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Onan engine ID


 
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Dude11
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PostPosted: Mon Nov 05, 2007 12:54 pm    Post subject: Onan engine ID Reply to specific post Reply with quote

Hi,Can someone tell me the difference between B43E,B43G,B48G,B48M Onan engine ID's.I have started work on one and have some manuals coming but it could take a week to get here.It's on a 1977 Sears GT18hp,B48M-GA 018/3417A.Could it be different types of carburetion,or just the age and model number.thanks,Dude11
 
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Newfy
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PostPosted: Mon Nov 05, 2007 6:38 pm    Post subject: Re: Onan engine ID Reply to specific post Reply with quote

B series engines were first manufactured in 1972 as a BF 16 bhp, 40 cubic inches, 3 1/8 bore X 2 5/8 stroke. The BG was released the next year, 3 1/4 X 3 stroke, 50 cubic inches.
B43M 3 1/4 X 2 5/8 and the B48M 3 1/4 X 2 7/8 were released in 1975. All were full pressure lubricated. Some were supplied without oil filters to keep the cost down. They all used the same type of flywheel, Walbro DD model carburetor with a carburetor mounted fuel pump on most models. The fuel pump was mounted on the blower housing on applications with high compartment temperatures.
In 1980 the G series was released, also know as the Power-Up series. The G series used an entirely knew cooling and fuel systems, carburetor no longer accepted a mounted fuel pump. The air cleaner was nearly square and had an improved attachment points. The flywheel had a venturi ring bolted to it to increase the air flow, the blower housing and cylinder covers were redesigned for maximum air distribution. New cylinder heads with relocated spark plug placement to improve combustion and valve stem seals were available on the intake valves.
B43E was basically a lower cost engine which did not have an oil filter or valve rotators and was rated at 16 bhp. (43 ci 3 1/4 x 2 5.Cool
B43G oil filter, valve rotators, slightly bigger carburetor, same camshaft as E, rated at 18 bhp.
B48G same as B43G but a bigger carburetor, high lift camshaft and intake valve seals. Rated at 20 bhp and 48 ci 3 1/4 x 2 7/8.
 
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Dude11
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PostPosted: Mon Nov 05, 2007 7:53 pm    Post subject: Re: Onan engine ID Reply to specific post Reply with quote

Newfy,A fisherman would call all this info,"A prized Catch".But,while I got you going,whats the difference between the Walbro and Marvel Schebler carbs?Did they both carry a mounted fuel pump?I've seen carb.on Onans with a main adj.screw on the bottom edge of the bowl,and they were sortda round.Mine has a square kinda body with main jet and idle adj.on the side and a mounted fuel pump,I thought it to be the Schebler.Thank again for all the info,Dude11
 
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PostPosted: Tue Nov 06, 2007 7:04 pm    Post subject: Re: Onan engine ID Reply to specific post Reply with quote

Your carburetor is a Marvel Schebler which is a square body with the fuel pump mounted on it. Bolens and Case used the same carburetor but the fuel pump was mounted in a cooler area on the blower housing and a cover plate was used on the carb for the fuel line connection. The pulse line came from the gearcase cover instead of the top of the cylinder block. If you look at the back of the body , where the adjustment jets are located you will see a model number and manufacturing date code stamped. The models range from DD11 through DD15. I think it was about 1980 when Walbro bought out Marvel Schebler mainly to get the rights to their pulse fuel pump. The Power up series, B43E, 43G, and 48G used the Walbro and later in '80's Nikki in Japan copied their carburetor and the pulse fuel pump. Onan then started using the Nikki carb and fuel pumps due to price. The engines again evolved in about 1986 to the P Series and were known as P216, 218, and 220. There was also a P224 engine which was 60 cubic inches, 3 9/16 x 3 and used in larger commercial equipment.
 
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