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I have a chart (attached) that shows jet sizes and settings for the various CB350 carburetor versions. It shows the sizes for primary, secondary, and pilot AIR jets. When I review parts manuals I don't see air jets listed. Are they available for sale? How would I check the installed air jets for sizes?
 

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As far as I know - Jets were never sold by Honda as seperate items.

Jets are not a wear item in the carbs.
Unless they have been abused by a previous owner/mechanic they should only need the O-Rings that provide the seal to be replaced.
This would go for ALL Brass parts in the carbs.

The Offical rebuild kits from Honda only had the O-Rings, Fuel Inlet Needle and Seat, and the Float Bowl Gasket.
 

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The air jets are under the diaphragm on the top of the carb. They are pressed in place, not a replacement item and not something to play like the fuel jets can be.

Make sure they are open and clean, that's all that is required.
 

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Sorry I missed your last Question.
The size of the Jet for the (2) with the O-Rings is Stamped into them.

The jets will pull out using the spring bracket they hang from inside the float bowl.
Just look on one side or the other (there is a top and bottom but I can't remember which side has the size stamped)
The Spring Bracket holds pressure on them in place using the bottom 1/2 of the fuel bowl.

The last one is screwed in under the rubber plug and requires a very small jewelers type flat blade to unscrew.

NOTE: About the Air Tube under the jets with the O-Rings - one has what "LOOKS" like a screwdriver slot - IT IS NOT a Screwdriver slot.
To remove them they are PUSHED out from the inside of the carb tyhroat after removing the Slide Top Spring & Piston.
Use a wooden Chop Stick NOT a metal Punch.

To Clean out the very tiny holes in the #38 jet & the Fuel Tubes use a Single Strand of wire from a Lamp Cord Wire.
Yes it will be tedious but it will NOT deform or scratch the brass jets.
Steel Guitar strings are a BAD IDEA.
 

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Gonna have to bump this up.

really? No air jets available? Without the stock air box I would think those might need to be changed for optimal performance.

I have open velocity stacks on my CB350, with a 2into1 exhaust (with dirtbike muffler) that’s longer than stock. Still rich in the mid range but smaller mains make it too lean on the top end.

I’m thinking increasing all of the air jets would help
 

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You should start your own thread and post your jetting and setup. Decrease your primary main and increase your secondary.
Why do you think tampering with the air jets would help?
 

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You should start your own thread and post your jetting and setup. Decrease your primary main and increase your secondary.
Why do you think tampering with the air jets would help?
Stock jets. 35/70/105. I think larger air jets might help because I’m running rich at high RPM and low throttle
 

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RockReef your set up in my experience runs lean. Also two into one exhaust on these 350's usually degrades performance and makes it tough to tune. Honda didn't spec those carbs to be played with like you want too. They work for what they were designed for.
For fun and games you need a set of Mikuni's ..... they will keep you occupied for hours and hours. Couple vendors do packages with the correct throttle cable and in the ball park jetting.
 

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He needs to start a thread as his issue has nothing to do with air jets, and tampering with them will make his bike run like crap.
Raise your float slightly, install a hotter plug and 115 secondary main and see how it does

Edit: in your first post to this thread you made it sound like you tried different jetting. Is that not true if you're at stock?
 

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Why do you think air jets have nothing to do with how these motors will run with v-stacks?
It’s definitely rich. Because 1. It runs better cold
2. Plugs foul quickly
3. Smells rich

not gonna do Mikunis- already tried that and hated it - and not going to try and find an ugly stock exhaust and air box. Yes, I know bike would probably run better with those but still not gonna happen
 

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Honda 'pressed in' air jets have never been available without buying a carb body. I've mader some in the past but they are so small I lose more than I save. Do not enlarge the pilot or primary main jet air jets, I've tried, it doesn't work. (thinking about it I realised the stock air-box doesn't pose any restriction at low/mid rpm)
The secondary air jet is the only one that needs enlarging slightly, around 1. 20mm on CB360, I would have to look up size for 350.
Some 350's run better with 360 pilot jets (38) and a 65 primary main. Float level needs adjusting to compensate for today's fuels. 26.5 works, 27mm if you still have problems.
Personally I can't afford to make Mikuni VM's work properly, they need way to many parts replaced. I did get a set working on my Yamaha XS'650' but I made new emulsion tubes to a 'secret' specification (I forget what I did :D )
 

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@RockReef

Are you sure your V stacks aren't blocking the carbs' air inlet ports? That doesn't make sense that you're running richer with stacks.
How does it run without any filter at all?

