Neptune model 500 carb/ Tillotson HS93A

[Edwin Howard]

I have a frankensteined Neptune Wc1 that has the carb, reeds, and throttle/mag plate advance lever from a Model 500. I have had trouble with it idling down, it runs fine at high speeds but coughs and dies at slow speeds. I have checked and the low speed passageway is clear. I believe that the low speed needle is damaged, and I wondered if anyone out there with a model 500 can find a picture of what a good low speed needle looks like. I can provide any pictures of the motor if necessary.

[joecb]

Correct me if wrong , but Tillotson carb low speed is an air bleed , so closing the needle richens , opening leans. Just the opposite from what might expect And might explain why you are having trouble.

Joe B

[seakaye12]

joecb wrote:

Correct me if wrong , but Tillotson carb low speed is an air bleed , so closing the needle richens , opening leans. Just the opposite from what might expect And might explain why you are having trouble.

Joe B

Joe;  is there a way to tell by looking at a carburetor whether it is an air bleed design?

[joecb]

Again I may need correction here , but the air bleed carbs usually have the low speed needle up high and to the side of the carb rather than the more common front location along side of the high speed needle

Post a picture if you can

Joe B

 

[A Hoskins]

A damaged needle, examined with a magnifying glass, will show a groove or irregularities in the tapered section. If you see such, chuck the needle up in your electric drill, spin it and polish it with some 600 grit wet-or-dry. When the engines “coughs” and dies, pull the plug. Is it wet or dry ? An overly rich mixture (wet plug) usually won’t cough to a stop but it will choke down and stop without spitting back through the carb if that is what you mean. Good luck.

"Fox News" isn't.

[Edwin Howard]

Here’s the carb, it’s not the typical outboard carb. I believe that it is related to some sort of chainsaw carb. The low speed needle is marked with an L in the casting. There is no packing, so a bit of gas ends up outside the needle on top of the carb and the spring keeps it in place. Once coughing and shutting off, the plug appears mostly dry. I also attached a picture of the low speed needle. I am not sure what it is supposed to look like, but I assume that it should taper down like most needles.

[Edwin Howard]

Here’s the carb, it’s not the typical outboard carb. I believe that it is related to some sort of chainsaw carb. The low speed needle is marked with an L in the casting. There is no packing, so a bit of gas ends up outside the needle on top of the carb and the spring keeps it in place. Once coughing and shutting off, the plug appears mostly dry. I also attached a picture of the low speed needle. I am not sure what it is supposed to look like, but I assume that it should taper down like most needles.

[Edwin Howard]

Here’s the carb, it’s not the typical outboard carb. I believe that it is related to some sort of chainsaw carb. The low speed needle is marked with an L in the casting. There is no packing, so a bit of gas ends up outside the needle on top of the carb and the spring keeps it in place. Once coughing and shutting off, the plug appears mostly dry. I also attached a picture of the low speed needle. I am not sure what it is supposed to look like, but I assume that it should taper down like most needles.

[George Emmanuel]

Folks, Edwin is my grandson…the carb on his motor is not the Tillotson but rather a pumper/diaphragm style, and I can’t remember the name. It think it is something like Walbro.

George

[Edwin Howard]

Here are 2 more pictures of the carb

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