Honda HS621 Snowblower Running Rich?


Old 02-06-11, 08:11 PM
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Join Date: Oct 2008
Location: USA
Posts: 38
Honda HS621 Snowblower Running Rich?

Just picked up this blower cheap. It hadn't been used recently, but the person I bought it from said they got it running, but the pull cord had broken so it was sold cheap as a non runner.

Pull cord was fine, just needed to be cleaned up as the pawl wasn't coming out and catching the flywheel. I sorted that out, changed the oil, swapped for fresh gas, cleaned and gapped the plug, and voila, it started on the first pull.

I started at full choke (about 25 degrees out) and it struggled and wanted off the choke immediately which seemed odd. Took the choke off and it revved up and sounded strong, but has a stumble, kind of like a miss. I let it run a bit hoping the stumble would clear up, but no such luck. Pulled the plug and it's black. Not oily, but more sooty. I didn't notice black smoke, but the muffler is [pretty sooty as well. It basically seems to me like it's running rich. I expected the exact opposite. I just assumed from sitting the carb would be gummed up and it would be running lean, and run better with the choke on, so i'm a bit puzzled.

I went to check the air filter thinking maybe it's clogged and the thing is starving for air, and now am even more puzzled. It doesn't seem to have an air filter. It's hard to tell because I didn't strip all the covers off, and it's tucked under one, but it seems like the intake is straight air, no filter. I have no experience with snow blowers, but I looked online and it seems that this isn't alltogether uncommon for a snow blower, since they aren't used in dusty conditions and filters can freeze or plug with snow.

Anyway, there seems to be little adjustment at all on this carb, so I'm not sure where to go next. I think there's an air screw for the pilot circuit, but I don't think that's my issue since it seems rich while revving. I will replace the plug with a new one first to see if it's any different. Maybe I'll get lucky and the plug is just old and shot. I'll also check/adjust the valve clearances since who knows if that's ever been checked, but after that I'm not sure what to check next. I guess a tear down of the carb just to make sure it's nice and clean, but I would hate to do that if I don't need to.

Anyone have anything obvious I'm overlooking? I've had experience tearing down carbs to clean them, but it's always been because of lean condition as a result of a clogged carb. This situation has got me a bit confused.
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Old 02-07-11, 09:18 AM
Join Date: Jun 2006
Location: St. Louis
Posts: 2,365
Since it hasn't been ran for a while try running some SeaFoam or Chevron Techron in the gas, either of the products will help clean any built up varnish and carbon. Have a good one. Geo
Old 02-07-11, 07:51 PM
hopkinsr2's Avatar
Join Date: Feb 2005
Location: canada
Posts: 1,561
Hondas are really picky when it comes to spark plugs.. Just for Goofs & Giggles, throw a new on in, (Sorry I dont have the #) that you are sure is the correct one & try it again,,, Roger
Old 02-07-11, 09:00 PM
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Join Date: Oct 2008
Location: USA
Posts: 38
I picked up a new plug and tried it, no better. I was hoping I would get lucky.

I thought about doing seafoam, some guys swear by the stuff for their motorcycles, but I've never had any luck putting it in my bikes. I always ended up having to tear the carb down and clean it anyway.

I popped the bowl off the carb and took the float and needle out. Shot some carb cleaner up through the bowl. Very half a$$ed, but I only had 15 min. Didn't try it after that, but I doubt it did anything.

At a glance it didn't look too dirty, but someones definitely been in this carb. The main jet shows signs that it's been out before(chewed up by a screwdriver a little). I guess I'll have to pull the carb out/apart, check it out and clean it when I have more time.

I was a little surprised at the price of a new carb, Honda is around $50, and a knockoff is around $20. At those prices, if it turns out I have to start replacing carb parts it would probably make more sense to just replace the whole carb.
Old 02-17-11, 05:38 PM
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Join Date: Oct 2008
Location: USA
Posts: 38
I didn't get much feedback on this, but if anyone is interested, it was the carb. The main jest was stripped by previous owner. I drilled it out using successively larger bits until all that was left was a tiny bit on the outside of the tube it sits in, but I still couldn't get that out. It was almost like it had welded itself in there.

I found a knockoff replacement carb for 12 bucks plus shipping, and threw that on. Replaced all the fuel lines for good measure, and it runs great. Starts first pull and now runs smooth. I am guessing some of the air passages were clogged. Perhaps those along the emulsion tube.

I also found the intake valve clearance was off by quite a bit. Enough so that it tended to pull back a little on the rope. Adjusted the clearances and the pull is now nice and smooth.

No doubt this thing will provide many more years of service now.

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