1980 CB750C jetting question

[sub1427]

Just bought her yesterday, ran an entire can of seafoam through her, after the first one the idle is better (by better I mean its staying at about 2200-2500 rpm, I know thats not correct but I hope that means that some of the gunk and junk is getting cleaned out, I adjusted the idle screw today and its back around 1500rpm.  Now here is my question, the previous owner put pod filters on the bike, I dont believe the jets were adjusted, there is a 4-1 pipe on it, what size are the stock jets? Can I tell by taking them out and looking at them? And what size do I need to compensate for the bogging midrange acceleration? Once I'm cruising above 6k rpms she screams like a bat outta hell, but now shes a little slow off the line, some back firing and popping during hard acceleration.  If I run with a little choke after shes warmed up it seems to be more responsive.  Any help would be greatly appreciated

[Re-run]

OK given that info, it might not be the mains you need to worry about too much. If it is slow off the line and such, you probably need to adjust your fuel screws to create a richer idle mix.
the jet size should be stamped on the bottom of the jet.

[woodsrider250-2]

Best (and only real way, IMHO) to get the pods to work on these DOHC VM's is to install specially tapered needles....These are only available in the K&N stage III jet kit ($100).  With the pods on I doubt you're even getting to the secondary main (aka "MAIN") jet.  This is only 3/4-Full slide lift which they won't get to without the correct vaccum (ruined by the pods).  Cheapest, best, and easiest thing to do is to ebay a factory airbox and put it back on with a plain paper filter.  Back to jetting all of these bikes pretty much regardless of location can benefit from bumping the PRIMARY main jet from the stock #68 to a #72 or #75.  This jet is 60+% of the slide travel.  These bikes were jetted lean from the factory apparently do to EPA BS (learned that somewhere else, but had already did this to my carbs).  Pods will worsen this condition, but don't expect the simple primary main jet richening to cure your problem.  Who knows what jets are in there now?

[Re-run]

Thing is, every bike acts different and that is why jetting advice is hard. My 78K uses different carbs to be sure but a change to pods rarely requires upping the mains and usually turning the fuel screw out to richen things a little does the trick. maybe some plug readings at various rpm will help decide which way to go.

[woodsrider250-2]

Yes, you're right jetting over the keyboard isn't very good, but this will work in most cases.  The DOHC carbs are completely different.  Yours function with some sensability.

[clay taylor]

if you add pods what do you do with the air lines that went to airbox?

[TOOLS1]

You did not like my answer in your other post?
TOOLS

[clay taylor]

--- [hidden email] wrote:

From: "TOOLS1 [via Honda CB750'S]" <[hidden email]>
To: clay taylor <[hidden email]>
Subject: Re: 1980 CB750C jetting question
Date: Fri, 14 Feb 2014 21:02:47 -0800 (PST)



You did not like my answer in your other post?
TOOLS



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1976 CB 750-A X 2
1977 CB 750-A X 2
1977 CB 750-K X 2
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
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