Installing a new Carburetor on a Cub Cadet ST 100 field trimmer mower

Two other videos of mine on the Cub Cadet ST 100 field trimmer mower:
Cub Cadet ST 100 field trimmer mower REVIEW
• Cub Cadet ST 100 field...
Install Fuel Shut Off Valve on a Cub Cadet ST 100 field trimmer mower
• Install Fuel Shut Off ...
How to change a carburetor on a Cub Cadet ST 100 field trimmer mower. Very easy job when cleaning the main jet does not work.

[@jessasdad]

Thanks for posting this. I couldn't figure out how to get the linkage out. Your instruction helped alot. This carburetor is such a bad design. Mine only lasted one season. It might be worth it to buy ethynol free gas, which were I live can only be bought at Home Depot in those small cans. I believe the linkage and plastic flap thing is part of the automatic choke system. As the RPMs increase, the airflow moves the white plastic paddle; and through the linkage releases the choke. Your ST100 looks brand new! You must take really good care of it.

[@starastronomer]

jessasdad Glad you found it of use! BTW, I have since found a farm supply place that sells ethynol free gas at the pumps. I've been using that on all my small engines since. Yes, I am very picky with everything I own. Got to keep things in good order and looking good.

[@deeclay2459]

You have the best video on this process on internet...very helpful.

[@starastronomer]

Thank you so much! I appreciate that.

[@richardburnett-_]

100% disassembly? Each part looks polished and waxed. Bit of OCD?🤨

[@charlessmith9134]

Thanks for your video! I bought a used Cub Cadet trimmer like yours a few months ago really cheap. I struggled to get it started so I put on a new carb. It still would not start and I spent hours trying to get it to run. I finally found a manual on the engine and discovered there is a tiny inline fuel filter that is in the outlet tube of the fuel tank! I removed that filter and the engine will now start and run! Pull that filter out and add a real fuel filter in line on the fuel line!!

[@MrBobm001]

When replacing that inline filter, having hard time removing fuel line hose from tank without cutting it off & replacing entire hose, any ideas? Soak wrap /soften hose or ?

[@toddjohnson147]

Can I see the video of the linkage being correct

[@philliphall5198]

Yep remove that filter and install a inline one

[@philliphall5198]

Just installed new hose with cut off and filter, done ✅

[@deeclay2459]

Does the manual show how to do that?

[@patmcgroyne784]

Very nice video man … well thought out and informative. Your observations about ethanol-free gas are spot on … been running all my new equipment that way, and dealing with the holdovers until maintenance/replacement. ✌🏻

[@starastronomer]

Thank you so much @patmcgroyne784 👌

[@charlessmith9134]

Forgot to say that hooked up the auto choke wrong and you really showed how it needed to be installed! Thanks!

[@starastronomer]

You're welcome Charles Smith.

[@marvinmiller7244]

For the love of god, THANK YOU FOR HAVING A STILL CAMERA!!! I was able to see what I did wrong, other videos it's like the person had the canera mounted on their wrist...

[@starastronomer]

I'm a professional, don't try that at home 😳 😉 I always use a tripod.

[@BigBlueTheFoo]

Amen

[@Zx14rrrrrrrrrrr]

Great help pulling it out. A tip for whoever is doing this after you get the carb back in. Make sure all those moving parts can swivel easily. I ran into a weird problem with the one in the back. (with the spring) It wouldn't turn freely. I kept thinking I did something wrong. I ended up pulling the carb back off. And it still wouldn't move. So turns out it had alot of build up which was keeping it from spinning. I had to remove the tiny bolt holding the butterfly plate on. Then the pin slides out. Then I used I tiny flat head and got all the gunk out. Put the pin back and it spun freely. Put everything back on... Bam motor running back to normal.

[@starastronomer]

Thanks spafro101.

[@John_Connor69]

Thanks for the video! This video helped me figure out that there was a linkage piece installed incorrectly on my ST-100 causing it to not want to start up. Got it running like a top now

[@starastronomer]

Glad to be of help, you're welcome!

[@Tom-xp7dl]

Dont throw the old carb out, you can soak it in straight Pine-Sol and use a bread tie wire to run thru the center of the jet and blow air to finish...now ya got another spare carb. Soak the bowl in vinegar and even sand, wire brush, or sandblast the inside of the bowl. Thank you for a great video.

[@starastronomer]

You're welcome Tom!

[@bigdogmack8692]

Thank you so much for this time saving video. I can now put the lawnmower back together correct ly

[@starastronomer]

You're welcome bigdog mack.

[@roush876]

Sure glad i saw this step by step video. I will most likely be buying a new carb for mine.

[@starastronomer]

bob ross Glad it helped.

