Topic: So, you want to run pods?

[Killer Canary]

Especially with motorcycles, alas, appearance will win over sensible every time.

[HondaMan]

When these bikes were first sold, they had what was considered high rpm engines.  This requires smooth airflow through the carb throats.  Honda made an induction system that would flow smoothly drawing in air, filtering it, and than provided space for turbulence caused by the filter to settle.  The v stack shaped carb inlet drew air from that quiet area and directed it into the carb throats.  This allowed predictable flow over a wide RPM range over the fuel exit points of the carb.   Pods or the breadbox place all the filtered but turbulent air right at the mouth of the carb (or v stack).  There is no doubt that the turbulence effects fuel delivery at unpredictable air speeds.  I have yet to see qualitative data, like from a dyno, to show the difference over the entire operating range of the motor between the stock air box set up and PODS or a bread box.  I just can’t accept an anecdotal opinion of “runs good” as an adequate endorsement, without some sort of measurement data to support it.  Honda spent a lot of money in the stock design.  Does it really make any kind of sense that tossing it for a $15 replacement barely engineered , will in any way actually improve the engine power?

Well said, TT.
Your comments remind me of 2 bikes I worked with that were 135+MPH CB750 roadracers. One had velocity stacks and the other had a much-modified K1 airbox. The one with the velocity stacks REQUIRED that the lower fairing be in place or it would not reach even 100 MPH. There was a baffle that reached across the bottom of the carbs in that one's fairing lower half that effectively directed the warm engine air downward and out both sides, while having a pseudo-box above that baffle that was enclosed by the oil tank acting like a 'wall' on the right side and a vented (sheet metal with some slots milled into it) baffle on the left side. The rear (still OEM plastic) fender completed this enclosure with a small duct of about 3 sq. in. section that went forward to the left top side of the engine to get incoming air. It was a complex arrangement, but taught me (and that rider's crew) about having quiet air for the carbs. It was all joined to the fairing, so it was easy to remove/install with 6 quarter-turn fasteners, but was full of cracks (and patches!) from much use and a few crashes.

[Floshenbarnical]

Having read this thread fifteen dozen times and had the carbs on and off more times than beers I drank last weekend (far too many) I've finally come to the conclusion I'd rather have a bike that runs like a top with an ugly airbox than an aesthetically pleasing podracer that runs like #$%* unless I'm WOT. Considering most of the riding I do is cruising through the twisties or commuting to work, I don't need the bike to travel back in time when I open it up - nor can I afford to get a speeding ticket, as I'd lose my job selling Honda cars.

I've gotten the tune to a point that's "ok", but it's not good enough. So I'm at a crossroads - do I find a good used airbox (plenty online) and drop my main jet back down, or do I order some carbs from Murray and call it a day. I'm leaning towards the Murray's carbs route purely because the carbs are knocking on the door of 50 years old, and I've had to helicoil most of the float bowl bolt threads and I'm a bit sick of looking at them.

The gruff old bastard did tell me over the phone that I should replace the clutch plates and springs before I install the carbs, which I need to do anyway as it's started to slip now and then.

Anyone got any thoughts?

PS - I feel very lucky to have found this community with its enormous wealth of knowledge. I could never have gotten this bike to the point that it's at without you all, so thanks.

[seanbarney41]

despite Murray's claims, you still gonna have the same jetting challenge...just wayyyy farther from a starting baseline and limited performance potential.  The only reason you would need new clutch, is because all the low end torque is gone and you are just pinning it and popping the clutch just to get going. 

Still not sure why folks asking questions on internet forums (as good and knowledgeable as this one is) are still thinking that their back yard tinkering is gonna come up with something better than dozens of highly paid and successful Japanese engineers.

[Floshenbarnical]

despite Murray's claims, you still gonna have the same jetting challenge...just wayyyy farther from a starting baseline and limited performance potential.  The only reason you would need new clutch, is because all the low end torque is gone and you are just pinning it and popping the clutch just to get going. 

Still not sure why folks asking questions on internet forums (as good and knowledgeable as this one is) are still thinking that their back yard tinkering is gonna come up with something better than dozens of highly paid and successful Japanese engineers.

That's very interesting, I was under the impression that his setup is fairly plug-and-play because he pre-jets them based on the info I give him regarding my setup? Do you have any more info regarding that? I tried running a few forum searches and didn't come up with much.

Regarding the clutch use on Murray's carbs, how does this affect the friction zone for low-speed maneuvers? Am I going to have to keep the bike revving over 3000rpm just to perform a U-turn in first gear?

[Mark1976]

   Just get an air box off of eBay, and rebuild/reuse the carbs, set it all back to the stock brass and settings. It run like a charm. It's just easier. If you're not familiar with carburetors you'll spend a large block of time and a small fortune on brass figuring it out otherwise. Even then you may not like what you get.

