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Spare 14H set - jetting for K&N

birdland

Veteran Member
Joined
Oct 3, 2020
Total Posts
578
Total likes
41
Location
Osoyoos B.C. Canada
I’ve acquired a spare pair of 14H carbs, and ordered new insulators from 4 into 1, new floats are also on the way. Gasket and o-ring kit as well.
The carbs have been cleaned (in an ultrasonic unit) - and other than leaking floats they are apparently ready to roll.


I’m running K&N pods at the moment off the installed carbs and plan to implement a version of this solution documented by Mike;


0hHxkzTl.jpg




When I purchased the bike it was equipped with crappy foam filters and as a result was running very rich. It was responsive and would wind out all the way with no issues, but it ate spark plugs (they would go black very quickly). At this point, with the K&N pods installed I’ve determined the rich condition has disappeared somewhat (I haven’t had opportunity to test fully with new plugs - that’s a spring time project), but I want to move the pods back so I can install the side covers.


I’ll be going through the new carbs and making sure all the gaskets and o-rings are new and then doing the same maintenance for the old units. I’m wondering if this main jet solution will provide enough variety to get the mixture settled and leaned out a bit.

Carburetor jet kit

Kit includes
2 x # 135Main Jets
2 x # 140Main Jets
2 x #145 Main Jets
2 x #150 Main Jets
2 x #155 Main Jets
2 x #160 Main Jets

I do want to be careful - the temp here runs into mid to high 90’s F in the summer (although cooler air is close by - I’m surrounded by mountain passes).


When all is said and done I’ll have two sets of 14H carbs to play with. Leaving one set stock and re-jetting the other is an option. I don't plan to change any parts but the mains, unless I run into obvious issues with old OEM brass.


I've been reading old posts and there's a large variety of ideas out there. I know there are a lot of variables here, but any suggestions on jetting and words of encouragement or warning appreciated.
 
Get the extensions on and fitted tight. This may very well change the mixture into the correct area. The extensions are going to improve the air velocity into the carbs and create a laminar flow at the same time, both of which are important.
 
I have usually had the best results running the 14H carbs with 130 main jets......
Bill Lane also preferred the 130 jets for his 450's, even with the foam Uni filters (run un-oiled).....IIRC.....
 
Well - the carbs I received are 723A's instead of the expected 14H. Not a big deal and my error and miscommunication. I understand the difference in jetting, and I think I'll go with the 14h and just rebuild, unless anyone has ideas I haven't considered.
 
My 450 ran great with 130 mains, K&N filters (no extensions) and stock exhaust
 
My 450 ran great with 130 mains, K&N filters (no extensions) and stock exhaust

I expect you have dyno data to prove it, because personally I never saw a good running CB450 (better then standard) with pods on the dyno. What was the air/ fuel ratio at any give rpm ? Can you share your stats so I can compare with my CB450 K0 with a standard setup ? The technical data, dyno stats and circumstances of my bike can be found here.

Many people think there bike is running good, or even great, but as soon as there is a comparison between a real good running bike (dyno'ed), things are in most cases different then expected. I know a few guys with CB450's which are running pods, not one of them pulls harder then mine, or reaches higher speeds. Two of them were on the dyno, and both bikes (one with mikuni's and one with the later CB450 carbs) showed a very rough torque and power curve due to air/ fuel mixture issue's. It took a few hours to dial them in to smoothen the curves a bit. The mileage isn't getting better either.
 
Hi Jensen, thanks for your question and reply with link, and additional explanation. I do appreciate your detail and perspective.

I am operating on butt dyno only. The 450 engine size is just about too much bike for me and I will never push it to its limits. I once drove the 450 like I drive my 350 and ended up at 60mph in a 30mph zone. The 450 cruises nicely at 85mph which is the top speed I want to achieve.

I know what you mean about bike performance. I had a friend with the exact same 250cc scooter as me and mine pulled noticeably harder than his. All was stock except mine has uni pod filter. We did not compare jetting, compression or clutch wear... it was not that important to us, and I don't think he made any modifications after. He was really into 50cc mopeds and spent a lot of time tuning his small 2 stroke dual variated bikes. To both of us, the scooter is just transportation. I installed the pod filter after I had an issue with the air box and never put it back on.

I have also been on many non-tuned 350s and have always used mine as a base line for performance (butt dyno, inconsistent gearing).
 
This is the only physical difference I can see between the 14H and the 723A carbs. What is this guy (red arrow)?

I assume it can be eliminated from the equation by swapping out the float bowls.

IMG_1831.jpg
 
Just the overflow tube, if the float sticks and it floods the excess fuel comes out of that tube, usually with a hose on it run into the rear motor mount plates behind the carbs so it drains to the ground and not on top of the engine.
 
Just the overflow tube, if the float sticks and it floods the excess fuel comes out of that tube, usually with a hose on it run into the rear motor mount plates behind the carbs so it drains to the ground and not on top of the engine.

