Topic: 1978 CB550K - Getting Acquainted w/ bike and have a 'tuning' problem

[Wharfcreek]

This is my first post as a new member.   So, please forgive me if I've erred in posting placement, however if this particular forum has guys on it the are familiar with 'race' tuning....then I'm hopeful they can steer me in the right direction.    I just purchase a 1978 550K that had been sitting for over 20 years.    It's prior owner had made an attempt to get it running and in so doing rather butchered on of the carbs.  There are some SERIOUS gouges in the throat of #2 carb body, and the slide has prey marks on either side at the openings.   In short, it's significantly damaged.   It also had the needle of the idle end of the idle mixture adjustment screw broken off and wedged into the opening.   However, I've managed to go through all 4 carbs, assured all have open passages, I replaced the idle mixture screw after removing the tiny tip, and I've successfully reinstalled them to the point where the bike now runs.    I did NOT replace the stock air box as I want to go with something like Uni Filters or just the cheap 'pods' on ebay.   As these are not CV type carbs, I was hopeful that I could use the 'cheap' stuff as I'm also on a pretty tight budget for this project bike.

So, let me get to the point:   The bike runs like crap!  Not only do I get a surging in the RPM ramp up, but it's slow and lacks the kind of 'pull' I feel it should have.   The engine seems to 'max out' at barely 7K and with a 9K redline there's clearly something wrong.   I might add that at idle the #2 cylinder has a intermittent 'hiccup' back through the intake which I blame on the messed up slide and the gouging internally.   But, at WOT I'm thinking this thing should still be able to ramp up smoothly........ UNLESS I have a 'tuning' problem.   To that end I turn to this forum and ask for some advice.    The bike is otherwise 'stock'...with it's original 4 into 4 pipes, and no mods anywhere.   In fact, it's a pretty clean machine, with only 11K on the ticker.   I live in Pasadena, MD and am literally on a 'creek' that is off the Chesapeake Bay........ so, 'sea level' is literally my tuning requirement.    With both dense air and no restriction from the stock air box, I'm hopeful that someone will tell me that everything is probably OK and I just need to put some AFs on it and it will probably run fine.   (PLease don't do that just because that's what I want to hear.....lol).   However, I'm thinking that 'jetting' may be an issue....AND.... there may be some other tuning tricks that I should learn in order to get this bike running properly.   BTW, I also swapped plugs around and believe them 'not' to be related to the problem.  But, I plan to replace them just for drill.   What I'm really wondering is 2 things:  1) What kind of Jetting / set-up is recommended for my circumstances here outside of Baltimore, MD.   And 2) should I be addressing anything with those low speed jets that seem to be pressed in to the carb body?   

I appreciate any help and advice I can get here.   I don't have any access to an exhaust analyzer....but my 'gut' is telling me I'm dealing with a 'lean' condition....and possible some badly out-of-sync carbs.    But....before I go spending too much more time 'guessing' about things, I figured I'd hit up the experts.   I was pleased to take the bike for a spin....and I think once running properly I'm going to really enjoy it.   My last 4-cyl bike was a CBR F/2 and a Suzuki GS750E.   That was 20 some years ago.   Since then I've had a fleet of Harleys and another Fleet of old Yamaha XS650s.    Down to 1 HD, but still have several XS650 bikes....which have been my real love since the mid '70s.   This 550 could change that!

Thanks for the consideration!!     Tom D.

[turboguzzi]

if the motor is not  hi performance tuned then you just need to restore it to original tune. ignition, jets, cleareances, etc. download the manual and start checking. messed up carbs just add a hard to judge variable to all this.

if the PO used a screwdriver to free a stuck slide and bent the edge, the carbs will not open fully, could be simply filed flat if money is an issue and its not too baddly mangled

youll get more help in the general forum rather than here IMHO, not because we are snobs in hipo (well some of us are ), the general forum has way more traffic and troubleshooters ready to give good advice for stock machines.

good luck

[Wharfcreek]

TG, the damage to the slide is more like teeth marks along the bottom edges.  It's not really bent, just gouged up in such a way that it now has a rough and scored surface at the bottom edge....so were it to close completely the cuts in it would leak.   It's also very rough along those edges, so the air flow is affected.   I've got quite a bit of 'carb' experience.....and this damage is minimal imho but still enough that it could be the source of the popping back through the intake.   I doubt it's the source for the poor overall running.

You mention 'stock' specs......and in reality that's where it is right now other than no air-box.   Without the air box I'm sure it's getting some additional air causing it to lean out some.   However, I'm also concerned that who ever was 'in' to this in the past may have messed up the 'sync' aspect of the carbs.   I noted that even when the throttle stop screw was unscrewed all the way to the point where it no longer contacted the throttle, the carb slides still did not 'bottom out' as I expected they should have.   With no experience with these carbs per se' I really wasn't sure if this was 'normal' or not.    But, since the bike now doesn't want to idle under about 3K, I suspect there's another problem there.    The long and short of it is that the carbs are going to have to come off again, and I'm going to have to take another shot at going over them.   I managed to find a used but good slide off ebay for a whopping $11.....so I'll try to swap that into the bad carb position....but there's still the carb itself to deal with....and the floor of that carb was also damaged just behind the idle bleed.   

I appreciate your suggestion about taking the question to the general forum...however I came here so as to avoid 50 responses from people with good intentions but perhaps lacking the expertise to address the issue properly and with the background and experience to do so.    I figured one or two 'good' answers was worth 10 or 20 'not so good' ones.   Again, like you....not being 'snob'ish, but just trying to be realistic.   I deal on several other forums.....and after a while you get the drift.   There are places within them where you can get some really good help and information....but other places where you can get lost in the minutia.   Thus my choice to come to this forum first.   I figured 'race' tuners would know their stuff.   

Anyway......... again, thanks for the response.   Hopefully I'll get a bit more from others.   I'd like to know more about the carbs themselves; ie what they're considered as being.   Is there some proper nomenclature for their type?   I'm used to dealing with either the CV carbs on HDs, or the Flat Slide conversions.....or my Kehins CVs on the XS650s bikes.    So, these mechanical 'lever-operated' round slide jobs are new to me.   Nice....but still 'different'.     Tom D.

[turboguzzi]

pics or it didnt happen..