Tune Any Carburetor On Your Weed Trimmer! (DIY Tutorial)

[@VintageEngineRepairs]

If this video helped you, please consider clicking on the THANKS button above to support my channel 🙌 and don’t miss this video on how to save a straight gassed 2 stroke engine! kzbin.info/www/bejne/Y5_GkoJ5rc6ZaNU

[@bobross9332]

This is easily in the top 5 " how to " videos in my collection. I was having one hell of a time trying to get my FS 36 weed trimmer tuned right until I saw this video. It worked so well I purposely undid my work and redid the tuning several times just because it worked so well...

[@VintageEngineRepairs]

Glad you enjoyed it mate :)

[@gridharris2206]

That is a great and informative video. Thank you for posting. No one ever discusses where to set the idle screw when tuning a carburetor. Now I know and thanks.

[@VintageEngineRepairs]

Thank you!

[@DarrenFurr]

You explain this as simple as anyone on KZbin! The way to adjust the low speed is effortless, even for dummies like me. I hope this question doesnt sound like it came from a dummy. I have a small echo chainsaw. I have adjusted the carb as you said, several times. The ideal, according to my cheap tack an my ear fluctuates between 2800 an 3100 rpms. Is that right? Ive read it is, but until I hear it from someone smarter than me, Im not sure. It passes the pressure an vac test. That I learned from you also.

[@VintageEngineRepairs]

Glad it helped :) yep, most rpm specs are +/- 200rpm 👍🏻

[@mohabatkhanmalak1161]

You are a great tech with a good, in depth knowledge of these machines. Thank you for an invaluable tutorial.🐞

[@VintageEngineRepairs]

Thanks for the kind words :)

[@bobmcl2406]

Very well explained. Thank you. I have always hated working on 2-stroke equipment because there have been a few that just resisted every effort I made. And of course every subsequent seat-of-the-pants adjustment only got me farther from the goal.

[@VintageEngineRepairs]

Haha glad it was helpful!!

[@jefftheaussie2225]

I have a wipper snipper with a rotary carby. I didn’t know this till I watched this video but I always wondered why it didn’t have any adjusting screws. Your tips are very handy indeed. Jeff

[@VintageEngineRepairs]

Glad it was helpful Jeff! :) much appreciated mate!

[@h4ppyleader]

watched all your videos mate keep them coming please.

[@VintageEngineRepairs]

Thanks mate!

[@darrenpierce9903]

Flow chart is an excellent idea Tom. Printing this one off for sure. 👍

[@VintageEngineRepairs]

Awesome :)

[@clintstevenson1214]

The BEST and most worthwhile videos to watch! Thanks Tom

[@VintageEngineRepairs]

Thanks mate!

[@tomasznumrych7187]

Love the flow chart. You should make one for chainsaw tuning too.😉

[@VintageEngineRepairs]

It’s identical :) glad you enjoyed it!

[@tomasznumrych7187]

@@VintageEngineRepairs I was under the impression that tuning a chainsaw requires for it to be "in the wood".

[@patrickvennard838]

Thats really comprehensive as ever I have a good tachometer but i do like to do it by ear, thanks Tom.

[@VintageEngineRepairs]

Thanks Patrick! Yep, a tach is an fantastic and incredibly important tool - I have two and don’t have anything bad to say about using them :)

[@rise_above]

This is one of the best videos on this. Great stuff

[@VintageEngineRepairs]

Thanks mate :) I really appreciate it!

[@keegantimber8571]

Very interesting and you taught me adjustments I didn’t know! Thank you! Thumbs up everyone! 👍👍👍

[@VintageEngineRepairs]

Awesome! Glad you enjoyed it :)

[@rockyholt4060]

A lot of good knowledge appreciate you doing that from Central Florida

[@VintageEngineRepairs]

Thanks :) you’re welcome!

[@Shawnee.Hills.Small.Engine]

Great video Tom, and thanks for making those flow charts 👍

[@VintageEngineRepairs]

You’re welcome! I’m glad you found them useful :)

[@valleycoastlawns]

Priceless info Great video mate!

