Durbans intake manifold qeustion

[durban]

the photo shows some grooves in , i would like to know do they have some thing to do with getting air to the reed valves , because the way ive worked it out is that suction is created by the pistons , & the only way air or suction comes to these groves is where the carb bolts on there are 2 recesses to the left& right by the studs , the other way is through the top & bottom crank shaft bearing housing both bearing housings have a hole in that line up with the top& bottom feeds to the groove ,
what does this groove do ? my brain is already thinking of something else to do after the rad conversion .

 

[Chinewalker]

Re: Durbans intake manifold qeustion

If you look at the bottom of the passage (top in you photo) you'll see a nipple on the outside of the intake. There is a hose that runs from that to the bottom of the carb cover/baffle. It is basically a recirculation circuit to keep blow-back fuel from getting into the cowling/environment. Fuel can dribble out of the carb mouths when choke is used, or even when the motor is running if some misted fuel blows back. That circuit collects that fuel and it works its way back into the motor to be burned. It's usually not much (unless the reeds are worn or broken), but over time it could accumulate in the belly pan making for a greasy/oily mess, which would in turn leak into the water.

 

[durban]

Re: Durbans intake manifold qeustion

thank you , iam aware of that as i have traced where it goes to with fishing line , there is also a hole bottom of photo that goes to the bearing housing top bearing crank shaft .

what i would like to know where does the pressure or air come from to get the reed values to open ,[flap in other words ] , as i cannot see the suction from the piston opening them from the inside as they are metal flaps that sit tight onto housing & there is no gap between the housing & flap , this tells me that they are opened from the carb side to spray the fuel into the piston chamber

photo that has been uploaded the flaps have been taken of as i am busy refaceing the faces were the flaps sit , with grinding paste & glass

 

[durban]

Re: Durbans intake manifold qeustion

If you look at the bottom of the passage (top in you photo) you'll see a nipple on the outside of the intake. There is a hose that runs from that to the bottom of the carb cover/baffle. It is basically a recirculation circuit to keep blow-back fuel from getting into the cowling/environment. Fuel can dribble out of the carb mouths when choke is used, or even when the motor is running if some misted fuel blows back. That circuit collects that fuel and it works its way back into the motor to be burned. It's usually not much (unless the reeds are worn or broken), but over time it could accumulate in the belly pan making for a greasy/oily mess, which would in turn leak into the water.

i understand this , but it does not explain why the hole is on the other end comeing from the inside of the block where all the suction takes place & if you follow the hole on the opposite end it also goes to the block suction as well as to the overflow pipe for feul like u explained the fishing line tells me all this k & thoes grooves go to each carb , so there is a reason for this , & i think its got some thing to do with suction\air for reed valves .

 

[Faztbullet]

Re: Durbans intake manifold qeustion

what i would like to know where does the pressure or air come from to get the reed values to open

The piston on the down stroke creates a vacuum in the crankcase, when this happens the outside atmospheric pressure(around 14 pounds) rushes thru the carburetor and intake ,opening the reeds to fill the void.

 

[durban]

Re: Durbans intake manifold qeustion

so i could be right then because those grooves have holes that come from the block top& bottom by the bearings that line up with the groove where vacuum will go & this is why they made the grooves go to each carb , so in my eyes its got something to do with getting fuel to reed valves

 

[Chinewalker]

Re: Durbans intake manifold qeustion

The only fuel going through those grooves is waste fuel that has dribbled/sprayed out of the carbs. They have no performance benefit, purely environmental...

 

[Haffiman]

Re: Durbans intake manifold qeustion

Mess with it and you will loose lubrication for upper main, lower main as well as suction of 'spit-back' from the air box.

 

[durban]

Re: Durbans intake manifold qeustion

iam just checking things out , that's why i come up with this question , because my next conversion is gonna be something to do with fuel/paraffin & reed valves after my rad conversion k

 

[tx1961whaler]

Re: Durbans intake manifold qeustion

Durban has a lot of free time on his hands.....

 

[daselbee]

Re: Durbans intake manifold qeustion

The piston on the down stroke creates a vacuum in the crankcase, when this happens the outside atmospheric pressure(around 14 pounds) rushes thru the carburetor and intake ,opening the reeds to fill the void.

The piston on the UP STROKE (not down stroke) pulls a vacuum in the crankcase. Atmospheric pressure pushes open the reeds.

Piston on the down stroke causes the reeds to close, and thereby builds pressure in the crankcase. As soon as the piston (going down) passes by the tops of the ports, the fuel air charge gets expelled from the crankcase into the combustion chamber area. Piston starts UP again, pulling new fuel past reeds and compressing the fuel/air charge into the combustion chamber...waiting for that spark.

 

[durban]

Re: Durbans intake manifold qeustion

well comeing back to this subject , ive prooved it for myself , there is a little hole on top & a nother little hole on the bottom ive made them bigger to 3mm it has improved my starting & idleing by 100% i wanted to know & got the anser as all the little grooves from these holes go to the carbs its got some thing to do with vacume for the carbs , if you havent tried it then you have nothing to debate about k .cheers