Topic: 77' CB750 carb jetting, throttle shaft and choke shafts o-rings

[77cb750speed]

I have a 77' CB750 that has wide open exhaust. Has full factory 4-4 exhaust just been gutted and both evenly slant cut on the end. Was like that when I bought it, I don't like how it looks but I love how it sounds. I am yet to get the carbs completely rebuilt. Wondering while I still have them in pieces and waiting on parts, should I need to replace the jets. I know its not a problem to do it while they are on the bike just want to get it done (if it may be necessary) while they are on the bench.

And any help on finding throttle and choke shafts o-rings would be great. I have one carburetor that already has throttle shaft o-rings and they look to be very warn.
I also need help finding the little plastic deals(pictured) that go on the choke shafts(3 on each shaft) If I don't find any I might try my luck at making some out of JB Weld(its gas resistant)

I hijacked your picture joedanger11 hope you don't mind.

[lucky]

Trying to change the jets on the 1977 CB750 while the 1977 carbs are on the bike will be almost impossible and you will probably strip the screws.

Needs to be done with the carbs off of the bike.

Those seals on the throttle shafts have to be air tight or they will not work. You would not be able to tune the carbs because of the air leaks.

Those seals on the throttle shafts have to be air tight but the shaft has to be moveable so you might try some teflon seals of some type. Google it.


If you give me ALL the info about the carb jetting etc., I could help you.

BTW...There was a thread all about replacing those seals.

[77cb750speed]

I have looked at so many threads on this site but have not seen any about the throttle shaft seals. I have searched many times and it always says Your search query didn't return any matches. Even when I search the title of this thread it says the same. I don't know if there is something wrong or if its cause I'm a new member.

Anyway I have completely stock carb jets 115 main and 35 idle. The slide needles are on the very top grove, that way when I got the bike. Thinking I should move the clip on the slide needles to the middle grove. The bike choked and gagged all over itself when I first got it and carb 1 and 3 was leaking fuel. Once it got up to about 4500 rpm it ran decent.
And I have read the floats need to be set at 12.5mm and at 14.5mm I set mine at 12.5 as that is what most say and one place said 12.5 for the K and 14.5 for the F. Did another google search and found that most with 4-2 exhaust run a 42 idle jet and 120 main jet. So would I need a higher idle with the 4-4 exhaust, it is more like drag pipes just has the baffle housings on it. I need to get a few pictures of it and post them.


Question for anyone... What do you think it looks like with red oxide primer. I have been thinking about just clear coating over the red oxide primer. Have been debating Sublime Green Pearl with metallic clear coat and some thoughts on Candy Apple Green. Maybe even a Copper Plate Coating or Stainless Steel. The Sublime Green Pearl with metallic clear and Copper Plate Coating are my main ideas.

[77cb750speed]

I was searching wrong I was using the search at the top right not the Google custom search at the right under Home. Glad I got that figured out much easier now. I have now found seals for the throttle shaft(kinda pricey) at motorcyclecarbs.com
And I found the o-ring sizes, found the throttle shaft o-rings 10mm id x 2mm cs 10 for $8.90 but can't find choke shaft o-rings 6mm id x 1.7mm cs found 6mm id x 1.5mm cs 10 for $5.90 and 6mm id x 2mm cs 10 for $6.90. I could buy some 3/16(6.07mm±0.13) ID x 5/16 OD x 1/16(1.78mm±0.08) CS 50 for $3.80. Give the extras away here if they work.

[77cb750speed]

Should I use Viton or Buna o-rings for the throttle and choke shafts?

And what screws are you referring to that I will strip out. If it is the bowl screw I think I have eliminated any change of stripping them out again. I have bought allen head screws for bowls, accelerator pump, and carb top.

[bollingball]

Should I use Viton or Buna o-rings for the throttle and choke shafts?

And what screws are you referring to that I will strip out. If it is the bowl screw I think I have eliminated any change of stripping them out again. I have bought allen head screws for bowls, accelerator pump, and carb top.

Viton is the best hold on I saw shaft bushing I will find them in a minute
Ken

[bollingball]

http://forums.sohc4.net/index.php?topic=108050.0

Found them it was lucky Don't know why he did not tell you on his last post he just said there was a thread on it but it was his
Ken

[77cb750speed]

Thanks for the help bollingball but I am rebuilding 77 carbs. They have the shaft going threw the carb bodies and have a felt seal on each side of 2 and 3 and one side of 1 and 4. I have found seals at motorcyclecarbs.com but they are 6.95 each. I will get them if the o-rings don't work out. I have been working on these carb for about a month now and just want to get them back together and get the bike back on the road.

Still needing info on possible carb jets for my wide open 4-4 exhaust. I love the look of the 4 pipes standing behind it. Might put a glass pack inside of each exhaust if I get pulled over for it being too loud but that is looking into the future.

[77cb750speed]

Lucky, you said you could help me with my carb jetting, just wondering if that offer still stands. I have 115 main and 35 idle jets. I have got the seals for the throttle shaft at motorcyclecarbs.com and have o rings on the way from oringsandmore.com.

[lucky]

Please let us know what kind of air intake this bike has.
Then I can advise you about jetting.
Moving the needle CLIP DOWN one notch will help.

[77cb750speed]

I have stock airbox with K&N filter. Down one to let more fuel in at WOT

[bollingball]

There was a post  about making the felt seals it takes a certain type of felt. If you search you may find the thread. If I find it I will PM you. You end up with a piece then use a hole punch to make them.

Ken

[lucky]

I have stock airbox with K&N filter. Down one to let more fuel in at WOT

Yes it will actually effect the throttle all the way from 1/4 to 3/4 throttle
WOT.

The 115 main jet is going to effect the WOT mostly and a little will bleed over into 3/4 range.

I still think you will need a Larger idle jet, but see if the mixture screw will get rid of that hesitation when first opening the throttle.

[77cb750speed]

Lucky,
I don't even have the carbs back on the bike yet. It ran like #$%* when they I think mostly cause 1 and 3 were leaking gas like hell. I am just seeing if I can fix a future problem before I run into it.

Bollingball,
I have O-rings on they way. I read the post your talking about and I just don't want to mess with the felt.