Zenith 321F7

[The Murf]

Hi ya’ll, I’m new to this forum so forgive me if I’m asking dumb questions about topics that have already been discussed. Recently a very old friend kindly loaned me his 1986 R4 gtl to use while rebuilding work takes place on my Alpine. This is proving to be somewhat problematic in that I cannot get the car to pull away cleanly from stationary withou revving the nuts out of the engine.
The car idles ok albeit rather tappety but once under load there is awful hesitation and there has already been one embarrassing stall when pulling away. I’ve checked for air leaks on the carb without finding anything and the filter at the end of the fuel line into the body of the carb is also clear. Having removed the air filter/housing I notice that the choke butterfly with the choke in the off position is still at approx 30 degrees to the axis of the main venturi. This doesn’t seem right to me. I would have anticipated that the choke butterfly should be edge on (ie parallel ) to the axis of the venturi for normal running. I disconnected the choke cable thinking that I could adjust the butterfly to achieve this but it only goes from that angle to fully closed.
Any suggestions would be very welcome.

The Murf.

 

[harbourseal]

Hi,
I have some reservations about the spring that is pulling on the choke assembly.
I don't think it belongs there. But the guys with Zenith carbs know that better then I do.
I only have Solexes.

The gas cable isn't sitting right either. The spring should be in the hole that stops the outer cable. And the outer cable should be in a springloaded cable holder inside the big hole on top of the rocker cover. That is probably the reason for the power lack.

 

[Cornish4]

Hi there. Harbourseal is right, the spring on the choke doesn't need to be there, the choke will work correctly without it. Also as he says the throttle cable should be in the bigger of the two holes, and the return spring hooked in the smaller one. Hope this photo helps. Regards Brian.

 

[The Murf]

Hi,
I have some reservations about the spring that is pulling on the choke assembly.
I don't think it belongs there. But the guys with Zenith carbs know that better then I do.
I only have Solexes.

The gas cable isn't sitting right either. The spring should be in the hole that stops the outer cable. And the outer cable should be in a springloaded cable holder inside the big hole on top of the rocker cover. That is probably the reason for the power lack.

 

[The Murf]

Hi, Many thanks to Harbourseal and Cornish4 for pointing out these deficiencies in the set up. Looking at the existing throttle cable more closely I suspect it is not necessarily for an R4. Certainly the adjustable screw clamp arrangement is very different to the illustration in the Franzose catalogue (art no 82055) for a 1984+ gtl.
I will reposition things as suggested and see what results.

 

[harbourseal]

Bare in mind @The Murf that the set up is not original to the R4 GTL

It is a set up for a R5.
So you will need all the parts for the gas cable .

Please don't try to set it up as a R4 GTL. You’ll be ending up with more grief.

 

[Jurjenz]

 

[The Murf]

View attachment 24253

 

[The Murf]

Thanks for posting that pic Jurjenz, it shows what I was trying to explain in that the choke butterfly is parallel to the barrel of the carb with the choke fully pushed in. Can the butterfly be rotated on it’s shaft?
I’ve not had an opportunity to reconfigure the cabling as yet but hopefully will get a moment tomorrow.

 

[angel]

Remove the choke spring and loosen the choke cable, then fully open the choke butterfly while the choke knob is pushed fully inwards. At this point retighten the choke cable, and it should be fine.
Check also that, with the pedal down to the floor you actually get the throttle butterfly to open fully.

 

[The Murf]

Remove the choke spring and loosen the choke cable, then fully open the choke butterfly while the choke knob is pushed fully inwards. At this point retighten the choke cable, and it should be fine.
Check also that, with the pedal down to the floor you actually get the throttle butterfly to open fully.

I've now re-configured the throttle cable as suggested and re-collared the outer where it goes through the larger of the two holes on the rocker cover bracket, replaced the solderless nipple at the end of the cable and taken up all the slack which was there before. the return spring is now secured in the smaller of the two holes on the bracket.
This all now works fine and when starting from cold the engine fulls cleanly from low revs but once the engine is up to temp then the old lag kicks in so I'm convinced that the choke butterfly is the problem. I've disconnected the cable and re-set everything but cannot get the butterfly to go to the position shown in Jurjenz's picture.

 

[mr-reno-139]

If you are local enough to me i could offer to have a look
Pretty sure someone with experience will sort this quite easy

 

[harbourseal]

Have you taken the spring of the choke assembly?

 

[The Murf]

Thank you for the kind offer mr-reno but I’m a long way from West Sussex on the Suffolk /Norfolk border. In response to harbourseal’s question, yes I removed the spring from the choke mechanism but it doesn’t seem to have improved the pick up so am now out of ideas.
My tame garage man is back from holiday at the end of next week so I’ll call him and hopefully get the car booked in for his experienced eyes solve the mystery.

 

[The Murf]

Mystery now solved. The garage found that the butterfly was being prevented from opening/rotating fully by the angled brass jet mounted in the Venturi which had become dislodged and fallen down the aperture. No idea how this happened but they re-installed it in the correct position and the car now responds instantly to the throttle and is driving as it should.
My thanks to everyone who posted, Murf.