# Stumped, HS724 MAX RPM issue



## JnC (Feb 21, 2014)

Every now and then I come across a problem that I havent dealt with in the past, at least pertaining to the Honda GX motors and Honda snowblowers.


I picked up a cheap HS724 for a buddy of mine from a junk hauler, machine was only $200. A bit of surface rust but mechanically its all there, no worn augers, no worn bucket etc.

The idea was to service it, check the belts etc and give it to him so he can have a dependable machine for years to come. Unfortunately the GX200 is giving me issues that I havent dealt with in the past, may be its a simple fix that I cant seem to figure out.

Before the service I changed the oil, put fresh gas in the tank and fired her up and she started first pull, idled fine but would die the minute I engaged the augers.

Since I didnt know the history of the machine I just went in doing the basic service.

Changed the impeller bearing.
Changed the drive belt.
Rebuilt the gearbox.
Changed the auger bearings.
Rebuilt the carb.

Since the machine was dying under load I thought the issue might be with the governor. I checked and adjusted the governor properly per the service manual. After the machine was put back together it fired right up, idled fine, governor kicked in fine under load and augers worked just fine when engaged.

I was suppose to deliver the machine to him tomorrow but when I went to load it up in the truck today it started acting the same again i.e. idles fine but dies the minute to move the throttle to high. Augers engage fine at idle, drive engages fine at idle. Machine does not like high RPM.

Any ideas? I am bringing the machine to work tomorrow and will try to solve the issue before handing it over to him.


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## JLawrence08648 (Jan 15, 2017)

Replace the carburetor.


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## orangputeh (Nov 24, 2016)

Well you rebuilt the carb. I assume you made sure throttle plate moved freely and made sure choke plate was properly adjusted before installing the control air box. Almost 96% of OEM Honda carbs can be successfully cleaned or rebuilt . ( ya I keep records ) . A new carb is about $70 I think. 

Does it run fine under high throttle with no load at about 3600? Or does it run rough?

I would check throttle cable and make sure it's not interferring with choke arm. I see this a lot. 

If you go from idle to fast throttle slowly does it still cut out? or only when you change fast? You're right . This is an unusual problem as explained to me also.


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## JnC (Feb 21, 2014)

+1
I have never bought a replacement carb either, I just rebuild the old ones with new gaskets, o-rings and clean them with the ultrasonic cleaner. 

Just spent some time on the machine and carburetor is not the issue. I have an older HS624 in the stable that is in good working order, it came with an aftermarket carb that the previous owner installed on the machine when he had carb issues. I took that carb off and installed it on the 724 just now to see if that solves the issue, no dice as the old issue is still there, what baffles me is that the machine worked fine when I initially serviced it last week, throttle kicked up fine, the augers engaged fine etc. 

Now, in the following short video you can see it idles fine, the augers and drive work fine and dont kill the engine when I engage either or both at idle BUT the minute you even give the machine a slight hint of throttle it dies. 

OT: Towards the end of the video I could have sworn I saw spark in the carb/tunnel. 

Could it be an issue with timing? But wouldnt that make the machine not work at all? I have worked on an HS928 in the past where the woodruff key on the crank got sheared and the flywheel spun a bit leading to timing being off and the machine not running at all.


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## JnC (Feb 21, 2014)

So it seems that the Cam is the problem. 

Some owners having the same issue in this old thread. 






Honda Gx160 won't accelerate - DoItYourself.com Community Forums


Honda Gx160 won't accelerate - Outdoor Gasoline and Electric Powered Equipment and Small Engines



www.doityourself.com







> Well, I installed a new camshaft & engine now throttles right up, and runs very smoothly. Thanks to all who have endured this saga. When comparing my cam to the new one, it was obvious that the high points on the lobes were almost non-existent. Originally, this was the only item on the engine that appeared not to meet specification, and I should have believed it. It's very clear to me in hindsight that the engine just couldn't breath, and therefore accept any more throttle. Hopefully this might help others who may have a similiar problem.
> 
> Thanks again Cheese, Puey, & all.





> in an effort to close out the original topic... my gx160 ran perfectly after cam swap.
> -dave


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## orangputeh (Nov 24, 2016)

your video not available.

thanks. the cam , huh? probably one in 10,000 issue and you found that machine.

what bothers me is your statement that the machine was running fine after you serviced it???


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## groomerz (Feb 7, 2015)

I listened to video 
You had to click on you tube logo not the picture

Sounds like fuel starvation
Have you test fuel flow ?


Sent from my iPhone using Tapatalk


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## JnC (Feb 21, 2014)

I made another video and the issue isn’t fuel starvation as the fuel filter is new and the tank is clean, plus there is a steady stream of fuel gushing out if I take off the fuel line.

when you throttle up you can see the fuel pumping out of the Venturi pipe and the moment that happens and the throttle lever opens the machine stalls.

I have ordered a new cam, hopefully it can get here this week and I can install it and send the machine off to its new home.


I’ll update the thread when the new cam is installed and I’ll take measurements of the new cam and old cam with a vernier caliper.


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## groomerz (Feb 7, 2015)

Did you pop off valve cover

you could check valve clearance and lift from up top

It’s strange that it worked for a bit. 

