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B&S 8HP change carb to variable venturi carb?

ehanson

Registered
I am just contemplating installing a variable venturi carb onto my genset. It is a 1975 8 HP horizontal shaft generator. I have some old motorcycle carbs laying around and wonder if anyone has tried this before? I would be very curious to know if it would improve fuel economy by any measurable amount (not that I know what it burns now).
the governor connection might be a bit of a challenge, but I think could be worked out.
Any one out there done this?
 

KeithW

Registered
Age
64
Having tried motorcycle carbs on a car before I suggest starting with the smallest carb you have. I went too big and jetting was a nightmare as the carbs were far too large.
 

Fifty7ChevyNut

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Last Subscription Date
01/24/2014
i have seen all sorts of small carbs put on briggs engines, and briggs carbs put on lots of other engines.

as long as displacement of motor cycle engine closely matches generator engine, i would think you would be on a close start.
 

KeithW

Registered
Age
64
I would reccomend a carb from a bike engine about half or a third the size of the B&S. Remember the bike engine turns 2 - 3 times faster that the B&S ever will. The carb from a 70cc or 100cc would be a good place to start.
 

ehanson

Registered
I would reccomend a carb from a bike engine about half or a third the size of the B&S. Remember the bike engine turns 2 - 3 times faster that the B&S ever will. The carb from a 70cc or 100cc would be a good place to start.
Yes, I have the tach from a 72 Honda 350-four, I believe it has a redline of 11,000 RPM.
I could start with one of those? Each carb from that = 125cc's, the air velocity through that would be considerable.
A 8 HP Briggs is 19 CID or 311cc's.
 

KeithW

Registered
Age
64
That would be a good place to start. Were those carbs the ones with the dash pots on top where the slide went up and down automatically with engine load? If so they have a much better chance of working over the ones where the throttle cable pulled the slide up directly.
 

RSCurtis

Registered
Last Subscription Date
11/20/2013
You could also get a carburetor and governor linkage from an Industrial Plus engine.

The reality is that a properly setup Flo-Jet (the one you have) should be just fine, and save you from reinventing the wheel.
 
L

Lead Head

Guest
Yes, I have the tach from a 72 Honda 350-four, I believe it has a redline of 11,000 RPM.
I could start with one of those? Each carb from that = 125cc's, the air velocity through that would be considerable.
A 8 HP Briggs is 19 CID or 311cc's.
The Honda CB350 was rated at 34HP, or 8.5HP per cylinder. One of those carbs should be a good match.
 
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