Topic: K1 petcock rebuild kit?

[Stev-o]

The petcock is leaking on my K1 tank, but only when the lever is in the off position.

I'm pretty good at finding parts but having a difficult time with this one.  I have not been able to source a genuine Honda kit and prefer not to spend $70 on a new petcock if all I need is a rubber valve gasket.  What have you guys used? 

New petcock:   https://www.ebay.com/itm/272332113104?fits=Year%3A1971%7CModel%3ACB750&_skw=cb750+1971+petcock+rebuild+kit&epid=1011843723&itmmeta=01JCGM71Y82NFMWZMB2F9448M6&hash=item3f684244d0:g:gFoAAOSwZ2FlLqdd&itmprp=enc%3AAQAJAAAA4HoV3kP08IDx%2BKZ9MfhVJKmTkfbPcJ3TUDz%2FhUh6ozmcxSdIWZ9ZfT0P%2B%2B%2BvmkrQ%2BCsAP%2BihQDknvDYg%2F17gmtKZF5scKIpc4T%2FjRfOoqK0Qlm8VUcHKgd6zJ4%2BvUP6ReFGAG5Y8Bt3yJwvCsfaJXLXv9B5GkiLn4a6LEGtZq77a05T3EfKLIaicJ3LQPJarrybTnSBmxfISu5zNC96wmWmVB1UlhtwZmzbaNDJQqBR%2BO2T%2FOVK1ZjLl8V5qTnHQIilbNVg7aK1%2FvDMOFzp%2BBWxLlYrXU5OXmfxpOWjtMUoC%7Ctkp%3ABk9SR56fnJTkZA

Rebuild kit:

https://www.common-motor.com/honda-early-cb550k-petcock-rebuild?srsltid=AfmBOoqIidiBhqOK84y5nWr4wfZiaIEJEb24NU9hhzxsHyf88k5TXi0J

[bryanj]

There is no "kit" you buy the circular seal, bowl O ring, petcock to tank O ring, fuel strainer and not forgetting the special fibre washers for the holding screws all as seperate parts, not sure if you can getvthe wavy washer seperate

[Nurse Julie]

This is the kit I sell.

[CycleRanger]

4into1 has a kit as well.
https://4into1.com/petcock-rebuild-kit-honda-cb160-72-77-350f-500k-550k-750k/

CB750supply has the whole petcock for ~$35. (repop)
https://www.cb750supply.com/search/?q=CB-70407

Scrambler Cycle has a kit too.

The round gasket is also still available from Honda.
pn 16955-268-020

[bryanj]

Sorry, should have said there is no Honda part number for a "Kit".
Out of the alternatives i would use nurse julies, just add the two thick fiber washers for the screws holding petcock to tank.
Theses are a non standard size, extra thick and expensive as Honda parts

[seanbarney41]

Steve-O, be sure to tear down, clean and inspect the petcock you have now before buying just the 4 hole rubber...I have seen Petcocks that were corroded internally and would not seal no matter what.  Also sometimes all they need is to have the wavy spring sort of re-tensioned or also sometimes flipping the four hole rubber so it faces the other way (Just flip it over!) can get them sealed up again.

[Stev-o]

This is the kit I sell.

Hi Julie..that is what I need but prime riding season here in Texas is now, dont want to wait for a package from the UK.  Thanks though...

[Stev-o]

4into1 has a kit as well.
https://4into1.com/petcock-rebuild-kit-honda-cb160-72-77-350f-500k-550k-750k/

CB750supply has the whole petcock for ~$35. (repop)
https://www.cb750supply.com/search/?q=CB-70407

Scrambler Cycle has a kit too.

The round gasket is also still available from Honda.
pn 16955-268-020

Hey Ranger...I did see that on 4into1, but am leery buying anything but genuine parts from them.  And I've had bad luck with re-pop petcocks in the past, not going there again. Did not know the gasket was available, thanks!

Going to go against Sean's sound advice and just order the valve gasket but will slightly tweek the wavy washer too.  Highly doubt the petcock is corroded inside.   Thanks all

https://www.ebay.com/itm/305671595089?_skw=Honda+NOS+16955-268-020&epid=1437277520&itmmeta=01JCK0Z4GMWG2JK6AK9MXNDSPH&hash=item472b726451:g:hCcAAOSwZLBmkjnp&itmprp=enc%3AAQAJAAAA8HoV3kP08IDx%2BKZ9MfhVJKl58%2Bx4K6uLR4lO%2BsrArWZoBITGdvO1WDNv8Mz1KlSf01%2BC%2F0PjBVd73r1b%2FiWtS%2BrFsagTr7SlUTWF3VnjZJY7IMFWxhPpihUL5l%2Bo8pIjWzVl2KxjqLoD37UgIAMiz6Iun6VfHTedjlKyyJUyiGxRWw%2BFtqwoF1PugFqP2tb5fcdbuC1647baKI53ViTH%2F4Tefso7iglZKcP0sIfI2xcYABE36jwXQHP5v5D%2FFbpbrvNKOShS9I5kTjiX6JIwuV5uGLGkQbyLu3taMZBuAqfWHlo4xIF7bgtuqBbC501jAw%3D%3D%7Ctkp%3ABk9SR7LI_ODkZA

