Carburetors VB52B information required

[cmsgama]

Hi there, I'm new in here, I'm from Portugal and recently buy a 1980 Honda CB750 F with the carbs VB52B. The information I have from the bike is that have been sitting around without start for more than 10 years, and the bike was imported from Japan in the later 80's. I don't have any information about these carbs, settings, pilot screw initial settings, which parts or rebuild kits fit in these carbs, the stock jets, etc A little help would be nice.

Already clean up the carbs, the jets have the size 68 and 75, are this correct?

Best Regards

 

[amc49]

The 75 should generally be closer to 98-102.............

Idle mixture from 2-2 1/2 turns, below 2 is for emissions, but idles better a little higher.

Any carb rebuild parts from '79-'83 Honda DOHC will pretty much work except for the jets, which need to be 750 jets. Euro carbs don't have the US spec accelerator pump on the #2 carb.

 

[cmsgama]

The 75 should generally be closer to 98-102.............

Idle mixture from 2-2 1/2 turns, below 2 is for emissions, but idles better a little higher.

Any carb rebuild parts from '79-'83 Honda DOHC will pretty much work except for the jets, which need to be 750 jets. Euro carbs don't have the US spec accelerator pump on the #2 carb.

Ok, thanks your fast answer. Is better then get some 98 or 102 jets right? Don't know why in some point the jets are changed. The bike have the stock air filter box and stock air filter. The exhaust is like stock 4-2, the mufflers don't know is are stock or not, but seems like stock.

Regards

 

[amc49]

'79 F used 100, '80 F used 98, and '81 F used 102, take your pick, all close and all using same OEM 4 into 2 exhaust piping.

 

[cmsgama]

'79 F used 100, '80 F used 98, and '81 F used 102, take your pick, all close and all using same OEM 4 into 2 exhaust piping.

Ok, thank you very much.

Another question, I see that these carbs are very sensitive at the vacum and flow at intake side of the engine, but at the exhaust how the system react? What about using the stock air filter and stock air box, but using a exhaust system like one 4-2-1? Have this a major impact at the carbs jetting?

Regards

 

[amc49]

Not much. For absolutely sure use the stock OEM arbox, anything else and the CV carbs go way off in operation. With stock airbox, CVs self adjust more than direct lift carbs do with engine changes like a header but they may need a SMALL amount more of jet, depending on if the exhaust is truly better or junk that just looks good. I've seen some of them have to be DE-jetted to run right, and the mark of an exhaust that actually REMOVED power.

Myself, I do not run 4-2-1 pipes, I prefer 4-1 and am firmly convinced the slightly more mid range torque the 4-2-1 supposedly makes is due to the 4-1 being slightly too big in pipe size and the loss of the megaphone. Because I have no trouble at all getting VERY good midrange out them at all. The problem is getting a good header to begin with, they are not as good as they used to be and ever since all brands pretty much set out to show you how much better they run with a can or canister on the end (it's bullsh-t) instead of megaphone. The megaphone made more power but the noise thing killed them and why everybody now uses a regular muffler there. I learned sound wave tuning on 2 stroke expansion chambers and hate to give that free extra power away.

 

[cmsgama]

Not much. For absolutely sure use the stock OEM arbox, anything else and the CV carbs go way off in operation. With stock airbox, CVs self adjust more than direct lift carbs do with engine changes like a header but they may need a SMALL amount more of jet, depending on if the exhaust is truly better or junk that just looks good. I've seen some of them have to be DE-jetted to run right, and the mark of an exhaust that actually REMOVED power.

Myself, I do not run 4-2-1 pipes, I prefer 4-1 and am firmly convinced the slightly more mid range torque the 4-2-1 supposedly makes is due to the 4-1 being slightly too big in pipe size and the loss of the megaphone. Because I have no trouble at all getting VERY good midrange out them at all. The problem is getting a good header to begin with, they are not as good as they used to be and ever since all brands pretty much set out to show you how much better they run with a can or canister on the end (it's bullsh-t) instead of megaphone. The megaphone made more power but the noise thing killed them and why everybody now uses a regular muffler there. I learned sound wave tuning on 2 stroke expansion chambers and hate to give that free extra power away.

Did you have any brands to advice? What about the systems from the cycleX?

Regards