Topic: CB550K3 PD46A Carburetor Intake Manifolds

[cocinero196]

Hi, would CB550 PD46A Carburetor Intake Manifolds work with a CB500 (627B) carburetor?
TIA!

[harisuluv]

Yes they would but you wouldn't be able vacuum sync your carbs.

Hint:  PD manifolds have the vac sync port on carbs (not on manifold), 627b carbs have access on the manifold (not on carbs)

[hsas.69]

Nothing a drill and a tap couldn't solve.

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[cocinero196]

Yes they would but you wouldn't be able vacuum sync your carbs.

Hint:  PD manifolds have the vac sync port on carbs (not on manifold), 627b carbs have access on the manifold (not on carbs)

Nothing a drill and a tap couldn't solve.

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Hi guys! Thanks for the info, newbie here. Is there another way to tune/sync the carbs without having to drill the manifold?

[hsas.69]

Only with either switching to PD carbs or finding the older style manifolds as far as sync. Cant tune well without a good sync either.

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[cocinero196]

Only with either switching to PD carbs or finding the older style manifolds as far as sync. Cant tune well without a good sync either.

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hi, switching to PD carbs is not an option i have. can you teach me how to "drill and a tap"? what do i need and how do i do it?
TIA!

[harisuluv]

what about just getting manifolds with the port intact?  They are a very common part that isn't really in high demand.  You could probably get them for around $20.

[cocinero196]

what about just getting manifolds with the port intact?  They are a very common part that isn't really in high demand.  You could probably get them for around $20.

yup, saw them on ebay...they are common, in your part of the globe...not in mine, sadly so, is the "drill and a tap" my next best option? would you care to give a crash course on this? :-)

[hsas.69]

Pretty strait forward and hard to teach through text. Pick a good spot for the hole. Lightly center punch to hold the drill bit from walking. Pick the appropriate drill bit for the threads size and pitch. And drill a nice strait hole. Then slowly run a tap through the hole turning it backwards a turn or so after every couple turns forward. All of this with the manifolds off the bike.

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[Steve_K]

I would also add,  practice on some aluminum of the same thickness.  It is not hard to do, but for the first time use some scrap metal to get a feel for the job.
Steve

[cocinero196]

Pretty strait forward and hard to teach through text. Pick a good spot for the hole. Lightly center punch to hold the drill bit from walking. Pick the appropriate drill bit for the threads size and pitch. And drill a nice strait hole. Then slowly run a tap through the hole turning it backwards a turn or so after every couple turns forward. All of this with the manifolds off the bike.

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I would also add,  practice on some aluminum of the same thickness.  It is not hard to do, but for the first time use some scrap metal to get a feel for the job.
Steve

Thanks for the tip guys!

[DaveBarbier]

Pretty strait forward and hard to teach through text. Pick a good spot for the hole. Lightly center punch to hold the drill bit from walking. Pick the appropriate drill bit for the threads size and pitch. And drill a nice strait hole. Then slowly run a tap through the hole turning it backwards a turn or so after every couple turns forward. All of this with the manifolds off the bike.

Sent from my SM-N900P using Tapatalk

I would also add,  practice on some aluminum of the same thickness.  It is not hard to do, but for the first time use some scrap metal to get a feel for the job.
Steve

Thanks for the tip guys!

Since you asked how to tap something, I just wanted have it mentioned that you don't put the tap into a drill. You do it by hand slowly and with cutting oil as a lubricant.

Just watch a few YouTube videos. It's not hard tapping aluminum.

[cocinero196]

Pretty strait forward and hard to teach through text. Pick a good spot for the hole. Lightly center punch to hold the drill bit from walking. Pick the appropriate drill bit for the threads size and pitch. And drill a nice strait hole. Then slowly run a tap through the hole turning it backwards a turn or so after every couple turns forward. All of this with the manifolds off the bike.

Sent from my SM-N900P using Tapatalk

I would also add,  practice on some aluminum of the same thickness.  It is not hard to do, but for the first time use some scrap metal to get a feel for the job.
Steve

Thanks for the tip guys!

Since you asked how to tap something, I just wanted have it mentioned that you don't put the tap into a drill. You do it by hand slowly and with cutting oil as a lubricant.

Just watch a few YouTube videos. It's not hard tapping aluminum.

Noted

[CBDee]

Those holes on the original manifold have a specific angle to them so the vacuum sync can be done. You can't just drill holes Willy-nilly and expect then to work. Also, they will need to be plugged with a screw for normal operation, so be sure you get one short enough so that it doesn't extend into the manifold and disrupt the airflow.

I'd get a real, proper manifold if I were you. Trying to drill these out and making them work sounds like a PITA to me.

[cocinero196]

Many "taps" come with a corresponding drill bit of the proper size. Because these manifolds are cast aluminum, they will drill easily and tap (cut threads) easily too. ITs best to use some type of oil when drilling and tapping threads. Aluminum heats up quickly then globs in the flutes, disrupting your cutting. Drilled hole should be a few thousandths smaller than the tapped hole dimension. For instance, vacuum ports on manifolds tend to be 5mmx0.8 pitch. So your bit will be smaller than 5mm (0.197) and a corresponding bit for that pilot hole would be 3/16" (0.187). Drill that hole, then chase the tap in. 1 full turn in, 1/2 turn in reverse. Repeat. Rinse with oil frequently.

Test fit your vacuum screws to block the whole. When you buy a vacuum synch tool, it should have different sized adaptors for the manifolds. Choose the correct metric size and away you go.

Here's a good read: http://www.hondatwins.net/forums/56-fuel-supply-carburation/2129-cb450-carb-sync-port-installation.html

Thanks, man! This made me think about buying & shipping a cb500 manifold instead, seriously

Btw, are the cb500's intake manifold same as the 74-76 cb550k's & cb550f's?

[cocinero196]

Follow up question: what manifold do i get? One that is right for the CB500 627b carb or the one that matches the CB550k engine block? Or are they the same exact manifold?

[Scott S]

 The '71-76 CB500 and CB550 manifolds are the same.

[cocinero196]

The '71-76 CB500 and CB550 manifolds are the same.

Thanks! although 77 & 78 CB550 manifolds aren't the same right?

[harisuluv]

Years 77 and 78 are the same manifold.  But I think you were asking if the years 77-78 are different from the previous years, the answer is yes.

[cocinero196]

Years 77 and 78 are the same manifold.  But I think you were asking if the years 77-78 are different from the previous years, the answer is yes.

Yes, that's what I meant Thanks for pointing that out