Topic: cb500//4 carbs

[goodtimes]

i am thinking about getting new aftermarket carbs for a cb500/4 1971
and i was just wondering what would be the best ones to go for.

thanks

[dave500]

unless you have a souped up motor leave them alone,you might want to try the later pd1 type carbs from a 550,they are the same size venturi but have a less fiddly syncronizing adjustment.,youll also have to have the airbox to suit.

[Deltarider]

... you might want to try the later pd1 type carbs from a 550...

I certainly wouldn't.

,they are the same size venturi but have a less fiddly syncronizing adjustment

I can't see why theirs is 'less fiddly'. Strange, there's so much synchronizing going on in this forum. I wonder if members realise you can easily do decades without synching. Why? Because Honda took the effort to build it that way. If the PO didn't touch the adjustment screws, it's unlikely you have to sync your carbs. Also when you have cleaned your jets - which is a good thing - you don't have to sync. If you're not satisfied with the way your bike performs, look at the electrics (ignition in particular) first. Still not satisfied? Look at it again and maybe again!

.,youll also have to have the airbox to suit.

Which is impossible to find.
Stay with the original carbs (627B or 649A). They're accessible and way easier to work on than the later PD's. And... couplers are widely available.

[dave500]

the later pds dont have all that monkey motion of a linkage set up,the locknuts dont alter the running as much when you tighten them., and it dosent hurt to at least check the sync on a decades old bike thats been tampered with by who knows who?youll get an airbox much easier in the US.

[Deltarider]

Just read on the German Fourclubforum that two members have swapped the PDcarbs on their 550 for the old style carbs (500/550F). Fed up with them, in their language:
_{Also ich hatte wie du mit den Vergasern der K3 nur Ärger.Hatte ebenfalls einige male gereinigt und es brachte nichts.Da hab ich die Vergaser der 550 F angebaut und das Teil lief super damit .Einzig den Chokezug der ja bei der K3 am Lenker sitzt hab ich entfernt weil die 550 F ja den Choke direkt am Vergaser hat.}

[dave500]

german??oh!! they must be superiour then i guess?or too slack to tackle the pd type.

[Deltarider]

german??oh!! they must be superiour then i guess?or too slack to tackle the pd type.

That's cheap, Dave, very cheap.
I can only advice you to study the content of this forum a bit more before you - in an impulse - treat us with out of place comments or unbalanced advices.

[dave500]

well i already advised goodtimes to leave them alone,or if he wants to tinker to try the pd type,for which he will have to source the air box,and the earlier do have a more complex linkage assembly,and i also recommended he syncs or gets them synced as they are old ,and i dont feel any of my advice is unbalanced or my comments impulsive,if i have offended you somehow i apologise.

[TwoTired]

FYI, PD carbs have different bore spacing.  So, the manifolds and forward rubber couplers are different, too.  They also use different throttle cables and need a choke cable.

I don't think one type is any better than the other type.  Just different.  In some respects, the PD style is harder to work on, particularly if you insist on separating the bank.  They both have the same venturi size, and operate on the same principle, with a variation in how the pilot circuit functions.  I don't believe any internal parts interchange. 
In one you'll find apple seeds, the other you'll find orange seeds. 

Cheers,

[dave500]

a bit like holley vs quadrajet?i like the qjet,no gaskets below fuel level,you can change jets and needles with out draining fuel,they are very tunable and cheap.,the holley is easier to get tuning parts and probably runs better on full out race cars!!