# HS621 that won't start



## garimh (Nov 21, 2014)

Just bought a used HS621 (for $50!) that won't start. Previous owner said he put a new carb in last year and it worked fine then but now won't start.

I'm a newbie with this but did open the fuel plug underneath, dropped the bowl (which was pretty clean) and also cleaned main jet (hole was closed up). Was hoping that would do it but no luck. 

I assume I need to take carb out and clean it but not sure how to do that. Is there a service manual around that shows proper steps to remove carb? Google search not giving me much. Also, please see below photo. What is that loose hose on right? Should that be hooked up to something? 











Thanks!


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## YSHSfan (Jun 25, 2014)

The hose showing seems to be the carb fuel overflow hose. Maybe there is a simpler way to remove the carburetor, but the way I do it, I remove the chute, chute base, engine main cover, exhaust cover, fuel tank with fuel shut off valve and ignition switch. Before you remove the carburetor I'd try to spray some carb cleaner or starting fluid on the air cleaner inlet and see if it runs, if it does it is a fuel issue and the carb needs to be removed, if it does not you may have a spark issue.


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## YSHSfan (Jun 25, 2014)

There is a free download for an owners manual, if you google it you'll find it. The Service Manual you have to buy. It is for sale at Amazon and eBay. I purchased one and I'll be able to help with some info as you need it.


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## YSHSfan (Jun 25, 2014)

I have an HS621 apart for service, if you need any pointers let me know.


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## garimh (Nov 21, 2014)

hsblowersfan said:


> The hose showing seems to be the carb fuel overflow hose. Maybe there is a simpler way to remove the carburetor, but the way I do it, I remove the chute, chute base, engine main cover, exhaust cover, fuel tank with fuel shut off valve and ignition switch. Before you remove the carburetor I'd try to spray some carb cleaner or starting fluid on the air cleaner inlet and see if it runs, if it does it is a fuel issue and the carb needs to be removed, if it does not you may have a spark issue.


Thanks all. I feel like an idiot asking this but where is the air cleaner inlet?


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## Tomatillo (Nov 11, 2016)

garimh said:


> Just bought a used HS621 (for $50!) that won't start. Previous owner said he put a new carb in last year and it worked fine then but now won't start. Thanks!


I won't presume to know an ounce of what hsblowerfan knows. You might have to remove that carb and clean the jets, but here's from my notes on a similar situation:



Neal McMichael saved me on this: He said to spray Berkebile2+2 Gum Cutter (JK Auto Parts Manassas) and spray it into the carb throat. IT WILL START. Have SeaFoam in fresh fuel and let it run. Itshould even it out after running it, and then letting it soak with the SeaFoam.


It worked for me onthe snow blower.​


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## YSHSfan (Jun 25, 2014)

garimh said:


> Thanks all. I feel like an idiot asking this but where is the air cleaner inlet?


Don't feel like that..., nobody "knows it all"
We are here to help, that's what forums are for.

This pictures are from the engine off the machine sitting on a bench. The first picture shows the air inlet, it'll be sort of under the ignition switch area, the second picture shows where I think the loose hose connects to, the other two are just the general area pictures.


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## bad69cat (Nov 30, 2015)

You should feel guilty for stealing that machine like that! :>P Nice!


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## jtclays (Sep 24, 2010)

Have you verified spark yet? Normally that engine will run even with a old gas, dirty carb. They can just about take anything. If you have no spark, grab a plug from anything in your garage that runs and try that one in the boot. If no spark still you may have a bad coil, but you need to trace and verify the engine switch wiring especially if the previous owner was tinkering around in there.
"Ran fine last year" is Latin craigslist code for, "I can't figure out what's wrong with it."


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## garimh (Nov 21, 2014)

Thanks to everyone for your help. I cleared the main jet again as well as the nozzle this time, which was a bit clogged but not too bad, and then sprayed some carb cleaner into the air cleaner inlet as suggested by hsblowerfan. Success! Started right up and stalled a few times when I pushed the choke down but I let it run awhile, put some fresh gas in and it seems to be running smooth now. Thanks again!


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## YSHSfan (Jun 25, 2014)

That's great.
Now enjoy the new toy.
:blowerhug::snow48:


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## jrom (Jan 10, 2014)

jtclays said:


> ..."Ran fine last year" is Latin craigslist code for, "I can't figure out what's wrong with it."


That is funny. 

If you google english to latin translator and type in "I can't figure out what's wrong with it." you get: _"Non possum discernere quid est mali."_ and it sounds cool too.

It would be funny if a voice popped up with that translation after you viewed the ad.


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## garimh (Nov 21, 2014)

Guess I spoke a bit too soon about this. Was warming it up today to change the oil and for the first 5 minutes or so, it was backfiring like crazy and stalling when I opened the choke. Once warmed up, the backfiring stopped but it seemed to be chugging a bit rather than running smooth. Could this be a spark issue or does it sound more fuel related? If the latter, is there a cleaner or something I can pour in there? 

Thanks again.


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## YSHSfan (Jun 25, 2014)

garimh said:


> Guess I spoke a bit too soon about this. Was warming it up today to change the oil and for the first 5 minutes or so, it was backfiring like crazy and stalling when I opened the choke. Once warmed up, the backfiring stopped but it seemed to be chugging a bit rather than running smooth. Could this be a spark issue or does it sound more fuel related? If the latter, is there a cleaner or something I can pour in there?
> 
> Thanks again.


I've read of using seafoam (I'm not sure exactly what it is) to clean the carb while the engine is running.
Make sure that the gas cap is venting, you can loosen the cap a bit, run it and see if it's better (it is a 2 part cap and sometimes people loose the inner part, happened to me on an HS520 that I bought).

If you have tools you can check the compression (spec is 85-120psi)

You can also check valve adjustment (spec is .15mm/.006" on intake and .20mm/.008" on exhaust).

Sounds like lack of fuel to me (running too lean).


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## robixx (4 mo ago)

I have a Honda hs621 I took carb off cleaned,and put back together. The bowl has fuel in it, but won't start. It will start with carb cleaner. Any ideas ?


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## tabora (Mar 1, 2017)

robixx said:


> I have a Honda hs621 I took carb off cleaned,and put back together. The bowl has fuel in it, but won't start. It will start with carb cleaner. Any ideas ?


I've posted in your other thread...



robixx said:


> took it completely apart cleaned everything


Completely apart would include the Pilot Jet #29, the Main Jet #28, the Emulsion Tube #14, the Float Needle Seat #2 and the Fuel Sediment Bowl #23. Did you get all of those out and clean and then clean all the hidden passages they obscure?


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## robixx (4 mo ago)

Tabora, what do you think it might be ?


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## tabora (Mar 1, 2017)

robixx said:


> Tabora, what do you think it might be ?


One or more of the things you have not cleaned yet.
Here are the Honda Carb worksheets...


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## robixx (4 mo ago)

Thank you ,I'm gonna give these a try.


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## Tony-chicago (Feb 10, 2021)

Usually it is the emulsion tube and the jet. On Hondas it is a bit out of my expertise. Luckily one is nearby. (Tabora) and many more here.

Then a thorough cleaning to get it running perfectly. How did it last run..etc...


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