It was originally surging, I cleaned that carb and no change. I put on a brand new carb, fresh ethanol free gas, no change at all. I cleaned and checked that new carb, no change. I found that I had a leaking intake valve, I corrected that and it is now running smooth with no surging. I have a video to prove it. I didn't touch the new carb after I corrected the valve issue so the surging was not the carb. Hard to say that a surging issue is ALWAYS a carb issue, that's apparently not true.
Leak down test
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Sorry to disagree. 100 to 60 is NOT a RATE. By its very definition a RATE always involves Time. "Miles" is not a Rate; "Miles per Hour" is a Rate. "Gallons" is not a Rate; "Gallons per Second" is a Rate.
100 to 60 is a percentage of leakage, but it does NOT describe a rate because NO Time was stated. Like I said if it occurred over a TIME of 24 hours there's no problem.
NOW, the OP has finally told us it occurred over a time of "Immediately", indicating in the vernacular approximately 1 to 2 seconds. 1 to 2 seconds is TIME. Finally we have true Rate of Leakage.... 40% per 2 seconds.
Ok I will bite. You guys read on here just like I do that filthy carbs = surging a lot more than gas additives drying up and intake leaks x 50.
Sure the Leaning Tower of Pisa could fall down. I get it. Gas prices might go up, check. And "A" carb might be flawed from the factory, noted.
slomo
Sure the Leaning Tower of Pisa could fall down. I get it. Gas prices might go up, check. And "A" carb might be flawed from the factory, noted.
slomo
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My lord Born2Mow are you saying you can read leakage in less than the measureable time it takes most people to do it? Most humans takes a second or two at the best realize a reading. As close to instant as it is there is still time lag involved. Even when a light is turned on it take time for it to be realize by the observer.
But the common leak down test we use on most four cycle engines is where we input air at fix amount with it continuously being replaced as it is lost so we can a fix amount of leakage. Now with two cycles we do a leak down test from a fixed amount over a period time. Any way we are not testing for the exact same thing or using the same testing method. Otherwords with the leak down use on four cycles it doesn't matter if you test for 1 second or 1 hour the difference of 40% is 40% over both time periods.
Most leak down tester for four cycles uses an orifice between the two gauges. Something like .140". With zero leakage the readings on both gauges the read same. But when a leakage is occurring the orifice delays the replacement air from instantly replacing the lost amount so there is naturally a time delay. The two cycle leak down test uses fix amount of air and the same gauge so you are looking a difference pressure reading over a fix time period. No air is replaced during the two cycle test so a 2 psi lost in 2 seconds is different than 2 psi lost in two minutes.
And Slomo there is and will always be an exception to everything. I was once told that electronic calculators could not add wrong but they can if someone screw ups the programming. I had to replace 100 cpu chips in Huntsville because someone did in the 80's in the Victor 600 series.
But the common leak down test we use on most four cycle engines is where we input air at fix amount with it continuously being replaced as it is lost so we can a fix amount of leakage. Now with two cycles we do a leak down test from a fixed amount over a period time. Any way we are not testing for the exact same thing or using the same testing method. Otherwords with the leak down use on four cycles it doesn't matter if you test for 1 second or 1 hour the difference of 40% is 40% over both time periods.
Most leak down tester for four cycles uses an orifice between the two gauges. Something like .140". With zero leakage the readings on both gauges the read same. But when a leakage is occurring the orifice delays the replacement air from instantly replacing the lost amount so there is naturally a time delay. The two cycle leak down test uses fix amount of air and the same gauge so you are looking a difference pressure reading over a fix time period. No air is replaced during the two cycle test so a 2 psi lost in 2 seconds is different than 2 psi lost in two minutes.
And Slomo there is and will always be an exception to everything. I was once told that electronic calculators could not add wrong but they can if someone screw ups the programming. I had to replace 100 cpu chips in Huntsville because someone did in the 80's in the Victor 600 series.
Surging is either a fuel blockage or air leak, not valve adjustment. Could also be a governor issue. When surging, if you slowly apply the choke, does the surge tend to want to smooth out? If not, then safely grab the throttle shaft, linkage or governor arm. Can you control the surge? If so, governor issue. Was the replacement carb an OE carb? Or, some China knock off?
When doing a leakdown, dropping both pushrods will insure both valves are closed, also for TDC, it doesn't matter what stroke you are on. Fuel does matter! Most engines are rated for E10 or less. Using over 10% ethanol not only damaged seals and gaskets, attracts water, it is also illegal to use. Lastly, I will post this everytime I see a post about replacing a carb. The only reason to ever replace a carb is if it is missing, broken, parts are not available, or you don't know how or are too lazy to clean it. Now days, you can purchase a decent ultra-sonic cleaner for less than the cost of some carburetors. Good luck.
When doing a leakdown, dropping both pushrods will insure both valves are closed, also for TDC, it doesn't matter what stroke you are on. Fuel does matter! Most engines are rated for E10 or less. Using over 10% ethanol not only damaged seals and gaskets, attracts water, it is also illegal to use. Lastly, I will post this everytime I see a post about replacing a carb. The only reason to ever replace a carb is if it is missing, broken, parts are not available, or you don't know how or are too lazy to clean it. Now days, you can purchase a decent ultra-sonic cleaner for less than the cost of some carburetors. Good luck.
A carb defect from the factory is extremely rare. And if there was a defect, it would be evident very soon in the engines early life. Carburetors DO NOT develop internal defects. Dirt, old fuel, or missing/ damaged parts are about all you'll have. Please prove me wrong. 40 years of working with carbs, hasn't happened yet.Ok I will bite. You guys read on here just like I do that filthy carbs = surging a lot more than gas additives drying up and intake leaks x 50.
Sure the Leaning Tower of Pisa could fall down. I get it. Gas prices might go up, check. And "A" carb might be flawed from the factory, noted.
slomo
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I agree completely with the above statement, although i've only been 30 years working with carbs.
Carb throttle shafts and the opening in the carb body do wear over time. This creates a vacuum leak. Yup needles and seats and other wear items....
slomo
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Yes they all do wear. I have seen both the shaft and carburetor bodies worn. Believe it or not I had at least two Nikki two barrel carburetors where the choke shafts completely worn through and broken along the carburetor bodies heavily worn. So much wear on the carburetor bodies that bushings had to be installed. Both of the ones I thinking about were on horizontal Kawasaki v-twins on the Z925A and Z950M mowers. Not something I would thought of until I actual seen it myself as chokes just don't get used that much.
Yes, normal defects usually show up very early on. I was only referring to the new carburetor. Damaged parts AKA worn parts do occur. Fuel itself is abrasive over time but is nil wear most times as worn engines actually needs it.
As far trying to prove you wrong I subscribe to the theory of Murphy's Law that anything is possible given the right conditions. Just because you haven't seen it doesn't mean it not possible as corrosion has a nasty habit of doing strange things.
I also am a firm believer that anything is possible. But, corrosion is not a manufacturing defect. Neither is dirt that wears the shafts. Good posts!