Topic: CB550 Bench Synch Question

[sniper1]

I am about to tear into the carbs on my '75 CB550. I have read numerous threads on it, and everyone talks about the 1/8" drill bit method. Question is: Where does the 1/8" drill bit go? I could not find a good pic of the process or anything specific to the 550 carbs.

If anyone knows of a good thread on the subject, please let me know.


Thanks in advance.

[luap]

the drill bit goes under the slide an then use I believe number 2 as your guide an set from there

[Dimitri13]

The drill bit goes in the intake side vvv



The manifold side should look like this when you're done (a tiny gap) vvv

[sniper1]

Dimitri,
So the drill bit goes in under the slide on the #2 Carb? Then what?  So how do you adjust so that once it (the drill bit) is removed, it doesn't move back down?

I notice in your pic that the slide on #3 is higher than the others? Any reason for this?

[sniper1]

OK, so I tore the carbs apart (or at least as far as I wanted to go tonight). Here was what I found. All of the slow jets were clogged up, 2 of the main jets were clogged. the rubber tube between #1 & #2 had a split in it, and the PO had the float in the #4 carb in upside down! No wonder I couldn't get this thing to synch up.

So questions:
1. I have not taken the top of the carbs apart to get at the main needle, Is it really neccessary?

2. What parts need to be removed in order to dunk in carb cleaner bucket?

3. Can I just spray carb cleaner inside everything and blow out with air compressor?

4. I hate to take apart any further than I need to, but how far should I go based on what I have found?

Below is a pic of the rubber tube that is split, will any rubber tube work for replacement?

Thanks again.

[Dimitri13]

Sniper, you need to get a manual. At the top of the Bikes forum, there's a link to all the manuals. In the manuals it will show you how you go about adjusting the slide height.

As for your first question, you just do the drill bit method for all the carbs. When you're syncing with the gauges, you'll generally want to use #2 as the "target carb" (you want to get all the other carbs the same as #2), because it doesn't really adjust.

For the second question, I didn't have the carbs bench synced at the time, so it was out of whack.

For your second set of questions:

1. Yes. Make sure you remove the emulsion tube as well and clean that.
2. All the rubber bits, and the felt washers on the bore of the slide shaft.
3. You can do that as well. The best method is to use an ultrasonic cleaner. Whatever method you chose, be SURE to blow out EVERY passage and ensure they're clear, unless you want to continue having problems and having to clean them again.
4. All the way.

Replace that rubber tube with a fuel-resistant tube.

[Spanner 1]

For bench sync., I really like TwoTired's flashlight method... no drill bits required...
Simply shine a small flashlight into each carb throat from the motor side and adjust each slide until you can just see light thru' under the slide. Tighten the locknut. Do the next one. Make sure the idle adj. screw is set 1/2 way on it's range first, before above work.
O.K.... if you have the later type carbs ( #2 carb not adjustable ), then use the main idle adj. screw to get light on #2 carb. Don't touch the idle screw after that and use the carb top adjusters on the other 3 carbs... good luck!

[sniper1]

Thanks Luap, Spanner & Dimitri. Yesterday, I was able to get everything sorted out on the carbs, and now have very smooth operation. I think I have everything right and am now waiting on a carb boot that had a tear in it. I ordered a set from David Silver Spares (they don't sell individuals) so I will have some spares just in case. Hopefully, it will run good now.