Engine Hiccups 1500 RPM and 2000 RPM

ngudsen

Joined
Aug 14, 2018
Messages
2
Location
Saline, MI
I hope someone can demystify an issue that I am experiencing with my "new to me" 2000 Honda ST1100.

My motorcycle has 138,000 miles on it and had a very well documented service history when I bought it. This bike replaced a 1982 Silverwing Interstate and is a really neat bike. It is everything that I wanted in a bike and in my mind it is a keeper.

Warmed up, the bike runs quite well (but of course I wonder if I can coax a little more power and throttle responsiveness out of it). But the thing that is truly worrisome to me is what I am noticing when the bike warms up....

When I start my ST, it makes a single "knock" (not very loud) as I rev through the 1500 rpm mark and then again at the 2000 rpm mark. At each knock, the engine stumbles a bit. It takes a lot of warm up time for the knock to not happen (or at least for it to be so subtle that I cannot hear/sense it).

From the service records, its been about 20,000 miles since the last time the carbs got attention. I presume that they could benefit from a cleaning/rebuild with new gaskets, diaphragms, etc. and I intend to do that at some point.

There is patter out on the web about a similar symptons and that this might be a carburetor balancing issue. There is one thread on this site, I think, that suggests that is could be a crank bearing issue. There are other threads that say it is a quirky trait of many ST1100's that is of no potential consequence and can be ignored.

Anyone experience anything similar with their ST1100? Any suggestions on where to start in troubleshooting this?

-Neil
 
if the 'knock' is abrupt and always at a specific RPM like you mentioned, then ignition would be my first guess. Carb issues are typically not abrupt, more of a gradual stumbling symptom, but you also mentioned stumbling. If what you're feeling is like an immediate misfire, then trace out ignition issues, if its a more gradual loss of power then trace out fuel issues. First thing to check because its easy is take off the right side cover and look for the vacuum fuel shutoff valve. If it looks like that valve has been bypassed, let us know, if it hasn't then ask how to do it because that's one of the first steps in fuel system troubleshooting.
 
ngudsen said:
There are other threads that say it is a quirky trait of many ST1100's that is of no potential consequence and can be ignored.
Click to expand...

My '96, when cold, will do this too, so did the '95 I had for 175,000 km, especially if the bike has sat for a few weeks, when fuel in the float bowls has had a chance to evaporate somewhat. I feel it is just the engine having a fuel mixture hiccup and misfiring while cold and running with choke on. It usually clears and runs fine, off choke after about a minute, but keeping a small amount of throttle on to keep the revs around 1200 rpm. Allowing the engine to run cold at low RPM - less than 1,000, can create a low oil pressure situation.

If the bike runs fine when warmed slightly, I would not worry about it.
 
dwalby said:
Interesting, my '97 has never done this, and I've owned it since new.
Click to expand...


But you live in California, where ambient temperatures are generally always warmer than here, or in the OP's home in Michigan. It happens more often to me in the cooler months.
 
After a short warm-up , how does it act on the road ( under load ). Mine makes a funny noise that could be described as a "knock" when warming up on the center stand. It's always done this since I owned it ( the last 8 years ). But no problem on the road or after it warms up a bit on the center stand.

If it's OK on the road, I wouldn't be too concerned.
 
I would suggest that you sync the carbs since it has been awhile since that was done. Good ideas to check the plug color to make sure it isn't running lean or rich, they should be a nice tan color. When was the last time the valves were checked?
 
I remember various threads about HT leads and the spark plug connectors. I recall the end-to-end resistance between two same-side cylinders should be 5k + 5k ohms, plus a little for the double ended ignition coil. If it's not right, the plug caps can be disassembled and cleaned up. (There's only a screwed in clip, a spring and a 5k resistor in there. If the carbs. are a bit 'off', as already mentioned, then that would add to the problem. Treat the bike to new plugs, stick some cleaner through the fuel system, check the HT circuits and balance the carbs..............
 
There have been a few reports of dodgy wire connections on primary sides of the coils causing issues. Solved by cleaning, tightening or replacing the primary wire terminals
 
ngudsen said:
I hope someone can demystify an issue that I am experiencing with my "new to me" 2000 Honda ST1100.

My motorcycle has 138,000 miles on it and had a very well documented service history when I bought it. This bike replaced a 1982 Silverwing Interstate and is a really neat bike. It is everything that I wanted in a bike and in my mind it is a keeper.

Warmed up, the bike runs quite well (but of course I wonder if I can coax a little more power and throttle responsiveness out of it). But the thing that is truly worrisome to me is what I am noticing when the bike warms up....

When I start my ST, it makes a single "knock" (not very loud) as I rev through the 1500 rpm mark and then again at the 2000 rpm mark. At each knock, the engine stumbles a bit. It takes a lot of warm up time for the knock to not happen (or at least for it to be so subtle that I cannot hear/sense it).

From the service records, its been about 20,000 miles since the last time the carbs got attention. I presume that they could benefit from a cleaning/rebuild with new gaskets, diaphragms, etc. and I intend to do that at some point.

There is patter out on the web about a similar symptons and that this might be a carburetor balancing issue. There is one thread on this site, I think, that suggests that is could be a crank bearing issue. There are other threads that say it is a quirky trait of many ST1100's that is of no potential consequence and can be ignored.

Anyone experience anything similar with their ST1100? Any suggestions on where to start in troubleshooting this?

-Neil
Click to expand...
Mine does the same as yours. It quits when it warms up while riding it.
 
I think the high speed jets kick in around 2000 RPMS - when my bike is still kinda cold, I can feel the sudden surge when pulling out slowly when it hits the 2000rpm mark.

Change your fuel filter, and if you decide the clean the bowls out - be sure you don't get carb cleaner on the daigraphrms at the top of the carbs as they are fragile. If those are torn, you would notice a fairly substantial loss of power. If you do the bowls, replace the bowl gaskets and the fuel valve aka needle - chances are that's all the parts that would need replacing.

If you check your plugs, do you see any signs - are they all similar in color/condition? Be very careful putting the rear plugs back in properly, as my previous owner stripped a plug on mine putting it in cock eyed.

And welcome to the ST1100 world - had mine 3+ years and ride every day - great bike!
 
Jim Van said:
After a short warm-up , how does it act on the road ( under load ). Mine makes a funny noise that could be described as a "knock" when warming up on the center stand. It's always done this since I owned it ( the last 8 years ). But no problem on the road or after it warms up a bit on the center stand.

If it's OK on the road, I wouldn't be too concerned.
Click to expand...

It is a funny noise. I have described it as a knock, but it is almost a dull "tink". The motor stumbles from about 1400 until 1500 before the tink, and then again from about 1900 to 2000 before the second dull tink. It is my experience also that riding it under load seems to clear the problem up, although on one occassion I thought I sensed the faintest tink at about 2000rpm while on the road....
 
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