Topic: restoring my CB750 K0 12/69

[jonda500]

so almost done with the final touches on the bike, but for some strange reason my throttle grip is stiff. it doesn't rotate easily, the cables are new and are not being pulled or stuck anywhere...any thoughts of what could be causing this?. regards


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Undo the switchblock and move it outwards 1 mm so the grip doesn't rub on the handlebar end?
John

[esantella]

hey sorry for the late response but was out of the country, today I will check and will let you guys know. I'm also going to do a complete carb clean and I have bought a rebuild kit for all the carbs so that's the next step. almost there..


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[Johnie]

Tell us about this rebuild kit? Emulsifier tube, needle & slow jet are all brass and can be cleaned. Some rebuild kits are not compatible with these carbs even though they say for the 750. What did you buy?

[esantella]

Johnie I have already taken my precautions.. Gonna open up the carbs later on today and will verify what works and what doesn't. I bought some kits from vintageCb750


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[Johnie]

vintagecb750 is a good seller. Let us know what you find out. If those old carbs have the brass floats you might consider getting rid of them. If they are not leaking now they will soon. You can check it by shaking the float when you remove it and listen for the fuel inside.

[esantella]

So wanted to give you all a rundown of what I have achieved:

Cleaned and restored all of my carbs and fired her up. Turns out carb 2 and three were not operating properly and that was fixed with the restoration parts. I do have a leak that was not present before coming from the Tachometer screw attached to the motor, really weird thought you guys could help me out. I also have a oil leak coming from underneath the motor guess it's coming from the oil pump..maybe a gasket?. I also would like to know what is the suggested float height on the carbs, maybe someone can help. Well these things came up once the carbs were restored. Any thoughts..

regards

[Johnie]

Never had a tach screw leak, but behind the area where the tack cable goes is a seal which usually needs replacement part #91256-425-003 for about $3 from Honda. The oil leak way on the bottom may be your oil pan gasket. I spoke to Hondaman about the float setting on my KO and here is what his response was:

"Honda used the 24mm off the notch until about 3/70 or so. The bikes fouled plugs a lot when ridden gently with no highway trips though. The Honda fix for the fouling plugs in the KO bikes was:

1.) change the float level to 26mm from this notch instead of 24mm, or...

2.) change the main jet to #115 and raise the slide needles to 1 notch (to 2nd from the top).

[esantella]

Never had a tach screw leak, but behind the area where the tack cable goes is a gasket which usually needs replacement part #91256-425-003 for about $3 from Honda. The oil leak way on the bottom may be your oil pan gasket. I spoke to Hondaman about the float setting on my KO and here is what his response was:

"Honda used the 24mm off the notch until about 3/70 or so. The bikes fouled plugs a lot when ridden gently with no highway trips though. The Honda fix for the fouling plugs in the KO bikes was:

1.) change the float level to 26mm from this notch instead of 24mm, or...

2.) change the main jet to #115 and raise the slide needles to 1 notch (to 2nd from the top).

Thanks Johnie! I will order it right away, found it on partszilla!.


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[HondaMan]

Check for one slide to be dragging: this can happen if the cable on top of that carb does not enter straight-down.
The acceleration symptom sounded a bit like the fuel petcock screen might be plugged up? Pull off the little bowl on the bottom of it and then the O-ring and screen, and make sure the screen is clean.

The idle air screws (the little ones, toward the front of each carb) are set at 1 turn from closed, give or take 1/8 turn in or out. The idle speed screws are a little tricky to master since each one is independent, but if you play with them for a while you can figure it out: if you get them all set the same and then open the throttle, the slides all move exactly the same at once. That is, until the cables start to stretch...

The clutch rattle: if the idle speed synch on the carbs is off a little bit between the carbs, the clutch "rattles" because the primary chain jumps a little with the uneven-ness of the engine power. To resolve this the easiest way, use the 4-gage vacuum gage set and adjust the idle speeds screws until they all have closely equal readings. then when you start to crack open the throttle, you will likely see one vacuum drop first, which means that one's slide is moving before the next one in the firing order. So, either adjust the other 3 up a bit on their cables adjusters, or the offending one down, until cracking the throttle makes all of them move at once. (Hint: put a fan in front of the bike, as your first time at this may take a while. The 2nd time takes 5 minutes... ).

[pipeguy]

love the rear seat on red cafe, where did you get it or did you make it?

[Terry in Australia]

Geez, what a nice bike, congrats! Honda must have really been working hard in 1969, I've got two 1969 engines, 1010XXX (October build) and 1012XXX in my 1969 bike with closely numbered frame, I have no idea when it was built, but if your 1016XXX was built in December, then I'm thinking my 1012XXX bike was an October baby too? Cheers, Terry.

[pipeguy]

Sorry to hi-jack, Terry mine is 1013XXX, but on title it's says 70, I was going to order a plate for neck I guess it would have been a 69?

[Terry in Australia]

Hey yeah mate, yours will be a 1969 bike for sure! Cheers, Terry.

