Topic: 73 500 Four K2 - Fitting Pod type Filters and Jetting changes

[Bear Four]

Apparently after 40 years and 3 moves, I have lost the air filter housing and associated pieces that connect the carbs to the air filter.

So I have been investigating the use of Pod-type filters. The bike already has a period 4-inti-1 exhaust, just a bolt-in muffler that has a fixed internal baffle and uses the stock exhaust pipes. According to another site, the use of this type of exhaust plus the pod filters would require main jets 3 sizes bigger than stock(100) size. Am I correct in assuming a 115 main jet size?  The bike currently has the stock jets #100.
So all that weight of the carb assembly is supported by just those Four rubber pipes that attach to the intake manifold?

I  remember when I got this bike it did not pull very well.  I was convinced it needed valve work. Sure enough the valves were leaking and I had a very nice valve job done, but never reassembled the bike.   I still have the old spark plugs, which were Champion R6-G. I now have new NGK D7EA plugs. The old plus have a brown insulator but are quite sooty.

Any suggestions on where to start would be welcomed.   I  saw a YouTube video where the pods would not fit, fouled the frame, so he went with velocity stacks, which I don't want to do. Please point me to something that will fit and work. Thanks!

[Bankerdanny]

My 550 had pods when I got it and the outside (1 and 4) filters were definitely squished a bit. You will likely need to jet up. I would order a couple sizes so you can trial an error to get one that works for you. You do give up some support, and the outside filters definitely pushed my carbs down slightly. The connector rubbers are quite thick and I think sufficient to support the carbs, and lots of owners use pods and are perfectly happy. The 500/550 seem to be harder to tune for them than the 750, but you can do it.

An alternative if you are willing to spend some money is the breadbox type setup from Cognito Moto. It solves some of the issues that come with pods by having internal stacks (pods don't, which is part of why they seem to not work as well). It's $225, but simple to install. https://cognitomoto.com/products/cb550-air-intake-box?variant=11585541697

[Gurp]

http://www.steeldragonperformance.com/air_boxes_7.html

 check out Steel Dragon Performance red boxes as well much cheaper than the Cognito Moto. Scroll down the page and you will see you once for your bike.
I have pods on a 74 550 and had them on a 73 500 I just went up to Idle Jet sizes and left my Mains alone as most of your writing is spent in your pilot circuit.

[scottly]

First, all "pods" are not created equal. The cheap pleated paper ones may actually flow less air than the stock airbox and filter, which would require a leaner main jet. The oiled cotton fiber gauze types, like K&N, have less restriction, and may need richer mains.
Second, IIRC each jet step on those carbs is 2.5, rounded off, not 5. If 100 is stock, look for a 107 or 108.
Third, yes, the rear of the carbs should be supported, even if only with a piece of bailing wire wrapped around the frame above the carbs.  

[Bear Four]

I only found one source of oversize jets, first is for CB550:  https://www.siriusconinc.com/pro-detail.php?pid=&product_id=177. Second is for CB500:  https://www.siriusconinc.com/pro-detail.php?pid=&product_id=176.
I believe the same carbs are fitted to both models.  Any idea what the Keihin carburetor model number is?  I can't see it anywhere on the carbs themselves.

I found the following pod filters:  https://4into1.com/set-of-4-black-foam-pod-filters-39mm-honda-cb500-cb550-cb750/#ProductReviews
and these:  https://4into1.com/set-of-4-small-black-pod-filters-39mm-honda-cb500-cb550-cb750/.

I'm sure this is basic stuff. They do claim these pods fit the frame without interference. You have to oil them,

I want to get this running to figure out what else needs fixing on this. It last ran in 1979.

If you have another better jet source let me know.  Thanks for the diagrams.  All comments are helpful and appreciated.

[Bear Four]

Are the CB500 and CB550 Main Jets Interchangeable? IE would the 550 kit's jets fit my 500?

[SohcCBs]

Personally, I don't know why everybody wants to install pod filters.  They only work better at full throttle.  The plenum (stock) filter works better under nearly all circumstances.  You can get replacement stock filter housing parts, even used, in good shape, or the whole thing.

[Bodi]

Wow! It took 9 replies for someone to dump on pods in a thread asking about how to tune for them... new record?

