Oliver 1550 gas stumble problem

ljw · Jun 18, 2023

I am looking to purchase a 1550. It starts and runs great however, it stumbles when I increase the throttle or when trying to start off in a high gear. The current owner says its been this way for a long time and says over time, he has rebuilt the carburetor, installed new spark plugs and wires, checked the timing, replaced the manifold gasket, adjusted fuel mixture but it has not solved the problem. It has the upgraded Petronics ignition. Hes asking what I think is a good price for it but I want to get some input on a possible solution before I purchase.

Gary Mitchell · Jun 18, 2023

The very first thing I'd check would be the points, face surface, gap, ground, etc. gm

TerryfromSWIowa · Jun 18, 2023

How do you check points on an electronic ignition???

rrlund · Jun 18, 2023

Sounds normal to me. I've got one with over 9800 hours on it now. I have to run it with partial choke. Mine has electronic ignition too. I chalk it up to being the nature of the beast.

oliver90owner · Jun 18, 2023

"Stumbles" Do you mean it loses fire and the engine would stop?

Our 90 was like that until a choke wire was rigged up to theplatform. A short pull on the choke and away no problem, ever. That was KD, mind.

Check the fuel level in the float bowl and reset if necessary. Could be the governor. Unlikely it is actually losing spark. More likely a too weak mixture, as the governor fully opens the carburettor butterfly.

ljw · Jun 18, 2023

It does normally run a little rich and the guy said he runs it that way to lessen the stumble. Its not losing spark. It
seams as though the governor opens the butterfly too quickly. Im not aware of any adjsutment for this or is there?

Mike(NEOhio) · Jun 18, 2023

Mine does that but not after it warms up. Sometimes I'm a little too ginger with the clutch.

super99 · Jun 19, 2023

My 550 did that, open the load screw on the carb a half turn at a time and see if it goes better

Mike(NEOhio) · Jun 19, 2023

I'm not sure about the 550 but on M-S carbs the idle mixture screw controls the air in the mixture, not the gas. Turning it in richens the mixture. That said, mine seems to have little to no effect. I suspect there's a clogged passage somewhere but haven't taken the time to go through the carb again.

Centerplate · Jun 20, 2023

Are you using 10% ethanol fuel? You need to bore the main jet then readjust the carburetor.

J.Wondergem · Jun 20, 2023

(quoted from post at 13:12:33 06/18/23) It does normally run a little rich and the guy said he runs it that way to lessen the stumble. Its not losing spark. It
seams as though the governor opens the butterfly too quickly. Im not aware of any adjsutment for this or is there?

That right there tells me the carburetor is too big for the engine displacement. Sounds the same as putting two four barrels on a stock built 283 Chevy. If it were me I'd try a smaller carb. That is smaller in the Ventura area. What happens is when you pop the throttle open, use lose all the vacuum and have to wait for it to come back. That's why using the choke will help it.

ljw · Jun 20, 2023

That makes sense to me, especially since all other typical solutions have been tried with no improvement. Being as old as
it is, I suppose its possible the carb has been changed sometime during its lifetime. Thanks.

ljw · Jun 21, 2023

I believe I have found the problem. The throttle shaft and or bushing appears to be very worn. When the governor has
tension on the throttle shaft, at idle or any given position, all is good. When the throttle is increased, and there is
movement in the throttle shaft, I believe excess air is coming in through the shaft and causing a lean mixture to the point
where it stumbles. If I choke it slightly during throttle up, no issue. Thanks for everyone's assistance and guidance.

Oliver 1550 gas stumble problem

ljw

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Gary Mitchell

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TerryfromSWIowa

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rrlund

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oliver90owner

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ljw

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Mike(NEOhio)

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super99

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Mike(NEOhio)

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Centerplate

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J.Wondergem

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ljw

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ljw

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