Seems like surging carby? Not?

zenchopper

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I have a Murray Sentinel with a retro fitted Zhongchen XP 620 17.5hp Briggs copy

Ran great first 18 months.

The problem I have is that it starts and runs fine for 20 mins then completely and abruptly cuts out.
I restart it and is it starts surging, (governor doesn't know what to do) and the revs go up and down, up and down.

After totally disassembling and cleaning Carburetor, total disassembling and clean out of fuel pump,
and draining fuel tank and drying, adding new fuel filter. Checking all wiring.

AND after I watched this brilliant video----



which made total sense and I performed the jet mod.... but it hasn't fixed my problem.

Runs perfectly for up to 20 minutes then does the same surging song and dance.

While the engine is still hot I drain the float bowl and blow out the fuel line with the air compressor, seems to fix it again for 20 minutes.


I'm not sure if draining the float bowl is actually doing anything because sometimes I have just let it sit and idle and play around with the throttle then it settles down and I can mow for another 5 minutes then again cuts out....same story. Driving me crazy, spring is here, grass is growing fast and I'm fighting a losing battle.

Any ideas?
 

ILENGINE

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Are you sure it is a carb problem and not possibly a spark plug problem (see plugs do weird things) or possibly loosing spark because of a faulty ignition module. Other than that I would be thinking that for some reason you are loosing fuel flow to the carb, or possibly the fuel is heating up maybe in the carb bowl causing a somewhat vapor lock issue. I have seen both conditions so don't rule out anything.
 

bertsmobile1

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Time to spend a little money.
Get an inline spark tester & a can of carb cleaner.
Fit the tester and run the mower .
When it stops crank the engine.
If the tester flashes then spray some carb cleaner down the crab and crank the engine.
if it fires right up you have a fuel supply problem.
If there is no flashes then the coil is dud.

Those trash engine use rubbish fuel lines that go soft inside and block off the fuel supply.
The junk fuel caps have very poor vents that block if the cap has not already fallen apart.
Good luck trying to find parts to fit.
While they look like a B & S engine, very few B & S parts will fit apart from the air filter.

IF it has a rubber float needle seat, these are also made from the wrong grade of rubber and go sticky preventing the float needle opening fully so eventually the carb runs out of fuel.

Don't know how you cleaned out the fuel pump as it is a sealed unit.
The discharge end has a non return valve so if you blew high pressure air backwards through the outlet you will have damaged the valve which could also be causing you problems.
The diaphragms are also made from the wrong grade of rubber and are prone to falling apart.
If you remove the fuel pipe from the carb and turn it upwards, cranking the engine should send a spurt of fuel higher than the top of the carb if the pump is in a good condition.

If I sound a little dismissive , I am not trying to rubbish you but those engines are total junk bought in by the container load and foistered off onto unsuspecting public as a "quality product" by a cartel of Toorak Terrorist & Potts Point Pirates who right now are laughing at you while they sip their $ 1000/ bottle champers.
You were probably told by the lieing sales person that it was the same as a B & S engine and B & S parts will fit.
Well they don't and it isn't.
The Magic Pudding is a children's fairy story and you will never get more than you paid for.

The last one of them I fixed, was the last one I will ever fix as the bill including labour came to the same as the owner paid for the engine in the first place.
That ended up in the courts, yet to be determined & I have better things to do that chase people who have been made fools of for money that would have been better spend on a 1/2 decient engine in the first place.
Yours outlived the 12 month warranty and that is all the retailer is obliged to cover, after that you are on your own.
 

zenchopper

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Thanks, I watched a few more vids and realised I haven't properly cleaned out all the jets.

I did at one point pull off the spark lead and wiggled it back on and it ran fine for a few more minutes, but I can't rule out chance as I tried the next time it did it but wiggling the plug lead did nothing.

My mind is thinking there is a stray bit of debris somewhere in the carb that blocks and unblocks randomly which I have missed..

Runs perfect for up to 20 minutes.

When it cuts out it usually shuts down like unplugging the fuel solenoid, which just to confuse me shuts down the same way as if you just switch the key off.
BUT sometimes is cuts out like it can't make up its mind to keep going for about 3 seconds then the rpms just drop till its completely still.

Then when I restart, it immediately does the surging.

Draining the float bowl and blowing compressed air down the fuel line, which takes me less than 3 minutes always fixes it for another 20 minutes.
I'm guessing that the engine sitting for 3 minutes while I do the fix is not cooling down enough to relate it to being a heat issue. I might be wrong though. But the weather is mild at the moment (under 20 C) and Ive had it running perfectly in over 30 degrees.

I will go through the carby one more time and make sure I check all the jets and remove any welch plugs and give it a good blow out.

Is carby cleaner essential ?
 

ILENGINE

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Electrical components can cool enough is a very short period of time sometimes to go from not working to working. Had a fuel solenoid issue on a Kohler command a few years ago with a bad fuel solenoid. Engine dies, shut key off, on, off, on, off, on/click all in about 4 seconds.
 

zenchopper

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Don't know how you cleaned out the fuel pump as it is a sealed unit.
The discharge end has a non return valve so if you blew high pressure air backwards through the outlet you will have damaged the valve which could also be causing you problems.
The diaphragms are also made from the wrong grade of rubber and are prone to falling apart.
If you remove the fuel pipe from the carb and turn it upwards, cranking the engine should send a spurt of fuel higher than the top of the carb if the pump is in a good condition.