[@VintageEngineRepairs]

Thanks mate! :)

[@steveriggenbach90]

A lot of good info. I’ve had to work on some units that I couldn’t see the idle adj. screw. You don’t need a hot pick, they have special screwdrivers with reverse threads. They come with different kits. Thread in and pull out.

[@VintageEngineRepairs]

Hey! Thanks! Yes you’re spot on, some carbs have reverse thread limiters :)

[@steveriggenbach90]

@@VintageEngineRepairs that too. But kits will have a threaded screw driver tool for pulling the plastic plugs out.

[@almclean4835]

Great video Tom.

[@VintageEngineRepairs]

Thanks Al!

[@danielzuluaga4232]

Man, I can't thank you enough. Thanks bro!!!

[@VintageEngineRepairs]

You’re welcome!

[@KensSmallEngineRepair]

I'd like to see what a tachometer says on your audible tune versus what the OEM specs are. As always, great stuff Tom!

[@VintageEngineRepairs]

Thanks Kenny! I’ll give it a go and report back 👍🏻

[@Big_Johns]

Tom you always explain it so well, thanks for the video brother. 👍👊

[@VintageEngineRepairs]

Thank you brother!!

[@tinkeringtaylor3053]

Your one clever man Tom, this has been excellent information 👍

[@VintageEngineRepairs]

Glad you enjoyed it nev!! Thanks mate :)

[@SandDsmallenginerepair]

thanks brother great video

[@VintageEngineRepairs]

Thanks mate!

[@moisty254]

Your videos are great, I always refer to your in depth carb troubleshooting video. Do you know if those filled holes on carbs can be drilled and used as impulse feeds? Also do you know if an impulse doesn't quite line up if you can make a gasket with a slot that'll line up an offset impulse hole on the carb? And have you done a video on a 2 stroke weed eater for crank seals, setting the flywheel timing, checking the flywheel key, checking the condition of the piston rings, and performing a leak down test?

[@VintageEngineRepairs]

Glad you enjoy them! I’m sorry I don’t really understand your question. You can drill and make new impulse ports on the crankcase with a barb, not in a carb though :) I have lots of videos like seal installs and rebuilds, yes :)

[@KensSmallEngineRepair]

Good Stuff Tom, as always! The Stens Carb tools are a bit pricey but I like the tabs on them to tell where you are (number of turns).

[@VintageEngineRepairs]

Hey mate! I have had some cheaper screw drivers in the past and they’re ok, especially for homeowners who don’t use them much, but I don’t find they hold up well, especially the small packman and other small heads, so bit the bullet and got something that has lasted really well :) thanks for watching mate!

[@tomasznumrych7187]

I ordered the Stens kit after watching the video, and because of the mentioned tabs, unfortunately my life is tab-less. Ken, would you happen to have the stens part number of the kit you have with the tabs?

[@KensSmallEngineRepair]

⁠mine don’t have tabs, Tom, the Stens link shows drivers with no tabs, do they have a part number on them?

[@VintageEngineRepairs]

Hey guys :) That screw driver I use is not part of the kit of specialist screw drivers, as mentioned in the video it’s a simple flathead screw driver by stihl. The kit, as you know, is stens and is only for the specialist profiles. Hope that clears up confusion :)

[@VintageEngineRepairs]

Hey Tom! There aren’t any tabs on them as per the kit I showed in the video and their appearance on Amazon too. That screw driver I use is not part of the kit of specialist screw drivers, as mentioned I use a simple flathead screw driver on these by Stihl. Sorry for any confusion!

[@jjrotogeek]

great video borther!! and i love how you talk into that gerbils butt on ya apron!!! :P

[@VintageEngineRepairs]

Thanks mate!! Hahaha

[@kencurtis228]

TY for Sharing

[@VintageEngineRepairs]

You’re welcome!

[@clivejames6918]

Hi. Thanks for the really clear instructions. Hope you can answer 2 questions. I have a Stihl FS100 4mix strimmer. Is the adjustment process the same for these type of machines? Also if your using a blade not line would you change the adjustment? Thanks for any help.

[@VintageEngineRepairs]

Hey :) yes, but note that they’ll be limited ignitions, so set it to where it just starts to limit. Don’t richen it back up on the high side.

