Topic: '74 CB550 Carb Rejetting

[TPIGroove]

Hello all. I'm about to acquire a 1974 CB550 that, despite being very clean and taken care of, has sat for a good while. I'm going to go through it and take care of all the maintenance/upgrades it needs, and of course carbs are something that's keeping it from running. The bike itself has what appears to be a muffler delete, although when I checked it out I forgot to see if it had a 4-into-1 or 4-into-2, either way it isn't standard. Since I'm already rebuilding the carbs, what jets should I use? I'm also concerned since there's no non-ethanol gas stations near me, and I've heard ethanol runs a little leaner. I'm worried that if the carbs have their stock jets it may not run as effectively, the pipes near the engine have slight discoloration and I don't know if it's normal or due to  slightly leaner burning in its life. I've attached a picture of the bike, maybe someone can identify the exhaust.

[TwoTired]

It's a 4 into 2,  Possibly a Jardine or Macs.

As long as you use the stock air fliter box arrangement, it probably won't need a re-jet.

The spark plug deposits tell you a lot more than looking at the exhaust pipes.  The single wall chrome can discolor from an oily rag or from running out of gas.  The latter starves the pilot system first and leans the motor while cruising before the jet needle and mains starve to stop the motor outright.   Not a problem with stock dual wall head pipes.  But few will spring the $1k to restore to stock 4 to 4.  But, IMO it's worth it if you take that into account before buying the bike.

If you have dexterity, you can make the carbs work and clean all the bits needed without removing from the bike.
Helps to be double jointed, though.  And I'm not.  Just have the right tools and will.  Don't be replacing brass bits, and make sure the main jet holder isn't corroded.  If so, its replace or have it weld back up to restore.

Check the tank for rust.  This model has a sediment bowl and screen, so check that too.

The 74 CB550 is what started me off with SOHC4s back in '75.  Put a lot of mile on it. Still have it, though not running at the moment due to other life distractions.

Cheers,