ST1100 Carbs

[Oldbikefixr]

Working away on reassembly of my bike, encountered a condition I thought I should pass on before I finish up.

My bike was garage stored for 20 years, a 1991 model with currently just over 20,000 miles. The PO had a shop bring the bike back to life before he sold it. One of the tasks was a carb rebuild. I had to remove the carbs to replace the hoses which I am done with and in the process of reassembling the bike. The clamps on the #1 carb manifold were both loose, both screws were misoriented. I put the new manifolds on the same orientation. Popped on the carbs and the throttle would rotate only a fraction. I thought some twisting may be causing shaft binding so off again. Throttle worked fine. Carbs back on, no rotation. Finally noticed the #1 clamp screw was interfering with the synch bolt. Off again. Turned out the #1 manifold was out of position by 180 degrees, putting the clamps that much off also. The misoriented manifold inspired the carb rebuilder to simply push the clamp heads out of the way and leave them loose. So, I fixed it, reinstalled the carbs, tightened the manifold clamps and the throttle linkage worked just fine.

When/if you do this job, note that the manifolds can be installed 180 degrees out and the index marks and locators are symmetrical. If the clamp screws end up between the 1/3 or 2/4 carbs, you will get interference with the throttle shafts that run between those carbs. The clamp screws should not be located between the carbs, but fore and aft.

So, there you go. Little problem. Short story. Long version.

 

[Slydynbye]

I

Working away on reassembly of my bike, encountered a condition I thought I should pass on before I finish up.

My bike was garage stored for 20 years, a 1991 model with currently just over 20,000 miles. The PO had a shop bring the bike back to life before he sold it. One of the tasks was a carb rebuild. I had to remove the carbs to replace the hoses which I am done with and in the process of reassembling the bike. The clamps on the #1 carb manifold were both loose, both screws were misoriented. I put the new manifolds on the same orientation. Popped on the carbs and the throttle would rotate only a fraction. I thought some twisting may be causing shaft binding so off again. Throttle worked fine. Carbs back on, no rotation. Finally noticed the #1 clamp screw was interfering with the synch bolt. Off again. Turned out the #1 manifold was out of position by 180 degrees, putting the clamps that much off also. The misoriented manifold inspired the carb rebuilder to simply push the clamp heads out of the way and leave them loose. So, I fixed it, reinstalled the carbs, tightened the manifold clamps and the throttle linkage worked just fine.

When/if you do this job, note that the manifolds can be installed 180 degrees out and the index marks and locators are symmetrical. If the clamp screws end up between the 1/3 or 2/4 carbs, you will get interference with the throttle shafts that run between those carbs. The clamp screws should not be located between the carbs, but fore and aft.

So, there you go. Little problem. Short story. Long version.

I have pondered that very issue, I knew the #1 clamps would interfere with the synch mechanism so have mis-oriented/re-oriented to prevent it in different ways. I will be pulling them again and try reversing the Boot if that is what you mean by manifold.

 

[paulcb]

Thanks for the tip Gary. I'll give you one back, if not too late and you don't already know it... replace the carb boot clamp screws with Allen heads to make it easier to tighten the clamp without rotating it.

 

[John OoSTerhuis]

Yeah, we’ve known about the #1 carb boot upper clamp orientation for a couple of decades now. It’s been documented. My webshots album is long gone but I think Jon Ransom’s (STOC 063) pictures* are still up (his screwdriver positioning pics** are helpful). Glad you got it figured out without any serious drama.

Folks doing their own work should take pictures while disassembling. But if somebody’s been in there before you, don’t assume it was put back together correctly...

edit: * Day 7 maint pics **#1 carb boot clamp

John

 

[Oldbikefixr]

Yeah, we’ve known about the #1 carb boot upper clamp orientation for a couple of decades now. It’s been documented. My webshots album is long gone but I think Jon Ransom’s (STOC 063) pictures* are still up (his screwdriver positioning pics** are helpful). Glad you got it figured out without any serious drama.

Folks doing their own work should take pictures while disassembling. But if somebody’s been in there before you, don’t assume it was put back together correctly...

edit: * Day 7 maint pics **#1 carb boot clamp

John

Thanks for the comments. I found some photo documents but not the one showing screwdriver/screw alignment. Seems like I read that one quite a while back but couldn't find it prior to beginning this job. I had a set of flexible shaft screwdrivers way back in my AF days that would have been ideal for this task. They were both 10 and 12 inch long shafts. Think I will add some lengths and bit sizes to my toolbox.

Paulcb's Allen screw substitution is useful as well. I have a set of long, ball end Allen drivers that were built for poor access screws. But...it's all back together and looks right so I will do that sub should I ever have to do this job again.

I took the bike down a bit to fix fuel and coolant smells and a very few drips that made it to the floor. What I found was old hoses, mostly, that I expected. Also found a near completely plugged main jet and three needle/slow jets nearly plugged. One float valve tip was rock hard, the other three not so much...that and hardened/split drain hoses were likely the source of raw gas smells and drips.

I'm really surprised the old girl ran so well with no indication of sluggishness or other issues that would indicate partially plugged jets.