[CycleRanger]

Sounds like a plan.
It's best to try to change that round gasket without removing the petcock entirely so not to disturb the other gaskets.
Imho that petcock is a poor design the way it seals to the tank.
Honda must have agreed since they changed on the later bikes.

[Stev-o]

It's best to try to change that round gasket without removing the petcock entirely so not to disturb the other gaskets.

Yes, my plan is to remove the tank but not the petcock from the tank. There's not much gas in it so I can tilt it so I dont have gas leaking all over when lever is removed.  Gasket ordered...

[ZTatZAU]

The petcock is leaking on my K1 tank, but only when the lever is in the off position.
...

Just curious Steve, but is your petcock leaking fuel out of the petcock itself?  Or is it simply not shutting off the fuel to the carbs when in the off position?
ZT

[Stev-o]

The petcock is leaking on my K1 tank, but only when the lever is in the off position.
...

Just curious Steve, but is your petcock leaking fuel out of the petcock itself?  Or is it simply not shutting off the fuel to the carbs when in the off position?
ZT

The petcock is leaking out of the lever area when turned on, it is still working properly when in the off position. It's an odd issue that I have not seen before, I write it off to the the nasty ethanol fuel.

[HondaMan]

The petcock is leaking on my K1 tank, but only when the lever is in the off position.
...

Just curious Steve, but is your petcock leaking fuel out of the petcock itself?  Or is it simply not shutting off the fuel to the carbs when in the off position?
ZT

The petcock is leaking out of the lever area when turned on, it is still working properly when in the off position. It's an odd issue that I have not seen before, I write it off to the the nasty ethanol fuel.

It's actually the wet-swell and dry-shrink action from the ethanol that causes the big 4-hole rubber part to shrink, leading to the 'weeps'. If you add an ounce or two of [any] oil to the gas in the tank when you fill it up, it will prevent (or at least reduce greatly) this shrink-expand cycle. It happens with lots of these older bikes with the 4-hole petcock seal.

There is also some facial wear on that seal from the years of use, and especially from when it was parked for a LONG time, then the lever was turned again. That one action tore the tiny raised ridges around the 4 holes, against the lever face. That's why sometimes just flipping the rubber gizmo over will make it work again for a while. Sooner of later the fuel will also start weeping out the back side of the hole(s) again, usually after the bike was parked for the winter and revived the next Spring. Then again, as the seal gets softened by the ethanol it starts to seal again.

Nasty cycle. ethanol on buna...

[Stev-o]

The petcock is leaking on my K1 tank, but only when the lever is in the off position.
...

Just curious Steve, but is your petcock leaking fuel out of the petcock itself?  Or is it simply not shutting off the fuel to the carbs when in the off position?
ZT

The petcock is leaking out of the lever area when turned on, it is still working properly when in the off position. It's an odd issue that I have not seen before, I write it off to the the nasty ethanol fuel.

It's actually the wet=swell and dry-shrink action from the ethanol that causes the big 4-hole rubber part to shrink, leading to the 'weeps'. If you add an ounce or two of [any] oil to the gas in the tank when you fill it up, it will prevent (or at least reduce greatly) this shrink-expand cycle.

Yes, I had hoped that the leak would stop once it got wet from fuel but I guess it had shrunk too much.

I may try the two-stroke oil trick, I have a gallon on the shelf that I use in my Kawasaki H bikes, thx.

[Oddjob]

I was experimenting for a while to see if I could make the 4 hole seal out of Viton, so it would be resistant to the ethanol, the problem was the thickness of the sheet, too thin and it leaked and the next size up was too thick for it to fit with the plate over the top. I was planning on seeing if I could plane a small piece of the viton sheet down to the correct thickness but other projects happened and the idea got shelved, still got all the stuff so I may restart it someday.

[ZTatZAU]

Interesting!  I rebuilt my petcock during the early stages of my K1's resurrection and think I used the kit from 4 into 1.  It seemed to work fine.

