Topic: Jetting for pod filters

[racemx51]

Hey guys, I put pod filters on my 73 CB 750.. Im wondering if you guys have any starting points for jetting. Im def no newbie when it comes to jetting, Ive been racing dirt bikes my whole life and back when two strokes ruled we jetted our bikes different almost every week to get peek performance...So dont be scared to get technical.. But do you guys have any starting points for jetting with pod filters. The bike already had a four into one exhaust so the only thing thats changing is the filters.. I heard two richer on the mains but what about needles and everything else? I live in the northeast so its starting to get a bit cooler now...60s or so..but during the summer is 80s and 90s where im at...
Any help?

[Retro Rocket]

Do a search for pods on a 750, have a read, then put the airbox back on and suffer none of the bull#$%* that goes with putting pods on a 750. The ONLY advantage with putting pods on the 750 for some is looks, they never run as good as the original airbox because the set up Honda uses on the 750 requires the velocity stacks that go into the airbox to run properly. It has been covered 100's of times on this forum and most of the time they screw around with trying to get an exceptable state of tune then give up and go back to what works. Now if you have a hot engine and are running different carbs then GOOD QUALITY pods like the K&N's may work, but with the stock set up, nothing runs as well as the stock airbox and velocity stacks that come with it.....

[racemx51]

Not really, honestly I havent done that much research on this kind of stuff yet.. Ive been around bikes my whole life so I didnt really feel like I needed to read into it.. Whats your opinion?

[Retro Rocket]

Not really, honestly I havent done that much research on this kind of stuff yet.. Ive been around bikes my whole life so I didnt really feel like I needed to read into it.. Whats your opinion?

These old Honda's were designed to use velocity stacks with the Keihin carbs. They run best with the factory stacks and airbox. I know it can be a bit confusing because there are plenty of bikes that run well with them but these old Honda's don't. King builds bobbers so the stock box doesn't fit with his style of bikes but i can tell you that the stock bike he owns runs the stock set up. He should tell people this when giving flippant advice.  Like i said, there are tons of threads on here about this and even some guys that were totally convinced that pods were better have now gone back to the stock set up because of its ease of tuning and stable performance. Actually, there's one in the "what did you do to your bike today" thread....

[tanman855]

what main Jets are you using with your exhaust and pods? I just baught the pod/jet set up from new motorcycle parts . c o m they are 115, I have a 1974 cb750.

[Retro Rocket]

what main Jets are you using with your exhaust and pods? I just baught the pod/jet set up from new motorcycle parts . c o m I have a 1974 cb750.

Read my posts mate.... If your bike is mainly stock and uses that stock carbs you will never get it as good as the airbox and standard velocity stacks, Honda designed it that way and thats what works best. There is a member here {tintop} that has made an after market filter he calls the "antipod" it uses a modified version of the standard stacks with a single exposed filter, this works correctly because it utilizes the stock stack design.

http://forums.sohc4.net/index.php?topic=79491.0;nowap

[tanman855]

$235 is a little steep for me(highschool student), I have a set amount of money put aside to turn this into a cafe bike (1k). And I can't get my stock airbox back on they are supper stiff. And it seems like they worked well for him.

[scottly]

Or so he says. Of course, he also claims to have divine intervention on his side.
The airbox rubbers can be softened with wintergreen oil; lots of info on here about it.

[Retro Rocket]

The biggest problem is that most people have no idea how well these bikes run when set up well, a lot of guys here think their bikes run great when in fact they don't. Most pods are cheap crap and have no stacks built in, K&N have some with internal stacks that will help, emgo and the rest are just rubbish. Do yourself a favour and keep the airbox, there is a knack to putting them on and once mastered its relatively easy, you may want to use it after screwing round with pods for little benefit.  Search the forum, you will find plenty of pod threads and funnily enough, some of the guys that swore black and blue that they wanted pods are now going back to the stock set up because it is simply the best way to get these bikes, particularly the 750, running well.. I've had 22 of these bikes and will NEVER use pods ever again..

[tanman855]

Ok, thanks a lot guys. I'm just trying to get this thing running as good as possible, Ill try that oil to soften them up. Right now I started a thread because it isn't running correctly any advice on that too would be much apreciated
http://forums.sohc4.net/index.php?topic=96898.0

[david 750f]

+1 with what Retro says...

[scottly]

Do a search for wintergreen oil. From what I've read, it can be found in drugstores as well as online. Personally, I've never needed it, as I moved well beyond anything close to stock many years ago.
 In your case, I think you would be better off sticking with the stock set-up for now, just to eliminate as many variables as possible. BTW, welcome to the forum!!!!

[RustyJC]

My 1971 CB750K1 has been running K&N individual filters since 1972.  Knowing what I know today, I doubt that I would do it again, but we thought that was the hot setup back in the 70s.

IIRC, with the K&Ns, I wound up with 120 main jets and the needles lifted one notch.  If I remember, I'll pop a float bowl and verify the main jet sizing when I get home from work.  I wound up with a pill bottle full of main jets, though, as I worked my way through them to find the best setup for the K&Ns, the Jardine 4-into-1 and the Yoshimura cam and pistons.

