Topic: 1975 550k - Beating The Gumption Trap

[CBsage]

Hi All! Finally found the time and energy to get back to work on my first project bike. A little over a year ago I bought a 1975 550k from a buddy who was about to move out of the country. I got it for a sweet price, and a parts bike included!  It wasn't running at the time, but after swapping the current modified wiring harness with the part bike one & some new oil, I got it to fire up! It doesn't run real smooth at the moment, but with a little elbow grease I'm hoping to get her running good.

Over the Winter I'm planning to do some frame/engine mods, go with a cafe/brat style look to it.  But I just need to dial her in before I start tearing her down. A harder task than I probably realize. But I've been spending countless hours on this site, and can really appreciate the experience and knowledge this community has offered. 

I plan to take my time with this build, so wish me luck and stay tuned!

Here's a look from when I got the ol' girl.

[CBsage]

One of the first issues I've got to deal with is this leaky carb.  After I first got it started I noticed a puddle of gas coming out a overflow tube.  I heard from other threads to tap on the bowl of culprit carb, but no luck.  So I'm guessing it could be either a stuck float, an issue with the float valve/seat or maybe a crack in the overflow stem attached to the bowl. I'm sure the carb could use a good cleaning anyway, so I'm going to mess with it tonight and find out what's going on.

[SOHC4 Cafe Racer Fan]

CBsage,

If the bike has been sitting for a while, the carburetors almost certainly need a thorough cleaning and possible rebuilding.  Gas degrades over time and the substance left behind is best described as varnish.  It clogs your carburetors, fuel lines and petcock.  You will want to thoroughly clean the gas tank, petcock, fuel lines and carburetors.  Period.

[CBsage]

Thanks Racer Fan.I drained the tank before trying to start it again recently, but I didn't even think about cleaning out the tank, petcock and fuel lines.  I best get on that next. Think I should soak the petcock in carb cleaner, or would that destroy any rubber that might be inside it?

 I pulled the carb yesterday and took a look inside. They're definitely a bit dirty, but glad they weren't too nasty.  No floats were stuck, and still springy.  The float valves appeared clean, as well as the seats.  None of the bowl overflow stems seemed cracked, so I'm stumped why it's leaking gas out of the overflow tubes. While i was cleaning up I recognized there were still stock jets, so that's good to know. Tonight I'm going to tackle the emulsion tubes, but I hear they're a bit tricky getting them out. Anybody know any good ways to safely get them out? I've got BBQ skewer, I 've heard that works.

[Davez134]

If the float valves needles/seats are not worn together (for example previous owner mixed them up in the past) they could leak even though they appear clean. That could be a cause of the leak. Whenever I rebuild carbs that have been sitting a long time without knowing history, I always replace those as a new pair.

[CBsage]

Thanks Dave, I'm giving that a shot. After i cleaned everything up and checking the float heights, it still leaked out of the #1 carb pretty quickly. So i ordered a new seat/valve needle and float bowl gaskets, and just waiting for them to show up.The emulsion tube didn't end up being that bad to get to and clean. Actually, as side from a little corrosion they were in pretty good shape. The only tricky part were those pesky tongue washer.