Topic: 1977 cb550K project - Tachometer

[bryanj]

I got several spare in UK but postage would be a killer

[Bankerdanny]

Finding a float bowl by itself is unlikely, but you might find an individual carb. While the bowls from any PD46 carb will fit, the drain screws for the 1-2 carbs face a different direction than the 3-4 so if you put the bowl from a 4 carb on a 2 carb you will have a hard time getting to the screw.

This would be a minor issue though, since needing to drain the carbs is very rare.

Are you sure the crack is the bowl and not the overflow tube (the brass tube in the middle of the picture)? I had a cracked tube and didn't see it until I looked very hard. I used JB weld to fix it. I only kept the bike for a few months after the repair, so I can't speak to the long term success, but while I had it the carb never leaked again.

If it is actually the bowl you could also have it micro-welded. There is a guy on the forum who does it and I don't think the cost would be huge, most likely less than buying a complete carb just to get the bowl.

So it's your call. Find a bowl or a really damaged parts carb you can get the bowl from, JB Weld (think of this as a temp repair while you look for a replacement), or having the crack welded.

[Seattle_Fauxpster]

So I reinstalled the carbs with the new bowl that I got (thanks a million harisuluv). They are definitely clean (jets are clear, in fact I don't even think they needed clearing, but cleared them I did), no leaks, great vacuum. However I still can't get the bike to start. Really I'm still experiencing the same symptoms

1. When I try to start the bike, with the choke fully out, I'm definitely getting something, but it sputters out after a couple of seconds. If I try to give it any throttle it immediately dies (it doesn't even sputter for a bit).

(It's worth noting that with the choke in I get nada)

If anything it seems worse, the sputtering is weaker, and it's dead with any throttle. These symptoms might be distracting, my question is this: What next?

I think the spark plugs are sparking properly (looks good when I ground them on the bike), I haven't really looked at the points. Does anybody have any really obvious notion of what this is? Otherwise I'm going to be banging around in the dark, maybe go get a salvaged ignition coil and see if the spark increases in strength (I can't tell if the spark I'm getting is strong or not).

Any thoughts will be greatly appreciated.

[motosan]

just to get some basics covered....did you check if all carbs are at factory spec?  (jet sizes, pilot screw turns, etc)?  also other basic things like tappet clearance, point gap?  any old gaskets or rubber boots leaking?  PD46 carbs have pressed-in slow jets, are they in all the way?

[Tews19]

I have 2 float bowls in interested,.... Send PM if you need still

[Seattle_Fauxpster]

just to get some basics covered....did you check if all carbs are at factory spec?  (jet sizes, pilot screw turns, etc)?  also other basic things like tappet clearance, point gap?  any old gaskets or rubber boots leaking?  PD46 carbs have pressed-in slow jets, are they in all the way?

The carbs are at factory spec, and I ordered all new gaskets for it. The jets are all fine and definitely in all the way. I haven't done the tappet or point gaps yet, could they really be to blame this badly thought?

[Seattle_Fauxpster]

I have 2 float bowls in interested,.... Send PM if you need still

Thanks for the offer, but I already got a replacement bowl and it's working well.

[Seattle_Fauxpster]

Contact http://forums.sohc4.net/index.php?action=profile;u=16522
He will be able to help I think.
Ken

Out of curiosity....wouldn't JB Weld work to fill the crack?  That might be a possible cheap fix...maybe...

I ended up getting a new one, but good call.

[InTheStreet]

just to get some basics covered....did you check if all carbs are at factory spec?  (jet sizes, pilot screw turns, etc)?  also other basic things like tappet clearance, point gap?  any old gaskets or rubber boots leaking?  PD46 carbs have pressed-in slow jets, are they in all the way?

The carbs are at factory spec, and I ordered all new gaskets for it. The jets are all fine and definitely in all the way. I haven't done the tappet or point gaps yet, could they really be to blame this badly thought?

Yes.  The points play a major role in your ignition, without which your fuel won't burn.  Your tappet adjustment plays an important role in the opening and closing of your valves, which let the fuel and air in and out of the engine.  If they were insanely loose, I guess your valves could just not open, if they are too tight, you can burn a valve.

I spent weeks messing with my carbs when I got mine.  Just couldn't seem to get them right.  I would tell my dad on the phone many miles away that the bike was pretty slow, but was fun.  He would say, adjust your points.  Finally, it got to the point that the thing wouldn't even pull itself from a stop without major clutch slipping.  Turned out, the 550 was not slow, and I should have just adjusted my points the first day I had the bike, like my dad said.

It only takes like 10 minutes if you know where your feeler gauge is.  It is way simpler than trying to tune a carb on a non-running bike.  Check your points for mountains and valleys.  I struggled with mine for a week this year before learning my condensers were bad.  The mountains and valleys on the surface of the points indicate this. (I learned later...)

[Seattle_Fauxpster]

Yes.  The points play a major role in your ignition, without which your fuel won't burn.  Your tappet adjustment plays an important role in the opening and closing of your valves, which let the fuel and air in and out of the engine.  If they were insanely loose, I guess your valves could just not open, if they are too tight, you can burn a valve.

Alright, my next move is the tappet and the points.

[motosan]

it might be a bit tough to hear but here is one of the things setting points wrong could do.

Setting up your points on a CB750A

22:00 mark - running with points set wrong
26:30 mark - running with correct setting

watch everything before 22min mark for a wonderful and exciting narratives by this gentleman who would never remind you of moonshiners.

[Seattle_Fauxpster]

Thanks for everybody's help!

Here's a summary of what I've done since I last posted:
1. I decided to wait on the points plate (I actually opened it up and it was pristine and in great working order), and the tappet clearance (because I started to doubt these were problems and I was right). Even though the spark on the old plugs looked fine I realized that they looked too black and fouled to be good so I replaced them.
2. I also discovered that my floats were upside down so I fixed that

With these two fixes my bike started great with the choke out and once warm started with no choke.

I had one remaining problem though, and that is that I was getting pops in my muffler. I decided to make sure the fuel mixture screws were turned to spec, and sure enough one of them wasn't (my bad). Now that the fuel mix screws are good I get no popping and the bike runs great (I think).

Remaining Problem:
I have one remaining problem that I think will be easy to fix. It was low on my list, but now it's high, because I want to set my bike's idle to be appropriate. My tachometer isn't working. I took the cable off and discovered that the needle/plate thingy that comes out of the engine is snapped almost flush to its base (the remainder of the needle/plate thingy is actually in the socket that attaches to the cable). I have three questions:
1. What is this needle/plate thing called (I will try to post a pic after work if nobody knows what I'm talking about)?
2. Is there a possibility of fixing it with bondo or welding (doubtful)?
3. Where can I order a replacement and how do I replace it?