Sticky throttle - 400SE

[B@man]

OK the jobs list is now growing, number one is the boot-lid which has now hit me on the head too many times, anyhow I digress.

The throttle is intermittently sticking at a fast idle approx 1200 RPM, if I pop the bonnet and rotate the part of the throttle spindle nearest the throttle body and the idle drops to around 900, moving the part of the linkage with the cable attached does not help.

I see there is a spring around the outside of the shaft on the throttle body which I assume is supposed to do the job - I've not had the inlet hose off yet to check the condition of the throttle plate - could this be caused by and accumulation of crud ?

[honestjohntoo]

Most likely, or friction on the shafts, linkages, throttle plate not centered or throttle pot binding.

The PDF here explains why it happens with a Twin Plenum and all the solutions are easily transferrable to a Single.

http://www.vintagemodelairplane.com/pages/Download...

[peaktorque]

I had what sounds like a similar problem.

It turned out to be the throttle cable fraying and jamming up in the sleeve (at the pedal end), worth checking as there was only two strands left connecting pedal to engine!

I nicked the cable from the rear brake on my daughters push bike as I had a 'hoon' to attend in the morning!

[grahamw48]

peaktorque said:

I had what sounds like a similar problem.

It turned out to be the throttle cable fraying and jamming up in the sleeve (at the pedal end), worth checking as there was only two strands left connecting pedal to engine!

I nicked the cable from the rear brake on my daughters push bike as I had a 'hoon' to attend in the morning!

How COULD you ?

[peaktorque]

I will replace it..........when she learns how to ride it

[B@man]

I think my daughters push bike is safe for now, the cable seems slack when it sticks at a fast idle.

AFM to throttle body hose has seen better days so I'm going to wait until I've got a new hose before I take it all to bits.

Re Children on cycles - she did worry me when I spotted her and the bike wobbling in the direction of the 400, luckily she fell off and missed the car

Edited by B@man on Saturday 21st February 20:39

[honestjohntoo]

peaktorque said:

It turned out to be the throttle cable fraying and jamming up in the sleeve (at the pedal end)

Except it seems the OP moved the quadrant and cable to no effect.

I assume your throttle assy is something like this one from the SP Vitesse, so many components in such a small space, to get frictional. Just a thought, do you also have the main throttle return spring item #15 shown here:

[B@man]

Hi honestJohn,

Yes it's got the big main spring which appears to be doing it's job, for some reason (wear ?) there is some slack in the linkage, If I get hold of the shaft near the spring (part ref 30) I can rotate the shaft and slow the idle, I suspect something is worn and causing the shaft not to return to it's closed position.

As I posted above I'll order a new inlet hose next week before I take it apart.

Thanks for the advice

[GreenV8S]

Make sure the inside of the throttle body is clean around the throttle plate, you can get a build up of gunge here.