However, when I had the #4 bowl off the other day to clean out the slow jet, I noticed I had to prop up the float to close the needle valve in order to keep fuel from flowing through the carb... even with the petcock in the closed position.

I also noticed the petcock is a little stiffer going into and coming out of Closed than it is going to and from Open and Reserve.  I figured there must be something going on with the four hole rubber valve/seal and bummed that I need to take it apart again to see what's going on.

When the bowl was in place without the flexible drain tube attached, the drain fitting dripped once every 30 seconds or so with the petcock OFF.  But now that everything is back together, I see no more fuel dripping from the bottom of the flexible drain tube.

Has this problem (weeping petcock - when off) fixed itself?  Or is the slow dripping fuel evaporating before it reaches the end of the drain line?

Or am I missing something else?
ZT

[Stev-o]

Has this problem (weeping petcock - when off) fixed itself?  Or is the slow dripping fuel evaporating before it reaches the end of the drain line?

Or am I missing something else?
ZT

I do not have a leaking petcock when in off position.    If I were you and had a leaking petcock after a rebuild, I would spring for a new genuine Honda petcock. 

https://www.ebay.com/itm/272332113104?fits=Year%3A1971%7CModel%3ACB750&_skw=cb750+1971+petcock+rebuild+kit&epid=1011843723&itmmeta=01JCGM71Y82NFMWZMB2F9448M6&hash=item3f684244d0:g:gFoAAOSwZ2FlLqdd&itmprp=enc%3AAQAJAAAA4HoV3kP08IDx%2BKZ9MfhVJKmTkfbPcJ3TUDz%2FhUh6ozmcxSdIWZ9ZfT0P%2B%2B%2BvmkrQ%2BCsAP%2BihQDknvDYg%2F17gmtKZF5scKIpc4T%2FjRfOoqK0Qlm8VUcHKgd6zJ4%2BvUP6ReFGAG5Y8Bt3yJwvCsfaJXLXv9B5GkiLn4a6LEGtZq77a05T3EfKLIaicJ3LQPJarrybTnSBmxfISu5zNC96wmWmVB1UlhtwZmzbaNDJQqBR%2BO2T%2FOVK1ZjLl8V5qTnHQIilbNVg7aK1%2FvDMOFzp%2BBWxLlYrXU5OXmfxpOWjtMUoC%7Ctkp%3ABk9SR56fnJTkZA

I have an attached garage and a wife that is a "super smeller", if she smells gas, I hear about it immediately! So, I cannot have fuel leaks to keep the peace.

[ZTatZAU]

Appreciate your reply Steve but I don't really think I need a new petcock.

At this point, if I notice any more leaking (through the carbs) with the petcock off, I'm more inclined to use or drain the fuel that's currently in the tank, remove the side hold down plate and lever, and replace the aftermarket 4-hole rubber seal with an OEM seal.  Then see what happens!

ZT

[newday777]

Appreciate your reply Steve but I don't really think I need a new petcock.

At this point, if I notice any more leaking (through the carbs) with the petcock off, I'm more inclined to use or drain the fuel that's currently in the tank, remove the side hold down plate and lever, and replace the aftermarket 4-hole rubber seal with an OEM seal.  Then see what happens!

ZT

Did you replace the fiber sealing washers that are under the screws holding the petcock to the tank? The will cause leaking in the off position into the bowl, then into the carb hoses, filing the carb bowls

[ZTatZAU]

Appreciate your reply Steve but I don't really think I need a new petcock.

At this point, if I notice any more leaking (through the carbs) with the petcock off, I'm more inclined to use or drain the fuel that's currently in the tank, remove the side hold down plate and lever, and replace the aftermarket 4-hole rubber seal with an OEM seal.  Then see what happens!

ZT

Did you replace the fiber sealing washers that are under the screws holding the petcock to the tank? The will cause leaking in the off position into the bowl, then into the carb hoses, filing the carb bowls

Not sure if I used the new washers in the kit or the original fiber washers; but the petcock has been on both the old and new tanks, on and off the bike with gas in it, and was not leaking or weeping gas out the exit ports in the Off position.

And it doesn't seem to be leaking now!  So I'll watch this and if I see a problem will try an OEM rubber seal/valve.
ZT

[Oddjob]

Remove the fuel lines from the tap, if the tap is leaking you'll see fuel dripping from the outlets. The fibre washers sit under the heads of the mounting screws and if they are old and used it's possible they'll start to leak as they get older. If so the tap will leak even in the closed position as fuel is leaking down the threads of the screws and into the fuel bowl. 

