand what's happening, you have to consider the inductance of the coil primary and the action of a capacitor inside the Ignition Module. The I.M. charges the coil primary ( inductor). Energy is stored in the coil primary because of the current ( E= .5 * L * I^2 ) . Then the current source is turned off, but with the help of the capacitor, current continues to flow ( now through the coil primary & capacitor). The current decreases while charging the capacitor. A change of current induces a voltage into the coil secondary. The primary tries to oscillate for a while ( because of the inductor & cap interacting ) and would if there was no load on the secondary and the primary voltage would get a heck of a lot higher if the spark plug was not connected. But with the spark plug connected, Like Bush said, the secondary voltage is limited and the energy is transferred from the primary to secondary and then spark plug.
By knowing the inductance of the primary & secondary, turns ratio, and some other parameters, a mathematical model using a Laplace Transform can show what happens over time with the spark plug disconnected.
But Ya, disconnecting the coils from the I.M. by unplugging that connector is the quick & easy way to protect the I.M. when the plugs are removed when doing a compression check.
With the CV carbs on the ST1100, it seems to me the slides also need to be lifted ( some way ) when doing a compression check. I did a compression check on a Moto Guzzi without holding the throttle open, and I got some really low readings until I realized I needed to open the throttle to get air into the cylinders.
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You just made that up, didn't ya?
Not really ..... but I forgot to multiply by .5 , so it should have been : E= .5 * L * I^2 For a capacitor the energy stored = .5 * C * V^2
For mechanical Energy : E = .5 * M * V^2 See the similarity between the three equations ? For an Inductor ( L ) the energy stored is a function of the current squared. For a Capacitor ( C ) the energy stored is a function of the square of the voltage stored in the cap. And for a Mass ( M ) , the mechanical energy stored is a function of the square of the velocity.
For mechanical Energy : E = .5 * M * V^2 See the similarity between the three equations ? For an Inductor ( L ) the energy stored is a function of the current squared. For a Capacitor ( C ) the energy stored is a function of the square of the voltage stored in the cap. And for a Mass ( M ) , the mechanical energy stored is a function of the square of the velocity.
BTW, a Capacitive Discharge Ignition system works much differently than the above explanation.
With a CDI system, the ECM charges a fairly high value capacitor, then it is discharged into the coil primary. This cause the primary current to increase , instead of decreasing, but the change in primary current still induces a voltage into the secondary, and a spark is produced at the spark plug.
With a CDI system, the ECM charges a fairly high value capacitor, then it is discharged into the coil primary. This cause the primary current to increase , instead of decreasing, but the change in primary current still induces a voltage into the secondary, and a spark is produced at the spark plug.