196-212cc pilot valve failure

#1
My Greyhound engine was hard to start, would not idle until it was warmed up and would die for no reason after running for over an hour under load when the throttle was dropped back to idle.
At first I though that the gaskets (3) for the carburetor had an "air leak"?... but that was not the case. I replaced them with new and the same thing napped.
I saw the video on Youtube about cleaning the carb and how he mentioned how important the orifice in the "pilot Valve"was to be clean. He just blew it out with air or carb cleaner.
I pulled mine out and you could see daylight through it. A even blasted the valve with Brake cleaner. There was no change in the engine performance.
All of the passageways and main jet and the pick-up tube were very clean and a wire passed through the holes with no problems.
The engine would rev up, sometimes backfire, and idle for a moment or two and them die.It didn't matter if the air cleaner was on/off the engine. Same thing happened.
Changing the gas to a higher octane did not help. New spark Plug did not help. Changing the coil gap did not help. Fuel filters were clean and easy to blow through using a spare piece of fuel line.
Back to the carb. The orifice in the plastic Pilot Valve is very small. Smaller than a Twist-tie wire than many folks used to clean their carbs.
I removed the idle set screw and removed the pilot valve assembly. Looking in bright sun light I could clearly see light through the orifice. I threw a microscope adapter onto my cell phones camera lens and really took a look at the orifice. Darned if there was not a microscopic ring of deposits around the inside of that tiny hole!
The unaided eye could not see this ring.
I dug out my "gas jet orifice" drill bit set and found a bit that fit the hole and I reamed it out. There was so little resistance to turning the bit it felt as if I had done nothing to remove the deposit. But I had.
I put the pilot valve back into the carb and remounted the engine. ( can't get to it while on the bike) And fired up the bike. The engine started right up and idles as well as any of my other Clone engines! all for a tiny ring of deposit on the pilot valve. The engine would run,just not idle well at all.
I jumped on the bike and rode down my dirt road out onto the pavement and there were no more back-fires. The throttle response was instant. Top speed was even faster ( by engine sound). All by a slightly restricted pilot valve that you could not see!
So if you have a Greyhound or older HF Predator 196-212 cc engine that has the black plastic pilot vale under the idle set screw check out the possibility that it could have this deposit ring around the orifice opening ( on the inside)
The valve is very easy to remove. Unscrew the idle set screw ( noting or photograph how far in it was set to)
The valve has two "wings" cast into it. Pry up Gently on each wing with a small flat blade screw driver and the valve will slide right up and out. It seals with two tiny o-rings. A thin sewing needle would probably also work just as well and the gas jet drill bit, to clean the orifice. Just spin it a little in your finger tips. Them blow it out with Carb or Brake cleaner.
I'm not sure what the deposit was ,or what caused it. I keep my engine very clean and the fuel system is always run dry before I shut the engine off. No gas are in any of my engines over the winter.
I only use alcohol free gas in these engines. Now you know what to look for if your engine is not idling well or stops after a good Rev or run. and the engine returns to idle.
Hope this helps some member.
 
Last edited:
#2
My Greyhound engine was hard to start, would not idle until it was warmed up and would die for no reason after running for over an hour under load when the throttle was dropped back to idle.
At first I though that the gaskets (3) for the carburetor had an "air leak"?... but that was not the case. I replaced them with new and the same thing napped.
I saw the video on Youtube about cleaning the carb and how he mentioned how important the orifice in the "pilot Valve"was to be clean. He just blew it out with air or carb cleaner.
I pulled mine out and you could see daylight through it. A even blasted the valve with Brake cleaner. There was no change in the engine performance.
All of the passageways and main jet and the pick-up tube were very clean and a wire passed through the holes with no problems.
The engine would rev up, sometimes backfire, and idle for a moment or two and them die.It didn't matter if the air cleaner was on/off the engine. Same thing happened.
Changing the gas to a higher octane did not help. New spark Plug did not help. Changing the coil gap did not help. Fuel filters were clean and easy to blow through using a spare piece of fuel line.
Back to the carb. The orifice in the plastic Pilot Valve is very small. Smaller than a Twist-tie wire than many folks used to clean their carbs.
I removed the idle set screw and removed the pilot valve assembly. Looking in bright sun light I could clearly see light through the orifice. I threw a microscope adapter onto my cell phones camera lens and really took a look at the orifice. Darned if there was not a microscopic ring of deposits around the inside of that tiny hole!
The unaided eye could not see this ring.
I dug out my "gas jet orifice" drill bit set and found a bit that fit the hole and I reamed it out. There was so little resistance to turning the bit it felt as if I had done nothing to remove the deposit. But I had.
I put the pilot valve back into the carb and remounted the engine. ( can't get to it while on the bike) And fired up the bike. The engine started right up and idles as well as any of my other Clone engines! all for a tiny ring of deposit on the pilot valve. The engine would run,just not idle well at all.
I jumped on the bike and rode down my dirt road out onto the pavement and there were no more back-fires. The throttle response was instant. Top speed was even faster ( by engine sound). All by a slightly restricted pilot valve that you could not see!
So if you have a Greyhound or older HF Predator 196-212 cc engine that has the black plastic pilot vale under the idle set screw check out the possibility that it could have this deposit ring around the orifice opening ( on the inside)
The valve is very easy to remove. Unscrew the idle set screw ( noting or photograph how far in it was set to)
The valve has two "wings" cast into it. Pry up Gently on each wing with a small flat blade screw driver and the valve will slide right up and out. It seals with two tiny o-rings. A thin sewing needle would probably also work just as well and the gas jet drill bit, to clean the orifice. Just spin it a little in your finger tips. Them blow it out with Carb or Brake cleaner.
I'm not sure what the deposit was ,or what caused it. I keep my engine very clean and the fuel system is always run dry before I shut the engine off. No gas are in any of my engines over the winter.
I only use alcohol free gas in these engines. Now you know what to look for if your engine is not idling well or stops after a good Rev or run. and the engine returns to idle.
Hope this helps some member.
Had something similar happen to me too on a new Wen inverter generator.. I bought 2 generators to parallel them for my travel trailer... one ran great and the other would only run ok at high idle, would pop and sputter at low Idle setting. I thought about it and knew it had to be in the Idle circuit..
I threw it up on the bench and pulled the carb off.. my father in law walked in and said I should just return it.. I said that is an hour of my life gone and
2 weeks to get another....10 or so minutes in, I found my culprit... I had pulled the pilot jet, and used my jewelers microscope and found a tiny sliver of what looked like aluminum in the jet... cleaned it out and reassembled.. runs perfect. Good catch on your issue!
97CB69B7-01CA-4A28-B4FF-E6284CCE295D.jpeg
 

