Chinese 16HP vertical shaft engine problems

[Wazrus]

My Chinese 16HP vertical shaft ride-on engine has been running well since it was installed about four years ago. I think the brand is Loncin. Recently it began 'surging', in that the RPM would fluctuate almost from idle to max RPM, or so it seemed. Eventually, after a relatively short time, the engine would simply stop. Now this said CARBURETION in capital letters, or at least fuel supply problems. I might mention that I could see the governor linkage moving as the engine surged. I replaced the carburettor, air cleaner, in-line petrol filter and the vacuum petrol pump. The engine started quite easily, as it has always done, before parts were replaced and even after a surging bout and a stop. I did note, though, that it would not start from quite warm without choke; I would expect a warm engine to start with at least a little throttle, but even with a lot of throttle, there was no start. It 'liked' its dose of choke!
So after the carby, air cleaner, filter and pump were replaced with new parts, the engine again started quite well - first crank of the starter, with choke - it ran quite well and I was able to mow effectively for the next fifteen minutes, then it simply died once again! No surging this time, it just croaked! By the way, I also replaced the spark plug. It still starts readily, but only with choke, even when warm.
By a process of elimination, I reckon it's pretty safe to say that the fuel system isn't the culprit. As I said, then engine is about four years old and it hasn't done all that many hours.
Any suggestions, other than a new motor, from the membership?
Thanks
Wazrus Sydney, Australia

 

[kc5dlo]

Perhaps a coil getting weak?

 

[Wazrus]

Perhaps a coil getting weak?

Thanks for coming back, KC. The coil was my next bit to replace: I think it's perhaps the only bit left! I had also considered a faulty oil level switch/sensor. I have made sure that the oil level is good. Might the diode/charging rectifier be a candidate, too, d'you think?
Wazrus

 

[Dave M7040]

I have found the carb on these engines to often be the problem.

These service bulletins from Champion Generators which use carbs like your engine would have show some jets which need to be cleaned by hand and not rely on soaking or spray cleaners to get the small passages clean.

http://www.championpowerequipment.com/media/3465/cpetb2050016-cleaning-the-pilot-jet-196cc-439cc.pdf
http://www.championpowerequipment.com/media/2052/cpetb2050018-altitude-jet-installation.pdf

Removing the main jet to get access to the emulsion tube identified as "A" requires you have exactly the correct screw driver or you will destroy the screw driver slot on the brass main jet.
I find having a set of screw driver tips as would come with a cheap screw driver where you can swap tips often gives you a large flat tip that just fits the slot in the jet. Dont even think of trying to turn it if the bit is not a tight fit.

It is not the charging system!!! Big clue is the need to use the choke. Fuel passages in the carb jets are partially blocked.

Dave M7040

 

[Rocky J]

I love a puzzle, turning on the choke would also cover up a intake leak, the vacuum would increase when closing the choke butterfly. You never mentioned the electric fuel solenoid on the bottom of the carb,did it come new with the new carb ? maybe it is starting to go bad. You might remove it and bench exercise it , see if with time it starts crawling back out and is leaning out the fuel delivery. It is a electromagnetic , when it cools down it starts working again. Using the propane around the air cleaner would tell you if it is electrical or fuel, but if it was a intake leak it would also cover it up by correcting the air fuel ratio .

 

[Soundguy]

On an antique tractor my bets would still be on fuel.

Good luck.

 

[Wazrus]

On an antique tractor my bets would still be on fuel.

Good luck.

Thanks to Dave, Rocky and Sound Guy.
You'd think that a brand new carb would have the engine up and away! I will strip it off -again - and give it a good once-over, as per the Champion links Dave sent and have a closer look at the carb-to-cylinder gasket. The gasket did seem to be of pretty hard stuff, so maybe there's chip out of the sealing face. For Rocky: the engine is probably an older model or something like that and it doesn't have a fuel cut-off solenoid, so that's one part that isn't going to go wrong! When I bought the new carb in Australia, I did notice many, many carbs on EBay, which seemed to be pretty much the same, except that most had the fuel cut-off solenoid, or fittings for it. I was a bit lucky in that I was able to source the exact replacement carb from a firm in Western Australia. I have had the main jet out, with no issues at all. I happened to have a really good fitting screw driver and the jet and tube came out easily.
I will post the results of the fiddling about in the next few days, but any further suggestions anybody has would be appreciated.
By the way, too I do note that the quoted engine capacity is 452cc, which is a bit different from the capacities Champion quote.

Thanks and regards
Wazrus

 

[Rocky J]

The idea of the fuel solenoid was to stop the engine from back firing when it is shut off. With time the top of the piston and cylinder head builds up with carbon and will get red hot like a glow plug in a diesel engine, when the key is shut off the piston continues to spin a few more turns and sucks in more gas /air mix and is ignited by the red hot carbon and fires when ever it wants and can break the connecting rod.So they put the fuel solenoid on it, probably more worried about warranty work then anything else cause that part is a ton of money. Idling the engine down and let it cool a bit before turning the key off works just as well.
Moving on to another thought, by chance is your fuel tank cap vent plugged up causing a vacuum in the tank? Is your gas tank under the seat ? or under the hood/ bonnet ?
Some engines have a black plastic spacer between the engine and carb and take a gasket on both sides of it. It is hard and brittle . This is where I drill my hole to tap threads for a hose barb to pick up the vacuum for my propane regulators safety device , I have used JB Weld to repair the ones I have broken.

 

[RandyT]

Can you hear the solenoid click into the on position when you turn the key on. If not, do you have 12 v to the solenoid. Also make sure the solenoid has a good ground.

 

[CCWKen]

I'm with Soundguy. Sounds like a fuel supply problem. Did you clean out the fuel tank when you changed the carb? There may be a screen in the outlet of the tank that's clogged.