[esantella]

Hello to all been off the forum for while working away. Like to see if you guys can help. So everything is now where it's supposed to be, but still the bike revs like crazy after while of driving it it starts reving up like crazy at 4,000 rpm. Even holding while holding down the clutch won't rev it back down to 1200rpm which is were it's set. My choke is not functioning correctly can it be this? Other than that I can't think of any other reason.

Regards


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[harisuluv]

What's wrong with the choke?

Runaway idle or not coming down from revs is often times a lean condition.

[esantella]

Sounds like I might be running lean; possible cause other than re syncing the carbs? The only way my revs go down is if I pull the choke up "open", weird...should be reving up?. I have also replaced my throttle cable with a original Honda part, I have no idea how it's routed, never found the factory recommended method.. the way I routed it may be pulling it causing higher revs.

Thanks suggestions welcome...

[Terry in Australia]

G'Day Mate, if your 4 throttle cables are a bit tight with no free-play it'll rev higher when warm, so make sure you've got a few mm's of free-play. if the carb boots aren't sealing well (old and cracked, for instance) it'll suck air, which will make it rev higher, pulling the choke lever up will close off some air, making the revs drop when the engine is warm.

If the slides are sticking  (you only need one sticking and the other 3 will go out in sympathy) it'll rev high when warm, if any of the 4 idle screws are set too far in it'll rev high and finally, if you've put one or all slides back in 180 degrees out (easy on K0 carbs) it'll rev too high. That should give you something to think about! Cheers, Terry.

[Sgt.Pinback]

Hello to all been off the forum for while working away. Like to see if you guys can help. So everything is now where it's supposed to be, but still the bike revs like crazy after while of driving it it starts reving up like crazy at 4,000 rpm. Even holding while holding down the clutch won't rev it back down to 1200rpm which is were it's set. My choke is not functioning correctly can it be this? Other than that I can't think of any other reason.

Regards


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I still believe you mixed up the slides and they dont go down the WHOLE way.

[esantella]

G'Day Mate, if your 4 throttle cables are a bit tight with no free-play it'll rev higher when warm, so make sure you've got a few mm's of free-play. if the carb boots aren't sealing well (old and cracked, for instance) it'll suck air, which will make it rev higher, pulling the choke lever up will close off some air, making the revs drop when the engine is warm.

If the slides are sticking  (you only need one sticking and the other 3 will go out in sympathy) it'll rev high when warm, if any of the 4 idle screws are set too far in it'll rev high and finally, if you've put one or all slides back in 180 degrees out (easy on K0 carbs) it'll rev too high. That should give you something to think about! Cheers, Terry.

Thanks for the information, this has been quite a headache. Are there any specific marks or labels for which slides go where!? I mean I just placed them in as they fit in on each carb... and yes my bike revs once it's hot...

Another situation im dealing with is the fact that my pipes 1/4 are not as hot once I shut down the engine, just 2/3. Might this be an indication of carb boots/slides..I checked, cleaned and set my ignition plate and point gaps at .014. I appreciate all the help I can get maybe someone has some compassion and offers me a magical solution, a phone number to call....... wishful thinking.. hahahhaha.

Thanks to all the valuable help guys, together with your help I can, I will fix this.
Regards.


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[Don R]

 My 1014100 was built 11/69 just for reference The sandcast is 5511, not sure what month it was, someone suggested June but it has a 70 title. Delivered to it's first owner 1/70 right after Christmas.

 I would recheck timing with a timing light since 1/4 are on the same coil and points set.

[esantella]

My 1014100 was built 11/69 just for reference The sandcast is 5511, not sure what month it was, someone suggested June but it has a 70 title. Delivered to it's first owner 1/70 right after Christmas.

 I would recheck timing with a timing light since 1/4 are on the same coil and points set.

Thanks Don, mine is a 9/69 build. What is the frequency setting for the timing light? When I crank the bolt both points are opening and closing accordingly, and the gaps are at .014 the main plate is set a bit off to the right thinking that might be the reason for the acceleration issue. Will be sending pics of the timing setting for some support.

Regards


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[esantella]

So guys fixed the royal beauty! thanks for all your valuable help!, the end issue was in fact the Slides had them on the wrong way... :/ Will be posting some new pics once I get her clean and detailed.

regards

[The Lone Builder]

That needs restoring?

I wish mine looked so good.

Good luck with whatever you do, but if it were me, I'd stick to as original as possible.

[esantella]

That needs restoring?

I wish mine looked so good.

Good luck with whatever you do, but if it were me, I'd stick to as original as possible.

Sean when I mean restoring it's actually mechanical work, finally got it running quite nicely. Esthetic is spot on!. Regards


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[esantella]

another update:

1. Carbs set correctly and tuned
2. Just ordered some new ignition coils (noticed some damage on the spark cables out of the coils)
3. Bike idle is at 1200 rpm... factory recommends 950rpm. Any thoughts or suggestions?.
4. While driving back home noticed the bike was misfiring and power was not engaged properly when pulling the throttle. Going to check my Timing again.. Any thoughts? Or could it be the damage in the coils causing the misfiring?

Looking forward to your thoughts!



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