750f1 carbs

[kifer]

Had a strange one today, The last time out on bike she started to run a bit rough so got around to having a look today.
Found the new inlet rubbers I bought about a year ago so thought I would fit them as old ones a tad hard, Removed carbs now for a full check and tune while there off, guess what removed float bowl on number 4 and main jet was inside bowl ? has anybody heard of one falling out before?
 
Will fit back to bike tomorrow set up and vacuum have a feeling she is going to run ok again.
Cheers Tom.

Quick question, Is the starting point for air screw on F1 1.5 turns.

[Spitfire]

Never heard of that one, here's some carb specs, the CB750F supplement to the CB750 Honda workshop manual gives 1 turn plus or minus 3/8.



Cheers

Den

[mick]

Hi Tom i've had a pilot jet fall out on me probably my own fault for not nipping it up  , cheers Mick.

[Waggles]

I concur with the book setting, my F1 carbs are at 1 turn out and she runs fine.

As for jets going AWOL, as the main jet isn't really used until 3/4 throttle not surprised she still ran ( albeit a bit rough )

My second ever bike was a BSA C15 which was ridden everywhere at full throttle ( anyone whos had one will know why ) and I had the main jet fall out, thing is all I noticed was a bit of a cough as you whacked the throttle open, apart from that it ran fine! think that says more about the crap carburation than anything!

[cb750stu]

Should you put a smear of grease on the threads of the jets etc to stop seizure and corrosion
Regards
Stu

[kifer]

Thanks for help, Bike sorted and running sweet will check balance as a matter of fact but sounds spot on.
Thanks for chart and yes Mick could have been me on Assembly the old brain not what it used to be. Have never put anything on threads have found things only seize when left a long time with fuel present.

One thing though always struggle refitting carbs to head took about an hour have never been shown so just fit best I can,
There must be an easier method ? How do you do it I would like to know? always willing to learn.
Cheers Tom...

[Spitfire]

I just hook the carbs onto the stubs on the head and lift, they pop on no problems, then I fit and tighten the clips, the only trouble I had was before I changed the inlet rubbers the old ones were hard and would not "give".

Cheers

Den

[kifer]

Cheers Spitfire do you fit inlet rubbers to head 1st?  I must admit fitting carbs to head on F2 easy but struggle with F1 with the longer inlet rubbers Cheer Tom
Any one else struggle or is it me getting bloody old and useless

[Spitfire]

To replace the carbs I do it in one hit, the carbs are complete with all their rubbers, the head is bare.

Cheers

Den

[steff750]

  i always put the rubbers on the head first because they are at a  angle coming from the head and you can then rotate the rubbers slightly so they are flush with the carbs, i then push the carbs home with a flat piece of wood levering it against the frame down tubes behind the airbox and against the carbs they just pop straight back on

[Waggles]

On my F1 I struggled a bit with new rubbers but hit on a good technique, I put rubbers on the head first, smeared a little washing up liquid ( only the teeniest tinest ikkle bit ) in the openings offered up the carbs and then tied them in position with a piece of rope going around the motor. I then used a bar to tighten this torniquet - like to put pressure on. Now the carbs didn't go on just using this but you can wedge the torniquet bar so the pressure is still on and that gives you your hands free to lever them the last little bit.

You could also use a ratchet strap but I am too tight to buy one just for that!