Topic: what does your '77 550F airbox cover look like?

[d_benet]

I've got a '77 550 F that I just got running (kind of rough); it sat with the PO for 20+ years. its got good spark on all 4, valve clearance ok and I just went through the fuel system pretty well. POR-15'd the tank, cleaned and put new rubber in the carbs, checked float heights etc. I just put new rubber boots between the air box and carbs, and the other sides all look good. I think it needs a carb sync but its missing the airbox cover. Will this severely effect performance? I just put some new plugs in it because it seems like its running rich which doesn't make any sense if the airbox lid matters. The new paper air filter I put in seals up pretty well with the opening of the airbox. Should I even bother trying to synch carbs without the lid on the airbox? If not, could someone please post some pics of theirs so I can fab one (can't find a replacement)?

[Frostyboy]

Mine is '76 but I think will be the same? The snorkel on the top is actually rubber.
[Edit] I can't see the presence of the lid having any effect in synching the carbs.

[d_benet]

Great, thanks. In the parts schematic I couldn't tell what that big slot was. Now that I see its a snorkel, I can't imagine that it could change the air flow that much. I guess I'll go ahead with the carb synch.

[TwoTired]

It won't change the carb sync.  But, it could have an effect on fuel mixture.

You do have the leaf spring that presses the filter element forward, no?

[d_benet]

Yes, I have the spring pushing the element forward and seems pretty sealed. If there is an effect on the fuel mixture this can be corrected by air screw adjustments once I've identified rich vs. lean, correct? should this be done before attempting a carb synch?

[TwoTired]

The air screw mostly effects mixture up to 1/4 throttle.  After that, its the slide needles and finally the main.
If you get lean mixtures at mid to full throttle, it's unlikely the air screw is going to help.  More critical is the stock exhaust back pressure.  If you have a more open exhaust on it, the main the slide needles will have to be changed/adjusted.

The carb sync is done after the rest of the full tune up items are performed.  The air screw adjustment can be done last.

Cheers,

[d_benet]

TwoTired - exhaust is stock 4-1. whole bike is stock (I think) with 069A K-1 carbs w/ #38 slow jets and #98 mains, original airbox minus cover etc. I reset all airscrews 1 1/2 turns out when I cleaned the carbs. Idle to 1/4 throttle are where I'm experiencing symptoms; some blubbering and occasional misfiring especially after releasing throttle, occasional high idle (only when bike is warm) and most significant is a big hiccup in power when accelerating from stop (first 3K). Also, bike stalls every time I bring it to rest at the top of our steep driveway (1st gear climb) after a long ride. Bike feels and sounds great on the open road, its just around town in traffic that's a little worrisome. I've done most of a full tune-up so far, I guess I should finish with the cam chain and timing before further carb synch. I've come up short on a search for a good old thread describing proper procedure for a bench synch. It seems some people use a paper clip, others a drill bit...I would appreciate a point in the right direction as this is my first. Also, I just borrowed a buddies home-made manometer...I'm pretty excited to finally put some miles on this thing. Thanks again for the help.

[TwoTired]

If you have manometers, you don't need to bench sync.   The bench sync method I prefer is the "light method".

http://forums.sohc4.net/index.php?topic=13937.msg12199#msg12199


I'll take your word for it that it has the stock 4 into 1 system.  It's just that aftermarket 4 into 1s share the same moniker but have very different back pressure characteristics (and carb tuning requirements).

...with 069A K-1 carbs

All the F models had 069a carbs from the factory.  I've not heard them ever described as K-1 carbs, though.  To me, a CB550 K-1 would have 022a carbs with a different internal set up from your description.

Just curious.  Why not use the stock filter cover with your otherwise stock bike?

Do finish the tune-up and vacuum sync the carbs.  Let us know if you find vacuum imbalance among carbs, as that it definitely a possible cause for idle inconsistency/uncertainty.

Cheers,

[d_benet]

You're probably right. Exhaust is 4-1 but could very well be aftermarket...I'm not sure. And I'm probably mistaken about what the K stands for, I simply meant it has the original Keihin - Type 1 carbs. Had a nice ride to work this morning...until I ran out of gas. I got only a little over 100 miles on that tank so less than 35 mpg and I guess the whole reserve setting isn't going to work on my petcock. I was a little relieved (and embarrassed) to discover it was out of fuel and not anything more serious as this is really the first week I've had the bike out of the garage. I guess I've got my work cut out for me between, the tune-up, carb synch and now the ever elusive electrical on the headlight out. A couple questions before I get underway; in your response to "I made a youtube video of my carb synch" you talk about selecting a carb to reference adjustments on the others. which one do you pick and why? also does it matter what its adjusted to initially? ie if no bench synch is required before going to the manometers how do you know the slide is adjusted properly to use a reference for the others? one last thing...the manometer I'm borrowing is "home-made" and therefore has no damper valve; should I just try and synch as close to idle as possible? thanks again in advance TT.

[TwoTired]

You're probably right. Exhaust is 4-1 but could very well be aftermarket...I'm not sure.

Post a pic. I can tell you if it is the stock type.  Now aftermarket types were ever made like them.

A couple questions before I get underway; in your response to "I made a youtube video of my carb synch" you talk about selecting a carb to reference adjustments on the others. which one do you pick and why?

I'll pick the the one with the highest vacuum reading.  That's the one that should be the most closed.

With the early carbs there is a possibility of skewing all the slide adjustments so the idle knob becomes ineffective.  If you pick the one most closed, and adjust other to it, that really should never happen.

also does it matter what its adjusted to initially? ie if no bench synch is required before going to the manometers how do you know the slide is adjusted properly to use a reference for the others?

Not on a running bike with an effective main idle knob.  But, you just need to make them all equal.  Aside from running out of adjustment travel, there is no correct individual setting, other than the same are the other three.

one last thing...the manometer I'm borrowing is "home-made" and therefore has no damper valve; should I just try and synch as close to idle as possible? thanks again in advance TT.

Idle is the most sensitive slide setting.  It is also where the intake pulses are farthest apart, which makes the damper so useful.   
Hard to comment on a "home made" unit I've never seen.
Just make the display "signature" the same for each carb, I'd guess.  That's the goal for all the other manometer sets I've encountered.

Cheers,