I ranthis on the KnN post from Bluebeard.

Hi: I'm trying to find answers to the same problem. 1978 CB550 k. I just put cone fillters on it and now it will move only with the choke half out but has clearly lost power and throtle response. I'm afraid to pass anything else on wheels. I assume there is now way too much air. I re-set the floats, and the external air jets and gotno change. Now it barely idles unless the choke is on and quits when I try to pull away from a stop. O_C

 

that is because there IS too much air flowing through the filters, and he needs larger internal jets in the carbs to compensate for the greater air flow. its STILL easier than putting the stock airbox back into that particular model. I remember that hell on my 75 550k. ugh.

 

thanks Hrricane:

Have I got this right? You said "larger jets" meaning repacing the existing ones with bigger jets? Adjusting them won't do it.

 

yes. internal jets though. is the bike running a stock or aftermarket exhaust? this also helps determine the need to rejet or no.

 

It has an after market 4 into 1.

The chrome is original but the actual silencer looks like a painted Thrush or similar auto type "rumbble pipe".
It came with the package and the bike has always performed well.
No hesitation from a stop, lot's of punch even in 4th gear. 5 ain't bad either. 125-130 KPH (75-80MPH) is no problem for short bursts.
Don't want to push the Old Crow.
Given the info I just got from the Keihin site, the jet change is a process of elimination with testing different diam., lengths, and tapers. Ouch!

My study of carb theory for the past few days is helping me understand the complexity of the problem. Wikipedia has some good stuff.

Hey.. I really appreiciateyour help on this.

 

I"m happy to contribute what I can to you. SOHC4.net is a wonderful resource for your bike.

Mine was a 75 with the 4:4 pipes on it, absolutely gorgeous and potent old girl. mine was completely stock, and the original airbox SUCKED to put in and remove. same for carbs. I nearly took up drinking I had to do it so often.

 

They must have done some changes by 78. It's not fun but I can't say I suffered doing it. In fact I'm putting the old one back. I'm missing way too much road time. Great weather here. I'll keep on the trail though. It's not over. I'm determined to solve this.
I'll check out SOHC4. Thanks for the lead.

I know this site is not really geared to old CBs but of all the onesI registered with you folks were the only ones to respond. The personal greeting from one of the moderators, the instant help, is very cool. I'll keep you posted on my progress.

Bye for now

John M

 

I"m glad to help keep another classic beauty from simply sitting. I sure know mine didnt sit for long when I got it. daily riding and I simply couldnt let her sit still, loved her WAY too much.