Topic: Possible parts hoarding-compatible parts swapping 77-78 550s

[b1jackson]

I have a lead on a 78 parts bike with a bad engine and the easily swappable parts between a 77 and 78.  Are main parts like starters, carbs, etc. compatible.  I imagine only a few cosmetic changes between these years but can't locate any info on specifics.  For $100, would it be worthwhile as these bikes are abit scarce in my area.  Mufflers are toast and so is seat.

[Mantree]

For $100 I'd say it's worth it I just got the carbs

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[DaveBarbier]

Very similar. Carbs are different. PD46c in the '78, PD46a in the '77. They should be able to work though with proper jetting. I'm pretty certain spacing is the same.

$100, I'd get it even if most parts weren't compatible.

[Mantree]

Very similar. Carbs are different. PD46c in the '78, PD46a in the '77. They should be able to work though with proper jetting. I'm pretty certain spacing is the same.

$100, I'd get it even if most parts weren't compatible.

They will fit the engine but not the airbox

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[DaveBarbier]

Very similar. Carbs are different. PD46c in the '78, PD46a in the '77. They should be able to work though with proper jetting. I'm pretty certain spacing is the same.

$100, I'd get it even if most parts weren't compatible.

They will fit the engine but not the airbox

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Dang, thanks a bummer

[Deltarider]

I imagine only a few cosmetic changes between these years but can't locate any info on specifics.

Why not consult the parts list? http://www.honda4fun.com/pdf_parts_list/pdf_spac500-550/CB500-550_K3-K4.pdf On p.72-3 I see no indication airbox differs.

[b1jackson]

Awesome.  Thank you. 

[Mantree]

Very similar. Carbs are different. PD46c in the '78, PD46a in the '77. They should be able to work though with proper jetting. I'm pretty certain spacing is the same.

$100, I'd get it even if most parts weren't compatible.

They will fit the engine but not the airbox

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Dang, thanks a bummer

I had a 72 with late models carbs that had pods because the carbs had a larger diameter on the intake side

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[Deltarider]

I had a 72 with late models carbs that had pods because the carbs had a larger diameter on the intake side

Yes, but his is a CB550K3 and CB550K4 parts are compatible.

[Lostboy Steve]

Ill take the bad engine. 

[Bankerdanny]

I had a 72 with late models carbs that had pods because the carbs had a larger diameter on the intake side

The airbox on 74-76 550's is different than the 77-78. The '78 carbs are externally identical to the '77 carbs and should swap right in. You shouldn't even need to change the jets, although in general the 77-78 bikes were tuned a bit leaner than the earlier bikes in response to changes in emissions requirements.

[Mantree]

By bad I didn't realize we were talking 550s

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[Lostboy Steve]

I had a 72 with late models carbs that had pods because the carbs had a larger diameter on the intake side

The airbox on 74-76 550's is different than the 77-78. The '78 carbs are externally identical to the '77 carbs and should swap right in. You shouldn't even need to change the jets, although in general the 77-78 bikes were tuned a bit leaner than the earlier bikes in response to changes in emissions requirements.

I was able to use the airbox cover off of a 75 on my 77 though. It isn't perfect but it's better than not having one.


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[Bankerdanny]

Its the plenum that connects to the carbs that is different. The spacing and the connectors. The actual filter housing is probably adaptable.