Just to illustrate how sensitive these carbs are with the individual K&N filters, if I do nothing more than stick my knees out into the wind at highway speed, the "scoop effect" causes the bike to go dead lean.  I still may wind up going back to the original airbox one of these days - if I can find it!


Rusty

[racemx51]

Well my plan was to try jetting it and getting it running well and if it didnt, just go back to the old airbox. Ive got two of them...So I wasnt worried if I needed to go back.. I got the pods at pretty much no money just because I know a lot of builders.. Ive got other problems to worry about right now anyways.. I fired the thing up and cylinders 2 and 3 are not firing now.. Points are, so I must have a damn wiring problem somewhere.. Guess thats my next situation..What do you guys think?

[Flying J]

haha a pods thread.

[Inkscars]

Not firing? Or not getting warm? If it's a spark issue, I'd check your coils. Don't be afraid to check your wires and ends. Some trimming may be necessary if they're not new. Now, If you're getting spark and you just threw different jets in there, You're going to have to start from square 1.
Jetting Isn't the only thing that comes into play. You change 1 thing, and it messes everything up. It's a process . Sometimes it involves taking the entire bank off a couple times to get everything right.
What kind of exhaust, what kind of filters, what climate do you live in? It all comes into play.

[Psychonaut]

Look inside the stock air box then look inside the throat of a pod.

[anotherCB]

I run pods and a 4in1 (Yoshimura) on my K7, 20 larger on the mains, 2 clicks richer on the the needle, runs pretty well (a little rough around 2,000 rpm) and idles perfectly at 1,200. No other mods to engine.

[racemx51]

I found it, just the plugs.. Tested the coil with a spark tester today and have spark on all four.. But not through the plugs.. Hadnt put new plugs in yet.. I was getting the whole bike in one piece but plugs are next so I can ride this thing around and get the testing underway..

[lucky]

I run pods and a 4in1 (Yoshimura) on my K7, 20 larger on the mains, 2 clicks richer on the the needle, runs pretty well (a little rough around 2,000 rpm) and idles perfectly at 1,200. No other mods to engine.

"20 larger on the mains" What does that mean?
Can you just tell us what size the main jets are?

"2 clicks richer on the needle"
Which groove is the clip on now of the FIVE grooves on the needle? We do not know where it was to start with.

What size idle jet?

How many turns open on the mixture screw?

If you suddenly snap open the throttle does it stumble or die?

Then we will have useful information

[anotherCB]

The reason that I say "20 larger" than standard is that my carbs are different to yours. The later CB models k7 and K8 have PD carbs and I went from a 110-130. Now maybe your original main jet is 100 (just gessing) and going 20 bigger would mean 120 for you, if you want to copy me.

Same on the needle setting. From the five setting on the needle, mine is standard on the top setting (leanest possible). I moved the needle to the middle setting (2 richer than standard). I might very well be that your standard needle setting is in the middle, than you would have to go to the bottom to copy my changes.

That's why I indicated changes I made and not absolute numbers.

I didn't do anything to the idle or mixture screw.

When I snap the throttle open at 2,000 or the bike goes like hell until 9,000 (if I let her), no hesitating or bugging at all. And I am using the cheapo pod filters. Between 1,200 and 2,000 is still a rough spot, but I have nod had the time and desire to figure that out yet.

[Danno]

replace the spark plug caps and cut the wires back a quarter inch and screw the new plug caps on it will work

[cb650PK]

The reason that I say "20 larger" than standard is that my carbs are different to yours. The later CB models k7 and K8 have PD carbs and I went from a 110-130. Now maybe your original main jet is 100 (just gessing) and going 20 bigger would mean 120 for you, if you want to copy me.

Same on the needle setting. From the five setting on the needle, mine is standard on the top setting (leanest possible). I moved the needle to the middle setting (2 richer than standard). I might very well be that your standard needle setting is in the middle, than you would have to go to the bottom to copy my changes.

That's why I indicated changes I made and not absolute numbers.

I didn't do anything to the idle or mixture screw.

When I snap the throttle open at 2,000 or the bike goes like hell until 9,000 (if I let her), no hesitating or bugging at all. And I am using the cheapo pod filters. Between 1,200 and 2,000 is still a rough spot, but I have nod had the time and desire to figure that out yet.

So when you have replaced the stock airbox with your cheep pod filters, you seem to have gained crappy running bike between idle and 2000 rpm. How is that a good trade of?

[anotherCB]

Many reasons:

1)No ugly airbox to look at
2)More power, in combination with the 4 in 1
3)Good looks for my cafe project
etc.

If I was going to leave the bike original, I would have stuck with the airbox, however that was not my intention. And as I said, I haven't even tried yet to figure out the rough spots between 1,000 and 2,000 because it is so little it doesn't really bother me that much.

[cben750f0]

which brings me back to.....just put the airbox back on....

peace