No Grunt

Neil67

Joined
Jul 31, 2014
Messages
9
Location
Southern England (UK)
Bike
St1100 abs/tcs
hi guys hope someone can help.
last year I had a problem with loss of power and no torque, dies under load.
well not really much change. the things I have done are
1 remove vac switch for fuel line and yes line is plugged
2 k&n filter cleaned and re-oiled
3 replace carbs all 4 with stripped down and cleaned/checked carbs
4 new plugs
5 changed fuel
now although I have seen some improvement the bike feels slow and lazy no grunt like there used to be in fact it is difficult to get bike above 70mph and mpg is drastic as in around 22mpg
I am thinking and I really don't know is this an ECU fault or coils or plug caps I just don't know.
the pan is a 96 plate cbs/abs/tcs 1100
any help would be greatly received
thanks guys an gals
 
Check the primary side of the coils. I had a wire break at the crimp on connector, hidden in the installation, Same type of symptoms, was running on only two cylinders most of the time. Took a lot of time to find it as the wire was broke with in the insolation.
 
If you look in the service manual or a Clymers manual you can find how to test the coils, wires and spark plug caps. All you need is a multi-meter. The hard part of this test is to make sure that the test leads from the multi-meter are touching the contacts on the spark plug caps and the leads connected to the harness if the coils are in the bike. If you have removed the carbs make sure you replace the carb boots and make sure that the carbs seat properly and that the clamps are tight.

Replace fuel filter.

Did you check the fuel pump flow and pressure? See manual for procedures.

Now one last question have you checked valve clearances? Tight valves will make the engine hard to start and will have a lot of popping on deceleration and performance will be impacted. Checking the valves are relatively easy.
 
Take a look at all plugs to see if some cylinders are running better than others.
Spark wires sound like a good possibility.
Except for the fact that you have replaced Carbs I would also vote for a torn diaphragm, might want to peak again.
 
Mark said:
torn carb diaphragms would be my guess.
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He already replaced the carb-bank with an overhauled one...

err... simple things: choke stuck/operating properly? Replaced carb-boots too? (serious vacuum leak if thorn)
 
Neil67 said:
....
I am thinking and I really don't know is this an ECU fault or coils or plug caps I just don't know.
Click to expand...

The ECU can be removed from your list, as the 1100 doesn't have one. The previous posts should get you going the right direction in your search, as the problem is most likely fuel or ignition related. You didn't mention the mileage on the odometer. When was the last time you checked valve clearances? Have you ever removed camshafts to exchange shims? If so, have you double-checked the cam timing marks to be sure a cam wasn't reinstalled one tooth out of time? That could definitely affect performance, if not creating internal engine damage. If you haven't done so already, try doing a compression check and/or leak-down test, especially if you can't find a fuel or ignition system problem.
 
Don B said:
The ECU can be removed from your list, as the 1100 doesn't have one.

If so, have you double-checked the cam timing marks to be sure a cam wasn't reinstalled one tooth out of time? That could definitely affect performance, if not creating internal engine damage. If you haven't done so already, try doing a compression check and/or leak-down test, especially if you can't find a fuel or ignition system problem.
Click to expand...

No ECU , but the ST1100 does have an ignition module that controls ignition timing advance. I carry a EBay spare in my top box, BTW.

+1 on the other above checks. If you do a compression check, make sure the carb slides are pulled up before you crank the engine. I'll be very surprised if low compression is your problem, tho. But if you do, check for tight valve clearances.

Also, if you have a timing light that has a trigger lead that clamps over a plug wire, you can use that to check to see if you have voltage at each plug wire. I had an intermittent voltage on my old Guzzi and I was able to track down the problem using the timing light trick.

I would also check for dragging brakes, too. Especially the rear brake. My bike had poor accleration above 75 MPH and it turned out to be a dragging brake. But my gas mileage wasn't 22 mpg , tho.

You may have more than one problem causing your symptom.

Check to make sure the plug wires from each coil are connected to the two plugs on the SAME SIDE / SAME HEAD. The ST is wired differently than the old 4-Cylinder Gold Wings. I bought an old GL1100I and thought the GL was wired up the same as the ST ( NOT !! ) when Ii replaced the plug wires. On the GL one coil feeds the two FRONT cylinders, and the other coil feeds the REAR cylinders. Wonder if by mistake , your ST is wired like a GL should be ???? It would start and idle OK, but had no power, since it was only running on two cylinders.

If I had to guess, my bet would be on a bad coil pack, primary wiring problem, or mis-wired spark plug wires.

Good luck, keep us posted.
 
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Check the enricher operation, may be stuck partially open/closed... would have another look at the carb diaphragms also.
 
No body else has mentioned it so . . . did this start last year AFTER installing the K & N, by any chance? Are you using the foam sleeve on the K & N as well?
 
does the motor cough or sputter?...... ANY indication of motor malfunction? no-grunt is so generic that it could be just about, anything!
 
Check the enricher operation, may be stuck partially open/closed... would have another look at the carb diaphragms also.
Click to expand...

I thought the "enricher" was just a fast idle lever. It actually "enriches"?
 
Grabcon said:
Now one last question have you checked valve clearances? Tight valves will make the engine hard to start and will have a lot of popping on deceleration and performance will be impacted. Checking the valves are relatively easy.
Click to expand...

Wouldn't you have to have several tight valves? And by tight I mean tighter than at the minimum allowable valve clearance. Would only one create the symptoms you describe? I thought the ST's engine was fairly stable and that the valve clearances move very very slowly if at all.
 
thanks guys a lot of sound advise I will keep you advised of what I find. the silly thing is it was running really nice and then felt like it dropped a cylinder.
all plugs are good, well they should be they are new and being such have no differential signs between them. nothing except what has been mentioned has been taken apart so leads put back where they came from, valves not touched, bike rolls freely no dragging at all. when I took the carbs off the boots they sit on were in good condition no cracks or splits so I am happy with them I will take the carbs off again and check diaphragm's and then check for sparking issue, she will rev nicely and sort od accelerate but no real power if you think about overtaking anything forget it crank throttle open and nothing I have also changed the fuel pump for a good strong one, oh yes.. I don't know if this will help but she smells of fuel like rich but choke mech is working and is off and there are no leaks internal or external. any way thanks again guys I will keep you posted
cheers
Neil
 
SMSW said:
Wouldn't you have to have several tight valves? And by tight I mean tighter than at the minimum allowable valve clearance. Would only one create the symptoms you describe? I thought the ST's engine was fairly stable and that the valve clearances move very very slowly if at all
Click to expand...

The reason I mention this is that I had this happen to my 1991. It got to the point where it would start. I went through all the things mentioned in this post. As a last resort based on a comment from a Honda service guy I checked the valve clearance and had several that were tight. And I mean very tight, I could not get a 0.0015 feeler gauge in to measure the clearance. Luckily the motor was telling me that it should not run or it will be bad. Once set the motor started immediately and has been fine every since.

Just because they are a stable motor does not mean that things don't change.
 
The ST1100 has no MAP sensors. Based on the OP's reported info, a K&N air filter would have absolutely nothing to do with this problem.
 
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