Topic: 550k revamp- first time build

[chris550k]

...

[fastbroshi]

50 miles before reserve is really low, even for city riding.  Out on the highway I can get a little over 100 if I keep it at 65 or so, and mines not running at its best.  You might start going through the carbs, ignition, and check the air filter.   

[wedoo2]

Your 550 looks good.  Go ahead and get the manuals that are here in the forum.
http://forums.sohc4.net/index.php?topic=17788.0

Like fashbroshi said, go ahead and do the basic things and get it running right.  There is a good amount of help, and helpers here.  Check out the vendors that people recommend as well.  I got my SS lines from Slingshot Cycles and they were around $65 and great quality.  If you get new exhaust, don't pitch the old ones as there are most likely several here that may want them.

Post your progress.

[Bankerdanny]

I typically averaged 40mpg or so riding around Chicago on my '77 550 last summer. I hit 50 a couple times when I was on a long trip, but 45-46 was typical highway mileage, with 37-40 for an all city tank.

So with the 4 gallon main tank you should easily do 115-125 miles before reserve around town. 50 miles is less than 15 mpg, so yes, that is very poor. The petcock has a large screen that sticks up into the tank. I wonder if yours is clogged and so you aren't getting the full access to the main tank. I replaced the whole assembly for about $50 from Powers Edge Motorsports.

One time I got like 60 miles before reserve. The problem was a loose wire from the 1-4 condenser to the points so that all 4 cylinders weren't firing and I was running wide open throttle just to hold 50 mph. It took 2 days to diagnose and 5 minutes to fix.

Also air cooled engines hate lots of idling. Normally I didn't have a problem in traffic, but one night I got stuck behind an accident and I ended up having to pull over to let my bike cool off, I could feel the heat pouring off the engine. You might want to consider an oil cooler if commuting is a primary use and use motorcycle specific synthetic oil, which stands up to the heat better.

Steel brake lines look cool, but I don't think in typical street riding they are worth the extra cost. I'm a big guy (225-230 pounds) and I never felt like the brakes were underpowered.

[Really?]

Wonder if you are leaking fuel out of the overflow tubes or the petcock is on at rest and/or it is draining down into the cylinders.  15mpg is oddly low.  I ran out of gas once because the fuel was flowing out the drain tubes while riding.

[fastbroshi]

  Sure.  Just a random question for you:  do you know how the choke works and which way is closed? 

[fastbroshi]

  My 550 just has a lever on the carbs, so I can't say for sure.  But just to reiterate, when I say open, I mean it's not engaged and not pulling any more fuel than normal, and this is how it should be operating when warm.  Closed is engaged and will force more fuel through the carbs, and is also not meant for normal riding.   Might explain your poor mileage.

  I'd say off the top of my head you've been riding around with it engaged all the time, which will make it feel gutless over a certain RPM, as well as foul the plugs.  Maybe someone with that type choke mechanism can comment.  If it is the case, I'd take your plugs out, clean them real well, set your valves, then check the ignition settings.