Topic: New 550 looks like it's gonna be a handful

[Zodo]

Hi folks,

A few weeks ago, I purchased a cafe'd out 1977 Cb550k. It has pods, and as I have recently noticed, a PD50B carb from a CB650. It had a few immediate issues, such as a slightly rough idle and sticky throttle, but it seemed to start up fine, and did great on the freeway home. When I got off the freeway, it was bogging somewhat, and had to be coaxed when applying throttle when starting from a stop, lest it stall out. I replaced the battery and throttle cables, which were new territory for me as someone who has never really worked on motorcycles before.

Unfortunately, the bike has proven itself to be virtually unridable in its current state. I can start it up with choke, and it will idle, missing the occasional beat. Occasionally as it warms up, the revs will climb for 10-15 seconds, then drop back down again. As soon as I take it off the center stand and start to leave my driveway (onto a slight hill) it begins to slow and struggle. Applying any throttle causes a gurgle and stall. On the rare occasions when I manage to get it going above 3k or so, it runs like a bat out of hell...until the rpms drop again.

After the bike has been idling for a while, the plugs look like it has been running lean. Choke helps, but doesn't fix the struggling idle. My initial suspicion is clogged slow jets, but the element involving worse performance while on a hill makes me wonder if the float height is way off, too. (everything I know about carbs I have picked up from this forum over the last few days, thanks!)

I haven't yet pulled the carb for cleaning, but I'm curious if anyone has any thought or suggestions that might help a newbie like me.

[scunny]

certainly sounds like clogged slow jets. they are pressed in but need to be pulled out to clean properly. also check your ignition advancer, make sure its rotating freely.

[dave500]

are they pods i can see?

[Zodo]

Yes, it has pods (I'm not sure of the manufacturer). I'll snap a closer pic of them with the side covers off tomorrow. I might even record some audio/video, just in case one of the geniuses here can diagnose any other issues based on the sound. The motor also does sound somewhat 'clattery', though I don't have any frame of reference.

Thanks for the confirmation of my thoughts/worries, scunny. Good to know that I'm not totally off base.

[dave500]

use the search function of this site and search pods.

[Zodo]

Yep, I've read thoroughly about the problems pods cause...if I'd had the option to switch back to the stock air box when I bought the bike I would've. At this point, I'm just going to try to wrestle it into rideability. I'll check back in once I've gone over the carbs. Thanks.

[dave500]

you never know what has been done a lot of the time,,so to be sure you have to double check things,,if you have time and some tools remove and clean out the tank,and the tap and any filters,if your getting crud in the carbs this is where it comes from,clean the carbs by taking them off the bike,you dont have to pull them off the rack,if you have an air compressor good,,blow any and all passages every which way with all the brass removed,set the floats perfectly,then see how it rides,,then start fiddling with your jetting,while its apart note the jet needle position and jet sizes.

[Ryan66]

certainly sounds like clogged slow jets. they are pressed in but need to be pulled out to clean properly. also check your ignition advancer, make sure its rotating freely.

By slow jets you mean pilot jets right? my pilots in my 550 are threaded. maybe im missing something?

[Bankerdanny]

You might want to keep your eyes open for a set of the correct carbs. They turn up now and then for a couple hundred dollars, it might be a worthwhile change, plus you can sell your 650 carbs to get the money back.

Fueling can be a fiddly thing, having the correct carbs will likley make your life much easier (although I would ditch the pods too)

[Zodo]

Well, I had the carbs apart last night. Idle jets were clear, but I cleaned em out anyway. Double checked the float height, and all were in the 13mm range that is correct for this carb.

Strange thing is, it now seems to run worse than before. I get intermittent single *pfft* noises from the carb. The idle is erratic, and applying throttle results in a "bogging" rattley sound before a delayed rev.

Even after warming up, applying choke helped it, so it must be running lean (waiting for it to cool down before pulling the plugs to be sure).

I imagine that I can probably improve things by adjusting the mixture screws...I did my best to put them back where they were when putting things back together. But can I safely change them without having a set of sync gauges?

At this point I would just love to get it going well enough to ride it to a nearby shop so that I can have a variety of things done on it (fork seals, rear drum return spring, assorted leaky seals, carb tuning...obviously).

Any idea as to the reason for the nasty carb noises?

[cameron]

Dave hinted at it.. but How is your fuel delivery?

I would start from the beginning.
Is there rust in the tank?
Does your petcock flow freely?
Are there fuel filters, in the tank or on the lines? If so, are they clean?
Do your LINES flow freely?
and FInally, does fuel pass the rails into the carbs evenly? (drop the bowls and you should be able to see.)

Any problems in your fuel delivery system can lean up your mixture. So I would check all that before I got to carb-fiddling.

[dave500]

did you note the jet sizes?

[Zodo]

The idle jets were 35s...forgot to note the size of the mains.

From what I can see inside the tank, it is very clean...the PO said he'd had it cleaned up. There isn't an inline filter. I do wonder if the bowls are filling evenly...the pfft sound it was making almost reminded me of slurping from an empty glass with a straw.

The odd bit is that it seems far happier when it gets up to higher RPMs...dunno how that would fit in to all of this. The couple of times I was able to ride it, it did just fine as long as I kept it above 3k rpm or so. It's just idle and the transition from idle to mains that seems to have trouble.

As far as the process of checking the levels in the bowls...I just turn off the petcock, then unscrew them with the carbs still attached to the bike, and hold them as level as I can while I look?

Thanks much for the ideas, all.

[dave500]

those pd type carbs are fairly lean set from the factory,pods will make it seem leaner,sure your slow jet wasnt 38?

[Zodo]

It's entirely possible that they were 38s...small text. 

[dave500]

find the standard airbox for it.

[Duanob]

You might want to keep your eyes open for a set of the correct carbs. They turn up now and then for a couple hundred dollars, it might be a worthwhile change, plus you can sell your 650 carbs to get the money back.

Fueling can be a fiddly thing, having the correct carbs will likley make your life much easier (although I would ditch the pods too)

That's what I was going to suggest. I bought a set that had never been opened up at a swap meet for $20! A good cleaning and a new gasket set for $60 and I had a nice set of carbs all bone stock. I wouldn't spend a bunch on someone else's "rebuilt" carbs because you may end up doing that again yourself. Also you will have to rejet to compensate for the pods and 4 into 1 exhaust, you might as well start from scratch so you know what you have.

Also it sounds like a vacuum leak the way you're describing the way your bike runs. So off with the carbs and intakes. All new o-rings will fix a lot of carb probelms. Check the intake boots for cracks.