Honda HS621 (GX160 engine) Snow Thrower - won't start - what next to check?

Old 02-02-11, 09:46 AM
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Honda HS621 (GX160 engine) Snow Thrower - won't start - what next to check?

Hi all,

Dad gave me an old Honda HS621 that's been sitting in the shed for years..and years. Got it home to discover it's a mouse apartment complex. Here's what I've done:

1. Pulled off all the plastic and cleaned, scraped, and hosed the thing down to get rid of mouse stuff

2. replaced spark plug

3. Drained old oil and put in new

4. pulled off carb, opened it up and sprayed it all out with carb cleaner. Also pulled out the main jet and cleaned that as well. Note the main nozzle came right out as well, so I cleaned that up and could see light through all the itty-bitty holes in it. I'm pretty sure I put it back in the right orientation (flatter end down against main jet). Also, while unscrewing the main jet, I did very slightly strip a bit of it - that soft brass is so touchy. However, the nozzle seems completely free of any obstructions.

5. checked fuel lines from gas reservoir to carb - all clear.

6. New gas (of course).

7. It has an electric start and the engine turns over but after multiple 5 second cranks I'm not getting the engine to catch.

I've confirmed I am getting a spark (pulled the plug out, reattached to the plug wire and gave it a crank - saw visible spark). The fuel line is open (carb is full of fuel).

However, when I pull out the spark plug it looks like the chamber and spark plug are dry. Shouldn't they be wet after cranking due to fuel infusion? Does this mean:
a. Carb jets are still plugged
b. Something else between carb and chamber is blocked?

The throttle is all way open (hidden up under the plastic top - have to reach in and adjust manually and of course the choke is fully up.

So, I'm stuck. What can I do next? Any thoughts appreciated.
Old 02-02-11, 07:37 PM
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I assume you feel good compression if you pull the start cord or can hear a good compression sound when turning the engine over on the starter. I would remove the air filter, squirt a quick shot of ether in the carburetor throat and try starting. If it catches or runs for a second then it points strongly to the carburetor. If you don't have ether you can remove the spark plug and put about 1/2 teaspoon of gasoline into the chamber. Re-install the plug and try starting. Again, if it catches or runs a bit then you're back to the carb. In that case then I'd do a thorough carb. cleaning which usually is total disassembly, soak overnight, blow out all the passages with aerosol carb. cleaner and re-assemble.
Old 02-09-11, 11:19 AM
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Maybe a stuck intake valve? I've never had to deal with one, but I would assume that would keep the plug dry. You could probably check that the valves are free if you pull the rocker box cover. With the plug out you can pull the cord and watch them

You could also check/adjust the clearances while in there. I just picked one of these up myself, and the intake clearance was pretty far out of spec. Even if this isn't the issue, it may need an adjustment.

As for freeing up a stck valve if you have one, not sure the best way other than removing the head. I read that the tip of a heat gun in the carb inlet could heat and free the varnish that sticks the valves, but I have no idea if that really works.

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