Mikuni VM24SS on my 1983 175 try moto.

[mastiff]

my 175 has the Mikuni VM24SS Carb on it which i assume is the stock carb it came with. I know these trikes came stock with oil injection. The oil injection has been removed on mine by previous owner. I know with the OEM oil injection there was a tube running from the oil injection to the carb in order to mix the oil/gas. I had read on the forums that if you are not using the OEM oil injection then you need to cap all the open lines on the carb besides gas line & overflow tube on the bottom of the carb. Besides the fuel line and bottom overflow tube my Mikuni VM24SS only has one other opening which is on the opposite side where the fuel line is. This opening has a pressed in black plastic 90 degree fitting which i assumed was the fitting the oil injection hose fits on. Even before ever starting the trike i capped that 90 degree fitting after reading the forums. After replacing axle bearings and painting the plastics i fired the motor up with no problems until i would get to 1/2 to 3/4 throttle and it would die and gas would pour out the overflow tube on the bottom of the carb. I have chased this problem for a month now and have adjusted the float and replaced the needle valve assembly and it still pours out gas and stalls. It will idle all day long with no problems until you give it 1/2 to 3/4 throttle and then it dies and pours out gas. So yesterday i pulled the cap off of the back plastic 90 degree fitting to open it up. I started it and ran it without that cap and it never stalled and it didn't leak gas out the overflow tube on the bottom of the carb.
My question is could this 90 degree pressed in plastic piece be a vent and when i capped it off it caused the carb to flood ?

[El Camexican]

Short answer, YES.

First off I don’t know your trike very well, but I think most oil injection systems feed directly into the crankcases, rather than the carburetor. I don’t see in the fiche where your oil pump hose leads to so I’m going to assume it is the crankcase. If it does, then that inlet needs to be capped off if your oil pump has been removed.

There is a vent above your float bowl #24 in this fiche. You have a fuel pump on that trike, so if you’ve capped the carb vent it would make sense that the added pressure of the pump at higher RPM could over power the float needle and push it off the seat and overfill your carb.

I don’t know where that vent hose #24 goes to, if it attaches back to the fuel tank, or just tucks up under it. Wherever it may go you don’t want it taking on water if you go swamping, so make sure the end is pointed down.

http://www.yamahapartshouse.com/oemparts/a/yam/5003882df870021f60a098f0/carburetor

[mastiff]

Thank you for your reply El Camexican.
You must be correct because it doesn't stall anymore and doesn't pour gas out of the overflow tube at 1/2 - 3/4 throttle. It does drip a little gas out of the overflow tube on the bottom of the carb but i think that is just a float issue i need to adjust.