[@mokhaz9372]

Thanks, well done. I was wondering how this process works for a ryobi back pack leaf blower. I’m having a difficult time adjusting the low and high screw. I don’t have an rpm reader.

[@VintageEngineRepairs]

What good timing ;) I’m working on that exact video (though not a backpack it’s the same process). Leaf blowers are very unique in that they’re under full and constant load and must be adjusted differently on the high speed circuit. Stay tuned, it will be released in a week or so!

[@garethparry6673]

Your vids are very good and helpful. I did a test on my coil today, the coil to spark plug was a good reading, but the kill wire terminal on the coil was showing a reading then going then coming again but had good contacts. Does this mean the coil is bad?

[@VintageEngineRepairs]

It could very likely indicate the electronic components on the primary circuit that is causing interference with the resistance. Some of which is made up of semiconductor material. I’m not saying this is the cause, but it’s been the most common in my experience. I say try the coil :)

[@garethparry6673]

@@VintageEngineRepairsthanks so much for the reply. I’ll try it👍 really appreciate it👍

[@Ckktopa]

great advice. Thanks

[@VintageEngineRepairs]

You’re welcome :)

[@alexchalcraft3513]

Brilliant

[@VintageEngineRepairs]

Thank you :)

[@raymondthompson4222]

Great video Tom, but why cut the line a inch below the cut off

[@VintageEngineRepairs]

Thanks Ray! The reason recommend tuning it at a slightly worn line length rather than full extension is this setup allows the engine to slightly "four-stroke" when not under load and "two-stroke" when under load, which is where it should be for a safe and effective tune. I've found that the high-speed adjustment screw becomes less responsive to fine-tuning when the line is at its full length too. Additionally, a slightly shorter line helps you hear the ignition limiter, which might not engage when tuning at full-length line. This is crucial, especially for people learning to tune, as a this can lead to setting the mixture too lean. Most weed eaters, (apart from brush cutters), lack good power when using a full-length line, often overloading the engine in thicker grass. Therefore taking a little load off by shortening the line a gives it more power under load, reduces the stress on the engine while ensuring it has a safe tune. Hope this helps.

[@raymondthompson4222]

Thank you

[@Stefano_B.]

Hi, really nice video. What about a blower? I have a BR450 and I have some troubles adjusting the H screw. It doesn’t 4stroke, it just drops the rpm but that point is really far away from the original point where the limiter cap sits. I don’t want the engine to blow up due to a lean setting. I’m used to set all of my carbs but with this one I don’t know. The thing is that I have to go really far away from the original factory setting. What I do is to screw in the H screw until the max RPM and than back out a bit but, as I just said, I have to go really far away from the original. What do you think? Can i trust myself? 😂 Thank you in advance

[@VintageEngineRepairs]

Hey :) thanks! I’ll be doing a blower video in about 4-6 weeks. They are tuned slightly differently on the high screw as they’re a constantly loaded engine!

[@Stefano_B.]

@@VintageEngineRepairs thank you, I will appreciate it so much. Can you just tell me if im right doing like that or if it’s normal that I have to lower the rmp that much?

[@VintageEngineRepairs]

Hey :) Leaf blowers, when tuned correctly, that are warm and running full throttle won’t 4 stroke, no :) my recommendation is set it back to how it was at factory, with the limiters in place and keep an eye out on the video !

[@clintstevenson1214]

Thanks!

[@VintageEngineRepairs]

Thanks again mate! I really appreciate the super chat!! ❤️

[@clintstevenson1214]

@@VintageEngineRepairs does this video apply to leaf blowers too?

[@VintageEngineRepairs]

@@clintstevenson1214 no don’t follow this for a leaf blower, at least not the high side :)

[@mikemccoyrpt]

Brilliant!

[@VintageEngineRepairs]

Thank you!

[@antoninoleone5386]

Great and helpful video. Just a question: some weed trimmer carburetor (rotatory type) has only idle screw and only another screw, no H and L screws. How can we tune these kind of carburator? Thanks a lot for your information

[@VintageEngineRepairs]

Hey, if no screws are present, the only way you can adjust them is by drilling the main jet :) thanks for the kind words!

