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MG Midget and Sprite Technical - Throtle Sticking


The throttle cable on my midget is sticking It feels like a switch either on or off.
I have lubricated the linkage on the SU carbs and replaced the cable.

Suggestions please?

Cheers
-=E
EF Frangiamore

The throttle shaft inside the car can tend to stick on its 2 bushings.
Does it feel like it sticks when you operate it?
Robert (Bob) Midget Turbo

One time I had a problem like this on the 1500 Midget. After lots of ideas I finally discovered what was happening.

The butterfly valves in the carbs were seating too well! The effect was that at tick-over the engine created an induction vacuum on the "downstream" side of the butterflys and the suction was holding them tightly closed. The solution was to increase the idle stop screws just a little - just sufficient to crack open the butterflys. After that it was much easier to drive in traffic.

Not sure how common this is but it sorted it for me and may be worth trying.

Guy
Guy Weller

Re-check the cable for complete free play...sometimes they can get crimped and look perfect on the outside,,, but an elbow on inside ...also your cable, is it the strands type (lots of wires twisted togather) (should be) not a solid wire inside like on the choke (not be)

prop
Prop

I had this problem recently and the cause/cure was a bit unexpected. I had a longer cable made up by a specialist as the original pulls tight across the heater duct. After fitting it, instead of being smoother as I expected, it was awful (jerky , on or off). However, when I removed the heater duct normal operation was resumed. I can't precisely explain why but clearly the cable is very sensitive to position. Being longer must have allowed the duct to force it out of alignment (the shorter cable was too tight to allow this and squashed the duct). I have reverted to the original cable. That's life!
Chris H (1970 Midget 1275)

Return springs come off? Cable trapped? Carpet jammed up on the pedal shaft? Linkage bar between the 2 carbs gunged up?

A-series or 1500?
rob multi-sheds thomas

I had my throttle cable snap just at the linkage last time out, with a bit of road side repair i just managed to get it back on.
They're pretty cheap so i bought two & have a spare in the boot now.
Brad (Sprite IV 1380)

do it methodical!!!

first disconect the cable from the carbs
move the throtle shaft open and closed
does it feel smooth? if so the problem is not here

The cable it up and down the sleeve while disconected does this feel smooth?
if not don't bother to lubricate go to the bike store and buy a new inner and outer they are cheap
if so procede to the next part in the chain


the pedal asembly
witch asembly you have does not mather they should all move freely
so try it and feel
lubricate it anny way (all pivots)you may need to loosen some bolts

if none of the above felt faulty then reconect and check the path of the cabel and look for annything that snags and/or kinks

as always go methodical and find it the easyest way
Onno Könemann

ok i tried all of your suggestions and ended up refitting the old cable and re routing it, I'm wondering if it was twisted inside in some way??? this worked fine for about 100 miles now its getting stiff again.
The pedal moves freely and I lubed and loosened the mounting bolts. The whole carb assy has also been re lubed.
I'm going to have to suck it and see

Thanks for all your suggestions
EF Frangiamore

Go to your local bike shop and buy a good quality hand brake control cable. Make certain that it is lined. Cut and fit for an awful lot less than an MG cable.
Sandy
SANDY SANDERS

Check the throttle shaft on the front carb. This one wears the most as it is exposed to dirt thrown up by the cooling fan. Spray the front bushing with carb cleaner and check for idle change. If it is badly worn, you can also move the shaft inside the bushing with a screw driver. When the wear at the front bushing becomes excessive, the butterfly no longer is centered and sticks open just enough to produce a high idle condition.

You may find that the front shaft is very worn. Although it is best to replace the bushings too, I have gotten away with replacing the shaft only and having the butterfly seat normally.
Glenn Mallory

Did you try adjusting the throttle stop screws up a fraction? - 1/8 to 1/4 turn on each screw would be sufficient.
Guy Weller

This thread was discussed between 15/08/2009 and 21/08/2009

MG Midget and Sprite Technical index

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