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Replacing CD 150 in '69 Alpine

Bill Blue

Platinum Level Sponsor
S&S also states that if you cannot get a decent idle with screw 2 1/2 turns off the seat, the intermediate jet is too small. I have found that size of the jet is almost immaterial. I even drilled an intermediate jet considerably oversize. Still required 3 turns to achieve good idle. Next, I drilled out the valve seat, no real impact, the same as the smallest intermediate jet. I really have no idea what the intermediate jet size should be. The main jet walks all over the intermediate whenever any power is called for.

S&S states that the air jet rarely needs to be larger. If it is, they state to go to .050".

Have not road tested my alteration to the air circuit. Been raining all day and I think safety calls for good driving conditions when experimenting, especially on this stretch of highway. You may recall it is crooked and hilly with poor sight distance at our driveway. Tomorrow is supposed to be clearing.

I know zip about the enrichment circuit, so hesitate to open a fresh can of worms.

Bill
 

Bill Blue

Platinum Level Sponsor
Shannon, if you scroll about 2/3 down "How to Disassemble and Tune" you will see a picture of the dude holding the "emulsion tube". Here is the picture.
Well, "sufficient unto the day the evil thereoff", I cannot figure out how it works....but, here is a replacement unit from "lowbrow custom" with pictures that suggest a pintle valve is lifted off a seat to provide enrichment. https://www.lowbrowcustoms.com/coll...choke-knob-enricher-harley-davidson-super-e-g
Screen Shot 2022-04-13 at 10.14.31 PM.png
 
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Bill Blue

Platinum Level Sponsor
Shannon, the emulsion tube is what I referred to as the main jet assembly. The main jet screws into the hex portion of the assembly. Note the small holes. My "emulsion" tube is missing those holes. Do you think it would be a good idea to modify my tube to look like his? If so, how many rows of hole do you think I should drill? Suggested drill size? I'd guess about 50 thou.

Bill
 

Shannon Boal

Platinum Level Sponsor
If it were mine, I believe I would do it. Not a problem to solder them shut....Maybe call S&S and see if the part from them is available, with holes? I see one hole down near the "belt", a space, and four more.... guessing 0.040-0.048"....maybe do some of them and test, then do them all. Not everybody could put the right size holes where they belong, but this is you.
Shannon, the emulsion tube is what I referred to as the main jet assembly. The main jet screws into the hex portion of the assembly. Note the small holes. My "emulsion" tube is missing those holes. Do you think it would be a good idea to modify my tube to look like his? If so, how many rows of hole do you think I should drill? Suggested drill size? I'd guess about 50 thou.

Bill
 

Shannon Boal

Platinum Level Sponsor
And, here is another thing: does the accelerator pump work properly? It is a diaphragm, having check valves (balls, springs)? for pump intake, and pump exhaust. If a ball is missing, fuel flows freely through, could cause richness.
If it were mine, I believe I would do it. Not a problem to solder them shut....Maybe call S&S and see if the part from them is available, with holes? I see one hole down near the "belt", a space, and four more.... guessing 0.040-0.048"....maybe do some of them and test, then do them all. Not everybody could put the right size holes where they belong, but this is you.
 

Shannon Boal

Platinum Level Sponsor
As for the other thing, the idle needles do not adjust to anywhere near 1-1/2 turn, despite changing intermediate jet. There has gotta be a reason for that, and maybe it is that this engine uses PCV?......naah, I got nothing!
And, here is another thing: does the accelerator pump work properly? It is a diaphragm, having check valves (balls, springs)? for pump intake, and pump exhaust. If a ball is missing, fuel flows freely through, could cause richness.
 

Bill Blue

Platinum Level Sponsor
Properly located? Naah. Drilled in somewhat of a strait line, rotate 90 and do 3 more. I calculate it would take 12, .050" holes to equal the area of a .170" hole. So I put in 16 - .052" holes.

Bill
 

Bill Blue

Platinum Level Sponsor
Eureka! - NOT
Installed a .054" main, plugged the air jet and drilled it out to .125". The only real change was performance on the 3,000 rpm, 4th gear hill climb. Absolutely went to hell. I'm going to drill the air jet out to the full.172". If that doesn't work, I will totally plug the main jet and see just exactly what the intermediate jet is doing. Hard to imagine that it is delivering enough gas to run 13"s (AFR) at 3,500 rpm. But that is appearing to be the case.
Bill
 

Shannon Boal

Platinum Level Sponsor
I like tuning the intermediate jet idea by blocking other circuit (s). Did you have A/F readings when it went to hell?
Eureka! - NOT
Installed a .054" main, plugged the air jet and drilled it out to .125". The only real change was performance on the 3,000 rpm, 4th gear hill climb. Absolutely went to hell. I'm going to drill the air jet out to the full.172". If that doesn't work, I will totally plug the main jet and see just exactly what the intermediate jet is doing. Hard to imagine that it is delivering enough gas to run 13"s (AFR) at 3,500 rpm. But that is appearing to be the case.
Bill
 

Bill Blue

Platinum Level Sponsor
Performance started to go south at about .09, and dropped, went down into the 30's with a lot of missing. Tis strange. It had been pulling good, even accelerating with MV of .70. The next run, with air jet at .172, performance on the hill was worse. At the halfway point of the run, I stopped and removed the air filter and housing cover. I could then see reading less than 500mv, but it readily jumped up into the 7's and 8's. Hill performance was downright sickly. It still liked the .9's when cruising at 3 grand until the throttle is opened to accelerate. Really am mystified as to why it leans out at open throttle. It does that almost regardless of the situation. I feel there is something about the relation of the throttle plate to the main jet opening that interferes with air flow at the main orifice, exaggerating it had low opening, disrupting it at higher openings. Orifice placed too low in the air stream?