[@antoninoleone5386]

@@VintageEngineRepairs , Two screws are present: one is for idle, and another for fuel mixture, but there is no indication if is L or H. Any suggestion for the carb tuning in such a scenario? thanks

[@VintageEngineRepairs]

Hmmm what is the make and model number on the side of the carb?

[@timsit]

I may have missed it, but after you set the high speed to two stroking and start backing it off slightly you want to leave it set to just when the engine sounds like it's four stroking again, correct? Basically, final setting is at the very top of the four stroking position.

[@VintageEngineRepairs]

That’s exactly right :)

[@timsit]

@@VintageEngineRepairs Thanks for making this video. I've wanted something simple like this for a long time. Time to pull out that old weedeater and get it tuned up.

[@Non-Stick_Pan]

Hi Tom, my Husqvarna weed eater with butterfly carb has no clutch - any tips for setting the idle/low speed adjustment?

[@VintageEngineRepairs]

Hey, on direct drive models, you can set it anywhere that it sounds happy. The process is the same as I demonstrate here, but you don’t need to worry about the head not spinning is all :)

[@Non-Stick_Pan]

@@VintageEngineRepairs Thanks for your great help as usual! :)

[@Thomas-nz4uh]

I have the butter fly type carb on my string trimmer, and a tachometer, the required two cycle fuel mixture is 50:1, but it's running a little hot on the lean side. So I dropped down to a 30:1 fuel mixture and still running it at the required 8000rpm's max speed and the required 3000rpm's idle speed, and it sounds like it's running better. But eventually I'll go back up to the 50:1. My question is, while I'm still running it at the 30:1 gas/oil mix would I need to adjust my carburetor to accommodate the 30:1 mix. If yes, how can I do that and maintain the required 3000/8000 rpm's or is that necessary? I'm not a professional at this, so I hope you understand my question.

[@VintageEngineRepairs]

Hey, changing oil ratios make no difference to lean or rich. At least not enough you’ll ever notice. Hope this helps!

[@grahamturner2469]

Can I check with you which Mityvac pressure and vacuum tester I need. Your link suggests the tester from Amazon that only has pressure. However in your video you use one that has both pressure and vacuum. Should I be getting the one in the link or the one with both???

[@VintageEngineRepairs]

Hey! The one I linked to in the description (mityvac 8500) is the one I use and does both pressure and vacuum. Just confirm it’s the 8500 model you’re looking at :)

[@grahamturner2469]

@@VintageEngineRepairs Thank you . I thought it would be the both pressure and vacuum model. however the link goes to the pressure only model. Thanks for clearing that up I will look for the model that has both.

[@VintageEngineRepairs]

@@grahamturner2469 how strange! Can you please share the link that comes up on your page when you click my link? I’ll do some Digging :)

[@alext8828]

That's a very nice tree you're standing in front of. What would that be, if you know?

[@VintageEngineRepairs]

Its common name is bottle brush I think! Though I’m not sure of the botanical name which is probably far more useful 🤣👍🏻

[@DanWallis86]

What about 4 stroke garden tools?

[@VintageEngineRepairs]

Yes for the low circuit, the high side I set them to where they run the fastest :)

[@DanWallis86]

@@VintageEngineRepairs thanks mate. I’ve got a Honda weed trimmer and it’s starting to get harder to start when cold. Thanks for all the advice you share, I love it.

[@scottduflo7348]

Just replaced a bad diaphragm. I put the settings where you say to. It will start up with the choke on and then when I switch the choke off, it slowly dies down and dies. Then I have to choke it again to get it to start. I've been bending the tab that opens the needle valve up and down trying to get it in the right spot. Is the tab too far down and it's not getting enough gas?

[@VintageEngineRepairs]

Don’t mess with the metering lever. Set it to factory recommended height and leave well alone. Why didn’t you continue with the tuning procedure I show?

[@scottduflo7348]

@@VintageEngineRepairs I don't have the metering tool. It's a WT carb so I need the M shaped tool. How far down does the middle of the M sit below the outside "arms" of the M? I could probably make one out of stiff cardboard. I didn't continue because the motor won't stay running.