Yes the stock airbox works well. Yes the carbs won't work well as-is and will need some jetting changes at minimum.
But some owners want to use pods, they look nice to some eyes and it frees up the airbox space for other things.
It is possible to get the engine working pretty dang well with pods. Doing so can be a major PITA.

But the question was about adapting his carbs to work with pods. What's the point of telling him not to?

[Bankerdanny]

On the 500/550 I totally get the appeal.

The airbox and carbs are so jammed into the frame and unlike the non-PD carb 750's all 500/550's have carbs with screw on bowls, so cleaning and jet changes almost always require removal, which is a major pain in ass. 750 carbs are so much easier to remove and deal with. Pop off the bottom 1/2 of the airbox, remove 2x10mm bolts, undo 4 clamps and boom, the airbox is off. 10 minutes tops.

The 500/550 plenum is a 25 minute wrestling job with scraped knuckles as you try to get to the nut hidden under the bottom of the box.

When I was having float sticking issues 1200 miles from home, the pods on my 550 allowed me to have the carbs off in about 10 minutes, 1/2 of which is unscrewing clamps and removing the throttle cables. With the stock box in place the job takes at least 30 minutes and reinstalling can take even longer.

[Gurp]

^this is why alot of people run pods.   
I'm going to buy a steel dragon breadbox for my next project. Lucked into a used "Antipod" for the bike im on now!

[SohcCBs]

It's true that I know little about the 500-550, tho I rode a 500 around when they came out.  I WAS impressed with their handling.  Removing the airbox and/or carbs on my 750F is easy and fast.  I did it many (20) times until I found the crack in one of my carbs.  I also particularly like throttling out of corners and the airbox is better for that scenario.  I used the foamy pods for a few months and switched back.
.

[Bear Four]

I'm going to have to increase the main jet size anyway, because of the 4 into 1 exhaust.  Remember, my bike had burnt valves (at 12K miles), presumably because the main jets  were to small after the exhaust change.

Haven't been able to find an airbox locally. 

Is it really that difficult to recalibrate the carbs?  You've got needle adjustment and slow running adjustment.  I had not planned to upsize the slow jet. It's  size 40 stock.  I assume if an upsize is needed a 42 should do, but I have no source for these. Unless I am not searching properly, Jets R Us no longer has the jets for these carbs.

Comments?

[Bankerdanny]

I wouldn't think that the pods and 4-1 would have enough impact on airflow at idle to require bigger jets.

[Scott S]

 "The bike already has a period 4-inti-1 exhaust, just a bolt-in muffler that has a fixed internal baffle and uses the stock exhaust pipes."

 What exhaust uses the stock 4-4 pipes and a bolt on muffler?
 Or do you have the F model with the stock 4 into 1?

[LastChancer88]

I'm going to have to increase the main jet size anyway, because of the 4 into 1 exhaust.  Remember, my bike had burnt valves (at 12K miles), presumably because the main jets  were to small after the exhaust change.

Haven't been able to find an airbox locally. 

Is it really that difficult to recalibrate the carbs?  You've got needle adjustment and slow running adjustment.  I had not planned to upsize the slow jet. It's  size 40 stock.  I assume if an upsize is needed a 42 should do, but I have no source for these. Unless I am not searching properly, Jets R Us no longer has the jets for these carbs.

Comments?

My bike is a '73 cb500k2 with 4into1 and pods.  I'm installing 42 slow jets, it's on the 4th clip from the top needle, and 115 main jets.  I'll let you know how it works for me.  I'm also in MT so high altitude leaning out my mix.  I've had some issues with lean running idle but I'm also in the process of making sure the float heights are correct with fuel in the bowl and not just the measure method.  Bought a vacuum connector attachment and clear tube off the advice from someone on the forum to check the actual fuel height. 

The bike has ridden well with the 4th clip, 115 mains past 1/4 throttle to full open but the off idle had a little stumble to it so I'm trying to find the issue.  You may not have the need for a bigger pilot/slow but that's what I've been through. 

[robvangulik]

I'm also in MT so high altitude leaning out my mix.   

High altitude makes bikes run rich, because of less airpressure...

[LastChancer88]

I'm also in MT so high altitude leaning out my mix.   

High altitude makes bikes run rich, because of less airpressure...

Ah you're correct.  What a dummy