[@bobtosi9346]

How did your repair turn out

[@markkulyas2418]

Thank you for helping me reassemble my Cub Cadet ST 100. 👍👍👍👍👍

[@starastronomer]

Glad I was able to be of help Mark, you're welcome.

[@davidnickels9301]

I have heard that the additive STA BIL will cause the carb bowl to do this. My SC 100 mower did the same thing as yours. When I pulled the bowl off the carb it looked worse than yours did. I just put a new carb on my mower and it started right up with no problems.

[@johnc3611]

My bowl looked a little worse than this. I used the stabilizer you are referring to. That may be why. Thanks for the video

[@TimWalter-q1q]

Very good step by step tutorial!

[@starastronomer]

Thank you so much @user-rb6qd6ym8n.

[@clarkgriswald9909]

Carb looks like it sat with Ethanol gas in it. Ethanol sitting for any amount of time will do this to metal fuel tanks, carburetors, fuel lines, you name it. Nice video, thanks!

[@starastronomer]

You're welcome.

[@ronsnow8342]

Great video. I'm having the same problem with my Cub Cadet two-wheeled trimmer. A 10mm ratchet wrench would help with removing that white vane gadget if there's room for it.

[@starastronomer]

Thank you so much 👌

[@MrChargerbob]

Got me up and running after watching the video... thx for the demo

[@starastronomer]

Bob Swanson You're very welcome!!!

[@charleshopkins4475]

Outstanding video, I had trouble with my string trimmer the first took the bowl off and it was full of debris gave up on taking carb off but I wont the next time. I installed the same kind of fuel shut off but it does not turn freely almost like its gaulding any idea what could be causing this I think I purchased 12 of them from Amazon.

[@starastronomer]

@charleshopkins4475 Probably a bad shut off valve. Replace it with a new one.

[@DominicMarcanio]

Worked great - thank you for taking the time to make this!

[@starastronomer]

Glad it helped you Dominic Marcanio.

[@fazjewls14]

Thanks alot for taking the time and posting this video. I'm having g to swap out carburetor. Where can I order it?? 👍💪😎

[@starastronomer]

You're welcome. Got mine off Amazon.

[@rickharris1295]

exactly what i needed. thanks a million!

[@starastronomer]

You're so very welcomed Rick!

[@erdenebilegbayaraa9826]

Thank you sir! Good tutorial for beginners and HD video.Good job!

[@starastronomer]

Thank you so much!!!

[@SteveFromWyoming]

I just picked one of these trimmers up from my neighbor. Followed your directions to the T, 2 pulls and it started but only seems to run at an idle. I'm guessing that's how it's supposed to run.?? Can you help?

[@starastronomer]

Thanks Steve. It only has one speed once started. When you let off the "brake" handle the engine stops.

[@user-ou5eo2ln7v]

nice video i feel confident replacing the carb on my trimmer now!

[@starastronomer]

Dina Lund Thank you. You can do it, good luck!

[@keystothekingdomrpa1428]

Awesome. Thanks for this. The throttle seems to be stuck all the way up. On this cub cadet. Not sure how to adjust it. Bless u

[@starastronomer]

You're welcome.

[@Zx14rrrrrrrrrrr]

Did you figure it? If not I'm pretty sure I can tell you what it is.

[@ChristinaCleghorn-n3t]

You are the man, thanks for the great video sir!!

[@starastronomer]

@user-it5us7fn5x Much appreciated!!!! You're welcome.

[@sarahmichelle9291]

Thank you, that was very helpful!

[@starastronomer]

You're welcome❗️

[@bobtosi9346]

@starastronomer do you know where to purchase the inline fuel shut off valve

[@starastronomer]

Amazon

[@gregosborne8268]

Great video. Just what I was looking for! Can someone pls. tell me where the two lines for the carbon cannister attach to? When I removed the engine shroud, one came loose. The other is attached to the back of the air filter housing, and from this video it looks like the other goes towards the fuel tank. That makes sense base on carbon cannisters on cars that I have worked on, but I don't see where it goes. Note to anyone from Cub Cadet who is reading this: it would really help if your parts manual also showed where items connect to each other.

[@starastronomer]

Thank you!!!

[@tommurphy9278]

Great video helped me a lot very detailed thank you

[@starastronomer]

Thank you so much!!!

[@tylermyers9414]

Thanks for posting helped out a lot

[@starastronomer]

You're welcome Tyler Myers.

[@martinpenaluna9385]

Very informative. Thank you!

[@starastronomer]

Glad it helped!

[@philliphall5198]

Still need a fuel filter also

[@benewell4162]

That thing looks brand new

[@starastronomer]

Thanks. I'm very picky and keep it clean.

