Topic: How would a CB750 run w/o an airbox?

[DORIGTT]

How would a 73 CB750 run without an airbox and filter installed?

I just rebuilt the carbs and it fired up, but runs rough and I know I need to synch the carbs, but I'm wondering if I need to install the airbox to smooth out the running or not.  I'll put them on if it's required, its just a pain to do it and I'd hate to have to remove and reinstall it.

Thanks,

[NewOldSchool]

Look up how to "Bench Synch" your carbs, there is a lot of good info on the forum. After you have done that instal the air box and see how it runs. In short, yes, it will run best with the air box and filter installed if it is already jetted correctly. Remember you should already have the cam chain, valves, points, timing, etc adjusted correctly before you synch your carbs.

[scottly]

If the carbs aren't synced, adding the airbox won't fix the problem....

[bwaller]

I'm not sure what the problem is, the 750 airbox couldn't be easier to install. Install the upper half first. If the stacks are hard it's a nuissance, granted.

[kerryb]

[quote author=DORIGTT , its just a pain to do it and I'd hate to have to remove and reinstall it.

Yeah, the airbox can be a pain to work with but you know what they say..."no pain, no gain".  Your bike will thank you for it by giving you longer life and smoother operation.  After you remove and install carbs and airbox several times, you will get better at and it won't be such a pain.  Look up wintergreen oil for the rubber parts and maybe try hex head socket screws and a ball-end allen wrench for the clamps.  Other tricks I have employed include softwood prybars and levers to encourage the parts on without marring them

[steam-powered man]

smear a bit of oil to the boot's ID, then use wifey's hair drier to soften up all the boots at the same time.  takes a coupla minutes, but they'll slide right on on.   

[DORIGTT]

My apologies, but I never intended to run the bike without the airbox.  My concern was HOW it runs without the box on as I'm working on getting the carbs synchronized and wondered if it had a significant impact on it's ability to idle and rev.

[Johnny5]

My apologies, but I never intended to run the bike without the airbox.  My concern was HOW it runs without the box on as I'm working on getting the carbs synchronized and wondered if it had a significant impact on it's ability to idle and rev.

Yeah, unless it's running extremely rich, taking away the airbox and replacing with pods will most likely make it running rich. Try running the bike for a few minutes without the airbox and see what happens. It'll probably spit and pop and run like poo until it's jetted right.

[NewOldSchool]

From what I have learned in the past, If you are trying to balance the carbs then yes have the airbox installed, its just one of the many parts in the equation to make the bike run like a top.

[Retro Rocket]

My apologies, but I never intended to run the bike without the airbox.  My concern was HOW it runs without the box on as I'm working on getting the carbs synchronized and wondered if it had a significant impact on it's ability to idle and rev.

Yeah, unless it's running extremely rich, taking away the airbox and replacing with pods will most likely make it running rich. Try running the bike for a few minutes without the airbox and see what happens. It'll probably spit and pop and run like poo until it's jetted right.

And it still won't run right because these carbs were designed to run with the stock velocity stacks...

[Johnny5]

My apologies, but I never intended to run the bike without the airbox.  My concern was HOW it runs without the box on as I'm working on getting the carbs synchronized and wondered if it had a significant impact on it's ability to idle and rev.

Yeah, unless it's running extremely rich, taking away the airbox and replacing with pods will most likely make it running rich. Try running the bike for a few minutes without the airbox and see what happens. It'll probably spit and pop and run like poo until it's jetted right.

And it still won't run right because these carbs were designed to run with the stock velocity stacks...

Not really correct. I have experimented all summer and found the right combination. My bike with pods runs just as good as with the air box on. You may not believe it, but it does. It just takes a lot of patience and trial and error with the jetting.

[tanman855]

Has anybody tried just pulling the stacks out of the factory airbox and just running those?

[Johnny5]

Has anybody tried just pulling the stacks out of the factory airbox and just running those?

I guess you could, but you'd also get zero filtration for the engine.

[Gordon]

Not really correct. I have experimented all summer and found the right combination. My bike with pods runs just as good as with the air box on. You may not believe it, but it does.

It may be running well enough to satisfy you, or you don't notice or care about the compromises that have been made, or it's been too long since you've run it with the factory box and carb settings that you've forgotten.  The factory intake system and carb settings are designed to make the bike run well through its entire range of speed and load capabilities.  The drastic changes caused by installing pods cannot be completely compensated for by changing jetting. 

[Retro Rocket]

Not really correct. I have experimented all summer and found the right combination. My bike with pods runs just as good as with the air box on. You may not believe it, but it does.

It may be running well enough to satisfy you, or you don't notice or care about the compromises that have been made, or it's been too long since you've run it with the factory box and carb settings that you've forgotten.  The factory intake system and carb settings are designed to make the bike run well through its entire range of speed and load capabilities.  The drastic changes caused by installing pods cannot be completely compensated for by changing jetting.

I'm with Gordon on this one. I have said it plenty of times here and if you know enough about these bikes you will know that it will NEVER run as smoothly without the correct size stacks. You may get it to idle correctly but that will compromise its capabilities somewhere else. The ideal set up with a stock or even mildly hotted up engine are the stock air box and stacks, add a less restrictive K&N filter and it will be about as good as you will ever get it. Why do you think Honda spent a small fortune having this system developed in th first place , if it was just as easy to change jets and run cheap crappy filters.?

+1, had decided to run my Amen Savior on the local Harley dyno to settle this but I don't have time right now.  Too many fresh hardtail builds, a cafe, and a restoration that have to come first.  Settling differences of opinion takes a distant second to actually applying my gifts.

