Carb fuel inlet, general question

[bricks]

Hello everyone. First post, thanks for having me

A friend gave me a 1983 Yamaha xs400 Maxim (wohoo!) and I just started fixing it up. It cranks but doesn't start/fire, so I rebuild/cleaned the carb, re-installed, set the petcock to prime and let it sit for a few minutes... It still won't start. At least it's all shiny now.



I have spark, and sprayed started fluid into the carb inlet and the bike will actually run and idle for a second, but after it runs out of fluid it dies. I took it back out and removed the bottom cover/pan of the carb closest to the fuel inlet and noticed that there was no fuel in there.



I put my mouth on the fuel inlet and blew but couldn't get any air through even with the needle valve set removed, so my guess is that it's clogged? My understanding of this section is that fuel goes into the inlet and pours into the pan through the needle valve set, and when the float rises it hits the valve and shuts off fuel. So without the valve shouldn't I be able to blow air through?

 

[dannyTheBoat]

You can try pulling out the brass plug that the needle float valve sits in. That has a little screen on it that could be clogged. That's a good starting point. Then you can work your way up through the feed tube to find a leak.

Is your gas tank rusty? Has there been fuel sitting in there for a long time without running?

 

[bricks]

The needle valve set is brand new and let's air through. Not sure how to get anything in there to clear the pipe though. I sprayed some starter fluid in there last night, so I'll try a pipe cleaner again to see if things are clear.

Am I correct in the assumption that air should flow freely into the fuel inlet if it's not blocked?

 

[bricks]

Score! In order to get to the other side of the 90deg bend of the fuel inlet I had to take apart the carbs. I used a coat hanger to clear the debris and some dirt came out! Air now flows freely.

I think what originally threw me for a loop was that there was gasoline in the carbs when I took them apart the first time, so I assumed that the fuel inlet had been clear the whole time. I guess that was not the case. Going to hook things back up and see what we get

 

[bricks]

It's alive! I'll need to get the air intake box hooked back up and the tires pumped, then I can see if my brake and clutch cables actually do their job.

 

[dannyTheBoat]

Yeah man!!
Might want to check the fuel tank for the source of that grime. Also, the clamp on that carb boot looks kinda mangled. It might be good to replace when you can to avoid air leaks.