I will second not murderfying your carbs air jets. I guarantree that you will ruin them if you do.
 

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Makes perfect sense to me
'The Kei-Hin 3 jet carb has a transitional phase between primary and secondary main jets.
As the slide starts to lift, the airflow and rpm hasn't increased enough to deal with the extra fuel being delivered so causes the 'classic' ~4,000rpm rich miss-fire. Fitting smaller secondary main jet causes lean mixture and a miss-fire around ~7,000rpm. That's the area I've been working on for the last ? years (more than 10 yrs, less than 40 :D )
 
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RockReef your set up in my experience runs lean. Also two into one exhaust on these 350's usually degrades performance and makes it tough to tune. Honda didn't spec those carbs to be played with like you want too. They work for what they were designed for.
For fun and games you need a set of Mikuni's ..... they will keep you occupied for hours and hours. Couple vendors do packages with the correct throttle cable and in the ball park jetting.
Generally not a good idea as it's very expensive to get them working right. (working and working properly are two entirely different things)
I don't know how many people read the follow up article in Cycle World about fitting Mikuni's to a CB350 in early 70's? (may have been a response on letters page, I forget)
Article stated they ended up with a "bucket full of additional parts" costing several times more than original carb purchase price.
Except for a very few places,( I would imagine Todd Hennings Racing and maybe Bore-tech?) no-one has spent enough time on a dyno with 5 gas analyser to state their carbs are 'correct' for CB350.
The modifications I do to stock carbs are only an estimation as exhaust length and diameter play a major role in overall jetting and running but it's good starting point with only secondary main jet changes to compensate and very very rarely pilot jet change from 35 to 38 or 38 to 35.
 

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Yeah we (my buddy Joe and I) already gone down this road on this specific bike with mikunis (he originally started out with mikunis) and we could not get it to run properly with the mikunis at all. I then suggested that he goes back to using the stock Keihin carbs and the bike started and ran fine after that. Granted he didn't have v-stacks on before so as far as I know that's the only change since.
 

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Sorry for the late reply haven’t checked this thread in a while. Bike is in pieces right now, getting rear sets, a fork brace and damper, frame reinforcement and might add a starter to make tuning easier, existing battery is big enough so why not, hopefully the starter clutch is still good. @76TWIN yes, the V-stacks were the only addition/change and they don’t block the air passages at the mouth of the carb. (Also tried other jet combinations but went back). It ran fine cold but once it got to operating temp it wanted to quit. I also noticed the stumble PJ mentioned at around 4,000 RPM and bike would take off after that but feel weak at the top end. Once I have it back assembled I plan to clean the original fuel jets and stick those in (in case the replacements from 4into1 don’t have precise measurements) and go from there again. Drilling out the secondary main air jet will be tried last but it makes sense to me that that would flatten the fuel curve where needed.
 

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RockReef

A couple things you need to check

1. Air vacuum leaks around the carb boots. This can show itself when the bike has warmed up and the rubber boots expanded,
2. Check your mechanical advance for looseness. Sloppy advance due to worn stretched out/loose springs can cause your issues as well. If the springs are loose, try tightening them up a bit.

I still think your muffler/exhaust is way too big for that bike.

You might want to start your own thread though instead of hijacking someone else's
 

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I'm late to this party. I'm curious about the 2-1 exhaust.
Is the ID of the pipe 1.125" or larger?
What is the length of the primary pipes?
What type of 2-1 collector are you using?
 
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