Topic: my new bike... and some issues

[hondaryder]

Well, I recently purchased a 1978 CB550K from a guy I work with. It is my first motorcycle. He took pretty good care of it when he rode it but it had sat in his garage unused for the last 8 or 9 years. Today was my first day to work on it. I drained the old oil. It looked pretty clean but I wanted to get some fresh stuff in there. I installed a new battery in it. And I drained the old gas out of it. Unfortunately he didn't drain out the carb bowls before storing it. I was able to get it running. The problem is that it will only idle if the choke is pulled all the way out. I was able to keep it running with the choke pushed in half way if I gave it some throttle. Looks like I'm going to have to go through the carbs (as soon as i figure how to get the tank off).

Does anyone know of a place to get some carb kits for it at a halfway decent price? I have found a few places that have carb kits for the earlier 550s but not too many for the 78. Also, they wanted over $20/kit. Maybe I'm just being cheap, but that comes out to over $80 just for the kits. This bike must be the bastard child of the motorcycle world. I'm not having much luck finding airbox rubbers for it either.

Any help or direction would be greatly appreciated. Thanks.

[mlinder]

I just cleaned my carbs, that had gasoliine in them from oh, 2001 or so.
I didn't need to rebuild. Just cleaned em up real well. They work.

[hondaryder]

I'm afraid that by disassembling the carbs to clean them, I will damage the gaskets, which will mean that I will need to buy rebuild kits.

[333]

The gaskets are rubber o-rings, so damage might not be an issue.  I've always managed to do an overhaul without replacing these o-rings.  I've also had sucess without seperating the carbs from the rack.  This makes it possible to bypass trhe need to "bench sync" the carbs.  Don't get me wrong, you'll still have to syncronize them, but it may save you time

I once helped a friend out with a CB900 Custom.  The bowls were green.  I didn't think gas could turn green.  Then I realized it was water.

[physician]

i purchased rebuild parts from Honda for 60$ cdn to rebuild my old carbs. i basicly use the bowl oring, idle screw oring, and the float rubber valve.
so you may need only this, they can be bought separatly at the dealer.

and dont forget to remove the slow jets to clean them so you don't have to remove them 2 times like me....

congrats on the buy!
is it stoll stock?

[physician]

and which rubbers do you need? those between engine and carbs, od those between airbox and carbs? and which do you need? i can check if my parts bike can help you

[sandcastcb750]

My 1978 CB750 had the same problem. Only run on choke out all the way. My neighbor up the street has a 1977 CB750 with the same problem too. The 1977-78 CB750 (550s too?) have press fit slow jets and accellerator pumps to help out on the lean issues during the late seventies. They are not as friendly as the early 1970s type. I suggested to my neighbor to put earlier carbs on the bike (even though it requires different intake boots). Perhaps an early 1971-1975 CB500-550 carb set would be a good idea?

[hondaryder]

The bike is still basically stock. The guy I bought it from (original owner) had put a windjammer fairing , saddle bags, trunk and custom seat on it, but gave me all the orignal parts that needed to be removed to install the fairing. Also the rear shocks were replaced with adjustable units and the front shocks were modified to air shocks. Pretty clean bike overall.

So you guys think that I could probably disassemble the carbs and clean them without damaging the seals?

Oh, and I'm looking for the rubbers that go between the airbox and the carbs.

Thanks.

[liaudio]

75% of the time you should be able to reuse the gaskets.

[physician]

The bike is still basically stock. The guy I bought it from (original owner) had put a windjammer fairing , saddle bags, trunk and custom seat on it, but gave me all the orignal parts that needed to be removed to install the fairing. Also the rear shocks were replaced with adjustable units and the front shocks were modified to air shocks. Pretty clean bike overall.

So you guys think that I could probably disassemble the carbs and clean them without damaging the seals?

Oh, and I'm looking for the rubbers that go between the airbox and the carbs.

Thanks.

ok, i'll check to condition tomorrow while i'll be at the garage

[OldSchool_IsCool]

Pulling and cleaning the carbs is the best thing to do.  In the mean time, run a tank or two of gas with SeaFoam gas additive.  Mix it on the strong side.  It probably won't get your carbs perfect, but might help loosen things up for when you do the job right!

[hondaryder]

Actually, I have a strong gas/seafoam mixture in it right now. I'm going to mess around with it again a little tomorrow and see if it improved any. I'm sure I will still have to disassemble the carbs though. The old gas that came out looked like iced tea. Nasty brown tint.

[Jonesy]

My 1978 CB750 had the same problem. Only run on choke out all the way. My neighbor up the street has a 1977 CB750 with the same problem too. The 1977-78 CB750 (550s too?) have press fit slow jets and accellerator pumps to help out on the lean issues during the late seventies. They are not as friendly as the early 1970s type. I suggested to my neighbor to put earlier carbs on the bike (even though it requires different intake boots). Perhaps an early 1971-1975 CB500-550 carb set would be a good idea?

The later CB550's carbs did not use accelerator pumps. I can't remember if the idle jets are removable or not. At least the mains are the screw-in type, rather than the o-ringed oned held in with a spring clip.

If you have a stubby phillips screwdriver, you can remove the outer carb's float bowls and have a peek inside while they are still on the bike. Having this knowledge may help guide your decision on furhter carb work.

[physician]

idle jets are press in on 77-78 550. remove them with vise grip. be carefull not to be to hard on them, they are  not that strong

[needswork]

Yeah, what physician said. vice grips and a rag and the pilot jets will pull out. The main jets will screw out. Don't sweat the gaskets. These bikes are full of o rings anyway.