1978 cb750 carb swap

[Lucky 1]

Which screws?? Do you have a pic?

[Re-run]

I just dont get how some have issues with these carbs. Also, why did you only go 1 turn out on the fuel screw? Base setting is 1.5 turns out. Plus, the 78F runs even leaner jets with a 4-1 exhaust. There is no reason for needing larger jets when all you changed is going to a 4-2 which, if you have the baffles in, are no less restrictive than the Fs 4-1.
Plus, intake has more impact on a/f mixture than exhaust does.
Seldom does a simple exhaust change require changing jets, maybe a bit of tuning but thats it.
I went from the stock pipes to freer flowing slipons and barely any tweaking was needed.
Ask on the other sohc site, few there have HAD to rejet just from and exhaust change.
Maybe instead of larger idle jets, turn out your fuel screw, that's what it is for after all.
Most likely the range of adjustment would equal having those 45s on.

Oh, my slip ons are not welded on or sealed either, so they leak out the front. I don't have a welder.

[Lucky 1]

Thanks for the feed back Re-run.
The exhaust is a 4 into 2 into 1.  Not a 4 into 2 system.

I actually did start with the mixture screws out 1.5 turns.

Would not idle and would bog and quit when trying to rev the engine.
1 turn out did not help. (Of course it would be too lean then)

Putting in the #42 jets completely solved the problem.

I agree with what you say Re-run but the #35mm idle jets are so small
I like the #42mms because they will not clog up as easily.

[Re-run]

I guess I dont have an issue with clogging. I don't even bother running a filter anymore. Only time I had an issue is when I left old gas in the bowls cause I thought stabil would help. Never used stabil again.
I guess I just don't have these issues. They have always worked for me.

[Lucky 1]

I was reading an article the other day that said that the 10% ethenol gas can only sit for 60 days before it breaks down.  The ethanol collects moisture.

[shultz_1978]

Just ordered these today. I think I will clean them and see if they are all stock and try running them stock.

Maybe if I would have just taken the shims out before I drilled the idle jets I would have been fine.  

[Lucky 1]

They look nice in that photo. Let us know what you find.

[Lucky 1]

I wonder what is going on right now??? No new news so far?

Got new carbs then.....

[Piute]

   Been following the tread myself,I'd like to think there out riding
  NO TIME to go on line.
     My stock set up ("77"F2) works great But, havn't road more then 100 miles away due to don't think electrical is 100% dependable YET
   
      points set at 16 , always high octain , 2.5 turns on screws , stock air box / filter ,Stk header pipe(4-1) with baffled 10" glass-pack with no glass fiber's ,But, no tags

[Lucky 1]

The vacuum operated slide was to compensate for atmospheric differences.
Hot and cold days and different altitudes.

It would actually help.

[shultz_1978]

Sorry
 The seller shipped me carbs for a kz1000. They told me they did not have the carbs in the picture. HHHMMM. So I am getting a different set and just clean and rebuilding them to stock to see what happens.

I will keep you posted.

[shultz_1978]

Will carbs came in today, look pretty bad, time to start taking them a part and see what they are made of and what all I need to replace.

[shultz_1978]

Okay
 My carbs are in like a hundred pieces. What is the best thing to use on the bodies to clear them up inside and out?  I just hope I can get them back together.

[Lucky 1]

I hope i catch you in time.

Do not drill the idle jet to 45mm.
Drill it to 42mm it will be perfect with 3/4 turns out on the mixture screws.
120mm main jets.

[Lucky 1]

The carb experts have two answers.
Carb dip and soda blasting.

[Lucky 1]

If they did that on EBay, and without prior notice, you can get a refund.

[shultz_1978]

I was gone to rebiuld them to factory spec. to start. no drilling they have a #35 in them and this set has ajustable needles. I will have to get some pic on here. Thank for the cleaning tip. I was hoping for a back yard mech. tip

[Re-run]

Don't drill at all before testing things first. Drilling removes the venturi effect required for proper fuel atomization.
As for cleaning, the best cleaning would be from ultrasonic cleaning. Other than this, it becomes personal preference on what cleaner is the best. I like simple green, some have had discoloration but I have never left them soak for days on end. It is safe on other bits though unlike carb dip which will eat plastics and rubbers.
I soak a bit in simple green and then scrub it with something that has long bristles, like a nail brush.

[shultz_1978]

Thanks
 I will not be drilling on these jet. I am going to put them to stock and go from there. I use Shinyribs secret weapon with the toilet bowl cleaner and water 30 - 45 minytes work nice. THANKS Shinyribs. now I need to start getting parts back together.

The guy I got the carbs from sent them with two # 1 bowls, one #2 bowl, and one 3.4 bowl. Will it hirt any thing if I run a # 1 bowl one # 3 carb?

I know that the drain screw will be going the wrong way but will it hurt any thing else?

I am thinking about painting the carb bodies with grill black and polishing the tops, bowls, and any thing esle I can. I think it would give it a different cleaner look.  What do you guys think?

I added some pictures of the carbs and needle. and the needlesthis is what my other carbs had But two different bike shops work on the carbs and the adjustable needles run off. hhmm

[Re-run]

No, it will be fine. The carb bowls are not special, except for maybe #2 but I think they are all the same.