SAS289

Active Member
#3
My Greyhound engine was hard to start, would not idle until it was warmed up and would die for no reason after running for over an hour under load when the throttle was dropped back to idle.
At first I though that the gaskets (3) for the carburetor had an "air leak"?... but that was not the case. I replaced them with new and the same thing napped.
I saw the video on Youtube about cleaning the carb and how he mentioned how important the orifice in the "pilot Valve"was to be clean. He just blew it out with air or carb cleaner.
I pulled mine out and you could see daylight through it. A even blasted the valve with Brake cleaner. There was no change in the engine performance.
All of the passageways and main jet and the pick-up tube were very clean and a wire passed through the holes with no problems.
The engine would rev up, sometimes backfire, and idle for a moment or two and them die.It didn't matter if the air cleaner was on/off the engine. Same thing happened.
Changing the gas to a higher octane did not help. New spark Plug did not help. Changing the coil gap did not help. Fuel filters were clean and easy to blow through using a spare piece of fuel line.
Back to the carb. The orifice in the plastic Pilot Valve is very small. Smaller than a Twist-tie wire than many folks used to clean their carbs.
I removed the idle set screw and removed the pilot valve assembly. Looking in bright sun light I could clearly see light through the orifice. I threw a microscope adapter onto my cell phones camera lens and really took a look at the orifice. Darned if there was not a microscopic ring of deposits around the inside of that tiny hole!
The unaided eye could not see this ring.
I dug out my "gas jet orifice" drill bit set and found a bit that fit the hole and I reamed it out. There was so little resistance to turning the bit it felt as if I had done nothing to remove the deposit. But I had.
I put the pilot valve back into the carb and remounted the engine. ( can't get to it while on the bike) And fired up the bike. The engine started right up and idles as well as any of my other Clone engines! all for a tiny ring of deposit on the pilot valve. The engine would run,just not idle well at all.
I jumped on the bike and rode down my dirt road out onto the pavement and there were no more back-fires. The throttle response was instant. Top speed was even faster ( by engine sound). All by a slightly restricted pilot valve that you could not see!
So if you have a Greyhound or older HF Predator 196-212 cc engine that has the black plastic pilot vale under the idle set screw check out the possibility that it could have this deposit ring around the orifice opening ( on the inside)
The valve is very easy to remove. Unscrew the idle set screw ( noting or photograph how far in it was set to)
The valve has two "wings" cast into it. Pry up Gently on each wing with a small flat blade screw driver and the valve will slide right up and out. It seals with two tiny o-rings. A thin sewing needle would probably also work just as well and the gas jet drill bit, to clean the orifice. Just spin it a little in your finger tips. Them blow it out with Carb or Brake cleaner.
I'm not sure what the deposit was ,or what caused it. I keep my engine very clean and the fuel system is always run dry before I shut the engine off. No gas are in any of my engines over the winter.
I only use alcohol free gas in these engines. Now you know what to look for if your engine is not idling well or stops after a good Rev or run. and the engine returns to idle.
Hope this helps some member.
Glad you found it. My Greyhounds and my Hisun 196's have those Huayi carbs. ARC racing has those jets but they won't fit the Huayi.
https://www.arcracing.com/dj-1241r-ruixing-low-rpm-jet/
 

wjustice

Active Member
#4
I'm far from an expert but most of these stock overhead valve engines are jetted very lean. It wouldn't take much to get them too lean to run properly. This leanness is a big factor on why you need to choke them to start. Many need choke even when hot.
 

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