Possible compression release issue. New cam should fix that though

Curious to hear the outcome

I’ve seen worn plastic cams on stihl 4 mix garbage. When they wear no more overlap and won’t rev up 

Sent from my iPhone using Tapatalk


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## JnC (Feb 21, 2014)

Honestly everything looks fine to the naked eye and these motors for the lack of better words are usually bulletproof. I have never seen such small variance cause an issue to this extent. The motor got fully disassembled yesterday


No out of the ordinary signs of wear.
Cross hatching marks are still there on the cylinder walls.
Valves, head looks fine.
Cam looks to be ok.
I have ordered a new cam and rebuilt kit, the whole idea of keeping this build on a budget is out of the window as I am already around 12~15 hours into it lol, more annoyingly I have a spare GX200 that I can throw on this machine and be done with it BUT whats the fun in that .


Here are the stock specs for the cam


Cam height:INTAKE27.500-27.900 mm (1.0827-1.0984 in)EXHAUST27.547-27.947 mm (1.0845-1.1003 in)

My caliper is out of battery but using it without the battery I am getting close to 28mm on both lobes which is about what the above suggests. There are some marks on the cams that may be from machine but I cant tell. The new cam that I am getting is high lift , I didnt want to get it but it beats buy a new OE one for $60ish ( I think) to this one that I was able to get for $15 shipped.

I have bought cheap machines before and usually they need a lot of work, this $200 purchase was $200 for a reason though lol.


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## CarlB (Jan 2, 2011)

JnC said:


> Every now and then I come across a problem that I havent dealt with in the past, at least pertaining to the Honda GX motors and Honda snowblowers.
> 
> 
> I picked up a cheap HS724 for a buddy of mine from a junk hauler, machine was only $200. A bit of surface rust but mechanically its all there, no worn augers, no worn bucket etc.
> ...


Did you check the valve lash especially the exhaust ?
Replace the carb they are cheap enough.


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## CarlB (Jan 2, 2011)

orangputeh said:


> Well you rebuilt the carb. I assume you made sure throttle plate moved freely and made sure choke plate was properly adjusted before installing the control air box. Almost 96% of OEM Honda carbs can be successfully cleaned or rebuilt . ( ya I keep records ) . A new carb is about $70 I think.
> 
> Does it run fine under high throttle with no load at about 3600? Or does it run rough?
> 
> ...


about 14 dollars on amazon for a clone. I have used several clones with no issues.


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## CarlB (Jan 2, 2011)

I should have read the entire thread before posting i see you found a cam lobe out of spec.


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## orangputeh (Nov 24, 2016)

WOW!.......hope its the cam......


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## JnC (Feb 21, 2014)

Fully rebuilt the motor, everything looked great inside btw. New rings, new gaskets all around, new cam, put it all back together and still the same freaking issue. 

Tested the coil and primary resistance came back erratic on the multimeter, ordered a new coil, installed it and guess what?? Still the same issue lol. 

At this point I am this close to pulling one of these moves 










At this point I am fresh out of ideas. 

Cam is good
Carb is good
No fuel restriction. 
No fuel cap vent issue. 
New coil. 
New Spark plug.
Air gap on flywheel is adjusted properly. 
Motor is fully rebuilt. 
Valve lash is properly adjusted etc.


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## orangputeh (Nov 24, 2016)

in your first post you mentioned that you adjusted the governor and then it worked fine......then didnt?

that may be a clue.

also , when you just rebuilt the engine and say you have the same issue , is that only when engaging belt? or does the idle and fast throttle work okay without the load?

I assume it is all the time or just works okay at idle?

I suspect maybe the governor/decompressor release??? even though I dont know much about them. Did you check decompressor? I did learn how to set the governor from your video and checked all my spare engines.

Thank You for that.


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## JnC (Feb 21, 2014)

So the machine had the issue of dying at full throttle when I first got it. I took that as a sign to do a small basic service on it i.e. rebuild the carb, etc. After that it still had the issue. I took that as sign to check the governor set up, the governor set up in this machine and the 160 is inverse of what my video has suggested as the video is for bigger 240/270/340/390 machines as the governor set up on the inside of the motor is on the front of the engine rather than in the back (as found on the 160 and 200 hondas). 

Non the less, after that I fired her up, she worked great and everything was in place for the machine to go to its new home. 

I loaded up the machine in the truck, brought it to work to later drop it off with the new owner. I fired her up to move it around and check to see if everything is still copacetic but much to my dismay it wasnt lol. 

The de-compressor mechanism looked just fine on the old cam and the new one as well. 

Motor isnt installed yet on the chassis, I wanted to make sure it'd work fine before investing more time in installing it and only to be disappointed again. 

I know the governor set up info in the service manual is wrong for the bigger motors but could it ALSO be wrong for the smaller GX motors? 
I am truly stumped.


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## JnC (Feb 21, 2014)

Sorted.

I knew it’d be something so stupid.
The throttle/governor apparatus that sits on top of the motor had a bent bracket and the max rpm screw was cranked all the way in, I had to get the service manual for gx160/200 and study the governor and throttle set up.

When you engage max rpm one of the springs that puts tension on the governor linkage was binding due to the bent bracket. No tension on the linkage was leading to the governor opening up the throttle butterfly all the way and killing the motor whenever you’d crank up the throttle.

When set up properly the mechanism is suppose to keep tension on the governor so that the load on the machine would dictate how much the throttle body is open and the spring would insure that the mechanism is smooth and no WOT all the time.

I fixed the linkage and lubricated all the parts and everything is working fine now.
At least it’s not all a loss as the new owner is going to end up with a fully rebuilt motor with high lift cam lol.


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