Bill
 

Bill Blue

Platinum Level Sponsor
Just completed a short test, running on intermediate jet only. Even had the air bleed blocked. Interesting, but as usual, mystifying. Ran lean when ever pushed, took quite a while to get up to speed with mv's in 100 range. Once at speed, it richened up to 900mv. Am I crazy, or is this backwards? I'm thinking of going a step smaller with the intermediate as the engine was good off idle, a main just big enough to help out on the hill, using a .04" bleed, then increase bleed until the hill performance starts to decrease. BTW, the engine performance was inferior to the previous run with the .172" air bleed.

Bill
 

Shannon Boal

Platinum Level Sponsor
I think you have a sensible plan. This thing is crazy, but I think it can be tuned to run well. I wonder about it being a knock-off.....The location of the fuel discharge nozzle/tube maybe was compromised because it is a "shorty"?....Maybe it is a left-handed carburettor on a right-handed motor?
Just completed a short test, running on intermediate jet only. Even had the air bleed blocked. Interesting, but as usual, mystifying. Ran lean when ever pushed, took quite a while to get up to speed with mv's in 100 range. Once at speed, it richened up to 900mv. Am I crazy, or is this backwards? I'm thinking of going a step smaller with the intermediate as the engine was good off idle, a main just big enough to help out on the hill, using a .04" bleed, then increase bleed until the hill performance starts to decrease. BTW, the engine performance was inferior to the previous run with the .172" air bleed.

Bill
 

Bill Blue

Platinum Level Sponsor
Just for laughs, I think I will make another emulsion tube and make it long enough to reach the center of the throat. Can't be any more of a bust than what I've done. I can't see any other possible way to attack its cute little trick of running lean when it should be rich and vice versa.

Bill
 

Bill Blue

Platinum Level Sponsor
Made another emulsion tube, will try to get a photo up tomorrow. It is 1/2" longer than the old one. It does seem to help my problem a bit. I fooled around with the jetting and found this to be the new magic combination:
Air jet .030"
Main jet .052"
Intermediate jet .024"

The Intermediate jet is probably a tad to too small, there is a slight hesitation when pushing it hard from a standing stop. A .024" jet solves that problem if it proves to be an issue.
This combo allows the micro volts to drop to the high 80's on my test hill and they hold up better under open throttle on level ground. The damn thing still cruises at .9+ mv @3,000 rpm. That figure, which is way too rich for cruise, does not vary much, regardless of main jet, air jet or intermediate jet. So I think it is a function of the progression jets drilled in the side of the throat. There are four of them, I'd like to temporarily plug (or cover) the 4th one. Any ideas on how to do that?

Bill
 

Bill Blue

Platinum Level Sponsor
Here is the photo of the two emulsion tubes. The long one is the one I made. The emulsion holes in both tubes are irregularly arranged because I drilled them.
74806A47-D39E-4E9D-BCA1-80D2DA5C6B28.png
 

Shannon Boal

Platinum Level Sponsor
Those magic jets are in the predictable range that S&S specifies! Four progression ports? Wow, all those hafta do is smooth transition into main circuit, so it makes sense that they could cause the crazy situation you have! How about put tiny bit of grease in the port, then a simple blob of J-B Weld on the surface? It could be scraped off if need be.....
Made another emulsion tube, will try to get a photo up tomorrow. It is 1/2" longer than the old one. It does seem to help my problem a bit. I fooled around with the jetting and found this to be the new magic combination:
Air jet .030"
Main jet .052"
Intermediate jet .024"

The Intermediate jet is probably a tad to too small, there is a slight hesitation when pushing it hard from a standing stop. A .024" jet solves that problem if it proves to be an issue.
This combo allows the micro volts to drop to the high 80's on my test hill and they hold up better under open throttle on level ground. The damn thing still cruises at .9+ mv @3,000 rpm. That figure, which is way too rich for cruise, does not vary much, regardless of main jet, air jet or intermediate jet. So I think it is a function of the progression jets drilled in the side of the throat. There are four of them, I'd like to temporarily plug (or cover) the 4th one. Any ideas on how to do that?

Bill
 

Barry

Diamond Level Sponsor
So I think it is a function of the progression jets drilled in the side of the throat. There are four of them, I'd like to temporarily plug (or cover) the 4th one. Any ideas on how to do that?

Bill



I think fingernail polish should work well for a temporary plug. It is pretty resistant to gasoline and ethanol, but can easily be removed with acetone. I would use colored (rather than clear) so the "plug" would be visible.
 

Bill Blue

Platinum Level Sponsor
Finger nail polish seems to be working. Held up for an 8 mile test run, still looks good. A big problem though. Did not lean out anything. Where could the gasoline be coming from? By nothing, I mean nothing. No effect at 1500 rpm town driving, no effect at cruise, no effect on the 3,000 rpm hill pull. Am going to try a larger (.040") air jet, but that should not impact very low rpm's. But I will find out.

Bill
 

Shannon Boal

Platinum Level Sponsor
This fingernail polish is a good idea! Maybe you could temporarily block off the inlet to the accelerator pump, or....? It has to be getting in somehow.
Finger nail polish seems to be working. Held up for an 8 mile test run, still looks good. A big problem though. Did not lean out anything. Where could the gasoline be coming from? By nothing, I mean nothing. No effect at 1500 rpm town driving, no effect at cruise, no effect on the 3,000 rpm hill pull. Am going to try a larger (.040") air jet, but that should not impact very low rpm's. But I will find out.

Bill
 
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