synchronizing carbs 40 hp 4 cycle 2005

srdumstorf

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May 11, 2012
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Service manual describes synchronizing the carbs on 40 hp 4 cycle 2005, It mentions to remove all three intake plugs and install the gauge adaptors then the procedure. I do not have these special adaptors so I made one that works fine however my gauge pulsates so rapidly and with such a large travel it's unreadable. I installed a mercury manometer instead of the gauge and readings are obtainable however I wonder if perhaps the other two plugs should have been left out or if the special adaptors have a restricted orifice I should take into consideration. Any help would be appreciated, Lord knows I'm not shy of buying tools but I've adjusted many carbs in my wrenching days, don't see why these should be any different. Please if someone has these adaptors if you'd be so kind.
 

boscoe99

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Aug 22, 2013
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Re: synchronizing carbs 40 hp 4 cycle 2005

Is this a Yamaha you are working on?

The adapter is nothing special. Just a means of connecting a vacuum gauge to the intake port. Screw plug comes out, adapter fitting installed and the vacuum reading device hooked up.

I find mechanical vacuum gauge almost impossible to use. As you note, the needle swings wildly. The intake manifold pressure/vacuum is varying as the valves open and close and this causes the gauge to be very erratic.

Beg, steal (not really), rent or borrow a vacuumate device. It is an electronic meter. It is internally dampened and very easy to use. I can't see synchronizing carburetors without one.

TecMate International - OptiMate Battery Chargers - DEALER: VacuumMate
 

srdumstorf

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May 11, 2012
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Re: synchronizing carbs 40 hp 4 cycle 2005

Hey Boscoe, sure enough is a Yamaha. I appreciate the input and I did check out the VacuumMate information. Looks like a
pretty nice tool too have for doing this job. If I see many more of these engines, or I loose my (probably hard to get these days) mercury I'll think harder. Again thanks for replying.
 
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