Topic: Solved: Choke, idle, fouling issues

[Paintedseat]

If you have stock air box I would try trying 38. That's what I have in mine and it is a tad rich. The exhaust doesn't have as much effect on flow as the airbox. 130 mains seem kind of big too.

It came with 130s and pods, I put on a stock air box, k&n filter, and 110s. It’s all in that novel of a post somewhere hahah

I’m hesitant to throw 38s in it now, think I should get the floats set correctly and see if that affects anythinh first, changing jets while it’s on the bike is easier

Got it. I missed where you went back to 110. Yeah do one thing at a time. Did you adjust the floats when you went from 130 to 110? Personally I think the 110 are too small. I would go with 120. Needles set to the 4th notch.

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Also looking at you float measurements and something is wrong. The difference between just touching and fully seated is way off on some. Are you sure the needles are closing all the way? Are they the correct ones?

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[wkong]

Yeah I set the floats when I went from 130 to 110 and then checked them a second time but I had them flat on the bench so I did it wrong plus the valves are from a cheap rebuild kit. Genuine ones are on the way and I’ll check the mains at WOT going uphill once I get it to idle. I have 112, 115, 120, and 125s to use if I need them.

I need another pair of hands to hold the rack of carbs sideways and see when the float just touches the valve spring... I really hate these carbs. But it’ll get done.

[ekpent]

 I've 'gently' mounted the carbs and rack upside down in my bench vice before to set the float measurement so I have two hands free. I also have one of those strap flashlights on my forehead so I can get good light at the weird angles it takes to peer in there to see the tang touch the needle spring end. Super easy to do if the rack is split when doing a major service but thankfully you are probably past that point.

[wkong]

Ah, I’ve got a headlamp and forgot about it, that’ll help immensely

[PeWe]

Is the bike standing on side stand so more fuel will flow to number 1, less to the other and float level is too high?

[Yamahawk]

I haven’t tried raising the needles yet, I’ll back the first air screw out half a turn and turn the last two in 1/8 after replacing the #1 plug and see if that helps first then on to the needles. If I raise the needle won’t that make it more rich off idle to 1/4 throttle? Would seem like I need to lower the first and raise the last two while #2 plug looks good as is, but that doesn’t make sense

If I understand what you said here, you are thinking of changing the needle heights on the carburetors, but not setting them all to the same clip setting... don't do that. All the carbs need the SAME needle setting, not individually different settings to 'cure' a rich or lean condition in each cylinder. You do that by adjusting the jets, and all of them need to be the same also. The same with float levels... every carb needs identical jets, needle and float settings.
If you have a rich cylinder, as in #1, check the o-ring in the intake boots, and see if it is not sealing. Hondaman was saying something about this causing adjacent cylinders to run rich from intake leaks...
Charlie

[wkong]

Is the bike standing on side stand so more fuel will flow to number 1, less to the other and float level is too high?

Nope, center stand.

I haven’t tried raising the needles yet, I’ll back the first air screw out half a turn and turn the last two in 1/8 after replacing the #1 plug and see if that helps first then on to the needles. If I raise the needle won’t that make it more rich off idle to 1/4 throttle? Would seem like I need to lower the first and raise the last two while #2 plug looks good as is, but that doesn’t make sense

If I understand what you said here, you are thinking of changing the needle heights on the carburetors, but not setting them all to the same clip setting... don't do that. All the carbs need the SAME needle setting, not individually different settings to 'cure' a rich or lean condition in each cylinder. You do that by adjusting the jets, and all of them need to be the same also. The same with float levels... every carb needs identical jets, needle and float settings.
If you have a rich cylinder, as in #1, check the o-ring in the intake boots, and see if it is not sealing. Hondaman was saying something about this causing adjacent cylinders to run rich from intake leaks...
Charlie

Yeah, I wasn’t going to use different clip settings on the needles, just pointing out that raising the needle to help 3&4 would have either not helped or made the problem worse in 1. I’ll check them all for leaks again once I get the float valves replaced.

[wkong]

Update: installed a relay for the coils, battery voltage at the posts now. Float valves should show up tonight so I’ll get them set and give it a go tomorrow night hopefully

[wkong]

Float valves replaced, heights set to 26mm just touching the spring pin, sprayed the idle passageways out again, sealed around the bungs just above the idle jets with seal all, replaced the larger torque clamps with 44mm Honda ones. I checked the fuel level via the clear tube method and had 3mm below the mating surface on 3&4 and 7m on 1&2. I triple checked all of them before mounting the carbs but oh well.

Still won’t start or run with choke unless I’m on the throttle the entire time and it sounds like it’s bogging down when I did keep it going with throttle, choke off and it peps up immediately just have to turn tbe idle screw up until it’s warm, then slowly back it down.

But! Eureka! As soon as it was warm I dropped it down to 1100 and it held there great! No strange popping, both 4-2 pipes have the same tone. All four plugs were... beige? Very light tan. Pic below.

Before I sync the carbs again, should I head straight to adjusting the 1&2 floats higher? Since it started and the plugs all look the same, should I just turn the air screws on 1&2 in to about 1/2 turn and ride it for a bit to see if the fuel level in 1&2 catches up eventually?

Lastly, any guesses as to how to get the choke to work as it should?

[Paintedseat]

I would get the height corrected. The air screws should be uniform. Your plugs look slightly lean to me.

[wkong]

I would get the height corrected. The air screws should be uniform. Your plugs look slightly lean to me.

Okay I’ll check with the clear tubes again, then pull them and adjust 1&2 4mm higher if it’s still low. I’ll throw 42 idle jets in too.