[ZTatZAU]

Remove the fuel lines from the tap, if the tap is leaking you'll see fuel dripping from the outlets. The fibre washers sit under the heads of the mounting screws and if they are old and used it's possible they'll start to leak as they get older. If so the tap will leak even in the closed position as fuel is leaking down the threads of the screws and into the fuel bowl.

Thanks Oddjob!  I appreciate your reply.
ZT

[jonda500]

and whilst the bowl leak has stopped you may find that the fuel can all be consumed without switching to reserve...
John

[HondaMan]

I was experimenting for a while to see if I could make the 4 hole seal out of Viton, so it would be resistant to the ethanol, the problem was the thickness of the sheet, too thin and it leaked and the next size up was too thick for it to fit with the plate over the top. I was planning on seeing if I could plane a small piece of the viton sheet down to the correct thickness but other projects happened and the idea got shelved, still got all the stuff so I may restart it someday.

That's ambitious!

[HondaMan]

Interesting!  I rebuilt my petcock during the early stages of my K1's resurrection and think I used the kit from 4 into 1.  It seemed to work fine.

However, when I had the #4 bowl off the other day to clean out the slow jet, I noticed I had to prop up the float to close the needle valve in order to keep fuel from flowing through the carb... even with the petcock in the closed position.

I also noticed the petcock is a little stiffer going into and coming out of Closed than it is going to and from Open and Reserve.  I figured there must be something going on with the four hole rubber valve/seal and bummed that I need to take it apart again to see what's going on.

When the bowl was in place without the flexible drain tube attached, the drain fitting dripped once every 30 seconds or so with the petcock OFF.  But now that everything is back together, I see no more fuel dripping from the bottom of the flexible drain tube.

Has this problem (weeping petcock - when off) fixed itself?  Or is the slow dripping fuel evaporating before it reaches the end of the drain line?

Or am I missing something else?
ZT

Yeah...that happens on the PD carbs with the single-hose feed from the tank: it is siphoning the fuel from the pipeline and the other bowls until one of them 'breaks' the suction with a bit of air getting into that one's float valve. It's not unique to the 750: the 550 does it, too, on the later carbs with 1-hose feed.

[70CB750]

I was experimenting for a while to see if I could make the 4 hole seal out of Viton, so it would be resistant to the ethanol, the problem was the thickness of the sheet, too thin and it leaked and the next size up was too thick for it to fit with the plate over the top. I was planning on seeing if I could plane a small piece of the viton sheet down to the correct thickness but other projects happened and the idea got shelved, still got all the stuff so I may restart it someday.

I tried that too, did not work.  Mainly because the original seal has small rims around holes to seal, it reduces friction of the petcock.  Maybe 3D printing?

On similar note, on the CB900C I noticed the reserve being hard to turn on on my trip Virginia - Detroit.  I decided to use the reserve more often and it helped.

[Oddjob]

I was experimenting for a while to see if I could make the 4 hole seal out of Viton, so it would be resistant to the ethanol, the problem was the thickness of the sheet, too thin and it leaked and the next size up was too thick for it to fit with the plate over the top. I was planning on seeing if I could plane a small piece of the viton sheet down to the correct thickness but other projects happened and the idea got shelved, still got all the stuff so I may restart it someday.

That's ambitious!

Yeah, I had an idea on how to plane the Viton sheet last night, sort of an epiphany, it may work or it may just chew the sheet to bits. I'll test on a small piece that can make 5 seals if the plan works. It doesn't matter so much if it leaves it a little rough, I can turn the untouched side to face the lever, just so long as the thickness is right. I already have a couple made, but as I said they are too thick to fit. Getting the holes correct is also a problem, I even made a metal template to see if that works, which it does in a fashion.

[bryanj]

A lot of work for a part that only costs a few $

[ZTatZAU]

and whilst the bowl leak has stopped you may find that the fuel can all be consumed without switching to reserve...
John

Thanks for your reply, John!

Coincidentally, I took the bike out the other day  and deliberately ran it until I needed reserve.  I was relying on 30 year old muscle memory to switch to reserve at the slightest hint of fuel starvation rather than waiting for everything to quit before going to reserve.  I remember wondering if the slight miss or burble I felt was really the beginning of no fuel flow but now I'm not so sure.

I'll try starting and going for a ride in the ON position and see what happens.  Then again, if it does run on ON, it may be the fiber gaskets leaking fuel through he threads as posted above. 

It's supposed to be 60° tomorrow so maybe I'll know more than I do today.

