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Post by wallace on Sept 9, 2020 15:56:30 GMT -5
Hello,
I am having a problem with this carburetor on a ST-180 string trimmer. The engine starts ,runs and idles for a few minutes, then shuts off.
It will not restart. The reason it will not restart is because fuel continues to run into carburetor. I can watch the fuel run in and start to rise in the carburetor throat.
I can pour it out and it just refills the carburetor throat, repeatedly. Left to sit the fuel runs into cylinder and out the exhaust. I rebuilt this carb with new diaphragms
gaskets and new needle seat and spring. Set the needle seat lever level with straightedge across carburetor body. Any ideas what I have done wrong with the rebuild.
Should I set the needle lever lower. Where is all this fuel coming from. Any help appreciated.
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Post by Jarhead ☠ on Sept 9, 2020 17:30:50 GMT -5
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Post by wallace on Sept 9, 2020 18:31:44 GMT -5
I am confident I put the carburetor together properly. The carb kit came with the same diagram you posted.
I obviously have something wrong. Runs great for 5 minutes or so, then stops, flooded. I will have to tear it apart and try setting needle lever lower. Thanks for your help.
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Post by Jarhead ☠ on Sept 9, 2020 19:25:42 GMT -5
The lever needs to be flush with the body of the carb, not the floor but the outer lip. If you didn't remove the circuit plate you might have crud below the needle so you may need to disassemble the entire carb. If you can post pictures of your assembly that could help.
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Post by wallace on Sept 11, 2020 14:42:15 GMT -5
I found my problem. The inlet needle seat is leaking. I did a pressure test and I can see and hear the leak. I have tried stretching the spring using two different need valves. The leak persists. Nothing I have done has changed anything.
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Post by Jarhead ☠ on Sept 11, 2020 18:49:32 GMT -5
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Post by wallace on Sept 12, 2020 9:42:09 GMT -5
I have already installed an OEM kit. The new needle and spring make no difference.
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Post by edju1958 on Sept 12, 2020 10:32:39 GMT -5
There may be some crud in the needle seat preventing it from seating properly.What I've been doing lately to ensure a clean seat is take a Q tip & pull off all the cotton on the end,then wrap a piece of cloth around the stick & dip it in Seafoam motor treatment (for cleaning carbs) & gently clean the seat.You'll be surprise on how much stuff comes out of the seat.I'd stay away from carb cleaner as it may be too harsh & damage the seat.
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Post by wallace on Sept 13, 2020 9:57:49 GMT -5
Thanks. I will give that a try
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Post by wallace on Sept 22, 2020 16:47:45 GMT -5
For what it is worth, I finally got the HDC-70B inlet needle to seat, I saw where people were using a cotton swab and brass cleaner to clean needle seat on bowl type carburetors. It worked for them. I bought some G-Tip gun cleaning swabs, mixed up some Bar Keepers Friend cleaner with water into a paste. Trimmed the swabs to just fit seat area. Chucked the swab into drill and polished away. After eight swabs the needle now seats and holds pressure. The down side is that I bought a NOS HDC -70B on Ebay, now I have an extra carburetor I do not need.
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Post by edju1958 on Sept 22, 2020 16:58:45 GMT -5
Glad to hear you got it going! If not needed maybe you can resell it here,or put it back on eBay.
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