Video of Gauges after Carb synch on 1997 ST1100 - good enough?

[PhotoDoctor]

Link to video:

At idle the needles all line up well - when I give it some juice the left gauge needle moves to it's own beat while the 3 others hang closer together.

I did the idle drop procedure after my first synch then did the sync process again a 2nd time.

I think this may be somewhat normal - I know there are a couple of very knowledgeable guys on the forum here and would like an expert's thoughts on this.

Thanks in advance.

 

[dwalby]

the sync is typically done only at idle, so not sure if it means anything, curious to hear other opinions. If one cylinder is a bit 'looser' than the others it may not pull vacuum as well, dunno. If it pulls normally under load, I'd forget about it, no sense looking for a problem that doesn't exist.

 

[bdalameda]

It looks like the damping valve on the LH gauge is closed too far and it cannot react fast enough to changes in vacuum.

 

[Slydynbye]

It looks like the damping valve on the LH gauge is closed too far and it cannot react fast enough to changes in vacuum.

I was thinking that gauge is having problems. Maybe swap tubes to see if it follows the cylinder or the gauge.

Then my Wild guesses start
Did you check/adjust the valves before synching carbs?
Possible cracked diaphragm on that cyclinder?
Possibly adjust the idle screw to see of that helps.

 

[Al st1100]

I have the same set. I get them to a point where the needles bounce a bit the set all the damper screws the same. I don't remember the number but made them all 1/4 turn out.

 

[PhotoDoctor]

Same thing when I swap tubes. I have several bikes so I don't have to be in a hurry to button this one up.

Another thing I often do is pull each plug wire - one at a time and check the rpm drop. The cylinder with the odd gauge reading behaves correctly on this test. However, there is another cylinder that has a good gauge reading but has no rpm drop when I pull the plug wire.

Yes, I know I'm being picky but it's a hobby and I'm still looking for the 50 mpg ST1100 that I occasionally hear about

 

[dwalby]

Another thing I often do is pull each plug wire - one at a time and check the rpm drop. The cylinder with the odd gauge reading behaves correctly on this test. However, there is another cylinder that has a good gauge reading but has no rpm drop when I pull the plug wire.

Interesting, I had a KZ1000 in the early '80s that did that same thing and I never figured out why. The bike ran at full power so I never bothered looking any further. Showed it to a mechanic once, he couldn't figure it out either.

Yes, I know I'm being picky but it's a hobby and I'm still looking for the 50 mpg ST1100 that I occasionally hear about

Mine has delivered 50mpg for the 24 years I've owned it, as long as I ride at 70-75mph or so. If I push it up to 80 then it drops a few. Now for the good part, I haven't done a carb sync in about 15 years. Never noticed any difference in 30 years of riding prior to that, tipped over my carb-stix and made it unusable, so I just quit doing it.

 

[PhotoDoctor]

dwalby - This bike is the same year as yours, 1997 and generally gets about 43 mpg. I did get 50 mpg once when riding with a friend who would not go over 55 mph. I believe all the ST1100's in the usa after 1996 came with main jets of 125 and pilots of 38 and call for the idle screw to be 2 5/8 turns out. When I did the idle drop all mine ended up around 1 1/4 turns out. It also appeared that I had two carbs with leaky float bowl gaskets. Thus, when all is back together hopefully I will have improved the mpg's some.