OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions on Other Engines Sanli Lazercut - Chonda - whilsting sound

Hey Guys,
I recently took in this Sanli Lazercut as a trade. I have a rule with Chonda�s�. I�ll only touch them when they are in good condition � This one just fit my requirements.
Before servicing the item I tried to start it and it started after a few pulls however it was making a horrible whistling type sound. It sounded like a valve wasn�t sealing or even some sort of exhaust leak.
I ended up stripping the unit down and giving it a good once over including:
Thorough carby clean
Reset valves (inlet. 15mm) (Exhaust .20mm). The unit had barely any valve clearance before servicing. I initially thought this might have been the source of the problem.
Regapped magneto as the distance between it and the flywheel was huge. Used a standard business card to gap to magneto.
Cleaned spark plug � was not replaced noted as good condition.
The choke was reset to ensure easy starts.
Cleaned the tank and replaced with fresh fuel.
I went to start the unit back up and it was still making this horrible whistling sound. When you get the unit up to full speed the mower runs quite well however back it off to idle and it really sounds like some sort of exhaust/ maybe vapour is excaping from somewhere causing the strange sucking/ whilsting sound. Sorry its hard to explain.
I thought the exhaust might be damaged so I replaced it with another very similar unit and it still has the same problem.
Yes the air cleaner element is not original however it is serving its purpose.
This one has me stumped so Im after some suggestions.
Thank you

never heared on making that noise , many others though yes whirring noises n stuff . not too long a bolt in the cooling cowelling or something rubbing on pto ? cant be a carb/vacuum leak or it wouldnt start ,
spark plug gasket washer cracked so blow by ?

a sort of piffing type sound or constant whistle ? odd mate . so just thnking . it will be simple for sure mate

Hey Dave,

You could call it a whirring noise I suppose. Thats a good suggestion about too long I bolt in the cowling so I'll check that out tomorrow after work.

Good point about a carb/ gasket leak as it starts very easily - 2 pulls from cold.
Not sure what you mean by the spark plug/ gasket washer cracked so blow by? Could you explain that one a little more?

Its deffinately a contant whistling/ whirring sound. For the life of me I cant work it out?

its what i meant , a strange word i know piffing . its the washer on the plug , it is a gasket i have seen one or two cracked make an odd noise when they do too . might even be a tough twig touching under the deck , had one ages ago making an odd noise turned out to be a rather large fish hook still with some line wrapped around an engine mount bolt , so when ya shut it down it dissapeared looked , nothing anywhere , started it up , noise is back , hahaha frustrating

G'day Jaffa,
I have a feeling it maybe to do with how the cowling went back on.
Pretty sure I had one with noise coming from the starter and cup making slight contact.

My thoughts, on top of what has been suggested.

Ok thanks for the suggestions.

1) Removed the starter and turned the engine over with some rope on the cup. Noise was still present so that eliminated that cause.
2) Replaced the spark plug and gasket in case of damage and no change.
3) Check the cowling to ensure no bolts were rubbing up against the flywheel.
4) Confirmed nothing was caught underneath the base of the mower.

I kept hunting around and pretty much confirmed it was some sort of sharp air leak contributing to the sound. Every time you pull the rope with the mower in the stop position you could hear the hissing sound. I ended up finding an air leak on the exhaust side just by feeling around the area whilst pulling the rope. (engine had to be cold of course) A sharp burst of air seems to be leaking out the exhaust gasket.

I�ll have to take it off tonight to take a better look. When I removed it the first time it only had the soft heat shield/soft gasket between the exhaust and engine block. A pretty standard set up for these Chonda�s in my experience.

Does it sound like I am on the right track?

I liked your fault finding procedure.

So your exhaust gasket is leaking.

If you are not sure.
You could make up a soapy solution and squirt it around the area and look for bubbles whilst turning it over.
Or talcum powder to show the where about of a leak.

Could there be a hole in the muffler or leaking seam.

Try a known good muffler.

Made a little more progress last night.

Replaced the muffler with a good known muffler. I also replaced the muffler gasket and still the same sound.

I continued to feel around the base of the head and pretty much confirmed the engine has a blown head gasket. I used mark�s suggestion of the soapy water (from underneath my bbq) and confirmed air was escaping out the head. You could also feel it quite considerably with the muffler removed. I have definitely found that strange sound.

Tonight I plan on removing the valves and pushrods to access the head gasket. I have a spare head gasket available from the GXV140 engine which the Sanli is a clone of so it should be sufficient.

What I am worried about in this instance is the cause of the blown head gasket. Could this just be poor quality control at the factory or could there be another specific cause of the problem.

I have not come across this problem yet on relatively new OHV mower engines and want to make sure my bases are covered.

great you found it . never seen one blown before but almost any other problem you might name hahaha . probably just bad assembling in china . just have a good looksee a straight edge across it and a good laping on a good flat surface normally does the trick . migth have just been loose from factory it doesnt look lke its done too much work .
good luck with it mate . had a few late model briggs' with that problem but all 4 were just loose and blew the gaskets cleaned up and back together , no problems again

Got some photos of my progress last night.

