Topic: Carb problems cb650

[nate sere]

I traded the 650 carbs for the 750 carbs so thats not a choice.  I need to figure these out.   I am running pods, open headers, and keihnin 750 carbs.  We put 110 jets and advanced the timing and it helped, but its still not right. 

I was thinking about dropping down to 102.5 jets.   I am looking into getting some type of muffler but hate to alter the look of the bike.   Its exactly what I want right now.....

The stock 650 carbs came with 90's I believe.     Will the 102.5's help?

[Pinhead]

With pods? The 650's carbs are a cast-iron #$%* to tune since you can't raise the needles or change the idle jets. The 750 carbs are a bit more tunable.

In my '79 with the stock airbox I run 102.5's since I removed the air filter cover. With just pods you'd probably have to go much larger than that. I believe a member with the 650's PD carbs went all the way up to 120 mains but I could be mistaken. I'm sure there's a thread or two out there with regards to the 650 and pods...

[nate sere]

but im using 750 carbs now.   is that what you are using?

[phil71]

you're on your own bro. You've introduced so many random elements here, that nothing any of us say is anything more that speculation. Keep dicking with it till it runs okay, and eventually it will. but nothing we say matters at this point... you have a one of a kind, and tuning is your problem now.

[nate sere]

so i'm the only person on this board who owns a cb650 custom, with pods and 4-1 open pipes who is using cb750 carbs?

[trueblue]

so i'm the only person on this board who owns a cb650 custom, with pods and 4-1 open pipes who is using cb750 carbs?

You are the first I have heard of, but I can't be certain

[Retro Rocket]

so i'm the only person on this board who owns a cb650 custom, with pods and 4-1 open pipes who is using cb750 carbs?

You aren't really listening to people that know mate, that combination is going to be extremely hard to get even close to running well.....
750 carbs hate pods at the best of times and it is well documented here, add in those pipes and you are going to spend a lot of frustrating hours trying to get it right......    Good luck

[scunny]

nothing wrong with tinkering Mick. anything is possible nate. you are sure giving yourself an uphill battle tho.

[Retro Rocket]

nothing wrong with tinkering Mick. anything is possible nate. you are sure giving yourself an uphill battle tho.

I am a born tinkerer mate, but some things just make life a lot harder.....

[Pinhead]

but im using 750 carbs now.   is that what you are using?

Nope, I have no experience with that Carb combination so I'll probably be of no help at this point.

[nate sere]

I thought that I was getting too much fuel from the CB750 so I went down from 110 to 102.5 and it was much worse.   I went the other way and went to 120's and it ran like a whole new bike.  Pulled very hard all the way through the rpm band.  Slight hesitation on very bottom end and very top end.   I am going to try 125's tomorrow just to see if it makes any difference, but I am pretty sure that the 120's are going to be the best solution. 

[phil71]

are those numbers honda, or dynajet? that hesitation out of the hole is probably the vast mismatch when the pilot jets hand off to the mains. At least you're getting closer.
125s seem awfully big for a 650 with no internal mods tho.

[nate sere]

no known internal mods.

It was really fast and pulled the front tire a little in 1st.