Topic: '77 CB550 Over revving (Carb issues)

[ATZ]

The choke is at the bars, it's a 550k with pd style carbs, the airbox is stock and the exhaust is not. Its a four into one- not sure what kind- it has black header pipes and a chrome muffler.

[TwoTired]

#48 pilot jet is just plain too frickin big.
What float height have you set for your carbs.  14.5 or 12.5mm?  I'd recommend 14.5mm and either #38 or #42 pilot jets.

How old is your air filter?  Either get a brand new one from Honda or use the UNI, NU-4055.  For the latter, get the UNI service kit for it, too.

For the exhaust change, raise the slide needles, 4th clip position from top of needle, and go ahead and use the #98 mains.
Vacuum synch the carbs.

Put in new clean D7EA plugs after engine warm up and at the test track start position.  Start and use full acceleration up to top speed. Hit the kill switch and, pull in the clutch and bring the bike to a stop.  Pull all the plugs and take pictures of them to post here.

Cheers,

[ATZ]

I'll put the stock 42's back in and do that plug chop your talking about. The air filter is pretty new

[ATZ]

So I tried the 98 mains and raised the needles to the fourth notch. I also put in a new battery, (the old one lost amperage) and new plugs. The bike won't start without the choke pulled and it won't idle either.
Judging by the choke I would say I need to go bigger with the mains. I have sizes 105, 108, 110, 115 and 120. What size should I go next? Probably just 105?
I couldn't do a full plug chop but I attached a pic of the plugs anyway. I also have video of the bike. The video shows the backfires and stutters of the engine. It also shows the revs getting stuck at 3k after revved up a bit. video: http://screencast.com/t/PWmzp27fy

[Scott S]

 Plugs don't look that bad but....MAN! I hope that's crappy sound quality on the video. That bike sounds like sh!t ! Are you SURE the cam chain and valves are adjusted? Did you at least bench sync the carbs? How much of an opening did you leave on the slides? Maybe you need to open the idle screw and check for air leaks again.

[ATZ]

The bike does sound like #$%*! I know the cam chain is adjusted right, I'm going to go through the valves again. I benched synced the carbs the best I could leaving a very small amount of space open under the slides. And I have check for airleaks a ton

[ATZ]

I need some help here guys, I'm really out of ideas, I put in the 105s and there wasn't much change, I'm just really running out of ideas. I checked out the forum about jetting PD carbs and I'm thinking maybe the float height could be a factor. The throttle is so inconsistent and can't even keep the bike idling. I'm looking for a stock exhaust system just to get rid of my issues but I can't find even a somewhat affordable one. Other wise I might be defeated by this thing and just cut my loses and sell it.

Any other suggestions? Anyone know where I can get a stock exhaust?