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new generation gas engines

5

55 50 Ron

Well-known Member
A friend has a 4020 gas and a 3020 gas. Both start hard and act "flooded" for awhile. I"m a 2 cylinder guy and know nothing about New Generation carburetors. Are they troublesome? What are some things to check and do to "fix" them?

Thanks folks.
 
Our 4020 gas works fine. Had to switch to a Zenith cast iron carb. to finally get it settled in though.
The colder it is (to a point) the better it starts ! Which is what we wanted for plowing snow.

A good complete tune up including compression check and valve adjustment is a good starting point.
Even with the alum. carb. ours started good but would load up at idle and or acceleration.
 
I have two w/loaders that I use around the shop.
Both worn out but start easily. The one with the 158 loader is started by pulling the choke before cranking and immediatly pushing it back in as it fires. It has electronic ignition and I replace one or two plugs as needed. It loads up idling and it idles most the time. Has the cast iron carb. Never saw the aluminum carb on a 4020 but I perferred them on the 3020s I worked on. They seemed to adjust better. I know guys on here don't like them though.
The other loader was propane now gas. Also starts easily. Has points instead of electronic.
 
I bought a 4010 gas a year ago and it runs very well. It has a Zenith carburetor and the previous owner had installed electronic ignition. It idles clean and accelerates without smoke and pulls very well. It sure sounds funny after using diesels for so many years. It starts very well, too. I had to adjust the governor linkage somewhat to make it a little more snappy and changed out the D21 Champion plugs to 3116 Autolites. The plugs showed to be fairly new but the Autolite plugs made a noticeable difference. The plugs are gapped at the standard .030". I thought about opening them up a little but the tractor runs well so I left them at standard gap. I'll be checking the valve clearance when I take the hood off later. Mike
 
I've had a 3020 gas (side console) since "86 and only tuned it up once. Starts and runs excellent. Likes to be lowest idle to start. Starts easily any weather. Use only premium gas with no alcohol!

Does your tractors emit black smoke when slowing down in 8th gear, blurble and then run with some black smoke? If so, there is a diaphragm in the carburetor that may have failed with a hole in it. It lets too much gas be sucked into the engine and you cannot adjust the carb correctly.

The diaphragm and spring acts like an accelerator pump when the throttle is rapidly advanced or governor kicks in. The lowered vacuum lets the spring push gas into the manifold/carburetor.
 
The NEW Zenith carbs from Roberts Carb are the only way to go. I put one on my 1969 3020 and 1970 4020. It takes care of all the problems. They use less fuel, do not smoke and do not foul plugs. They are worth every penny they cost.
I also have electronic ingnition and I run solid core wires and Autolite 389 plugs. I have the heat exchanger set to hot all year around as advised by Roberts Carb. I tried all the other stuff before the carb and the basic tune up stuff didn't work. They always started good just used too much gas and fouled plugs. I should also say the tractor has between 130 and 140 lbs compression.
 
Actually when its cold out like we get here in Ohio come winter time you want to switch that manifold block to HOT setting and in summer switch it back to COLD I think you will get the carb. too HOT on the HOT setting in the summer and may even vapor lock.
 
That's what I thought but Gary at Roberts Carb said differently and I set it to hot. The tractor runs beautifully and has never vapor locked. They are very helpful and knowledgeable there. I would buy another carb in a heartbeat.
 
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