Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

Hi all. I recently purchased a used HS621 that wasn't running too good and have begun getting it back to (or trying to) reliable service. I purchased it for my folks so it needs to start easy and work consistently. There are problems with the carb, it only runs with the choke on. I got it to a point where it'll run with the choke almost off but it surges at that point. So, a complete carb dissassembly is in order and I'll be tackling that once the gasket set comes in. In the meantime, I wanted to ask whether any of the other HS621 owners could comment on the air cleaner on this thing. This is all new to me but there doesn't seem to be any kind of air filter on this thing. Not sure if it's related, but the float bowl on the carb was full of debris and sediment. This either came from the gas or could it come from the air intake?? Like I said, I'm new to this.

The parts diagram here:
http://www.boats.net/parts/search/Honda/Snow%20Blower/0/HS621%20AS-B%20SNOW%20BLOWER%2C%20JPN%2C%20VIN%23%20SZAN-1038359%20TO%20SZAN-1099999/AIR%20CLEANER/parts.html

shows a strainer of some sort but I don't have that. Also, they don't sell it (part #8 is not in the list).
So, is the diagram correct? Does anyone else have this snowblower that can comment? If i am indeed missing this piece can I just improvise something and what would be an appropriate material to use?

Thanks
Steve

Back again.

I have replaced the choke cable and I removed the carb tonight and cleaned it and replaced a couple of the o-rings. Now, I didn't remove any of the jets because I was nervous about breaking them and this is probably where I went wrong. I was nervous because I know one of the jets (is it the pilot jet?) breaks if you take it out and I don't have a replacement. In any case, the thing is running way better now and it starts no problem but it's still surging :/

Here is a video to show you what I mean....

http://www.youtube.com/watch?v=pi5SdAsWZYQ

I'm guessing this is still some sort of carb issue. If I dismantle the carb again, which jet should I really be focusing on and should I be worried about busting any of them?
Thanks!

This can sometimes be frustrating. Don't give up. Does the surging change (increase or decrease) as you adjust the choke setting? I had a similiar surging issue on a HS520 Honda snowblower this year and replaced the carb (it was cheap) and the problem went away.  I think you'll be more successful if you remove the jet and follow the cleaning instructions carefully. Find a screwdriver that is a really good fit (I use a metal file to file mine down to get a custom fit, nice and square and flat on the end.) and wrap the last inch of the screwdriver in masking tape to it does not damage the thread in the carb housing. If you follow the directions outlined in the video that you posted for cleaning all the passages you should be fine.

 http://www.youtube.com/watch?v=n_eTqL0C3gQ

Ok, back again to dig up this old thread. I took the carb out AGAIN last night to deal with this "once and for all" and cleaned it all out really well. I think my problem is with the linkage or springs. I've no idea what this is supposed to look like now. One of the springs seems a little loose and I can see the cam that moves the throttle plate move back and forth when the motor surges. Is it possible that there isn't enough spring tension? Thus allowing the throttle plate to "float"? If I hold the cam in place the surging stops. I suppose I should order new springs for the linkage. But before I do that I'm just going to put some wire on the cam to hold it in place at a set throttle position and see if that does anything. The snowblower doesn't have a throttle control anyway so the throttle is fixed from the factory, the only way to change throttle position is by manually moving the throttle lever on the carb. This is under the cover of course so not a user accessible control. Can the spring tension on the linkage cause surging?

smp22 wrote:
In a word, yes.  Sounds like you ruled out a carb mixture or clogged jet problem.  Can you hold the throttle steady with your finger and see if the surging stops?  If it stalls, then it is a mixture problem or some fuel obstruction still.  Does it run well under load with the choke fully open?

If, by holding the throttle steady by force, the surging stops, then the throttle linkage and spring can cause surging.  I've seen this with two and four strokes.  In my experience, I had too much tension toward wide open throttle where the governor and spring were in contention.  The spring forced the RPM's higher and ultimately the governor would counter.  This cycle would repeat.  I loosened the tension, in my case by bending a tab and the RPM's stabilized.  This was with an air vane style governor with no adjustment.  Yes, bending a tab is what the service manual called for.

In your case, the float of the throttle implies there is not enough resistance in each direction to stabilize the throttle.  It sounds like you want to increase tension. 

Careful with your "wiring of the throttle" such that you don't over-rev.

Incidently, it is not necessarily bad for the surging as long as under load the surging stops.  At least that is the case with my 2-cycle Toro.

Thanks for the fast response. When I put my finger on the cam that opens the throttle plate the surging stops. This is the little cam that the throttle assembly, springs and all, control. When I move it, I can change RPM without surging. The springs are very fine and I believe I stretched one of them out, the return spring I think. I am ordering new springs. However, before I do that I'm going to clean out the pilot jet because I have not done that. I did not know where the pilot jet was when I cleaned the carb the first .. oh, three times! So I guess that could still be it. However, I do suspect the linkage as the cam moves around with the surges and that return spring appears "loose" when the throttle is in the closed position.