Topic: CB650 carbs model PD50B questions

[Flyin900]

I am doing a cleaning for an acquaintance who took this CB650 bike in on a trade. Update the bike is a 1980 CB650 model.

I have downloaded the 1979 CB650 manual off this site which I am using for the specs to set these back up after cleaning them. The carbs on this bike are a PD50B setup while the manual notes the 1979 CB650 carbs were PD50A.

The floats are way off the mark shown for the PD50A carbs in this FSM of which the factory setting is noted as 12.5mm float level. These PD50B's on the bike are more like 20mm's set level, so not even close.

Does anyone have info on the PD50B carbs and correct float specs? These carbs have been into previously, as the main OEM jet (for PD50A carbs) is supposed to be a #90 and I found #142 aftermarket jets in there. The bike has pods on the intake and a 4 into 1 exhaust, yet I don't see any reason for such a crazy jump in jet sizes from a #90 OEM size.

Much appreciated if you can help here with actual knowledge or a link to a correct spec for the PD50B carbs.

[robvangulik]

PD50's don't even show up in the lists I have..A nor B

[Flyin900]

Thanks for the chart it helps me decode it a little more. After some further investigation it seems the PD50B models are for a 1980 model year. The slow speed jet has also been update to a #42 aftermarket jet from the #35 stock size. I am quite sure that possibly both the float and fuel valve may also be from a cheap aftermarket kit.

I am going to try to set the floats at 14mm where they at least look somewhat correct and somewhat level in the set up procedure. I will do a clear tube check on the bowls to verify where the fuel levels actually are once I am ready to do a leak test on the rack.

I have never seen such a messed up set that someone clearly had no clue of what they were doing inside there.

[Jetpilot1]

When you do the clear tube fuel level check- what level are you looking for?