[wkong]

Simple mistake - fuel line was routed wrong and 1&2 had to go uphill, fixed that but I’ve learned I have intake leaks. I tried the original clamps, 46mm and 44 mm clamps all to no avail. A moderate spray of starter fluid doesn’t get caught, I have to hit it for a full second. Anyone have any tips? I had zero leaks before I replaced the boots, the old ones were as hard as rocks. I soaked them in alcohol and found the leaks so just ordered new boots from 4into1. Using the new boots now.

[wkong]

Threw a second set of clamps on the part of the boot that’s closest to the head, just inside the stock clamps. It helped, but still gets a little increase in rpms after dousing them with starter fluid. One second spray doesn’t have an effect anymore but they’re still leaking.

Plugs look good though after it got warmed up and idled at 1100 for 5 minutes.

I think the fuel line routing is as good as I can get it but it’s definitely not perfect. I’ve got carbs off a K1 and a tank off a K6, so the fuel line has to take a sharp 90 to go over the carb rack, there’s no hole in the rack on the left side. After the 90 it goes up about half an inch to clear the rack and then downhill from there.

So in summary so far it’ll idle and the plugs aren’t fouling anymore. Still won’t start or run with choke on, got some small leaks, and the fuel line routing isn’t ideal.

[wkong]

Fuel levels all 4mm below mating surface, air leaks gone, it sounds much better and while it will run with the choke on when it’s cold it drops the rpms down to about 900. Sounds rough. Will sync the carbs next and check the plugs.

[Paintedseat]

Make sure high idle screw is adjusted correctly

[wkong]

Make sure high idle screw is adjusted correctly

When it’s warm it idles at 1100 great, thats where it’s set now

[Paintedseat]

No the high idle. You can adjust whee the bike idles when the choke is on. You want it to be around 3k.

[evanphi]

No he can't. He has K1 carbs.

I also have K1 carbs on my bike. Similar routing of fuel line from the left, crossing over, then back behind the carb, tee over 3/4 carb inlet, etc... Seems to be the best setup I've done.

You will not get the bike to idle with the choke on. Period. End of story!

These aren't set and forget chokes like modern bikes. You have to work them a bit to get it running, then you can take off riding and once warm the bike will idle no problem (as you have found out).

When I start my bike I have the choke on full and a slight twist of the throttle, get it going while slowly feathering the throttle up and down. Reduce choke to half and hold steady on throttle. Take off in first gear, and by the time you reach the end of your street, you should have the choke off. Modify as necessary when temps are closer to freezing.

[wkong]

Thanks, Evan. I’m not overly concerned about the choke anymore but that’s good to know. I ended up getting a petcock that’s at a 90 degree angle back for CB400Fs (I have a 75 or 76 tank) and it’s downhill the whole way now.

[Paintedseat]

No he can't. He has K1 carbs.

I also have K1 carbs on my bike. Similar routing of fuel line from the left, crossing over, then back behind the carb, tee over 3/4 carb inlet, etc... Seems to be the best setup I've done.

You will not get the bike to idle with the choke on. Period. End of story!

These aren't set and forget chokes like modern bikes. You have to work them a bit to get it running, then you can take off riding and once warm the bike will idle no problem (as you have found out).

When I start my bike I have the choke on full and a slight twist of the throttle, get it going while slowly feathering the throttle up and down. Reduce choke to half and hold steady on throttle. Take off in first gear, and by the time you reach the end of your street, you should have the choke off. Modify as necessary when temps are closer to freezing.

So no bike pre 1975 will idle with choke? Please explain the reason they will not idle with choke? If the carb is set up correctly I can't understand why. I'm just curious.

[evanphi]

No he can't. He has K1 carbs.

I also have K1 carbs on my bike. Similar routing of fuel line from the left, crossing over, then back behind the carb, tee over 3/4 carb inlet, etc... Seems to be the best setup I've done.

You will not get the bike to idle with the choke on. Period. End of story!

These aren't set and forget chokes like modern bikes. You have to work them a bit to get it running, then you can take off riding and once warm the bike will idle no problem (as you have found out).

When I start my bike I have the choke on full and a slight twist of the throttle, get it going while slowly feathering the throttle up and down. Reduce choke to half and hold steady on throttle. Take off in first gear, and by the time you reach the end of your street, you should have the choke off. Modify as necessary when temps are closer to freezing.

So no bike pre 1975 will idle with choke? Please explain the reason they will not idle with choke? If the carb is set up correctly I can't understand why. I'm just curious.

The choke is just extremely restrictive. You would have to keep the idle speed up quite high to keep it running at full choke. You can back it off a bit and it'll idle, but very rich. The round-top carbs do not have a high-idle setting.

I've had it happen myself... I was riding and switched  to reserve and my glove caught and flipped up the choke lever by mistake. Bike instantly went incredibly rich and lost all power until it sputtered and died, so I coasted to the side of the road.

[Paintedseat]

Interesting. I have never messed with those bikes. I would imagine that it's a pain in cold unless they warm up quicker than mine.

[wkong]

It doesn’t take very long in 50 degree weather for me to not babysit the throttle. Less than two minutes. Im rebuilding this bike for a friend who has never had a bike so originally I was more worried about it with him being a first timer then I remembered I ride year round in the PNW and most people up here store them when it hits 45.

[wkong]

Plugs a nice caramel color, idles great at 1100. All told I got battery voltage to the coils, fixed some very slight air leaks, got the fuel level to 3mm below the mating surface, and rerouted the fuel line (got a rear exit petcock) so its downhill the entire way. Choke is still just about useless but it warms up quickly.

No clue which part did what, but who cares! Thanks everyone!