Jump to content
Sign in to follow this  

quick carb help, I imagine its simple but im/were dumb! (PICS)

Recommended Posts

ok heres the problem; a young friend of mine says hes having problems with the mikuni carb off his 91 rm80... it just shoots gas out of the 2 circled holes in the pics.

205sgsk.jpg

90mwdt.jpg

so I tell him to bring his carb over ill help him... turns out he has his fuel screw tightened in all the way, as well as the air screw 👍, so I unscrew the fuel screw and set it to 1.5 turns out (guess), I also turnout his air/idle screw about 2 turns out just to see.

he had a tab on his float bowl that he also bent trying to fix his problem.. so we bent that back so it was straight.

then we hooked up a hose to his fuel intake nipple on the carb and tried to push water through it.. nothing. we couldnt get water to flow through the carb, it seemed plugged, or are we just idiots? but water will pour like a tap out of the hole in the bottom picture (the silver hole not the gold one) he doesnt have the needle in the carb, nor is the top cap on, so I figure that might be part of the problem.

I would really like to get this figured out for him as he just spent 120$ in parts and only needed a few of them... hes not the smartest mechanically but hes an amazing rider for someone of his age/bike.

maybe it will be different when its on the bike with the throttle and needle hooked up to it? otherwise.. why does the fuel nipple not let any fuel through?

thanks.

Share this post


Link to post
Share on other sites

Take out the float valve and valve seat to see if it's clogged. Take those out, hook up fuel supply and make sure gas comes out through the float valve hole.

  • Like 1

Share this post


Link to post
Share on other sites

The tube at the bottom of the carb that you circled is the float bowl overflow. It sounds to me like you have a problem with the float and valve assembly. I would remove the four screws at the bottom of the carb and remove the bowl. There will be two hollow floats that can pivot up and down. They pivot on a pin. Just above the pin is a little valve. The idea is that when the bowl fills with fuel, the floats rise with the fuel level until the valve closes. So you want to run fuel or water down the fuel input that is attached to the gas tank. Holding the carb so that the float is down, liquid should pass through the valve. But when you lift the float with your finger, the liquid should stop flowing because you have closed the valve. I suspect you have a problem with the valve, it could be clogged, missing, or worn. It is also possible to have a bad or mis-adjusted float, but the valve is the most likely culprit. You should also use a workshop manual and parts diagram, they will help alot.

  • Like 1

Share this post


Link to post
Share on other sites
The tube at the bottom of the carb that you circled is the float bowl overflow. It sounds to me like you have a problem with the float and valve assembly. I would remove the four screws at the bottom of the carb and remove the bowl. There will be two hollow floats that can pivot up and down. They pivot on a pin. Just above the pin is a little valve. The idea is that when the bowl fills with fuel, the floats rise with the fuel level until the valve closes. So you want to run fuel or water down the fuel input that is attached to the gas tank. Holding the carb so that the float is down, liquid should pass through the valve. But when you lift the float with your finger, the liquid should stop flowing because you have closed the valve. I suspect you have a problem with the valve, it could be clogged, missing, or worn. It is also possible to have a bad or mis-adjusted float, but the valve is the most likely culprit. You should also use a workshop manual and parts diagram, they will help alot.

ok perfect, thank you very much for that detailed explanation, I really appreciate it.

that float valve is part number 8 on the micro-fiche that I posted earlier right? we took those 4 screws off to adjust the bent tab on the float that I believe the float valve is hooked up to. I will go get the carb from a friends house and mention what you have said and report back with an update as as well as more pics.

thanks a lot!

Share this post


Link to post
Share on other sites

hey, I just called my friend and turns out he already has the carb installed and has been riding already!!

turns out nothing was actually wrong, I think its just because we didnt have the needle or top assembly inside is why it seemed plugged!

thanks for all the help guys. + gas to all that replied!

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×
×
  • Create New...