# HS 724 Carburetor Replacement



## yeuker (Sep 8, 2017)

Hey Everyone,

I purchased a used HS724 in very nice condition but it is surging. I figured it just needed a good carb cleaning but upon removal of the carb I noticed someone had been in there and the main jet was mashed up a bit from who ever removed it last. Worse yet, I dropped the bowl on the ground and bent the edge. With the replacement bowl being over $50 Canadian and the jets needing replacement anyway, I ordered a replacemnt carb (not Honda) as shown here:

https://www.amazon.ca/AISEN-Carburetor-Primer-Honda-Snowblower/dp/B06XRB352X

I've done some small engine work before but am no expert so looking for help. A few questions::

The same seller has this carb which I think is identical but doesn't ship with the primer bulb (which is OK because the HS 724 doesn't have a primer: 

https://www.amazon.ca/AISEN-Carburetor-Honda-Snowblower-HS521/dp/B06XSYMNDL

Both of these are same manufacturer, both say for the 724 but one comes with fuel filter and primer. Do you think one of these two is 'self priming' and the other (one I bought) is not and needs the primer? There is no where on the 724 to install the primer. I'm asking because I installed the new carb last night and she won't start. Have spark but clearly there is a fuel supply issue. It was late last night when I started so didn't troubleshoot for long after it wouldn't start. Any advice would be great. My first thought is to confirm the fuel supply issue by drying the plug, reinstalling and ensure it is still dry after I try to start again. Thanks in advance for your help. It is appreciated.


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## yeuker (Sep 8, 2017)

Also worth noting:
- Yes I remembered to turn the petcock on when I was done (fuel is on). I'm not above forgetting, but in this case I did not forget .
- To confirm the fuel made it into the bowl, I loosened the bolt on the bowl enough for gas to leak out. I.e. There is fuel in the new carb bowl.


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## Kiss4aFrog (Nov 3, 2013)

:welcome: to SBF yeuker

I'm not a Honda guy so I'm just thinking out loud here.

Have you tried to hit it with a little bit of starting fluid to see if it fires ?? The primer is for colder temps where just having a mechanical plate choke isn't enough for some engines and a primer to pump raw gas into the throat of the carb is needed.

Both appear to be the same carburetor from the description, it's just that one comes with a new primer assembly. That means there should be a nipple for a primer to be hooked up on both of them. Any chance there is an open nipple that needs to be capped ?? I did look up the owners manual and that 724 doesn't have a primer as you've said. Have you checked when you push the throttle all the way to the choke that the choke plate is physically closing fully ??


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## yeuker (Sep 8, 2017)

Thanks for the reply Kiss2aFrog. I have not tried starting fluid but will give it a go tonight. I agree, the 724 has no primer so pretty weird they are selling the replacement carb with one. Even if I wanted to hook it up, no idea where I'd put the bulb. I did not see a nipple for the primer to be hooked up but it was really late in the evening when I was working on it. I haven't pushed the throttle all the way but will for sure. I did check that the choke is closing the choke plat fully and all good there.


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## Kiss4aFrog (Nov 3, 2013)

Is there a plastic/rubber cover over that nipple ?? You wouldn't want that uncovered as it's likely open to the fuel bowl.

It's there simply because it's easier and cheaper to make one carb that works on a lot of models rather than a dedicated one for each specific application. If it works with the starting fluid you might want to recheck the float setting. I know it's new and it should be spot on but if the float setting is a little low it could be leaning out the carb and that can cause hard starting.

I might be inclined to see if I could find some place to install a primer. That or wait for one of the Honda guys to chime in on why this engine doesn't need one. I was thinking maybe it's jetted lean but it looks to be for snowblowers only and non adjustable at that (except for idle). 

(edit) Sorry I didn't see that you said you didn't find a nipple for the primer on the new carb.

You can also PM [email protected], his user name on this site and attach a link to this post and see if he has any ideas. He's THE Honda expert :bowing:


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## YSHSfan (Jun 25, 2014)

No honda GX engine has a primer (at least that I know of). On most Honda HSXXX (hydrostatic) including the HS724 the throttle mechanism is interconnected with the choke. After the throttle lever is at high speed, it moves further and that is what actuated the choke. I'd make sure that the carburetor linkage replacement set up is the same as the old one, if is not you may not be getting choke. Honda snowblowers engines almost always start on first pull when properly service and maintained, but the throttle has to be fully open and the choke on.


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## yeuker (Sep 8, 2017)

OK... sorry for the late reply, kids just started back into sports and its busy .

I took it apart, put it back together just mounted carb on engine, choked and first pull starts and runs great. My problem is this. The old carburetor (Honda)'s choke mechanism was engaged when you put the blower to full rpms (fast). The new carb (knock off) only has a manual choke and it can not be hooked up to the choke arm on the snowblower.

When I start the snowblower, it must be choked even when warm but does start crazy easy. It runs excellent right up until I put it on high rpm when it starts surging. I'm pretty sure the stock carb when at high rpm, gets choked automatically by the choke arm... but the new one is not the same. So so coles notes: Starts good, but at high RPM must be half choked. Pretty sure a stock honda carb would be good but this one may have to do. Any ideas on how I can get this to run at full rpm without choke or is this engine just setup to be like that?


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## yeuker (Sep 8, 2017)

One more thing... It surged before the Chinese carb so probably not the carb. Any chance I just need to adjust the governor arm or tighten the governor arm spring?


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## yeuker (Sep 8, 2017)

So at half choke, it starts, idles and runs at full speed well (with a very very subtle surging at the highest rpms). 
With no choke, it idles well, good at mid rpms but at high rpms it needs choke or it surges.

Should I just use the carb air fuel screw to make it a bit richer (which would be similar to choking it 1/2 all the time?)


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## Kiss4aFrog (Nov 3, 2013)

Most of the newer carbs are set up to be lean for emissions. Surging is not uncommon even on new machines from the factory. Most of the replacement carbs only have an idle adjustment and to change the high speed mixture you either need to drill a jet or replace the jet.
Once it gets colder it might surge a bit more since the air will be denser (colder) and the mixture will be a little more lean than it is now.


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