Pump has a few phillips screws holding both halves together , Just prise it apart, careful not to lose the spring and stainless cap that goes over the spring.
Diaphragm seemed in good condition, no gummy bears, felt a little gritty in there, My new fuel filter is pre pump. Pump assembled like new and squirts like an 18 year old.

Also I know that no Briggs parts fit, it's not a clone...

Since my Enduro days I've serviced and rebuilt my carbs...actually before my enduro days, when I was 12 and had to put new rings in my dad's embarrassing 100cc road bike.

Oh yeah and the Rochester Quadrajet from the GS 455 on the Rivieara , and the Gas research carby on my Studebaker with the 327 and the Windsors and Cleavlands in my stupid Ford days, and yeah The KTM 495 and the RG500 square 4 2 stroke that I completely rebuilt when my mate put the rod through the crankcase at Phillip Island. I don't want to talk about the Monaro and the 253 days OK? It's just too sad a story.

So I can spot junk and sub standard parts and so far this Chinese engine, luckily has ok fuel lines that still look and feel newish.
And it doesn't come with a fuel tank. I'm using the standard Murray Sentinel fuel tank. USA USA :banana:

Don't get me started about the pure prejudice against Chinese Chainsaws and the misinformation the main dealerships crank out about "you'll never find parts" to gullible baby boomers who want to spend $1700 on a saw , and hundreds of dollars in service fees because everyone knows that the more you spend... the better it is...right? Gotta find some way to spend your super and fortnightly pension cheques.

And please I refuse to get into debates about Chinese made Large Diaphragm Valve Condenser Microphones....
 

zenchopper

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Electrical components can cool enough is a very short period of time sometimes to go from not working to working. Had a fuel solenoid issue on a Kohler command a few years ago with a bad fuel solenoid. Engine dies, shut key off, on, off, on, off, on/click all in about 4 seconds.

Thanks, Yes, I guess I'm in denial. I can't remember why but imprinted in my mind is the knowledge that things that happen when everything is warmed up is usually an electrical problem.

I might just put a fuel tap and temporarily take out the solenoid and put a bolt in the hole and test it.

But just so it doen't play on my mind I am going to go over the carby again. Then I may surrender to the fact that it just might be ignition related.
 

zenchopper

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Yours outlived the 12 month warranty and that is all the retailer is obliged to cover, after that you are on your own.

Not 100% accurate. Consumer law says that a product should last as long as normal person would expect it to last.

For instance If you by a refrigerator with a 12 month warranty and it breaks down in 2 years, most people would agree that a refrigerator should last around 10 years and that would be a reasonable expectation.

In Australia consumer law goes beyond the warranty. That's why companies that sell you extended warranties are charging you for something that is already covered by consumer law. If you have an extended warranty go back to the store and say you want to give it back and they will most likely refund you the money of the extended warranty. All you have to say to them is that you were misled that you were getting protection that didn't exist under consumer law.

Unfortunately, if you tried to return something after the warranty, some retailers don't know consumer law and would rather cut their right arm off than be wrong and you'd have to go through the crap of getting ACCC to go into bat for you.
 

bertsmobile1

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Not 100% accurate. Consumer law says that a product should last as long as normal person would expect it to last.

For instance If you by a refrigerator with a 12 month warranty and it breaks down in 2 years, most people would agree that a refrigerator should last around 10 years and that would be a reasonable expectation.

In Australia consumer law goes beyond the warranty. That's why companies that sell you extended warranties are charging you for something that is already covered by consumer law. If you have an extended warranty go back to the store and say you want to give it back and they will most likely refund you the money of the extended warranty. All you have to say to them is that you were misled that you were getting protection that didn't exist under consumer law.

Unfortunately, if you tried to return something after the warranty, some retailers don't know consumer law and would rather cut their right arm off than be wrong and you'd have to go through the crap of getting ACCC to go into bat for you.

This only applies to products that are made in Australia and not to temporary diverted land fill that is brought in by trash merchants under WTO regulations that are only required to be of "servicable quality" when purchased.
Thus a lawn mower sold at Aldi for $ 175 is not expected to last for the same time as one bought from a mower shop for $ 750.
And just so you know, I am an independent mower technician so there is no turf protection written into the response.
There was talk about a mandated service life which went nowhere & the EU tax on short lived consumer durable items just vanished along with the tax on no recyclables .
I think the end of life disposal tax is still there but am not sure.

I but some parts from China. China now has more satelities in orbit than any other country despite the USA, the EU & Russia having a 40 year head start.
Just like factories any where else in the world, Chinese factories can make good stuff or they can make junk.
Chinese factories make what we ask them to make so if we order garbage that looks like a quality product to sell in our chain of shops that is what we get sold.
I have nothing against a lot of good quality engines that come out of China other than there is little to no service information available and no spares.
The same for a lot of whole good.

