Topic: CB550K Needle Position

[HondaMan]

Hello HondaMan I Purchased them on ebay from a guy named georgefix out of Daytona but it looks like he may be out of stock unfortunately

George is a great guy. He sells K&L not J&L kits.

Sorry I ment K & L not J & L thats what happens when you get old LOL

Ah, that's just as good info!
There's currently just those 2 brass makers out there (non-Keihin) for the 500/550 that I've found. in recent years I've received carbs for rebuild from supposedly running 500/550 bikes (022/A carbs) that had the K&L brass, and the owners later reported the bikes were running, which was good news. In the 750 the K&L & Keyster parts are a troublesome swap because they are calibrated way differently (thicker needles, larger emulsifier throat holes, varying aeration holes and different jet numbering). They can eventually work, but it takes some fiddling. I haven't yet seen the 750 come out as well with those parts as with the Keihin, though, and it's all done by "feel" to get there. For example, in a 750 with roundtop carbs it took #140 mainjets (normal would have been #105-#110) and needles in position #5 (instead of #3 or #4) to get the [successful] bike to run to 90 MPH, which was enough for the owner. It would have been 100 MPH+ with the Keihin brass, but the owner was only an in-town rider, so it was OK for him.

[ddcook10]

Hello again Does HondaMan or Anyone else know of a source for Genuine Honda or Keihin Jets, Needles and Emulsion Tubes. For the 1975 CB550 Four K 4 pipe version

[jlh3rd]

you can check CMS. Not the cheapest place.

[HondaMan]

Some of the jets can be had at JetsRus online. They have sometimes substituted off-brand jets when i have ordered their 'genuine Keihin' parts before, though: I have a set of those type of slow jets in my 750 now. They are marked as #38 (I had ordered Keihin #37.5) with no logos on them, and act quite lean. I suspect they are K&L idle jets, from the way they actually work and previous experience with other's 750s in the same situation. At this altitude (6000 feet) I normally run the #40 Keihin idle jets with a 3/4 (summertime) to 7/8 (cold weather) idle-mix screw setting, while these 'mystery jets' are requiring 1-1/8 turns to get a similar idle. They are still a bit lean at that setting.

My OEM Keihin #40 idle jets (originals from 1972) have enough damage in them from the years of MTBE gas here that they were getting to be uneven between the carbs - hence the change. It showed up about 3 months ago when I did a vacuum balance with some new gages I got, and helped explain why 2 cylinders were slowly fouling plugs: the metering holes in the idle jets are badly scarred under high magnification.

[ddcook10]

Thanks Guys I did order the OEM jets from CMSNL and yes they were fairly expensive! They no longer have the needles or emulsion tubes in OEM only Japan only Aftermarket probably Keyster or K & L. I'm using K & L needles and Jets now but the K & L kits did not come with the emulsion tubes so I used what I have. Like HondaMan says it seams just a little lean here in Florida near Sea Level. Found some on eBay with the oem part number but nobody has a full set and they are very pricey!

[jlh3rd]

eh...there is one.

[HondaMan]

The things to look for in emulsion tubes of the 550 variety are:
1. Discover how 'loose' the needle is in the needle jet at full closure: this particular item is where the mixing of non-Keihin with Keihin parts doesn't always work well - or at all. If you are stuck with using the aftermarket emulsion tubes in the 500/550 carbs, match up the aeration hole sizes and positions (depths into the bowl) by drilling matching holes into the new parts. Check that your needle doesn't bind tightly in the needle jet's hole, which can happen if the types are mixed up (aftermarket needle and Keihin needle jet, usually). While this takes a portable vise, magbase dial indicator and steel baseplate to check, there should be 0.0008".0.02mm clearance between the needle and the jet at full slide-down cutoff position. It will be larger than this if aftermarket needle jets are used under Keihin's needles in some of these kits (not all, though) and can be needle-stuck-in-jet if the other way 'round.
2. Assume the aftermarket jets will be leaner than the OEM Keihin jets, for the same number stamped on them. I've long know that the K&L and Keyster numbers on their jets are 7% leaner than the same number in Keihin parlance, which just means you need a 7% (or so) 'larger' aftermarket jet to get the same mixture.
3. If you can get within 3%-5% of the same mixture numbers, the bike will run OK. It will then take a little bit of finessing, like altering the float bowl depth up (richer) or down) leaner) within 10% of the original float depth value to make it mix like OEM again.
4. Today's gasolines burn MUCH slower than the 1970s versions when the carbs were designed. This means today's Regular grade burns closer to 1970s Premium rates, which tends to darken the sparkplugs a little, all else being equal. Always keep that in mind when tinkering. You can also improve the burn rate of the gasoline (if it has ethanol and/or butane in the mix) by adding a little bit of oil to the gas in the tank - like 2 ounces to a full tank. These bikes like that very much, and I'm now finding that this reduces carbon buildup in the mufflers over time - an unexpected benefit. (Not sure 'why' yet?)

[Deltarider]

NEVER add oil to fuel! It soots like hell and you don't want that. If you have trouble reading sparkplug noses you may add a spoonful of ricinus oil (aka castor oil) before examining the sparkplugs, but that's about it. There are special additives in the market. Use them. Oil is a no no.

[newday777]

NEVER add oil to fuel! It soots like hell and you don't want that. If you have trouble reading sparkplug noses you may add a spoonful of ricinus oil (aka castor oil) before examining the sparkplugs, but that's about it. There are special additives in the market. Use them. Oil is a no no.

😅😅😅 you are so full of yourself.

[Deltarider]

[...]
😅😅😅 you are so full of yourself.

Ofcourse I'm full of myself, who else?!

[HondaMan]

Keep in mind, Delta, that the USA has more than 70 different "fuel zones" across this country. I don't think you suffer that problem: every fuel recipe for each of these 'zones' here is edicted by politics, not science, in accordance with the rules of engagement of the particular State, locale, and the US EPA and its "rules". When I ride my 750, for example, from Colorado to Missouri, then up into Iowa and back across Nebraska to Colorado again, the gas mileage changes more than 15 times, using the same fuel on similar terrain, by more than 7 MPG at the same interstate speeds. In the 1970s when this very same bike was new and I did those same trips, I could count on 1 Miles-Per-Gallon difference figure for most of the trip until Colorado's high altitudes were engaged, when it would drop. That's how different our fuels here are now, and my having many connections with other engineers over my 40+ year engineering career in the oilfield and automation (like running petroleum distillation plants) has taught me many things about our gasoline.

I truly hope yours is better.