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1959 Rapier Carburetor Idle

C

Chrisp Rapier

Donation Time
I have cleaned the carburetors. Twice. Installed new gaskets. I rebuilt the fuel pump last year. The gas tank is the original, which I cleaned as I could and ran a new fuel line to the pump. The tank is far from perfect, so I put a temporary fuel filter between the tank and pump. I synched the WIP 36 carbs. I have a surging idle. I checked with carb cleaner for leaks...none. I plugged the vacuum port...no effect. I noticed the glass bowl of the fuel pump is over 3/4 full in idle when it is revving and drops down to halfway and then the idle drops down. does this indicate anything? Maybe improper gas cap venting or a fuel line restriction of some sort? It is a big fuel filter I have under the car and it has accumulated quite a bit of sediment. I will need to check the float levels tomorrow I think, but I have started driving the car around the block. It runs at speed pretty well but bogs down at the stop sign and I have to goose it to get it to idle and not stall.

Two carburetors. How annoying! Ha
 
C-R,

Just to refresh my memory, you are trying to motivate a sII Rapier with a 1500 engine with an iron head?

Hopefully, your carb numbers are similar to:

WIP2

C1629F & C1629R
 
I may be wrong, but to me it sounds more like a fuel supply rather than a carb issue. Check fuel line , tank and cap venting at first. Specfically the low fuel level in the pump makes me curious. If all of that doesn't improve the situ, we can talk carbies...
 
bernd_st said:
I may be wrong, but to me it sounds more like a fuel supply rather than a carb issue. Check fuel line , tank and cap venting at first. Specfically the low fuel level in the pump makes me curious. If all of that doesn't improve the situ, we can talk carbies...
Click to expand...
Yes it seems odd to me that there would be a big fluctuation in the glass bowl level simply from surging from high idle to bogging down. I will first check the gas cap. The fuel line is new and I have fuel filter towards the back of the car near the tank, so I would suspect from the filter back to and including, the tank.
 
So I simply opened up my fuel cap and started the engine. It ran without the surge. I then unscrewed the bolt to the inner workings of the vent. Apparently The rust and corrosion around the shaft and plate that allowed air to vent around the bolt was preventing proper air flow. I cleaned it all up and it is now venting properly. So now I am left with a very high idle. I have done all the right things to tune the carburetors, so now I think there is the issue of potential excessive play around the spindle. I will have to remove the carbs again. The good thing about getting a basket case car, is you get a basket of extra carburetors. I have two extra rear carbs and two extra front carbs. They are in need of serious cleaning and looking over. I did free up some of the linkage. One of the front units has serious play in the spindle. The other extra front and one of the back carbs, has a modest amount of play. The second back carb seems to have a well fitting spindle. We shall see after cleaning if that is true.

Is it not possible to drill out the ovalled out opening for the spindle and press in a bronze sleeve? I have not looked them over well yet to see what looks possible.
 
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Good. First step successfully taken!
Regarding the high idle -and if there are no detected air leaks- first thing is to check whether both Zeniths throttle butterflies are properly returning to idle position. Sometimes and because of lacking return spring power they are not returning to idle adjustment screw position. Needless to stress that both butterflies needs to be well synchronized. If not readjust and make sure the clamping interconnector is really tight and forcing the rear carb to proper idle position as well. Idle is defined by a) idle adjustment screw & b) idle mixture screw. Does the turning of idle mixture screw show any change ? If this is assured we can approach next phase investigation...

P.S. The 1688F/R Zeniths are for an Alpine S1 and jetted for wire mesh airfilters. As far as I understand Rapiers having an airfilter box with paper element. So in other words they are wrongly jetted for your application, unless you run them with wire meshs. Some pictures would help here...
 
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P.P.S. : Usually the bronze throttle spindles are worn out not the bushes/openings in the carb throttle body. I can provide you with reproed spindles if needed...
 
Chrisp Rapier said:
So I simply opened up my fuel cap and started the engine. It ran without the surge. I then unscrewed the bolt to the inner workings of the vent. Apparently The rust and corrosion around the shaft and plate that allowed air to vent around the bolt was preventing proper air flow. I cleaned it all up and it is now venting properly. So now I am left with a very high idle. I have done all the right things to tune the carburetors, so now I think there is the issue of potential excessive play around the spindle. I will have to remove the carbs again. The good thing about getting a basket case car, is you get a basket of extra carburetors. I have two extra rear carbs and two extra front carbs. They are in need of serious cleaning and looking over. I did free up some of the linkage. One of the front units has serious play in the spindle. The other extra front and one of the back carbs, has a modest amount of play. The second back carb seems to have a well fitting spindle. We shall see after cleaning if that is true.

Is it not possible to drill out the ovalled out opening for the spindle and press in a bronze sleeve? I have not looked them over well yet to see what looks possible.
Click to expand...
yes, it is possible. Need to have precise location of the drill and steady support of the carb.
Bill
 
bernd_st said:
Good. First step successfully taken!
Regarding the high idle -and if there are no detected air leaks- first thing is to check whether both Zeniths throttle butterflies are properly returning to idle position. Sometimes and because of lacking return spring power they are not returning to idle adjustment screw position. Needless to stress that both butterflies needs to be well synchronized. If not readjust and make sure the clamping interconnector is really tight and forcing the rear carb to proper idle position as well. Idle is defined by a) idle adjustment screw & b) idle mixture screw. Does the turning of idle mixture screw show any change ? If this is assured we can approach next phase investigation...