[@VintageEngineRepairs]

I don’t have my gauge here to measure I’m afraid! They’re not expensive to purchase though fortunately.

[@innerman7096]

I use the procedure in the video on a Stihl FS91 and it didn’t work.any ideas why it didn’t.

[@VintageEngineRepairs]

Tuning is the final step to an engine running correctly. It won’t account for air leaks, blocked fuel filters, damaged or kinked lines, old diaphragms / carb kits :) if tuning didn’t work. Start from the beginning - check that the fuel system is clean, free of blockages, leaks and kinks, the carb is good and clean, the carb kit is goood. Also inspect the machine - air leaks etc. Hope it helps :)

[@TheAstronerd]

What about a rotary carb that has no L or H adjustment?

[@VintageEngineRepairs]

If it’s non adjustable it’s non adjustable lol. May need a new carb kit to get it running right again.

[@AyuPerezsaucedo]

hola maestro buenas tardes una pregunta maestro tengo una cortadora dé pasto de la marca Toro cuando jaló la cuerda del arranque siento el reporte el rebote como que me jala hacia adelante la siento como con mucha compresión qué podrá estar pasando ahí con mi apodadora de pasto de la marca toro maestro

[@VintageEngineRepairs]

Hey! Could be sheared flywheel key, or possibly vapour lock !

[@AyuPerezsaucedo]

Gracias maestro por su atención saludos y cuídese

[@johnwyman6126]

In order to work on equipment properly, you need the proper tools. In order to adjust a carburetor properly, you need to have a tachometer. I don't care who you are or what you say you can do, but no one can hear a 50 RPM difference at 12000 RPM. This is what differentiates a professional from a hack, and unfortunately there's a lot of hacks that work in shops. I have never been to, or even heard of any manufacturer training that teaches to do it without a tachometer, and they are the ones that engineer and build the thing in the first place. Having said that, I do like the flow chart for beginners though.

[@VintageEngineRepairs]

I completely disagree. A good mechanic doesn’t need to rely on a tachometer-they can tune an engine by how the engine feel’s, responds and how it sounds. While a tach is a useful tool, the best tuning comes from responding to how the engine handles load, acceleration, deceleration, hesitation, and more. The factory-recommended specs are just broad guidelines; not every machine will run optimally at those settings. Consider an older engine with worn rings, different tolerances, or fuel that isn’t fresh-there are countless factors that affect the ideal RPM for tuning. If you stick to manual specs with slightly older fuel or slightly worn rings, for example, you could end up running the engine too lean. Same with slightly worn skirts that won’t seal ports correctly. Leaning the engine out to reach a manual specification will set them too lean and can lead to damage. I own two of the most expensive, professional-grade tachometers, yet I still get better results by tuning based on how an engine sounds and feels / responds to load. A tachometer is a great tool to get you close enough to avoid major issues, but what if you don’t have specs for a particular machine? If you can’t tune by feel and sound, you’re stuck. Also, regarding the 50 RPM swing: just a few degrees of temperature change throughout the day can cause an engine to rev higher than that. Unless you’re tuning every 20-30 minutes, you’ll never be at the exact RPM. That’s why manuals typically allow for a +/- 200 RPM range. I have also found on occasion different manuals for the same engine give a different specification of rpm. I can tune to within 100 rpm by ear. Often machines with limited coils can be higher or lower, by 800-1000 rpm of manual specifications too. So you won’t even hit the rpm the manual states before the ignition limiter kicks in. Another example of how a tach can’t get the optimal result from the engine or setup.

[@Robert-uh6bx]

I also believe tuning by tach was best until I learned to tune by ear. Once you lean to tune by ear it’s as good as a tach and once you learn how to have it 4-stroking without load and 2-stroking under load you don’t have anything to worry about. And tuning the low side is very easy. I do it just like how you do it in this video. It’s flawless. And if it doesn’t tune right like how you do it in this video then you got other problems.

[@DarrenFurr]

Thanks!

[@VintageEngineRepairs]

Thank you! :)