[seanbarney41]

despite Murray's claims, you still gonna have the same jetting challenge...just wayyyy farther from a starting baseline and limited performance potential.  The only reason you would need new clutch, is because all the low end torque is gone and you are just pinning it and popping the clutch just to get going. 

Still not sure why folks asking questions on internet forums (as good and knowledgeable as this one is) are still thinking that their back yard tinkering is gonna come up with something better than dozens of highly paid and successful Japanese engineers.

That's very interesting, I was under the impression that his setup is fairly plug-and-play because he pre-jets them based on the info I give him regarding my setup? Do you have any more info regarding that? I tried running a few forum searches and didn't come up with much.

Regarding the clutch use on Murray's carbs, how does this affect the friction zone for low-speed maneuvers? Am I going to have to keep the bike revving over 3000rpm just to perform a U-turn in first gear?

All I really know is what I have seen....guys showing up to bike shows or group ride with brand new Murrays set-up and the bike is spittting, bangin, hanging revs, etc.  I don't really understand how Murray would be able to pre-jet based off info when that is not even 100% successful with stock set up.  Maybe these guys ordered off a website, not directly from Murray?  idk

If you do some searching, there are numerous build threads using Murray's, and I do not remember a single one having bolt on success.  In fact I remember more never getting the bike to run satisfactorally at all with the twin Mikuni set up.  At least one fellow with a 550 recently was well pleased semi recently.  I even saw a u-tube video that plain dropped my jaw with the video creator raving about how great his Murray's carbs were, starts up the bike on video, and showed on camera how much "better" it ran with the idle hanging unsteadily around 2500rpm, lets out the clutch and it falls on its face, etc.!

[dave500]

probably have better success trying to adapt a fuel injection system from a later bike?NOW THERES AN IDEA!!

[PeWe]

probably have better success trying to adapt a fuel injection system from a later bike?NOW THERES AN IDEA!!

Possible with a modern bike's charging system too.

[Floshenbarnical]

Alright, alright, you grouchy old-timers. Hopefully the flavor of your kool-aid is enjoyable as the tasting notes. I found an air box + stacks in staggeringly good condition on eBay, and an OEM air filter on the way.

Lucky for me I have stock (40), 42, and 44 slow jets, and 105 through 140 main jets sitting here at my house. I bought every jet size available through JetsRUs when I bought the bike. I'm not a rich man, but I don't spend my money frivolously. I hoard it like a dragon unless I'm spending it on tools and a money pit bike that's almost twice my age.

As far as I'm concerned, it's money well spent. I'm 33 but all the music I listen to was recorded prior to 2007, and that's only because The Strokes made all their best music from 2001-2006. There's something transcendent about finding a decrepit piece of history and bringing it back to life, putting your signature on it, and sharing it with a bunch of nerds who will forget more about your bike than you'll ever learn. For that, I will always be thankful to the members of this forum.

Looking forwards to this bike running like Linford Christie.

[seanbarney41]

I hear ya loud and clear on the decrepit pieces of history.  Saturday I rode my 2004 599 Hornet.  Sunday I rode my CB750F0 (with a few sensible upgrades) and I will be damned if I didn't have more fun on the older more decrepiter one!

[Floshenbarnical]

Absolutely. Anyone got a good starting point for jets if I'm running 4-1 with stock airbox? Was thinking 42s with 110s.

[Scott S]

 

Absolutely. Anyone got a good starting point for jets if I'm running 4-1 with stock airbox? Was thinking 42s with 110s.

 Nearly all aftermarket 4-1's will run just fine with the stock jetting. MAC, Delkevic, etc., are all designed to be factory replacements. No jetting changes required.
 If you have done engine work, removed the baffle, etc., you may need to re-jet slightly.

[Floshenbarnical]

My muffler is essentially an open header, will that make a difference?

[TwoTired]

My muffler is essentially an open header, will that make a difference?

Yes

[seanbarney41]

Where did you get 42 pilot jets?!  Are they for roundtop cb750 carbs?  Keihin manufactured?  Been trying to get a set for years.

[Floshenbarnical]

Where did you get 42 pilot jets?!  Are they for roundtop cb750 carbs?  Keihin manufactured?  Been trying to get a set for years.

They are the press-in jets for the PD Keihin carbs on a 1977 CB750 Super Sport. I got them from JetsRUs. I spoke to the owner, who said they are not OEM but he vouched for their quality, whatever that's worth. He said he has had them manufactured by the same manufacturer for years. He does stock OEM main jets for those carburetors.

[seanbarney41]

Oh gotcha...yeah, those are different than the earlier 750 carbs.  Yeah, jetsrus are good peeps.