Couldn't help blowing your own trumpet again....
Typically stupid response King, these are FACTS {something i don't think you quite understand} NOT OPINIONS...
 and running your chopper on a dyno will prove absolutely nothing without having the complete stock set up with all the jets required to take it back to the stock set up for a complete comparison...More hot air as usual. You know king, through all your narrow minded crap you fail to understand that some of us have been working, building and fettling these bikes { and lots of others}  for over 30 years, been involved in racing, worked in bike shops and generally lived bikes all our lives, some of the #$%* you carry on with is just plain laughable and makes you look extremely small minded and ill informed.

[Johnny5]

Not really correct. I have experimented all summer and found the right combination. My bike with pods runs just as good as with the air box on. You may not believe it, but it does.

It may be running well enough to satisfy you, or you don't notice or care about the compromises that have been made, or it's been too long since you've run it with the factory box and carb settings that you've forgotten.  The factory intake system and carb settings are designed to make the bike run well through its entire range of speed and load capabilities.  The drastic changes caused by installing pods cannot be completely compensated for by changing jetting.

Wow, you assume a lot. I actually spent all this summer experimenting. I first got the bike to run like a top with the air box on just a couple weeks ago. I've just put a 73K engine with a 77K head on. Totally different than what Ive been running for a couple years. Then for the heck of it, I put my pods back on to see what I could do. The bike literally runs the same with some mild jetting. I actually went down in main jet size. It took a lot of patience but it runs just as good. I have to hang on when I twist the throttle, it's a great feeling.

But true, I have a 77K head on my 73 engine, so who knows. My friends stock 74 bike runs excellent after we jetted it pods. Im no expert, but would love to show off my bike to anyone at anytime.

[Johnny5]

I sure do wish we could settle this like old times on an open stretch of road somewhere.........ton up.  ;-)

That would be awesome. Next year, King. Im only a few hours away.

[Gordon]

Wow, you assume a lot. I actually spent all this summer experimenting. I first got the bike to run like a top with the air box on just a couple weeks ago. I've just put a 73K engine with a 77K head on. Totally different than what Ive been running for a couple years. Then for the heck of it, I put my pods back on to see what I could do. The bike literally runs the same. It took a lot of patience but it runs just as good. I have to hang on when I twist the throttle, it's a great feeling.

The Butt-Dyno is not a widely accepted measuring device.

I have no doubt it runs well enough for you, and that it seems to you like it's running just as well as with the factory set-up.  There's nothing wrong with making some compromises to do something you want to your own bike. 

In all the discussions on this forum about pods and all those who have claimed they can make a street-ridden sohc4 run as well as or better than with the stock intake, I have never seen any proof. 

[Retro Rocket]

Retro is puffy again.  Your credentials are impressive.

Well King, i have never posted my credentials {unlike you, repeatedly} you are once again full of #$%*, and if you continue to follow me around here spreading misinformation i will continue to shoot you down in flames. As am matter of interest my mechanic builds some of the fastest Honda 4's in the world, and most of the fastest 750/4's are built right here in Australia. He showed me around a stroked race bike on Sunday with 150 HP, yep, thats 150 HP, these are type of guys i listen to intently, not religious fruit loops from afar....

Gordon, you will never see any proof, the only these bikes run better with pods is if the carbs are changed out, these old carbs were designed to run with the stacks mainly and in conjunction with the airbox and its as simple as that.... Tintops "antipod" is the only other filter system that works and that is due to the incorporated stacks designed around the stock items, i still think it would suffer a little in the rain or in crosswinds...  There is NOTHING stable about pods, if you don't believe me then try opening your knees while riding down the highway, you will feel it in performance straight away....

[Johnny5]

Love the hostility.

[Retro Rocket]

Apparently, Johnny5, you just THINK it runs strong.  Now that is laughable. Anybody near Indiana with a stock exhaust, stock jetting, and a dry paper element in their big ole airbox wanna line up with my Amen Savior?  reports to be published here? The Amen is stock except for pods, jets, and open 4-1 Kerker?  Lets settle the BS.

So why would they have to run stock exhaust if yours is jetted to suit the kerker....You really are an idiot.....

[Retro Rocket]

So jetting for open exhaust is fine, but not for open intakes (pods)?  I don't get it.

Thats exactly right, you don't get it....

[Gordon]

Apparently, Johnny5, you just THINK it runs strong.  Now that is laughable. Anybody near Indiana with a stock exhaust, stock jetting, and a dry paper element in their big ole airbox wanna line up with my Amen Savior?  reports to be published here? The Amen is stock except for pods, jets, and open 4-1 Kerker?  Lets settle the BS.

There's no need to put words in my mouth.  I never said it won't run strong, but it's not going to run as strong, throughout its entire range, as it would with the stock intake.  No matter how meticulously calibrated your butt may be,  its readings can't be quantified for use as proof of an hypothesis.     

[NewOldSchool]

So jetting for open exhaust is fine, but not for open intakes (pods)?  I don't get it.

Thats exactly right, you don't get it....

I lol'd

[KRONUS0100]

wow.  gotta llove all the hostility here.  I personally tried pods on my 76 750F.  it ran somewhat ok until the first time it got wet.  ran like #$%* after that, even after cleaning and re-oiling the pods.  Baby now runs the stock air box with a few extra holes in the backside with a K&N...................and runs wonderfully.

[crazypj]

For the OP,
remove the trumpets from airbox, fit them to carbs then, sync carbs.
 You will have to re-jet for pods or bellmouth's.
 If you don't want to spend a lot of time messing with it, use stock airbox.

So jetting for open exhaust is fine, but not for open intakes (pods)?  I don't get it.

Thats exactly right, you don't get it....

Yep, jetting for open exhaust is much easier than jetting for pods