However it is greedy selfish wealthy Australians who seek to steal money from their fellow Australians by importing garbage that is unfit for it's intended use that is the problem.
Under WTO rulings, if the product is sold in other WTO countries then the Australian government can not prevent it being sold here except under a very limited and specific set of circumstances, containing asbestos is an example.
People continually bring me junk they have bought at a tool store ( mostly ) or a hardwear store that is out of warranty.
I have repaired 4 Ross chainsaws all fitted with neoprene fuel lines so they leaked like a sieve after 18 to 24 months. You can check this problem by looking at the posts on Not Good Enough or Product Review.
Three of them had a chain that was bent at the joining link, ( defective from new ) thus the chain ( counterfeit Oregon) , bar ( suspect counterfeit Oregon) & sprocket were all trashed, the carb can not be cleaned because the solvent to remove the rubber will also wreck the check valve which is not available.
Certified parts to repair the saw plus my labour at $ 60/hr for the scheduled service time ( a lot less than actual service time ) in most cases exceeds the original purchase price.
And don't start me on all of the "ebay only" brands of chain saws.

There are a dozen chippers, compressors & generators with Chonda engines that have come in for new starters because the original ones , melted , metal cracked through, drive pins bent backwards or cords broke.
Most can be repaired with a Honda pull start but it has to be modified to fit .
So do I do it for free for the $ 10 mark up on the $ 40 starter or expect the customer to pay for the 1/2 hr I spend modifing the starter that the counter staff would "bolt strait on" ?

Then you get the strait out & out criminals who send an item to China with the instruction to "make 10,000 that look exactly like this as cheap as possible " then sell the defective products door to door generally using back packers as the sales people.
A lot of this stuff is both defective & dangerous, as an example, I had a customer with a problem Honda/Onga fire pump.
The Honda was actually a H.Onda and the governor was nothing more than a shaft ( no seal) through the crankcase internally bent over and secured with a spring on a self tapper, thus when a load was put on the engine it just stalled.
The generator engine was the same story. Honda was aware of the counterfeits and Onga was aware of the counterfeits , three container loads of them but no one had been prosecuted over them.

IT takes the same amount of energy to make junk as it does to make a quality product and the extra cost of better materials is minute.
The logistical costs are identical between a quality product knocked down & junk
If we could stop trash being made & sold then we would not have to worry about Carbon pollution because it would be reduced by 30% overnight .
And this goes for anything from a cloths peg to a motor car.
Using raw materials of which there is a finite amount of to make land fill is just about the most destructive thing we can do to the planet shot of a nuclear war.
 

zenchopper

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T
And this goes for anything from a cloths peg to a motor car.
Using raw materials of which there is a finite amount of to make land fill is just about the most destructive thing we can do to the planet shot of a nuclear war.


Agree with a lot of what you're saying. Still the original Briggs motor needed at least $500 worth of work and couldn't really grantee how long that would last so I took the punt on a $550 motor. I'm sure there's been many $8k mowers that had a faulty ignition, or bad fuel gummed things up..I'm sure that if this happened to a new mower 6 months after the warranty ran out it would still cost you hundreds to get repaired.



Totally agree with the rip off copies that are inferior and badly designed.
There are some diamonds in the rough, this motor does all the right things and I think the probability of something going wrong is not too different from new brand name mowers who's manufacturers also get components made in China.

And preventing things from going to landfill is what I'm all about. That's the reason I haven't thrown it out and WILL get it fixed. (i've kept the old Briggs, dropped a valve, and one day if i'm bored I'll fix it with second hand bits and have it as a spare.).


Also before I bought my Chinese chainsaw ,with "Oregon chain and bar" I googled Oregon Counterfeit chains, and Fake Carlton chains, and I couldn't find one story with any credible evidence. Some typical "everything from china is bad "comments but nothing substantial, no consumer authority investigations, no " man to loose more than tree limbs from fake chainsaw chain"...


******UPDATE *****

Pulled off the carb this morning, cleaned out every jet with tip cleaners,(paying attention to not enlarge them), Checked float, needle and seat, working perfectly no visible signs of anything worn out, Pulled out main jet and ran tip cleaners gently through any tiny holes..
I felt pretty stupid as everything is so clean and residue free.

Assembled it, Ran perfectly, I even fooled myself into believing that it had more power. Then same thing, Dead stall....restart, surging.

Don't have any carb cleaner so when it was idling and surging I sprayed couple a tiny puff of WD 40 In the air cleaner hole and made no difference at all. Please tell me if that was dumb, but I wasn't going to use hair spray. :wink: I think that a mist of wd 40 would at least have had some effect...

To rule out operating heat effecting anything I just let it sit for 15 minutes, started it and still the same surging...

The stupid paradox is that I know if I drain the bowl and blow air down the fuel line it works good again.

Tomorrow I'll try to test the coil and ignition module, any tips on what to look for with a multi-meter??

And just for fun , I'll drain the bowl and blow it out and mow for another 10 minutes. jeez the grass is growing fast.
 
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