Throttle return sticking
Discussion
I've had the carbs off my old Thunderace to clean all the ethanol-related crap out of them, but when I put them back, the throttle doesn't return from wide open, it just sticks there. The throttles on the carbs are free and snap shut when you release them. The cables have been lubed, and are also free and smooth. Everything is free 
I have checked and double-checked the routing of the cables and can't see any problems there, the inners are completely free from where they leave the outers to where they connect onto the carbs. They're not the wrong way around either 
Anything obvious I'm missing? I've had this before, on other bikes which also have a return cable, but I can't get my head around what's causing it?
TIA.
I have checked and double-checked the routing of the cables and can't see any problems there, the inners are completely free from where they leave the outers to where they connect onto the carbs. They're not the wrong way around either Anything obvious I'm missing? I've had this before, on other bikes which also have a return cable, but I can't get my head around what's causing it?
TIA.
Can you feel binding in the twistgrip or the cable?
If you put some slack into one of the cables you'll be able to see which one is binding. Also double check the routing that one cable doesn't sort of slip behind the other like it's twisting around but comes back. Unless you've managed to actually twist them around each other!
Also, if you've had the throttle apart they can sometimes be a bit of a fiddle to get back together without getting something or other out of whack.
If you put some slack into one of the cables you'll be able to see which one is binding. Also double check the routing that one cable doesn't sort of slip behind the other like it's twisting around but comes back. Unless you've managed to actually twist them around each other!
Also, if you've had the throttle apart they can sometimes be a bit of a fiddle to get back together without getting something or other out of whack.
rodericb said:
Can you feel binding in the twistgrip or the cable?
If you put some slack into one of the cables you'll be able to see which one is binding. Also double check the routing that one cable doesn't sort of slip behind the other like it's twisting around but comes back. Unless you've managed to actually twist them around each other!
Also, if you've had the throttle apart they can sometimes be a bit of a fiddle to get back together without getting something or other out of whack.
That's the weird thing, if everything is disconnected then everything feels free! I haven't had the throttles apart on the carbs themselves, so I don't think that's the cause, and if I operate the throttles on the carbs with no cables attached, they snap back as they should. I think I'm going to have to take it all out and start again, have done it twice and can't get it to work If you put some slack into one of the cables you'll be able to see which one is binding. Also double check the routing that one cable doesn't sort of slip behind the other like it's twisting around but comes back. Unless you've managed to actually twist them around each other!
Also, if you've had the throttle apart they can sometimes be a bit of a fiddle to get back together without getting something or other out of whack.
By all means do that but test the operation as you go - be that from carbs backwards (operate the cables manually before you put the throttle grip assembly back together) or grip downwards (don't hook up to the carb before testing the throttle action).
My point about the cables being a bit out of whack happened to me. One was kind of trapping the other behind it, putting a tighter bend and making it bind. One cable might be very slightly longer than the other and if that longer cable gets trapped it'll go out of whack and bind. It might become more noticable when you try the throttle action from lock to lock. You mentioned Thunderace - this happened on my ZX9R. The cables run freely on their own but they aren't as slick as they are new when they get a bit of a bend too far in 'em.
My point about the cables being a bit out of whack happened to me. One was kind of trapping the other behind it, putting a tighter bend and making it bind. One cable might be very slightly longer than the other and if that longer cable gets trapped it'll go out of whack and bind. It might become more noticable when you try the throttle action from lock to lock. You mentioned Thunderace - this happened on my ZX9R. The cables run freely on their own but they aren't as slick as they are new when they get a bit of a bend too far in 'em.
Edited by rodericb on Friday 8th September 13:40
My Fireblade did similar.. if revved the rpm would hang. It was just the twist grip rubbing against the switch gear housing.
In the short term I literally put a tiny smear of grease on the grip where it rubbed. I have replaced the aftermarket grips with oem Honda and no issues at all now
In the short term I literally put a tiny smear of grease on the grip where it rubbed. I have replaced the aftermarket grips with oem Honda and no issues at all now
When I took the carbs off, I disconnected all the cables (including choke - remember those?!?) at the carbs and not at the bars, so nothing has changed. Further investigation, there is a bracket on the carbs which holds all three cable outers, and it seems to be bent. In particular, the return cable part of the bracket doesn't line up with the snail/quadrant on the carb throttle mech, so that's why it doesn't return freely.
Strange thing is, I've had this bike since it was 6 months old (bought in '96) and as far as I know the carbs have never been off before, so how the bracket is bent I have no idea. Throttle didn't stick before either. Only possible explanations that it somehow bent whilst I had the carbs on the bench, but it seems more meaty than that, and I didn't exactly go at the carbs with a club hammer. Will have a go at re-aligning it and I think we'll be good to go.
Strange thing is, I've had this bike since it was 6 months old (bought in '96) and as far as I know the carbs have never been off before, so how the bracket is bent I have no idea. Throttle didn't stick before either. Only possible explanations that it somehow bent whilst I had the carbs on the bench, but it seems more meaty than that, and I didn't exactly go at the carbs with a club hammer
. Will have a go at re-aligning it and I think we'll be good to go.I got to the bottom of this - it was/is very sensitive to where the cables are lying and routing as they come down the front of the headstock and into through the frame to the top of the carbs.
However, having sorted that, I fired it up and ....... it's now pissing petrol out of one of the little tiny link tubes between the carbs. Which means pulling them out again and then splitting them, which is never going to end well on a bike this old.
Having had it so long and from being almost new, I'm mildly attached to the old thing (and despite press reports from back in the day, it was more than capable of holding it's own up against other bikes in my then social group) but it's looking tattier than I remembered, and I own much better bikes now, so it's teetering on the edge tbh.
However, having sorted that, I fired it up and ....... it's now pissing petrol out of one of the little tiny link tubes between the carbs. Which means pulling them out again and then splitting them, which is never going to end well on a bike this old.
Having had it so long and from being almost new, I'm mildly attached to the old thing (and despite press reports from back in the day, it was more than capable of holding it's own up against other bikes in my then social group) but it's looking tattier than I remembered, and I own much better bikes now, so it's teetering on the edge tbh.
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