Topic: 069a carbs better than PD carbs?

[Greyhound]

I came across a very clean rack of 069a carbs (only came on CB550F).

I understand that these 069a carbs are easier to dial in and get power out of them when running pods and open exhaust, so I’m thinking of swapping them into my 77 CB550K, which has the stock PD carbs, since I’m running pods and open exhaust.

I’m also planning on installing a hotter cam in the coming months.

Is it a good idea to install these 069a carbs?

[dave500]

yes but get the inlet manifolds with them,the pd manifolds dont have the vacuum port for syncing,its on the actual carbs with the pd type,also the cables will need to be changed.

[Greyhound]

Awesome. Thanks!

Was there a year of 069a carbs which didn’t include the “069a” stamping on the carb?

These supposedly came off of a 1975 CB550F, but I don’t see the 069a anywhere.

How different were the 069a carbs from other earlier type carbs? Was it only the jets? If so, would any earlier style carb suffice, since I’ll be resetting anyway?

[dave500]

each carb has a stamp on this flange,they can be very light and maybe hard to spot?

[Stev-o]

Was there a year of 069a carbs which didn’t include the “069a” stamping on the carb?

I believe all 550F's had the 069A carbs, my '76 has them.

[Greyhound]

Indeed, all CB550F’s surely only had the 069a carbs, I was just wondering if there were cases where 069a carbs weren’t stamped, but sounds like the stamp may just be quite faint.

[Greyhound]

Did the CB550F intake manifolds differ from the CB550K prior to the PD carbs?

Can I use CB550K manifolds as long as they are 1975-77 (and have the vacuum ports on them).

[Deltarider]

Did the CB550F intake manifolds differ from the CB550K prior to the PD carbs?

No.

Can I use CB550K manifolds as long as they are 1975-77 (and have the vacuum ports on them).

You can use CB550K, CB550K1 and CB550K2's. Even all CB500s except K3.

[Greyhound]

Thanks!

What jet sizes would I start with to match pod filters and open 4 into 1 exhaust?

120 and 38mm with a 1.5-2 turn air screw, and 23mm float height?

[dave500]

your on your own with pods.

[kerryb]

Thanks!

What jet sizes would I start with to match pod filters and open 4 into 1 exhaust?

120 and 38mm with a 1.5-2 turn air screw, and 23mm float height?

I  ran 38's & 100's with air screws 2 1/2 out.  This setup worked well enough with pods and non-stock 4 into 1.  I'll be putting the airbox back on to cure the low-throttle stumble and quiet things down a bit.  Like dave500 says, make sure your ignition is just right so you can be sure the problem you are solving is carb-related.  (Experience is a powerful teacher)

[Greyhound]

Awesome. Thanks for the insights on the jetting. Too bad the 550 doesn’t have enough room to add silicone hose/pipe in between of filter and carb like the twins do, which creates constant atmosphere like an airbox, and would likely achieve what you are trying to do.

[Bankerdanny]

Functionally all 550F and pre-77 550K carbs are identical. The numbers indicate the jet and needle sizes that came in the carb and don't have anything to do with the carb bodies themselves.

The primary advantage of the non-PD carbs is the availability of jets for tuning. Design wise I don't think that the PD's are inferior to the earlier carbs, and they have the advantage of a fast idle cam, which helps keep the bike from stalling after a cold start.

[Greyhound]

Does anyone know where to source genuine Keihin jets to tune 069a carbs?

(or even PD carbs for that matter?)

Anyone have experience with jetsrus.com?

550 jets here: https://jetsrus.com/a_jet_kit_street/honda_550_CB550_1977-1978.html

Are these legit genuine Keihin jets??

[Bankerdanny]

Yes, Jetsrus sells the real deal and you can trust the Keihin jets you get from them.

[rosewood]

Yes, Jetsrus sells the real deal and you can trust the Keihin jets you get from them.

I read this on this forum all the time but when I emailed jetsrus Mike there responded saying that:


they are NOT genuine.  Keihin no longer makes those jets.  If anyone is selling them and states they are GENUINE, they would not be telling the truth.

This was for 069a type carbs anyway...PD carbs may be a different story. In saying that it does sound like most people are satisfied with there products though.

hope this helps clear up a few assumptions...
rosewood

[Greyhound]

Hmm interesting, thanks for posting that, the jetsrus website calls the “genuine Keihin”, so something is up. 

[PeWe]

There are plenty of information to read.
Hondaman has his thoughts describing things.

Good idea to make sure that ignition work fine before doing the carbs. I have wasted lots of time jetting carbs when bike had a bad HT lead that had intermittent problems. Graphite lead. Changed to copper.

Ignition:
Cut the springs on the advancer 1/2 wound. Both my CB750 have that. Good improvement I found in Hondaman's posts that recommend that for 5x0 too.

http://forums.sohc4.net/index.php/topic,7401.msg67245.html#msg67245

http://forums.sohc4.net/index.php/topic,17374.msg179632.html#msg179632

[Greyhound]

Good call on refining ignition and timing. I’m actually in the process of trying to order the Hondaman transistorized ignition system, but somehow the ordering process isn’t working for me.

I put an order through the SOHC4 shop site, the order was processed, but how do I pay?? (The invoice says payment will be “cash on delivery” ... is this accurate?).

If anyone has ordered one of these, please let me know how you got it.

[PeWe]

I ordered both my modules by sending PM to Hondaman.

[Jakey_H]

Hey guys, long time reader first-time caller.

Does anyone have experience with using 069A carbs on a 77K? After rebuilding the engine and carbs, I've put it all back together to realise that there aren't sync ports because the bike should obviously have PD carbs on it.

Ive replaced the intake and inlet rubbers with all the 77K stuff (had to slide the airbox forward 10mm to suit). Does anyone know if it's worth replacing the intake manifold so I can sync the 069A carbs (the standard tuning on these are way to rich also), or cut my losses and find a set of Pd carbs and tune them? I think id love the PD's for simplicity sake, but they don't seem to be all that available.   

I'm running stock intake and 4 into1 550F exhaust.

Cheers!

[robvangulik]

Why don't you simply drill 4mm holes in the intakes and thread m5 in them?

[commander60]

I also emailed jets r us he said they were not genuine.

[Jakey_H]

I had thought of drilling holes, but my inner engineer opted against drilling and tapping a cast part without form around the hole, specifically one that gets warm.

[robvangulik]

I think Honda did it the same way, and those carbs won't get hot...