Honda Spree and Elite 50 Forums

Why don't you tap it where all the stock af18 motors have the vacuum inlet?

it really needs to be tapped into the case pressure.The pumps are pulse operated and the pulse isnt strong enough from the intake .I fitted a afo5e to a af28 frame with the same floor tank and ran a airline off the mani like you have but couldnt get it to run at its full potential as it was starving for fuel.A friend of mine who has worked on alot of these said it needs the direct pulse from case pressure .So i tapped a nipple into the case tested it and my problem was solved .Hope this helps you .oh you have a pm

This is great information

Just drill out one of your pump plugs and use the threaded part to put a nipple on it like everyone else has done. I can't imagine it'd be hard for you. Just surprised the manifold isn't strong enough and makes me want to drill a plug and nipple it to see how it does on the petcock vac.

The reeds are what causes poor signal strength I'm assuming. They open over 160 times per second at 5k rpms. 10,000k rpm/60 seconds is a lot of reed movement. A lot of time to allow the tiniest balance of pressure to happen which in short makes the pressure "less" for a fraction of a moment.

Start selling modified plugs! I bet you could charge double for the drilled and nipple plug.

This may be part of my problem

I suggested tapping into the case and emulating the Af18 setup, because it's the setup you're trying to substitute with an af16 motor. Fuel pump and floor mounted gas tank doesn't care if you're running an af18 or af16. Nipple still needs to be in the case.

G9..,can you post a pic of the tap please..? I need to do this also

Oh no! What's it looking like?

Take a look at the area directly below the oil pump plug opening. That's where the tap should be.

DSC_6264 Honda Dio ZX

That OEM vacuum nipple is a 90 degree tube. This allows it to clear the starter motor. If you don't run a starter, you can use a straight inlet instead.

I hope it works out.

Fwiw, the vacuum source point on an af18 is connected to the oil pump cavity via a passage. So essentially the oil pump will be a exact replica of vacuum conditions. The problem with it being near the reeds is the pressure drop every time the reed opens and the source point being right there only mms away.
In order to replicate the hole where the af18 is on an af16 and also 90 or 45 degree the hole routing into the oil pump plug may be a feat most couldn't do.

Greetings:

Fuel pressure regulator?

Hmmmm. I've run three different carburetors with the af18. The tm24 carb was the most finicky, but the others required no adjustment.