Topic: Need diagram/manual for KeiHin PD 42A carbs for '78 CB750F3 Super Sport

[Wayne Meuir]

John, or anyone who has one:  I am really stuck on my carbs until I can see a close up or exploded view pic of the way the choke rod springs are attached.  My Clymer has nothing.

I am finished with the carbs and I have tried for a couple of hours to figure out how to connect the two choke rod halves.  There are actually two springs, I think I have the one closest to the #2 carb hooked up correctly, but the smaller spring that connects the 3-4 choke shaft has me stumped.

Wayne

[joeb]

Hope I' m not to late but you can get teh rebuild kits for you 78 at serius they went way up got mine 6 months ago for for about 25 bucks a carb.  http://www.siriusconinc.com/carb/parts.asp#.  Sorry got ahead  of myself you already have that info.  When I got my kits the float needles were garbage had to use my old ones. They kept getting stuck closed no fuel when you needed it at high rpms , but the rest of the kit was good. Let me check my manuel. Be right back.

[joeb]

Well lets give this a try.

[Wayne Meuir]

Joe, you got it my man, I thank you a bunch.  That is exactly what I needed.

Wayne

[Wayne Meuir]

I got the carbs reassembled according to the diagram.  However, the chokes don't work very smoothly.  The are not binding or anything they feel real smooth and free if you work them by hand, but when you acuate the lever by hand, the don't close very smoothly.  When you release the lever, they open back up really well and without any binding.  I replaced the butterfly screws with stainless allen head screws and put lock tight on them because the original screws were toast by the time I got them out.  Has anyone every had one of them back out?  I suspect that would make a mess at 8000 RPM's.

Can't put the carbs back on the bike until I get the accel pump I ordered.

Thanks for the help guys.  I hope it runs correctly once I get everything adjusted properly.

Wayne

[joeb]

Just make sure they open and close with the cable  attached . Never lost a screw ,well maybe a had a few loose screws . lOL 

[Redman]

Hope this helps. If not I`ll try to take a better one.

http://i219.photobucket.com/albums/cc197/Canman_album/100_0957.jpg

[mustangcar]

had the same problem after rebuilding them k7/8 carbs,the choke butterflies would move only when you move them by hand(touching the butterfly valves) but not when you moved the top mechanism,drove me nuts,till i compared the pressure to another set of carbs,,, the buttlerflies seemed loose enough but they weren't they were binding in the bores,,had to adjust the butterflies(two screws each) a milimeter here and there sideways,they were binding a bit thats what causes  the choke not to work,they have to have no binding anywhere for the choke to work with the chokecable

[Wayne Meuir]

Redman, good pic.  That is exactly how I have the spring hooked up.  I was not quite sure how much tension to put on it, so I just wound it one revolution and it would not even budge the chokes, so I went around again.  It works partially but not the way I think it should.

Mustangcar, I had not thought of that, but I expect that is what is wrong.  I'll bet the bufferflies are dragging on the inside of the bores just slightly causing the chokes to hang up.  I will loosen them one at a time and try to center them tomorrow.

[Wayne Meuir]

Mustangcar, You got it right.  I loosened the butterflies one at a time and when I loosened up #3, everything got right.  Now the chokes work smooth and easy.  Thanks a lot, it never occured to me to check that.

Wayne

[tofan]

Well lets give this a try.

Does anyone have the full book of this? Or at least the pages showing the other 3 carbs?

[madmtnmotors]

Well lets give this a try.

Does anyone have the full book of this? Or at least the pages showing the other 3 carbs?

PD Carbs:  http://forums.sohc4.net/index.php/topic,100352.msg1669248.html#msg1669248
                http://forums.sohc4.net/index.php/topic,110931.msg1248354.html#msg1248354
                http://forums.sohc4.net/index.php/topic,48858.msg515204.html#msg515204

[tofan]

Found it: https://4-stroke.net/download/workshop-manual/101-workshopmanual-for-honda-cb750-k8-1978.html

[tofan]

Thank you

Well lets give this a try.

Does anyone have the full book of this? Or at least the pages showing the other 3 carbs?

PD Carbs:  http://forums.sohc4.net/index.php/topic,100352.msg1669248.html#msg1669248
                http://forums.sohc4.net/index.php/topic,110931.msg1248354.html#msg1248354
                http://forums.sohc4.net/index.php/topic,48858.msg515204.html#msg515204