Topic: Has Anyone Ever Found the 26mm Float Height Spec to be too High?

[kaysystems]

And this one is really stupid. Make sure that you have enough gas. I have a new gas tap that only provides gas to one pair of carbs, not long after I go to reserve.

David

[Bob Wessner]

Thanks all. Re: fuel tank, lines, etc. I even gave up on an aux. tank and have been doing the work, such as it is so far, using the main tank set up fairly high to the rear of the bike with extended, straight lines. They are clear so I can see good flow and the tank is nearly full, still has the winter fill-up (with stablizer in it). I think I just have screwed up something carb-wise. They are off the bike again, will dive into them tomorrow once more.

[Raul CB750K1]

I opened a topic a while back about the gas efficiency. I'm making 38 mpg and in my opinion it's a low figure. Float heights are at stock specs (26 mm) but still my plugs are sooty black. The best advice I got was to lower the needles a notch (rising the circlip a notch) so the amount of gas at the last part of the throttle will be lower. I'll do it but when winter comes. Why don't you try that?

Raul

[MRieck]

That's good advice as having the needle to high will quickly foul plugs at low speeds.

[Bob Wessner]

Right now, my issue is idle, or lack thereof. I would think the high speed needle setting would be secondary, though I hope some day to get to the point where I can address it.

Also, so my understand of the jet size is wrong? Maybe if things are still rich I should have put the 110's back in??

[kghost]

Since we go way back to the beginning Bob..........

I thought the pictured fuel level looked a tad high.

Make sure you clean the plugs between checks if you are going to use them as a tuning aid. It takes them a while to change if you don't.

As I understand it..... Idles like crap. How does it run off idle?
Sounds like you need to sync them and ajust idle screw settings.

Heres some observations from my bikes

None of my 750's will idle warm with the choke on. Its the nature of the Choke design.

All of them idled rough to various degrees before syncing the carbs. Uneven fuel distribution = uneven power pulses. Idle will be loping and uneven prior to sync.

I have had to turn the idle screw quite a bit from 1 1/2 to make a couple bikes idle well.

[Bob Wessner]

Today's effort is to;

1) Go back and reset the float heights to 26mm and at the same time determine why suddenly the #4 bowl would not fill at all when I set them to 30mm. I'm wondering if that was way too high and perhaps one side of the #4 float is cocked a bit and hitting someplace.

2) Take one of the carbs apart with the Keyster kit in it and carefully compare jets, float valves, etc. to see if there is a significant or any difference. I probably should have done that last year when I stripped and cleaned the carbs initially. I shouldn't have assumed anything.

As to the syncing, don't I at least have to have an idle without the engine dying to start the syncing process? 

[Jonesy]

1) Go back and reset the float heights to 26mm and at the same time determine why suddenly the #4 bowl would not fill at all when I set them to 30mm. I'm wondering if that was way too high and perhaps one side of the #4 float is cocked a bit and hitting someplace.

I forgot to mention this on the phone with you yesterday, but Carpy told me once how the brass arms holding floats could easily be bent during adjustments and hang up on the central portion of the carb casting that contains the main jet. Throwing it out as an idea...

2) Take one of the carbs apart with the Keyster kit in it and carefully compare jets, float valves, etc. to see if there is a significant or any difference. I probably should have done that last year when I stripped and cleaned the carbs initially. I shouldn't have assumed anything.

If they're not worn, I'd go with the OEM needle jet. I know it's not really the problem now, but it can become one later on.. (voice of experience)

As to the syncing, don't I at least have to have an idle without the engine dying to start the syncing process?

You can get the carbs roughly synched at higher speeds, then do the fine tuning at idle (provided it will stay idling!)