[Floshenbarnical]

I saw some conflicting opinions on reddit re: pods - people were suggesting that CV carbs absolutely do not work with pods, but PD carbs can actually be tuned properly to run really well with them.

I don't trust reddit. Can some old head(s) give me the word of god so I can stop thinking about it?

[TwoTired]

I don’t trust Reddit, either.  Opinions aren’t science or physics facts.

[Scott S]

I saw some conflicting opinions on reddit re: pods - people were suggesting that CV carbs absolutely do not work with pods, but PD carbs can actually be tuned properly to run really well with them.

I don't trust reddit. Can some old head(s) give me the word of god so I can stop thinking about it?

 Honestly, I've found quite the opposite to be true.
 I've run pods on several XS650 twins; K&N, UNI foam, velocity stacks and even cheap pods. The XS's were easy to tune with them. I even swapped from K&N pods to a stock air box and found no difference at all.

 On the CB's, I've run dual inlet K&N pods on CB650 CV carbs. I did have to rejet and change the mixture screws, but it ran well. Those pods were dual inlet, so I think the shared throats help "calm" the air a bit.

 On the 500/550's with mechanical carbs, stick with the stock intake whenever possible.

[seanbarney41]

I saw some conflicting opinions on reddit re: pods - people were suggesting that CV carbs absolutely do not work with pods, but PD carbs can actually be tuned properly to run really well with them.

I don't trust reddit. Can some old head(s) give me the word of god so I can stop thinking about it?

the only bike I have ever had run truly awesome with pods has cv's and it's a Suzuki GS1100e with Mikuni bs carbs.  That's because there was a Dynojet kit installed.  If Dynojet ever did a kit for sohc4, they have not offered it for many years.   The other is any bike with Mikuni VM carbs (4 of them, not 2 carbs into 4 cylinders!)  Look at how much more is offered for Mikuni VM's at JetsRUs, and you may start to understand how wide a spectrum of jets is needed.  Especially different profile needles...

And to continue my frankness, I have never been able to get a bike with Keihin PD's to even be able to make it down the street.  I gave up and put early roundtops on my CB750F3 and it ran excellent.

[Floshenbarnical]

I saw some conflicting opinions on reddit re: pods - people were suggesting that CV carbs absolutely do not work with pods, but PD carbs can actually be tuned properly to run really well with them.

I don't trust reddit. Can some old head(s) give me the word of god so I can stop thinking about it?

the only bike I have ever had run truly awesome with pods has cv's and it's a Suzuki GS1100e with Mikuni bs carbs.  That's because there was a Dynojet kit installed.  If Dynojet ever did a kit for sohc4, they have not offered it for many years.   The other is any bike with Mikuni VM carbs (4 of them, not 2 carbs into 4 cylinders!)  Look at how much more is offered for Mikuni VM's at JetsRUs, and you may start to understand how wide a spectrum of jets is needed.  Especially different profile needles...

And to continue my frankness, I have never been able to get a bike with Keihin PD's to even be able to make it down the street.  I gave up and put early roundtops on my CB750F3 and it ran excellent.

Thanks for your input. I have pods on my 77 CB750F with PD carbs and it runs down the street "fine", and comes into its own under heavy acceleration.The carbs themselves are super finnicky, but I did do a pretty meticulous rebuild. "Fine" isn't good enough for me however, and I have absolutely no interest in taking the carbs off two dozen more times and spending a thousand dollars on plugs to get it to "pretty good", so this weekend I'm refurbishing the airbox, rejetting (hopefully) once or twice, and calling it a day. I can put the pods on once a year to take pictures, or something.

It's fun to strip the paint getting on the highway, but I'm concerned about long-term engine damage and honestly if I want to travel back in time I'll buy something brand new that isn't assembled from a box of scraps, in a cave. I accidentally got it 80+ the first day I got it synced and timed and adjusted, and when I looked at the speedo the icy hand of Death gripped my shoulder and whispered in my ear "one of your wheels could fall off, lol" and so I coasted to a sensible speed and crept home.

Can't impress the ladies if you're raspberry jam

[seanbarney41]

Floshenbarnical, props to you for working successfully with the pd's.

I think the fact that I love old bikes IS because they are slower.  I do currently own a 2004 599 Hornet, and going silly speeds on it is just effortless.  I guess riding a slow bike fast IS more fun than riding a fast bike slow...cuz I don't need the speeding tickets, and I am just not a good enough rider to use what that 599 has got.

[dave500]

im with seanbarney,two things i like about my 550 powered 500 are,it makes the right noise,and feels like your going faster than you are,it satisfies that need for speed!man im 65 shortly,ive found the reflexes are a little less sharp,ive done plenty of dumb fun fast stuff over the years and gotten away with it,im gonna rest on my laurels.