93 st 1100a has 40 amp upgrade. Starts, idles and runs perfectly for 35 ish miles then hesitates pulling through lower rpm at 3 to 4k RPM. Above that it kicks in strong for as hard and long as you wish. New fuel filter. Have run with loosened cap to no effect. Red wire done. Previously removed fuel shut off, hasn't had one since before I owned it. Emissions blocked off/removed as well. After market exhaust also on when purchased. Tried it today ran the same route got weird same spot. This year had balance angle sensor problems and I don't know the status on this one or symptoms. Stumped. .
Hesitation 3000 to 4000 rpm
- Thread starter kris aimless adventure
- Start date
jfheath
John Heath
I can only throw ideas at this problem based on vaguely similar experiences.
i. It sounds similar to what I noticed when my HT leads were giving up. Althought at was on a 1300. At low speeds it would pull OK, but the feeling was like one of riding over a bumpy road surface. Ask it for more power, it would heistate until the engine picked up enough revs to provide the power for the spark. It would run OK when the revs were high. But that problem turned out to be HT leads corroded inside, and two of the plug caps failing.
ii. Make sure that the cylinder closest to your right knee, has its vacuum tube plugged properly. It is normally the thing that opens the fuel shut off valve, but that has been removed. Make sure that it is capped off - the other vaccum feed points (for carb balancing) have a long rubber tube which is capped as they emerge behind the cam shaft covers. The point to which he tubes connect is deep down in the vee. I think that you would experience some backfiring if it was this though.
iii. Make sure that the choke lever / cable is actually doing what it is supposed to at the carburettor end of the cable. Its a long time since I rode with a choke lever, but I recall on the odd occasions that it 'choked' it would run fine - if a little fast at tickover, but would heistate when accelerating.
That's all I have got, I'm afraid. Its throwing solutions at a problem without knowing what the fault is, I know. But if the comments trigger ideas from people who actually know what they are talking about .....
i. It sounds similar to what I noticed when my HT leads were giving up. Althought at was on a 1300. At low speeds it would pull OK, but the feeling was like one of riding over a bumpy road surface. Ask it for more power, it would heistate until the engine picked up enough revs to provide the power for the spark. It would run OK when the revs were high. But that problem turned out to be HT leads corroded inside, and two of the plug caps failing.
ii. Make sure that the cylinder closest to your right knee, has its vacuum tube plugged properly. It is normally the thing that opens the fuel shut off valve, but that has been removed. Make sure that it is capped off - the other vaccum feed points (for carb balancing) have a long rubber tube which is capped as they emerge behind the cam shaft covers. The point to which he tubes connect is deep down in the vee. I think that you would experience some backfiring if it was this though.
iii. Make sure that the choke lever / cable is actually doing what it is supposed to at the carburettor end of the cable. Its a long time since I rode with a choke lever, but I recall on the odd occasions that it 'choked' it would run fine - if a little fast at tickover, but would heistate when accelerating.
That's all I have got, I'm afraid. Its throwing solutions at a problem without knowing what the fault is, I know. But if the comments trigger ideas from people who actually know what they are talking about .....
Thank you! I shall take a deep dive and see what I find. Those are great points of action. Love this bike.
Slydynbye
Will ride for Pie
Take a reading on the Plug wires . In my case there was some corrosion on the little resistor in the plug caps causing an open on the bike that otherwise ran pretty well.
Carbs building up corrosion, can cause a hesitantion as well.
Thanks for the info. All these suggestions make sense. I'll follow all these leads until resolved. Some puns intended.
ST1100Y
Site Supporter
I'd also check the supply/feed to the coils for faulty/dodgy crimping... (IIRC some issues that year...)
jfheath
John Heath
This was my experience with the 1300. The plug caps coils and HT leads for the 1100 are a similar design
www.st-owners.com
ST1300 Poor Running - HT Leads & Plugs - Solved | ST1300 Related
Describing an issue with poor running on my ST1300. Symptoms were engine seemed to be running fine except with little low end power and a sensation of always riding on a rough surface. Revs had to be kept up in order to set off safely. It turned out to be HT leads and plug caps. Details...