P.S. The 1688F/R Zeniths are for an Alpine S1 and jetted for wire mesh airfilters. As far as I understand Rapiers having an airfilter box with paper element. So in other words they are wrongly jetted for your application, unless you run them with wire meshs. Some pictures would help here...
Click to expand...
Yes I check all around with carb cleaner. No air leaks. I plugged the vacuum port for the advance. No difference. The carburetors were synched and the spindles were secured to one another. New return spring for the carbs and they return properly. I tried to find a low idle with the front carb with the set screw. too high. There is no doubt an air leak. Must be. I have two sets of the Alpine mesh airfilters but they are super rusted. The gauze inside is terrible. I tried soaking in a mild acid but they are not going to go on my car. I do not have the proper oil bath airfilter set up for the Rapier. I have had my eye out for it for two years now. I bought after-market, cone shaped, filters that fit the carbs. They are two tall so I cut them in half and inserted the top down into the lower half. I think it is good. They have very good draw with little resistance, probably like the Alpine units.
 

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bernd_st said:
P.P.S. : Usually the bronze throttle spindles are worn out not the bushes/openings in the carb throttle body. I can provide you with reproed spindles if needed...
Click to expand...
Ahhh! Now I understand. Are the spindles the same for the front carb and the rear carb? In other words, if I have a good spindle on an extra rear carburetor, can I transfer it to a front carb?
 
bernd_st said:
.... Idle is defined by a) idle adjustment screw & b) idle mixture screw. Does the turning of idle mixture screw show any change ? If this is assured we can approach next phase investigation...
Click to expand...
On the front carb, I bottomed out the set screw and the idle is too high, over 1,000. There is change with the idle mixture on the front carb. It is my understanding that the mixture screw adjustment is to set it to a point where the engine sounds good right? Then I am to go back to the idle adjustment screw to bring it down. Since it is at the end already I cannot reduce the idle. Bear with me, carburetors are not my strong suit. Actually none of it is my strong suit. :)
 
Thanks for the picture. Your airfilter setup looks a bit weird, but should do. The throttle spindle interconnection is homemade and not as original. Wonder whether the carb butterflies are really moving in sync.Looks like no sync adjustment possible. Check whether both butterflies are really in exactly same position at idle. On top I'm wondering why you have 2 vacuum advance tubes on the front carb. There should be only one. The one not connected @ the moment is the correct one. Switch the vacuum advance to the free tube and close the other one. Let see whether this works.

P.S. Yes, the throttle spindles are the same front & rear but the rear carb one normally carries an extension piece.

P.P.S. Yes, the idle mixture screw indeed needs to be set so that the idle "sounds right". However wonder whether you still have an airleak somewhere. Spray around the isolator block between butterfly housing and main carb body. Have seen many cases where the 4 connection screws were sitting loose with the whole body moving.
 
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bernd_st said:
Thanks for the picture. Your airfilter setup looks a bit weird, but should do. The throttle spindle interconnection is homemade and not as original. Wonder whether the carb butterflies are really moving in sync.Looks like no sync adjustment possible. Check whether both butterflies are really in exactly same position at idle. On top I'm wondering why you have 2 vacuum advance tubes on the front carb. There should be only one. The one not connected @ the moment is the correct one. Switch the vacuum advance to the free tube and close the other one. Let see whether this works.

P.S. Yes, the throttle spindles are the same front & rear but the rear carb one normally carries an extension piece.

P.P.S. Yes, the idle mixture screw indeed needs to be set so that the idle "sounds right". However wonder whether you still have an airleak somewhere. Spray around the isolator block between butterfly housing and main carb body. Have seen many cases where the 4 connection screws were sitting loose with the whole body moving.
Click to expand...
Yes my filter set up is weird. No doubt. The throttle spindle connection was not visible in the photo I showed. I think you were looking at the tube that connects the two manifold halves. Photos below of the two spindle connector halves on the carbs. The vacuum advance tube was disconnected in the photo so you thought there were two ports.

I have removed my carburetors to inspect the spindles. I did not remove the actual spindles, but rather just wiggled them to check play. The carbs I had on the car seem pretty good. I do not think a massive air leak is happening there. I was actually oping they were bad so that I found the problem.
 

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The 4 extra carbs are set up very different than the two I had on the car. The linkage to the accelerator pumps are different and the throat of the carbs are set up differently. Most of the extra carbs have bad spindles. See photo of one I removed. You heard of a basket of deplorables? I have a basket of deplorable carburetors. :)
 

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Unfortunately I'm not familiar with Rapier manifolds. Ok, the interconnection is correct and original. Good, but did you check the synchronous butterfly movement before taking everything apart ?

Talking about the spindles your photo shows exactly the wear pattern which most of them suffer from. Wear occurs on the spindle and mainly on the non bushed side of the butterfly housing. If yours on the 1688's are ok though it's a googstarting point. Wonder whether you can find the high idle idle root cause with everything taken apart, but would start with a careful inspection of the idle jets and clean ( the small bore tends to get blocked) the related fuel channels...
 
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