Topic: 1978 CB550K Carb Concerns

[romeyd]

Hi All,

I am new to this forum and in the past week enjoyed reading many posts which are really helpful.  I bought a Honda CB550 78 model a few weeks back as a project bike which on the surface looks ok (I will post some photos, the fuel tank looks like a 74/75 even though the bike is a 78).  I actually started it the other day for the first time and have really no idea when it was started previously.  It did not hold idle but I was just happy to hear it run.  I have since removed the carbs (PD46C) to give them a clean and noticed one main issue, corrosion.  Before I go ahead and buy a kit from http://www.cmsnl.com I want to know if someone can give me advice on the corrosion.  It seems as though the main jet housing although corroded does not have any play in it and the jet screws down well and tight.  The overall carbs look good although some rust visible on the throttle.  I will post some photos for reference.  I am also concerned that I do not have any original manual reference points for the carbs and perhaps someone can suggest these.

Thanks All,

Roman

[Toolmaker]

Its caused by ethanol in the gas. This is why alot of people ONLY run non-ethanol fuel in their bikes especially if they aren't going to be riding them for a little while. If I know I am going to be doing alot of riding, I will fill up with e-10 gas because its not gonna be in the carbs long enough to hurt it. You should have seen the massacre that happened inside the carbs of my 76. they were pitted up everywhere from the ethanol eating the aluminum over 10 years. Luckily they weren't too far gone and are still usable, but barely.

Best way to get that mess off is just to scrape it. Normally carb cleaner won't blast it off. I haven't found anything that will help cut it. Don't get too rough with the pilot jets or you will enlarge them and possibly cause more issues.

[harisuluv]

Does look pretty bad, but it might be ok, you will have to really inspect the bowl cavity and the brass float valve seat. 

When you get that white looking stuff, that is the final stage of gas evolution, long after the lacquer phase.  Often times it is hard as concrete.  Sometimes depending how thick it is, you can get a lot of it off with soda blasting.  But if it were me I would be very careful in doing so cause the metal is already very weakened and if you're not careful you will blast off more metal.

Just remember there will be threads showing, they aren't meant to screw down all the way, and doing so will cause major damage.  (seems like you already know this but just in case..)

[romeyd]

Thanks Toolmaker and harisuluv!!

Some parts inside the carb look nice and clean (i will post another couple of pics)...  1 Jet was completely blocked and one barley had any daylight when put into the light, some light scum in all the float bowls.  I did take a strong bristle toothbrush and rubbed some of the corrosion off but I do not want to blast it as I am worried about weakening the housing the main jet screws into which you guys mentioned.  Harisuluv, I have never done this type of work before even though I like using tools (and perhaps a little over confidant) so any insight is great..  I have just been reading a lot of posts through this forum one in particular called 1978 CB550K Carb Rebuild.  Just hoping to get a better understanding on the set point of the main jets or is it a trial and see how it runs scenario once cleaned and put back together.

Thanks again and look forward to posting my progress as I slowly make progress.

[ChopSticks]

Where do you get non ethanol gas from?!

[romeyd]

Hi Guys,

thought I would send an update on how my carb build has gone...  Very slowly I should add, not really spending a lot of time on the rebuild..  I finally rebuilt the PD46C carbs with out purchasing any parts for it at all..  I really did it on the cheap.  the reason for this was whilst I was cleaning the carbs I noticed all the slow jets blocked and 2 of the main jets blocked.  This made me think that if I can clean these parts I could get away with not buying anything. 
In the end I bought, fuel hose, spring clamps, grey spray paint, felt (to replace the felt seals). 
Once I put everything back together and tried starting the bike I found the fuel overflowing in all the fuel bowls, guess I did something wrong  
I removed the carbs again and reset the floats to 12.5mm (I think I had them around 14.5 before) from the middle of the float to the body whilst just sitting on the float needle.  I had the carbs on a slight angle doing this.  I connected the carbs back and this time I only had one Bowl leak and I slightly tapped it and it stops leaking..  This makes me think I might end up changing the needle float and perhaps the floats..  Someone could perhaps give me a tip there.  Once running I got the bike idling nice and am so happy the bike runs and the engine sounds ok...  First time I could hear the bike idle as I never heard it run before buying it.
The only problem at this stage is that I do not believe I placed enough tension on the chock spring as it does not draw the flaps closed.  I will post some photos online for people to see and am happy to share my experiences with any one.

[romeyd]

more pics

[romeyd]

more pics

[harisuluv]

The choke mechanism is a little weird, sounds like your spring isn't hooked up correctly.  Either that or your choke flaps are binding.  You can loosen the screws and see if that helps.

On a side note, what's going on with all the grit?  Looks like you used some pretty coarse/agressive blasting media.  Sand?  I think it was too much, especially with your already weakened metal.  If not the grit itself causing an uneven mating surface with the float valve, the pitting that aggressive media can have can also mess up the seat.

[romeyd]

Hi Harisuluv,

The method was fine plastic blast, not sand..  I knew someone at a metal fabrication/machinery company who let me use it who said it should be fine.  I tried everything to remove the corrosion from the pitting areas but struggled.  I soaked the parts again after and used an ultra sonic bath.  The pitting was always my concern from the beginning.  When you talk about the seat you mean the brass fitting the needle sits in?

[AlekStooge]

 "I am also concerned that I do not have any original manual reference points for the carbs and perhaps someone can suggest these."                                                                                                                 This might helphttp://forums.sohc4.net/index.php/topic,124332.0.html