1974 Aermacchi Z-90
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Stage III
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From: Cochran,GA
1974 Aermacchi Z-90
Hello, I can't find a good forum that covers these specific so I hope someone here can help. I have a 1974 Aermacchi Z-90 thats got about 7,000 miles on it. The bike is in real good shape and hasn't been run in years. I mixed some 2 stroke gas and put in it and got it running. I have removed and cleaned carb and put new air filter on it. It runs good but when you start going in first gear it has a bog and I shift to 2nd it boggs a little and then takes off and runs good until I stop and then same thing all over. In the meantime I wanted to hook the oil injection pump back up. I put new clear lines on it put new oil in oil tank ,bled and I keep getting air between the pump and intake. I removed the fitting on the intake and it is stopped up or is that a check valve. I have tried a piece of wire thru it but if it is a check valve I dont wanna damage it. Does anyone know if it is a check valve. Thanks
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picture would be nice
running without oil going through the pump will mess it up, could lead to clearance issues and aeration.
are you sure the carb is clean, there are air passages also so just spritzing cleaner does not do it. then there is the issue with bloom, aluminum corrosion where it swells and blocks the passage, sometimes the carb becomes a brick, also of note this era is not alcohol friendly.
with oil injection, the issue became less but not saying it cannot happen, a carbon block in the exhaust port. this will cause issues like you described.
do you have the FSM
running without oil going through the pump will mess it up, could lead to clearance issues and aeration.
are you sure the carb is clean, there are air passages also so just spritzing cleaner does not do it. then there is the issue with bloom, aluminum corrosion where it swells and blocks the passage, sometimes the carb becomes a brick, also of note this era is not alcohol friendly.
with oil injection, the issue became less but not saying it cannot happen, a carbon block in the exhaust port. this will cause issues like you described.
do you have the FSM
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,034
Likes: 981
if you are talking about the intake manifold, yes there is a check there.
when bleeding the pump using oil mix in the fuel, do you let it idle with the injection pump lever in full open position till it pumps nothing but oil?
if so and then you get air, the pump has issues. these pumps are NOT robust and fail commonly. if you get a pump, there was an upgraded one that can out in 1973 that solved the issue with over lubrication.
if i remember right, these pumps are plunger type and not gear like the yamaha and when they wear out they leak internally chamber to chamber. there were no seals, just a clearance fit. the suzuki use this type of pump also.
you might be consigned to pre-mix life.
when bleeding the pump using oil mix in the fuel, do you let it idle with the injection pump lever in full open position till it pumps nothing but oil?
if so and then you get air, the pump has issues. these pumps are NOT robust and fail commonly. if you get a pump, there was an upgraded one that can out in 1973 that solved the issue with over lubrication.
if i remember right, these pumps are plunger type and not gear like the yamaha and when they wear out they leak internally chamber to chamber. there were no seals, just a clearance fit. the suzuki use this type of pump also.
you might be consigned to pre-mix life.
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