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SL350 K2 carb questions


Well-known Member
Dec 31, 2023
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San Diego
I'm actually on a search for more info on the Kehin carbs for the K2 SL350, but didn't want to keep asking questions that may have been answered elsewhere. I found this post:

But although it somewhat addresses the adjustment of the air screw (I got far enough to figure out that I have an air screw, not fuel) I want more for these specific carbs. There is a video showing rebuild of a CB175/200, I won't mention who...that is a very similar carb. The CB350 and SL350K0 have lots of available info, just not the K2. In the past, I've always gotten away with extremely basic adjustment on other bikes, and learned a lot more about riding than fixing. But want to make this perfect, and with as few stupid questions as possible.

BTW, I've got a 17tooth front sprocket on the way from Sprocket Specialists, they finished making it, just need to ship it. That should help the freeway riding somewhat.
I tried to find info on these carbs, I swear...but something has been troubling me. My choke will kill the engine if I close it completely, and I have been having trouble finding a good position to start the bike in. Sometimes it takes a lot of kicks, but if I turn the idle up far enough for it to be easy, it's too high at warm-up. If the bike is warmed up, it's always a 1-kick deal. I don't know if this has anything to do with it, there's an off-idle hesitation.
Obviously I don't know exactly what cold starting procedure you're using but if you're not aware, most Hondas prefer the throttle to be left at idle or just slightly above during start-up. Opening the throttle wider, whether the choke is on or not, will tend to hinder the engine drawing in fuel as well and it will often take many more kicks. And you should never touch the idle speed or mixture adjustments when cold, the carbs perform differently when warmed up with engine heat and you'll have to go through it all again. In your climate you might only need 1 kick on choke, then at least partially turned off for the next kick. Then let the engine warm up fully (taking it for a short ride works well), then once warmed up put a box fan on it to he;lp keep it from overheating and then do your carb idle speed adjustment followed by mixture adjustments, and bringing the idle back down to 1200 or so as the adjustments improve the idle and speed.
Thanks, I found from experience with this bike that leaving the throttle alone works best. I got good results this morning at 56 degrees with the choke almost all the way, and no throttle whatsoever.
Fuel hose is leaking slightly at the petcock now, but that's pretty straightforward and it only leaks when the petcock is open. What's important was the fact that I got to ride it around most of the day and found a little mud.2CFBF5D6-CE60-49C7-9F45-690CF55536A4.jpegEB49A4B9-2680-4B70-896D-8DA98EA25EA5.jpeg
You want to change that fuel line to the 5.5mm Honda brand. Lose those hose clamps since they distort and cut the hose.
The Honda fuel line really doesn't need clamps but the original spring wire ones are more than sufficient.
I would not run fuel filters. There should be a screen in the petcock that will protect your carbs.
Filters are just extra restriction that a gravity fed fuel system doesn't need.
I would not run fuel filters. There should be a screen in the petcock that will protect your carbs.
Filters are just extra restriction that a gravity fed fuel system doesn't need.
I had a feeling they were over-kill or Honda would have installed them in the first place.
I think the screen is a little to coarse for my taste. If I had a new one with a new tank, the screen is fine. It will keep acorns out of the carbs. Rusting tanks, and anything 50+ years old has some corrosion, can make some might fine particles. The emulsifiers in the carbs have some really fine holes. So my vote, for what it is worth, is add filters.


By the way, if you look at a finished photo of my bike, the sock filters are gone, back to stock airboxes, back to relatively stock exhaust. Bike runs better than ever.

Also I put a filter on my 1991 NH750. It's the fine stuff that clogs the carbs. I have no issues with fuel supply, even at WOT for long times. These little bikes run hard.
I’m thinking the tank is due for cleaning. Is vinegar a realistic solution? I have muriatic acid but don’t trust the internets with a realistic ratio.
I posted this already on the wrong thread…It was starting to take too many kicks to start and the choke wouldn’t help, so I pulled the carbs to take a look. The slow jet on the right carb was clogged. Going to soak it tonight and blow it out tomorrow with my compressor. I pulled the peacock apart too, because I think that was where my fuel leak was coming from and found some very crusty o-rings. I may have some fresh o-rings to match, or buy a “rebuild kit” for a fresh screen as well. I love finding problems, even if these aren’t the exact issues I get that much closer to cool runnings.
A torch tip cleaner is the best tool for cleaning plugged jets. People will scream "you will ruin the jet", but the jet material is hardened brass and the ridges on the tip cleaner will do no damage. Just use it to poke thought the crud. Don't use it as a file.

I have been using one for at least fifty years and have never ruined a jet.
I view fuel filters as band-aids. It's a good temporary fix for the real problem.
Bandaids often keep the wound (real problem) from getting infected by keeping dirt out. The filter on my NH750 is over 15 years old. Still clear. No issues, but if rust starts, I'll see it in the filter before the carbs are dirty. Even with plastic tanks, cars have multiple fuel filters. A filter sock on the suction line, and a filter on the outlet of some sort.

And not to be argumentative (oops, too late), but the screen on the petcock inlet and the screen on the petcock bowl are also bandaids as they are filters too, or rather "strainers". I would of prefers a better filter right in the petcock for a more integrated look.

I’m thinking the tank is due for cleaning. Is vinegar a realistic solution? I have muriatic acid but don’t trust the internets with a realistic ratio.
Vinegar is acetic acid. It will clean the tank. The caveat is to make sure to rinse well and coat with a petroleum product immediately. Marvel Mystery Oil, ATF, some WD 40, even fill with gasoline. The vinegar leave bare metal that will flash rust quickly. Once coated with oil or gas, it will no longer rust. I cleaned my tank this way. I used short Sheetrock screws in the tank to loosen scale. The screws are hardened and will knock scale loose. The are easier to remove than some other options.

I also considered a tank coating, like POR-15 or equivalent, but I found that the coatings are difficult to apply really well. If not done well, the coating scales off the inside and causes as many problems as it solves. Siince I keep my tank full when the bike is stores, I haven't had any internal rusting issues as my petcock filter and external filters have remained clean.
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