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TR4A Sticky throttle lever

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rsanford Raleigh Sanford
Millington, Tennessee, USA   USA
Hello all. In the process of adjusting my SU HS6 AUD carbs using the SU instructions posted by Jim a while back and instructions from the guy who rebuilt them earlier, I have come across a problem. The throttle lever on the rear carb is sticking. I first thought it was grime build up and I replaced the springs and have sprayed carb cleaner and lubricants on it and that seemed to free it up. By working it manually and with the gas pedal, it seems to work freely when the car isn’t running. However when the car is running and I give it gas, it does not release causing the car to rev up to 3000 or so. Sometimes a strong tap will drop the rpms down some and sometimes not but nowhere near the 1000 or so idle I have it set at. I think I did everything according to instructions and have also tried to oil anywhere I could see in the linkages between the pedal all the way to the lever. I can’t figure out why the engine running makes a difference. Thanks. Raleigh.



Edited 1 time(s). Last edit at 2017-11-01 08:15 AM by rsanford.

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Geko Avatar
Geko Stef SG
Kuala Lumpur, WP, Malaysia   MYS
There are many potential sticky points. Below, the main ones:
- Notchy copper bearings at the pedal assembly shaft
- Wrong assembly of the throttle recall springs/ weak springs
- Loose assembly of the throttle linkage rods
- Horizontal connecting shaft below the carb rubbing against the carb mounting plate (red arrow)
- Bolt too tight or no spacer (orange arrow)


Attachments:
SUlinkages.jpg    37.2 KB
SUlinkages.jpg

ric350 Avatar
ric350 Jim Feeney
Holmdel, NJ, USA   USA
Raleigh,
I had a similar problem (HS6 carbs) where occasionally the car would idle at 2-3k, mostly after coming off the gas. Sometimes blipping the gas pedal would drop it to normal, other times not. Turned out the PO had used a carb mounting bracket from a TR6, causing the throttle return springs to be mounted at an angle. After some investigation it turned out that the spring on the rear carb did not have enough force to always bring the rear carb throttle back to its stop. I mounted a stronger spring, and attached both springs in a more vertical manner. No problems since.

Jim

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Trike4 Avatar
Trike4 Marcus G
Brighton, Michigan, USA   USA
1963 Triumph TR4
1963 Triumph TR4 "Trike"
I have found many times that PO's have made "improvements" and modifications that cause problems. Throttle linkage being one area, mufflers, wire splices, relays, brake lines, deleting parts like brake cylinder backing plates, starter shims, caliper shims, the "H" support under the dash....I totally understand because there was a period of time in the late 70's early 80's where parts were getting scarce and no one had money or the inclination to be restoring these old rattle traps.

When you put things back the way the engineers designed them these cars work pretty darn good!

Sometimes throttle linkage gets put on wrong, upside down, or backwards.

rsanford Raleigh Sanford
Millington, Tennessee, USA   USA
Thanks for the help. I still don’t understand why the one carb was sticking with the engine running and not with it stopped but I guess it has something to do with vacuums or pressures or suctions. On the one that was the problem, I had a stronger spring I was going to try but I decided first to add to my new throttle spring the old one. I routed the old one around the other side of the lever and it was a longer path which of course tightened it up some. After doing that, everything seems ok and the lever is returning to idle even with the car running. The car seems to be running good. Starts right up with the choke and then idles at around 1000 after a short warm up. I may try to get the idle down a little. I don’t have my overdrive working yet and only recently drove it in 4th gear. When I shift from 3rd to 4th, it is an incredible difference in smoothness. It just glides in 4th. So I guess I am ok until maybe I have a face to face with an expert who thinks more needs to be done. Raleigh.

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