Confirmed my suspicion of a blown head gasket.

Tonight�s Plan

1) Lap the valves whilst the head is off.
2) Re-assemble the head and reset the valve clearances to spec
3) Re-install the remaining componentry (cowling, starter, valve cover etc)

I have included some photos which show:

1) Where combustion gasses where escaping on the head
2) The blown head gasket
3) My replacement gasket suited to the GXV140 engine which was exactly the same upon testing.

I am fairly confident this should be ok after its all finished because if the damm mower was running ok with the blown gasket (minus the strange sounds) it should run perfectly with a fully intact head gasket � Lets just hope there is no other problems.

This is a good post Mr Jaffa.

was it loose or just blown ? check to make sure everything is nice n flat before you reinstall jaffa (but im sure you know that) strange though unless bad assembly from factory , a lot of other things go wrong mainly fuel worries but not really engine problems so far as i have seen except just too abused and dusted

Nice work Peter, your methodical approach works well for fault diagnosis. I would have never guessed a head gasket but admittedly i've come across the same problem on a Chonda powered VE40 victa.
As you can see this one had blown out on the top and didn't have the fire ring around it.

Thanks for showing the head gasket Jaffa,
Yes, I would also like to know if head bolt or bolts where loose.

So engine was starting OK with a gasket in that condition?

I remember a power torque engine I had was hard to start, but did run.
It made a strange noise, like a air chuffing.
Found a piece out of the head gasket on top of the cylinder, you could see the combustion fire through gap. Dont often get to see inside the engine while its running.

Great stuff.

I usually find things like this using a homemade leak down tester. I find quite a few Briggs 310000 series blown head gaskets that leak between the cylinder and the push rod galley.

Ahhhh, you just inadvertently given me an opportunity to raise a query I've been harbouring for some time.

Why is the leak down test not used more widely.? Briggs advocate it and sell a tester. I can't speak for other brands.

People seem to go for the huff and puff test. All this gives is an indication of bad ( real bad) compression. A leak down gives very valuable diagnostic information on where and how much.

I'd like to hear people's views on this one.....

....and apologies to jack if this is considered a change of topic and therefore in the wrong place.

Probably a lot haven't learned that it saves a lot time hair pulling time and some the expense for parts.

It like those that don't even use a compression gauge and try go with the finger over the plug hole to test for compression. Here I get borderline compression on two cycle equipment quite a bit. I have learned that if I don't have at least 100 psi I need to be looking at the cylinder condition before spending an hour so trying to get an engine to run when the cylinder is bad. And most 4 cycles here need around 70 psi to start even when a decompression is involved. There are a few exceptions but are few and far in between.

I understand that some don't have the funds to purchase the commercial equipment or are once in a while repairmen but for the professional tech they are invaluable. And I am one of those start-ups on a shoe string budget that took me as few years to budget for my tools; hence, the home made version of the leak down tester. As funds come available I can add the orifice and the second gauge but current setup sure saves time.

Since I got the leak down tester and a compression tester I spend a lot less time troubleshooting problems and more time repairing as I know rather quickly if the engine have internal problems or not.

There is one other tool that very handy to have for 2 cycles especially the handheld here and that is a hand operated vacuum and pressure pump for testing crankcases and carburetors for leaks. This one on my Christmas wish list.

No orifice? Not sure how that would work.
I just had a quick stooge round on goggle and there is a few places that give instructions on how to make your own. Some of the suggestions were a bit odd (And a bit dangerous) to say the least but there were a few good ones too. On a couple they suggest filling the fitting between the two gauges with 'metal set' type epoxy then drilling the orifice in this once set. Not a bad idea. Orifice size is critical. .040" seems a consensus but I'd need to confirm. I also recall that the lead in to the orifice and the length of the orifice play a part in calibration. I have source I can look up but I don't have it here. There are also a few people out there advocating 100 psi inlet pressure. Can't say I agree. 80 psi for safety- and it's all you need.

Speaking of safety, it should be said that they are dangerous to the uninitiated. Your introducing compressed air to the cylinder which will spin the engine sharply to BDC if it is not clamped. Seek training and be careful if not familiar.

Work fine as long you not looking a percentage of leakage as I use an adjustable pressure regulator. Most times I just looking either a leaky valve or head gasket.

As for the working pressure you don't need 100 psi for testing just makes reading of leakage easier. Otherwords 100 psi in before the orifice and 90 psi out or 50 psi in 45 psi out equals 10%
leakage either way.

I usually use less than 40-50 psi. Even at these levels the crankshaft needs to locked in place on good engines. I start at zero pressure and work up as major leaks will show up even low pressure.

Air coming the following places:
Muffler - leaky exhaust valve
Carburetor air horn - leaky intake valve
Breather hose - worn or damaged cylinder/rings
Head area - leaky head gasket or warped head

Example I have Briggs 130000 series in the shop with an intake valve that is leaky even after grinding. I actually think it is leaking around the valve seat itself. It shows up even at only 20 psi when listening at the intake manifold.

Finally found the specs on the orifice I have here. It is .040" x .250"