Topic: Airbox/Lack of power?

[Super Sport 550]

I have been working on a 1977 CB550 Super Sport that I bought 3 days ago at a junkyard. I have the bike running now, but I've got some performance problems to work out.

The bike sounds good and doesn't smoke. I've tightened the cam chain, set the timing, point gap, and dwell. I also put in new spark plugs (I think they were D7ES, but can't remember for sure) and cleaned out the carbs.

I have started to run it up and down the drive way, but the bike doesn't have any power. To get moving I have to rev it to around 5500 rpm and s-l-o-w-l-y let out the clutch. Once moving, it will only reach about 3500-4000 rpm. It feels like it has a rev limiter. I have tried different throttle settings and it doesn't seem to make any difference. I have also found that if I open the throttle in neutral it won't go over about 6000 rpm, but doesn't seem to misfire.

I do not have the air box connected. Stupid question: Will having the airbox disconnected make that much difference?

Thanks!

[Lumbee]

Yes, not having the air box on will make a huge difference.  The airbox acts as a restricter to the amount of air entering the engine/carbs.  With the airbox off you will have an extreamly lean air/fuel mix.  Thats why it won't rev over 5K rpm.  Put the airbox on and see how it runs...

[eldar]

Put in the filter too! There was a person who put on their box then said there was no difference. We finally found out he did not put in the filter! Big difference then.

[Lumbee]

   thats a new one...havn't heard of anybody running the airbox with no filter...but that would give you to much air...

[dusterdude]

at those speeds,if you will,in a driveway,i cant imagine not having the airbox/filter would cause those problems.

[TwoTired]

Since you're dealing with  unknowns...

1. Check to make sure that all the throttle slides are opening fully and in unison.
2. Are all cylinders firing?  Do the head pipes get evenly hot both at idle and with the throttle opened?
3. Are you certain the slow jets and slow ciruits were clean and flowing freely?  These are pressed in and difficult to clean without removal.
4. Describe the carb deposits you found while cleaning.
5. Do you get better RPMs with the choke partially applied?
6. You are going to notice a difference with an air filter installed.  Don't tune carbs with out it.

Cheers,

[Super Sport 550]

Thanks for all the responses!

I haven't tried it with the airbox hooked up yet. I'm going to have to buy an air filter. There wasn't one in the airbox when I got the bike. I guess I'll have to get one. I hope they are not too expensive.

All throttles are opening properly. They are synchronized fairly well, it seems. The bike will sit there and idle at 1000 rpm and doesn't sound like it is going to break in half while doing it.

All cylinders are firing. The pipes all get good and hot. Slow jets are clean. I cleaned them when I bought the bike, and they flow well.

Carb deposits were varnish on three of the carbs, heavy corrosion on the fourth. The carb bowl on the fourth carb was filled with a wet, whitish substance with about the consistency of cottage cheese. I cleaned it out good, though, and all the jets are clear as well as the needle/seat. All the carbs are getting fuel.

It didn't seem to perform better with the choke partly applied, but I didn't test it really well that way.

One other thing I guess I should mention. The battery I have been running it off of is pretty weak. I think that may be having some effect on performance.

at those speeds,if you will,in a driveway,i cant imagine not having the airbox/filter would cause those problems.

My driveway is several hundred feet long. I had it up to about 30 mph on it, but that is downright as fast as it will go right now. 

[Stevearino]

Before you go too far, check the condition of the gaskets around your jets.  If these dont seal well, you will be fighting a moving target when you try to tune it further.  There is no reason to ask how I know this.

[VitaminCB550]

Does the bike pop and spatter? I forgot to put the air filter back in one day and my bike popped and spattered all over the place!

[cbfreaky750]

dude check your ignition timing something from a junkyard could easily be way off so it makes no power it will run and fire but just have nothing at all for power

[Super Sport 550]

Question: Inside the airbox I found a gold colored metal plate with a bunch of holes in it and a bunch of dirt on it. I also found another part which was similar in shape, but had, as I recall, something sticking up on it and some sort of rubber piece on it. I assume these have something to do with either the air cleaner mounting or the PCV system (or both). What do these do and how are they supposed to be positioned? Keep in mind that I have never seen how the airbox looks with the air filter installed...

Does the bike pop and spatter? I forgot to put the air filter back in one day and my bike popped and spattered all over the place!

Occasionally. I will get the airbox and filter hooked up and I am hoping it will run better then.

dude check your ignition timing something from a junkyard could easily be way off so it makes no power it will run and fire but just have nothing at all for power

I checked and adjusted the ignition timing and dwell when I got the bike. Both sets of points are properly adjusted.


Thanks!