xs400 carb, throttle, and idle adjustments

[RattyRatBikes666]

Hey all. First off, i'm a honda guy. been riding em my whole life. decided to try a yamaha and i like it quite a bit. So to start off, she is hard to kick start sometimes but other times it'll start 1st or second kick. that i am not too worried about. what annoys me is that i have yet to find a way to adjust the carb air fuel ratio. i looked on trusty old youtube and there was a video of another 1980 set of carbs that had adjustment screws right on the side. mine doesn't have any adjustable anything other than idle but the thing that the idle screw moves isn't even touching it. also when i turn left, rpm drops, turn right and it raises. this paired with the stalling when it tries to idle makes it difficult to ride.

my fuel regulator thing {on, off, res} doesnt really do anything because it was bent or pinched or something by the previous owner. because of this he put another valve on. if i park the bike without turning the fuel to OFF it floods and wont start back up for a while. do yall know of anything that would cause this?


basically i just need to know what to fix on the throttle, how to get the air fuel mixture correct, and why the idle isnt being adjusted due to the arm being about a 1/5 of an inch above the screw.

thanks all. have a nice day

 

[BBS360]

On your carbs (also 1980?) the mix screw should be directly on top of each carb, pointing up, on the engine side. It might be covered by a brass plug.

Have you done a carb sync?
Does the bike have stock filters, intake, and exhaust?

The throttle/handlebar issue indicates that the throttle cable adjustment is too tight. Readjust at the handlebars, maybe reroute the cable. There should be enough slack in the cable that moving the bars doesn't affect idle rpm.

 

[RattyRatBikes666]

On your carbs (also 1980?) the mix screw should be directly on top of each carb, pointing up, on the engine side. It might be covered by a brass plug.

Have you done a carb sync?
Does the bike have stock filters, intake, and exhaust?

The throttle/handlebar issue indicates that the throttle cable adjustment is too tight. Readjust at the handlebars, maybe reroute the cable. There should be enough slack in the cable that moving the bars doesn't affect idle rpm.

all thats after market are the handle bars and 1 baffle in the exhaust. also how do i get to that adjustment screw? do i have to take the tank off?

 

[RattyRatBikes666]

all thats after market are the handle bars and 1 baffle in the exhaust. also how do i get to that adjustment screw? do i have to take the tank off?

and even when there was a good ammount of slack in the cable it still did it.

 

[BBS360]

Tank off or a really short stubby screwdriver, assuming there's no brass plug in the way.

My throttle cable was actually pinched inside the handlebar housing. Haven't seen anyone else with that problem.
Rerouting the cable under the tank and adjusting the nut where the throttle cable enters the housing at the handlebar.

 

[RattyRatBikes666]

Tank off or a really short stubby screwdriver, assuming there's no brass plug in the way.

My throttle cable was actually pinched inside the handlebar housing. Haven't seen anyone else with that problem.
Rerouting the cable under the tank and adjusting the nut where the throttle cable enters the housing at the handlebar.

did some fiddling and it idles a tad better and doesnt rev nearly as high when i turn. now for air-fuel. ty