Cool. Thanks man. If I use these bowls I'll route some fuel hose accordingly.
 
Assumptions, negotiations and surprises.

Here's a bunch of thoughts coming as a result of finishing up my carburetor rebuild. The bike had been running rich and leaking from the left side carb. I decided to refurb the intake side of things and rebuild both carbs over the winter. I found a set of 14H's that turned out to be 723A's when they showed up. Not a big deal. Surprise #1.


I've decided to go with K&N pods and I'm going to extend the pipe out 2" so they'll fit under the side covers - attempting to make things look stock. I was thinking I might go to 140 jets - but I'll wait until I run them with the stock brass until I can determine if the K&Ns lean things out enough so I don't have to worry.


Opened the 723A's shipping box and discovered that neither fuel adjustment screw was included. Surprise # 2. Oh well - I'm talking with the seller and we'll come up with a solution. He was generous enough to ship them without payment saying - and I quote - "...take your time. Make sure you're happy." I'm good with that.


So I took my 14H's off the other day and went through the whole process of ultrasound, cleaning, changing out floats, setting float level. new gaskets, seals, etc. and noticed that these are jetted to 135 on the mains and standard 38 on the pilot. Surprise #3.


I reinstalled everything today, including new intake boots and I have to tell you - the idle and running of this thing is miraculously solid. I've never heard it purr better. I'm able to dial in a perfect 1200 rpm idle, it falls back to idle perfectly and all in all - very successful maintenance.


It's amazing to me however, that digging into and purchasing parts - nothing is as expected. It's like a previous owner, parts seller, existing pieces piñata - every time I open something there is a surprise.


I suppose though, once I've touched everything there is to uncork here I'll finally be certain of what year, what configuration and what parts I'm actually riding on.




Onward - I'm certain there's more to come.
 
Well that was an interesting journey, highlighted by a decent seller for once - you just don't get that kind of honesty these days. As long as these bikes have been around and as varied as their life's journeys have been with respect to maintenance and repairs, it's no wonder so many things are no longer original. At least your surprises haven't led to a worsening of performance and the mysteries to solve to get it right, and it's good to hear it's running as well as it is.
 
Other than the shape of the mixture screw, there are 3 holes under the butterfly (14H) and 2 holes under the butterfly (723A). The 14H’s respond beautifully down low, while the 723A’s just respond.
 
Other than the shape of the mixture screw, there are 3 holes under the butterfly (14H) and 2 holes under the butterfly (723A). The 14H’s respond beautifully down low, while the 723A’s just respond.

Interesting. Thanks for this - I just checked the 723A's on the bench here. I hadn't noticed.
 
Just got around to installing the extensions for these pods. A pretty simple solution and inexpensive way to get the air filters back under the side covers where they belong. I have 135 mains in the carbs at the moment. As mentioned earlier in this thread - I've been chasing a mild rich condition - this may help with that, if not I have 130's in the parts bucket and I can swap those in.

IMG_2468.jpg

32BEAB21-0719-48DB-805B-31A7F2853D51.jpg

D5502D02-FC2E-4BFA-A938-9837F55FA4C8.jpg

Thanks again to Mike for the idea and the mock-up in this thread.
 
Nice job, and glad the sidecovers conceal the lettering on the extensions. You should pick up some 3.5mm fuel line for the bowl vents so if the carbs dribble a little it will go down toward the pavement instead of all over the upper case of the engine. Run them inward and down between the 3 bolt motor mount plates at the upper rear of the bottom end
 
Nice job, and glad the sidecovers conceal the lettering on the extensions. You should pick up some 3.5mm fuel line for the bowl vents so if the carbs dribble a little it will go down toward the pavement instead of all over the upper case of the engine. Run them inward and down between the 3 bolt motor mount plates at the upper rear of the bottom end

Thanks Tom.

Absolutely. Ya know - I HAD 5 feet of hose two years ago, but after installing a dual shutoff for the lower tank line (twice due to routing issues) and replacing the carb feeds, I'm down to a couple of 3 inch lengths. I'll source some more and tidy that up. :).
 
Thanks Tom.

Absolutely. Ya know - I HAD 5 feet of hose two years ago, but after installing a dual shutoff for the lower tank line (twice due to routing issues) and replacing the carb feeds, I'm down to a couple of 3 inch lengths. I'll source some more and tidy that up. :).

Remember though, the overflow hose is smaller than your fuel line, it's 3.5mm vs 5.5mm for the carb inlets
 
I managed to get a short test drive in today. 5 miles on the highway and through town. All the carb work paid off nicely. It feels like a new bike. It's funny, you think it's running well and then some carb cleanup gives you a taste of something better. Trying to describe what the difference is - all I can come up with is that it feels light on its feet. Very responsive from a standstill and it feels like it loves cruising at 6000 rpm. Acceleration is wonderful, Idle is steady and yeah - just light on its feet. