Throttle Cable question

[kanem]

Just installed new throttle cables while I had the carbs off to change the water hoses. Finally got everthing back together today and fired her up. Now the problem. The throttle won't return to idle by itself. The shop manual isn't very clear on the subject of adjustment. Anyone have any ideas?

 

[DAS]

I'm watching this one. I have my cables off and the carbs out to install a audiovox and replace hoses. I have new cambles but the throttle is sticky too but the carb linkage turns freely and have a lot of spring tension.

Also, when I pulled my tank the gas cap breather tube has a Tee a little below where the cables attach to the carbs but the branch side of the Tee doesn't have a hose attached. Some one mentioned this on one of the autovox install threads but I don't think there was a reply.

 

[wjbertrand]

Be very careful about the positioning of the carb boot clamps on cylinder #1 (forward right when seated). If you position this clamp the way the remaining three are positioned with the screw head accessible between the carbs it will interfere with the throttle linkage. You have to rotate it down so the screw head is underneath the boot, oriented toward the "V" of the engine. I used a long screw driver and approached it from the rear underneath the carbs with the fuel tank out of the way in order to tighten it.

The other possibility is that you have a vacuum leak somewhere but it sounds like you are talking about the mechanical operation of the throttle?

 

[John OoSTerhuis]

Hi Mike. Something's binding, or the return spring on the throttle bellcrank is broken. You need to figure out what's different/changed from when you started on the R&R. First check the handlebar twist-grip for interference/binding, and work backwards from there. Beyond the throttle bellcrank would have to be the throttle linkages as Jeff mentions:

Be very careful about the positioning of the carb boot clamps on cylinder #1 (forward right when seated). If you position this clamp the way the remaining three are positioned with the screw head accessible between the carbs it will interfere with the throttle linkage. You have to rotate it down so the screw head is underneath the boot, oriented toward the "V" of the engine. I used a long screw driver and approached it from the rear underneath the carbs with the fuel tank out of the way in order to tighten it.
quote]

Not sure what you're trying to describe here, Jeff, but I agree that the carb boot clamp screw should not be positioned between the front and rear cylinders. Here's what mine looked like when I pulled my carbs:

Click on the pic and then the zoom button for a closer look. The screwhead is on the forward side of the boot.

HTH

Regards, John

 

[wjbertrand]

John, in my case I had positioned the upper clamp on cylinder #1 (upper right) so that the screw would be easily accessible from between the #1 & #3 cylinders with the carbs reinstalled. In your photo the clamp screw appears to be rotated to about the 10:00 position, whereas I tried to position mine at the 6:00 location, which caused the interference. I finally moved it to about the 9:00 position to clear all the linkages.

 

[John OoSTerhuis]

John, in my case I had positioned the upper clamp on cylinder #1 (upper right) so that the screw would be easily accessible from between the #1 & #3 cylinders with the carbs reinstalled. In your photo the clamp screw appears to be rotated to about the 10:00 position, whereas I tried to position mine at the 6:00 location, which caused the interference. I finally moved it to about the 9:00 position to clear all the linkages.

OK, I understand now. Don't like the idea of having to remove the fuel tank to access the #1 cylinder upper carb boot from below and rear of the carb assy though. My #1 clamp has the screwhead pointing to the side of the bike for easy access by a screwdriver. [what I'd call the 11:30 position] The little positioning tang on the clamp is seated in its notch also.

John

 

[kanem]

John/Jeff,
I had the problem with the carb boots. Found that one by operating the throttle linkage after I installed the carbs. Pulled the carbs back off an repositioned the clamps to the "outside", that is forward on the front boots and rearward on the rear boots, just like in John's picture.
I hooked up the cables and everyathing seemed to be working smoothly until I started tightening the nuts on the bellcrank. Somehow I think I've got something too tight or not enough freeplay but the book isn't very specific on how exactly to do the adjustment. It just says you can do minor adjustments near the throttle grip and major adjustments near the carbuerator.

 

[John OoSTerhuis]

John/Jeff,
I had the problem with the carb boots. Found that one by operating the throttle linkage after I installed the carbs. Pulled the carbs back off an repositioned the clamps to the "outside", that is forward on the front boots and rearward on the rear boots, just like in John's picture.
I hooked up the cables and everyathing seemed to be working smoothly until I started tightening the nuts on the bellcrank. Somehow I think I've got something too tight or not enough freeplay but the book isn't very specific on how exactly to do the adjustment. It just says you can do minor adjustments near the throttle grip and major adjustments near the carbuerator.

Aha. Mike, I think you may have hit upon it... what's causing the problem/binding, assuming you've ruled out everything else. You need to put in some "throttle grip free play" when installing those new cables. The spec is: 2-6 mm (0.08 - 0.24 inches). Back off the nuts that secure the cable ends to the bracket above the throttle bellcrank so there's a bit of slack when the throttle is in the closed position at the handlebar end. Especially the throttle 'pull' cable end. You can fine tune the free play with the adjusting nut below the handlebar. The grip should be able to be turned slightly, 2-6 mm, before actually moving the throttle bellcrank (you feel resistance).

John

 

[kanem]

Thanks John,
I'll try that when I get back to working on her later this week.

 

[wjbertrand]

OK, I understand now. Don't like the idea of having to remove the fuel tank to access the #1 cylinder upper carb boot from below and rear of the carb assy though. My #1 clamp has the screwhead pointing to the side of the bike for easy access by a screwdriver. [what I'd call the 11:30 position] The little positioning tang on the clamp is seated in its notch also.

John

Your's is a better idea John, but since I'd had a b***h of a time getting all four carbs seated into their boots, and the fuel tank was already out, I just rotated the clamp downward without removing the carbs again. If I had it to do over again though................

 

[knockerjoe]

Try this: remove the lower cable from the bell crank. then adjust the upper cable (the one with 2 nuts) you want this one adjusted OUTWARD as far as possible. when you get a firm snap going put on the bottom one and tighten up. Also make sure your cable routing is correct or no adjusting will matter.
Let us know how you do. I just replaced cables on my 2 ST11's.