[Bob Wessner]

Eureka,

It's running, and even idling though a tad high, and not perfect, can't believe it! I took the carbs off again (have lost count of times now). Reset the float heights to 26mm. Then I did a closer examination and comparison of the Keyster vs. carb parts removed last year, you know, the comparison I should have done back then  . Interesting results. The Keyster kits came with 120 mains and 40 low speeds. The mains removed last year were 110's. I believe 120/40 is correct for the K0 (can someone verify this for me). I checked the Solcal sight and it list these ase correct starting with the 70 K1 and since 110 is richer? I certianly don't think I want that so I left the Keyster jets in.

What I did find was a difference in the float valves. The Keyster valve itself is ever so slighty longer, but probably more important, the spring in the valve was much stiffer to the feal when I compressed it as compared to the valves removed last year.

Sooo, I removed the Keyster float valves and seats and replaced them with what I had removed, connected the fuel lines and turned on the petcock..no leaks at overflows, so far so good. She fired right up, gave her some throttle for a minute or two (still had to get it off choke pretty quickly though, but it is quite warm here right now). I had a fan turned on the engine and let it warm up, let go of the throttle (look, no hands!) and it idled about 1200 on the bike tack, but fairly smoothly. Once good and hot, I held the throttle at about 3000 for several minutes, then cut the ignition. Plugs still look kind of rich, but they are the same plugs I have been fooling with all along. I'll pick up some new tomorrow.

I'm still trying to sort out in my mind how all this fits together and makes the difference between yesterday and today, but I don't plan to lose sleep over it either. 

Just for verification, is the 120/40 jet consistent with the K0 and is my assumption that the higher the main # the leaner it is? Thanks for all the support on this, going for a cold beer right now.

[Jonesy]

Yeah 120 main, clip in middle notch and 40 slow are the correct settings for the K0. Just for grins, did you check the carb casting number to the jet lists on HondaChopper.com?

The higher the number, the larger the jet size, so a 110 allows for less fuel passage than a 120.

[Bob Wessner]

No, did not check any casting number on the carbs. Where are they located, will I have to remove them 'again' to find/read it?

OK, found the casting number, it's on the carb stay plate connecting all the carbs. It's B750A and according to HondaChopper it is supposed to have 120/40 jets. Wonder why PO used 110's? But then, I've wondered about a number of PO mods I've come across.

[Bob Wessner]

I'm thinking of patenting glass carbs with clear plex bowls, tired of guessing about what's going on in there.  But then, the industry has since moved on to fuel injection so I guess there's a limit market, eh?

[Jonesy]

Somewhere I have an ancient Holley carb with a glass float bowl. You can see everything in there!

[057 adnoh]

Bob, the higher the number the richer the jet. You will never be able to get the bike on the main jet untill you have a load on it at full WOT.  Ride it and do a blast through the gears, hit the kill switch and coast to a stop, then do your plug check.  If you really want to dial it in check out Dyno Jet they sell a gauge called wide band $560 which has a wide band bosch 02 sensor, and a mixture gauge that lets you read air fuel ratio as you ride. You can even download to your PC.  If you want your K0 to idle the same day-in-and-day-out save the four cable carbs for bike shows. Buy a set of k2 carbs jet them 120/40 and raise the needles to the top; do you still have the stock coils!! guess you have not ridden in the rain yet!!! Where do you live; I'll come and smoke you with my KO and then you will believe me? Dave

[MRieck]

Bob, the higher the number the richer the jet. You will never be able to get the bike on the main jet untill you have a load on it at full WOT.  Ride it and do a blast through the gears, hit the kill switch and coast to a stop, then do your plug check.  If you really want to dial it in check out Dyno Jet they sell a gauge called wide band $560 which has a wide band bosch 02 sensor, and a mixture gauge that lets you read air fuel ratio as you ride. You can even download to your PC.  If you want your K0 to idle the same day-in-and-day-out save the four cable carbs for bike shows. Buy a set of k2 carbs jet them 120/40 and raise the needles to the top; do you still have the stock coils!! guess you have not ridden in the rain yet!!! Where do you live; I'll come and smoke you with my KO and then you will believe me? Dave

The wideband DynoJet unit is nice- I've seen it up close and personal.