Need help in Idaho please

[Bonz]

I note you said a can of Seafoam in a half dozen tanks. Berryman's B12 is a more powerful substance as it has toluene in it, and will do more to clean than Seafoam from why I understand. May try a can of that over the appropriate number of tanks, don't see it doing any harm. Opinions?

Otherwise, you are in it to win it over the long haul and lots of highway miles, so the carbs are doing well with the mpg you are getting, but B12 would be in my book of tricks to use next.

I may have missed this... What are your pilot screws set at? My thought is to open them up a touch to add a bit of fuel, may help your lower rpm skippiness. Since you can't adjust #1, adding a bit to the other 3 pilots may help.

[BA80]

[Bonz]

What's that face mean in BA80 speak?

[BA80]

[BA80]

Mikuni Motorcycle Carburetor Theory 101

Carburetor troubleshooting is simple once the basic principles are known. The first step is to find where the engine is running poorly, fig 7. It must be remembered that carburetor jetting is determined by the throttle position, not engine speed. If the engine is having troubles at low rpm (idle to 1/4 throttle), the pilot system or slide valve is the likely problem. If the engine has problems between 1/4 and 3/4 throttle, the jet needle and needle jet (most likely the jet needle) is likely the problem. If the engine is running poorly at 3/4 to full throttle, the main jet is the likely problem.

[Bonz]

Thus add a bit of fuel to see if that helps via the pilots, and throw some B12 at it...

[BA80]

[Bonz]

Am I that far off?

[BA80]

The amount of fuel added to cruising RPM by opening up the IDLE mixture screws will be nill, it will only make it IDLE richer. Off idle the pilot jet (where the fuel for the idle mixture comes from) is already in play as fully as it can be. It won't force any more fuel through the pilots because it is limited by the orifice size.

Simple (very) physics.

[cajun31]

Hey Bonz

I do believe you missed it. Early on in this thread it has been stated that the pilot screws are still more then likely at factory settings because the caps have never even been removed.

[Bonz]

I only share that as I just spent a couple months adapting carbs from a ZZR1200 onto my ZRX 1200, and the fuel screws made a noticeable difference in lower rpm drive ability. Adding a bit more fuel via the pilots did affect in a positive way a lean stumble upon lower rpm throttle application and lean burps at lighter throttle between 2-3k rpm as I accelerated up through the gears.

With the pilots inducing a fixed amount of fuel via a separate circuit unto themselves, more fuel via the pilots can help lower rpm drive ability and at lighter throttle are noticeable in the way they affected lower rpm response.

Sure, you can go too much and mess up idle mixture, but they are a part of it all and worked well in my case.

[BA80]

The amount of fuel added to cruising RPM by opening up the IDLE mixture screws will be nill, it will only make it IDLE richer. Off idle the pilot jet (where the fuel for the idle mixture comes from) is already in play as fully as it can be. It won't force any more fuel through the pilots because it is limited by the orifice size.

Simple (very) physics.

I only share that as I just spent a couple months adapting carbs from a ZZR1200 onto my ZRX 1200, and the fuel screws made a noticeable difference in lower rpm drive ability. Adding a bit more fuel via the pilots did affect in a positive way a lean stumble upon lower rpm throttle application and lean burps at lighter throttle between 2-3k rpm as I accelerated up through the gears.

With the pilots inducing a fixed amount of fuel via a separate circuit unto themselves, more fuel via the pilots can help lower rpm drive ability and at lighter throttle are noticeable in the way they affected lower rpm response.

Sure, you can go too much and mess up idle mixture, but they are a part of it all and worked well in my case.

I will add that if the 3 little feed holes for the pilot jet (just behind the throttle plate at the top) are somehow restricted opening the idle mixture screw may help slightly at or below about 1/4 throttle.

You can argue that opening it up and FUBARing the idle will help but the fact still remains that the pilot jet METERS the fuel coming through itself by the size of the orifice and that orifice won't get bigger if you open the idle mixture screws more. It will just redirect more of what can get through to the idle circuit. 6 of one and half a dozen of the other.

[motoman]

IMO Howard, would not even touch them(they still have the factory tins covering them). The problem being, those teeny o-rings likely more resemble a minature dried doughnut, in color also. Any movement of the idle-mix screws will unseat any sealing effect they may have had, and likely break them into thirds(DAHIKIJD). NOT a good option out on the road.
When he gets it home, that's when I would be taking apart the carbs more complete(he's already had bowls,emulsion tubes, ect. out while making the journey), FIRST, lightly seating the screws, counting exactly the factory setting of turns.
I have yet in all these years seen anyone do this, or it was long ago they don't remember. The previously broken float post makes it obvious someone HOPEFULLY got THAT far, and decided to quit before they just a pile of pot metal. The factory tin inserts on mix. screws lead me to believe that's what happened.
If float tang doesn't look like it had been scored by someone messin' with float levels, that would ALSO be an excellent time to measure the float heights, as those ALSO may still be at factory settings.
If both those settings are 'suspect' facory settings, that could be of some help, especially if he replaces the float needles with new.
Those, in K&L's seem to function okay, but I WOULD change the little hanger clips, since the Mikuni clips are a continious piece of wire, and the K&L ones are open ended at the float tang hanger end.

[BA80]

IMO lightly seating the screws, counting exactly the factory setting of turns.

Which brings about another myth to be dispelled. Counting turns

An excellent way to get to a starting point but I see many here setting ALL the mix screws in ALL 4 carbs exactly the same. Very rudimentary.

The factory settings will be irrelevant with the fuels we have available today but if you take notice when disassembling the settings will all be slightly different.

No 2 carbs will be set correctly with the exact same setting, unless it just happens randomly.

I have found through experimentation that the vacuum drop method is the most accurate. Highest vacuum +1/4 turn out is nearly perfect if the carbs are right.

[motoman]

Totally agree with you BA80 with last post and post #72.
Were I don't agree is 'factory settings will be irrelevant with the fuels we have available today'.
Billy Rok's new to him ride is a prime example of likely factory settings with over 40mpg@75mph reported.......can't be noticably far off with factory settings.
Another example I've spoke of on occasion is a nearby neighbors 81 Special.
Those carbs I personnally know for a fact have never been touched, in side or out cept for him bringing it over to my place, wondering why the idle had went from its normal 1100rpm down to 900rpm at operating temps.
Idle mixes have never been disturbed, still having the factory caps(not dealer installed ones after service work) in place.
Idle drop was due to the carb pairs out of sync. Each pair was still matched perfectly after 32yrs..
Pairs brought back together, idled perfectly at 1100rpm's again.......no physical change to idle setting. And, as I've noted bout the bike in the past, it is one of the quickest, smoothest at any rpm, even lugging it 81Specials I've ever encountered and ridden......everything stock.
Not questioning the MISSING BTU's of todays fuel, but with a couple examples, and also noting Bonz's seen settings on his 80Special, I lean towards the factory settings on the later carbs,(which includes under 2.5 turns out from seated, with slight varrience included) working fine........ decades later.

Now, where the heck is Billy?...........Hope all is still doing well for him.