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General Tech Midget Stromberg 150 Adjustment

TR6BobNF

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Hi Folks:
I'm a TR6 driver (former Midget owner too! :cool:) but was helping a buddy with his 1976 single-carb Midget tonight and I brought my Moss mixture adjusting tool to see if I could help out with his carb problems. I know my way around a Stromberg fairly well and how to use the tool but the metering needles on my TR6 move easily with the tool and his just doesn't want to move and although the Allen key fits the needle, indicating that it is in fact an adjustable version I am hesitant to apply too much pressure. Can these needles get gummed up with carbon or varnish requiring the carb to be removed and soaked in cleaner (Gunk) or can I just horse it loose? I know enough to check all his vacuum lines, diaphragm and bypass valve but I'd really like to see if it's running rich first, which it appears to be judging by the sooty plugs and the exhaust and I really don't want to bust a buddy's carb by forcing the needle. Are they pretty robust or should we take it off, soak it and just rebuild it - any suggestions?
Cheers,
 
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TR6BobNF

TR6BobNF

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Gee, over 150 hits and no replies. Guess I'll just go back to the Triumph forum and ask them for help. :confusion:
 

JPSmit

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Sorry to say that Zenith Strombergs are a black art for most of us. I took mine off and put on an SU. If you like i can see what the manuals say.
 

JPSmit

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Oh, and just realized this is on the MG forum not the Spridget forum. Might be worth a re-post.
 

JPSmit

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just looked at the manual - and there is no indication of how robust. I would suggest a rebuild - and, FWIW, they tend to run rich, especially if the original air cleaners or the smog equipment is missing.
 

injunjoe

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Bob,
Its been a looooong time since I've messed with a Z/S carb, last 90s in fact, so I'm working with fuzzy memory here. First, I think its probably very possible that the needle is gummed up or corroded to the piston. I know SU carbs suffer this too, so dissasembling and soaking would probably do a world of good here. Take off the diaphragm and soak the piston assembly in a can of carb cleaner for a few hours, or squirt some PB Blaster, penetrant or a 50/50 mixture of atf and acetone to help free the needle. A rebuild is probably in order here so prepare your buddy for that.
Second, John Twist has a lot of great videos as most of us know. Pop over to youtube and check out University Motors Ltd. He has several dedicated to the Z/S carb: one shows how to change the O-ring at the bottom of the piston where the needle resides that keeps oil in the damper tube. The second is a 3 part series rebuilding the water controlled choke. Very informative stuff and may be good to view them just for see how that needle area breaks down. I cant remember if the Midget has a water choke on the Z/S but the MGBs do.
Good luck with the project, let us know how everything turns out, get your buddy on the forum here and remember; we love pictures. :encouragement:
 

JPSmit

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Yes, Midget had a water choke - I changed it for manual - then for SU
 
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TR6BobNF

TR6BobNF

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Thanks guys and kudos to Joe for the good advice. My buddy will be happy with that so I think we'll take out the piston and soak it first thing. Will post results (and pics) when completed.
Cheers,
 

DrEntropy

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The small O-ring around the needle/adjuster is the likely culprit. The ATF/acetone soak helps.
 
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