HONDA CB750F1

[The smudger]

Hi all, thought i might try this one on here as there's a lot of experience D).

I have a Honda CB750F1 SOHC of a 1976 vintage. The short version of the story is i bought it as a non runner earlier this year and when i got it home found the fuel tank full of water . After extensive clean up/carbs off, stripped/ultrasonically cleaned, new plugs, points, coil, tappets adjusted, etc, etc, etc, the thing still runs like sh*t!

Basically when it does start, it runs and smells rich. It doesnt want to know if choke used, and seemed to run better when the air filter is off. I really think it's a matter of setting the carbs correctly, but after downloading the a-z of honda carbs, reading it cover to cover, i'm still none the wiser as to how to weaken the carbs off, this i think would cure the problem?

Pleeeeease help?

Smudger.

 

[(RIP) Kaister]

Plastic carb floats or brass ?

do they still float ?

is the mechanical choke mech working properly on all 4 ?

valve and ignition timing correct ?

 

[bubba zanetti]

re; carbs

are the carb needles not set to high,and the air screw tips ok, just done the zed carbs, set everything to the base settings and went from there, balanced them and its much better

 

[D6]

are the float needles/mains/emulsion tubes worn?, its an old bike, double check float levels
condensors can cause odd faults on the ign side , modern condensors are crap,junk em an use boyers box,s that retain the points

 

[Nice 'n' Fat]

I have a Honda CB750F1 SOHC of a 1976 vintage. The short version of the story is i bought it as a non runner earlier this year and when i got it home found the fuel tank full of water . After extensive clean up/carbs off, stripped/ultrasonically cleaned, new plugs, points, coil, tappets adjusted, etc, etc, etc, the thing still runs like sh*t!

I'm not surprised. You were no bloody good at fixing Land Rovers either

 

[The smudger]

Plastic carb floats or brass ?

do they still float ?

is the mechanical choke mech working properly on all 4 ?

valve and ignition timing correct ?

Floats are plastic and still floating, mechanical choke slides/flaps working OK, Ignition timing OK, Valve timing, dont know about that one, although i would suggest OK because sometimes, not that often though, it seems to run OK. Incorrect valve timing would surely, as its a mechanical thing, make it run rough all the time?

Thanks,

Steve.

 

[The smudger]

Thanks

for all the tips guys, (except the 'fat' one) i think looking at all the answers it is carb related, the main jets were blocked, i tried filing them out first so may have opened them out too much? I'll measure them & let you know the outcome!

 

[cookie]

filing out main jets?

small gauge copper wire is usually the strongest recommended form of attack.

 

[(RIP) Kaister]

for all the tips guys, (except the 'fat' one) i think looking at all the answers it is carb related, the main jets were blocked, i tried filing them out first so may have opened them out too much? I'll measure them & let you know the outcome!

theres your feckin problem

the owner

buy some new jets

 

[Timpo]

main jets were blocked

Basics!

I tried filing them out

Holy mother of God!

May have opened them out too much?

No sh!t.....

I'll measure them

If you've not got access to some seriously accurate measuring equipment (internal) your wasting your time.
Just buy new ones, they are about £1 each.

NB. Do not over tighten the emulsion tubes or mains as the holes in the elumsion tubes twist and totally knacker the carburating properties.

Timpo.

 

[The smudger]

Whoa..

I think i may have opened myself up to huge amounts of ridicule here, and reading my original post, rightly so

When i said 'file', i did use the term 'loosely'. The jets were blocked up with the old dried/gum petrol. I quite literally couldn't see through them. I bought a set of jet cleaners, like a fold out set of minature round files, with which i just about made a hole though them, then found out an old freind had an ulrasonic bath, so popped them in there, result was i can now see the original shaped perfesct roundish hole through them.

Thanks for the advice guys, and yes, i would have ridiculed myself had i read it as someone elses post!!

Definately interested to know where i can buy new jets fir a pound each though, I suppose jets do wear out eventually, and it wouldnt take much to make it run rough?

 

[Mzokk]

See if you can get a set of flatslides off one of these last and best!!

Mine in 1984