...Yeah...that happens on the PD carbs with the single-hose feed from the tank: it is siphoning the fuel from the pipeline and the other bowls until one of them 'breaks' the suction with a bit of air getting into that one's float valve. It's not unique to the 750: the 550 does it, too, on the later carbs with 1-hose feed.

Your explanation makes perfect sense except this is a K1 750.  I'm not exactly sure what PD carbs are but mine are Kehins marked 7A on the manifold flange and my petcock definitely has two fuel outlets and lines to the carbs.

Could the scenario you described occur on a K1?
ZT

[Oddjob]

A lot of work for a part that only costs a few $

Likely though Bryan that the original seal is made out of Nitrile, so it will suffer with the Ethanol if it is. Maybe someone can test one and see what it's made of. They are about £6 I seem to recall.

[newday777]

I've wondered if the vinton seal for the GL1100 petcock would fit.

https://www.randakks.com/gl1000-gl1100-petcock-repair-kit-included-in-gl1000-and-gl1100-master-kit.html

[Stev-o]

I've wondered if the vinton seal for the GL1100 petcock would fit.

https://www.randakks.com/gl1000-gl1100-petcock-repair-kit-included-in-gl1000-and-gl1100-master-kit.html

It should, details from from the listing:


"Special Petcock Sealing Disk (Reproduction of Honda Part# 16955 268 020 "Valve Gasket" a ubiquitous part used on dozens of Honda models over the years...the Honda part is sporadically "discontinued")
Diameter: 20.18 mm
Thickness: 3mm
4 holes in disk...each with diameter of 6mm"


BTW - it is made of Viton rubber [not vinton]

[Oddjob]

Surely this would be better, cheaper and doesn't waste parts not needed.

https://www.randakks.com/randakks-cbx-petcock-seal-not-included-in-cbx-master-kit.html

[HondaMan]

...Yeah...that happens on the PD carbs with the single-hose feed from the tank: it is siphoning the fuel from the pipeline and the other bowls until one of them 'breaks' the suction with a bit of air getting into that one's float valve. It's not unique to the 750: the 550 does it, too, on the later carbs with 1-hose feed.

Your explanation makes perfect sense except this is a K1 750.  I'm not exactly sure what PD carbs are but mine are Kehins marked 7A on the manifold flange and my petcock definitely has two fuel outlets and lines to the carbs.

Could the scenario you described occur on a K1?
ZT

It does, and on the other "K" bikes with the roundtop carbs, but only a little bit: often the bowls don't all run the same exact depth, so the ones that go low first end up draining the fuel from the line, then from the other carb if its bowl is slightly deeper than the one we're talking about. Most of the time this isn't noticed, the engine just starts stumbling on one cylinder and then Reserve gets flipped ON. With my old SuperHawk, the bowls ran exactly the same (because I was anal about it) so when it hit RESERVE, the engine often just died. I had equal-length hoses routed from the petcock to the carbs on the bike (supposing it made a power difference in my virgin technician days) and it could put me out of gas and dead, in the fast lane of the freeway. Pulling over to Chicago's 4-foot-wide inner lane on a 4-lane expressway with a dead engine made it REAL hard to get back into traffic at rush hour. especially before the 55 MPH speed limit came out.

When I got my first 750 (K1) I really rejoiced over this one feature: when the bowls ran low you could ACCELERATE on the other 3 cylinders while waiting for the fuel to re-arrive in the lean one.

[Oddjob]

I lost the first of the group of riders we had when he went onto reserve on the motorway, the engine just died and a car going over 100mph rear ended him, he was catapulted off the bike and his helmet flew off, he landed on his face and was killed instantly, only 18 years old. The driver who killed him got away with it.   

It was a closed casket funeral due to the horrific injuries he had, his dad never got over identifying him,.

[Stev-o]

Update:  received the genuine Honda valve gasket fairly quick and pulled the tank off the bike.  The old gasket looks good but is a little less flexible than the new one but I see no damage.  I'm guessing I installed the new petcock when I rebuilt the bike about 6[?] years ago after the engine blew.

old one on bottom:



Did not want to open a can of worms by removing the petcock so I just set the tank on my tailgate leaning against the generator, luckily only had a gallon of fuel in there...



It was as easy as removing the old gasket and popping in the new one.  The wavy gasket looked good and provided resistance when assembling the petcock.
Popped the tank back on, fitted the fuel lines and cranked it up, no leak!



Took the time to clean the bike while the tank and seat were off, now time for a ride!

[HondaMan]

Good job!
It only takes 0.01mm (about 0.004") difference to make it leak. The compression seal of the rubber against the face of the petcock lever is only that much.