[@MrBuffalosoldier34]

Can you drain the carb bowl without removing it?

[@bobtosi9346]

Yes very simple. Use a 10mm wrench on either the drain plug or the bolt that holds the bowl to the carb. Be careful not to loose or damage the O ring seal

[@Tebazi]

How do you keep It so clean. Mine has lasted at least 5 yrs or more and used on 20 acres with lots of brush. Will never look like yours.

[@starastronomer]

@Tebazi Thank you. First, I am very picky and try to keep all my equipment in tip top condition. Second, I have 4 acres but only really need it for my south side line and a few other spots. I always blow it off when done and will clean it every so often. At the end of the season it does not get put away dirty and I even use furniture polish on it. My car has two seat covers on it. Not sure what color they are :) The plastic panel on the "rocker panel" of my 2014 CR-V looks brand new. I do not drag my shoes over it. Like I said, picky :)

[@Tebazi]

⁠@@starastronomerthanks for replying, hey I just got a 2024 CR-V great car!

[@starastronomer]

@Tebazi You're welcome. My 2014 Honda CR-V [bought in April 2014] has 161,500+ miles. It has been the best vehicle I've ever owned; VERY RELIABLE. The others were Chevy's which I will never buy that brand again. I change my oil every 5,000 miles.

[@Tebazi]

@@starastronomer i had a 2014 Nissan Rogue 160+k mi never had a problem also changed oil n filters religiously. The last year it started to decelerate on interstate doing 75 -80 on hot days (Fl) apparently for safety reasons(I would pull over turn it off and after 5 mins start up again np) I read somewhere. Nissan couldn’t find the issue so it was time to upgrade and gift to 15 y/o grandson learning to drive. :) I was longtime wanting the CR-V EXL. So it worked out. :)

[@philliphall5198]

Folks take a picture or two before you tare it apart of linkage

[@jerryhines5659]

Thanks

[@starastronomer]

You're welcome 👌

[@bobtosi9346]

@starastronomer I’ve followed this tutorial to the letter and mine won’t run it all. It fires off ether but dies immediately. There’s fuel in the carb bowl. I have a new carb on the way. FYI the carb has been blown out with carb cleaner. The main jet is clear, the float works fine the pilot is clean and the mid range jet is clean. I’m stumped

[@starastronomer]

@bobtosi9346 Whenever I clean a small engine carb I use "Oxygen-Acetylene Torch Tip Cleaner Kit with 12 Stainless Steel Reamers" similar to these: www.homedepot.com/p/Lincoln-Electric-Oxygen-Acetylene-Torch-Tip-Cleaner-Kit-with-12-Stainless-Steel-Reamers-KH575/100341101 I have one bought at a local welding supply shop that has many different sizes. You want to use the largest diameter that fits but WILL NOT STICK in the holes. You do not want to make them bigger. I have found you can use cleaner but really need to "ream" the holes too. Do all the holes. Give that a try.

[@bobtosi9346]

@@starastronomer new carb new plug new filter. Fires up on fuel but dies right away like it choked. The in tank filter is removed and I have a new inline filter. Gar is flowing through the filter.

[@starastronomer]

@bobtosi9346 Linkage is on properly? Is anything stuck or binding that the linkage moves? Is the choke working; did you see it work properly?

[@bobtosi9346]

@@starastronomer yes no yes

[@bobtosi9346]

@@starastronomer I’m pretty convinced now it is the ignition module. Something is happening as soon as the mower starts running. Maybe wires coming loose????

[@MiguelRamirez-qi3vx]

Thank you so much thank you thank you thank you

[@starastronomer]

You're welcome❗️❗️❗️

[@bobtosi9346]

@starastronomer is it possible my machine won’t run with ethanol mix fuels? It quit last year after I forgot to drain the old fuel

[@starastronomer]

@bobtosi9346 Very possible old gas, not necessarily that it has ethanol fuel. I always start the year out with new NON-ethanol gas I get locally for all of my small gasoline engines.

[@starastronomer]

@bobtosi9346 AND I drain out all gas at the end of a season.

[@jamesconner9021]

The drain on the carburetor is a poor design. It doesn't drain to the bottom of the bowl. It leaves a little gas in it. I think what you were seeing was varnish from dried gasoline not rust. Being that there is no iron/steel in the system it wasn't rust. If you want to drain all the gas out of the carb, you need to take the bottom bolt out. This holds the bowl on, but nothing will fall out of the carb.

[@starastronomer]

I think you are correct.

[@philliphall5198]

Carb is so easy to clean why replace it Just wash out with carb cleaner good

[@starastronomer]

Did you watch the ENTIRE video??? I think not...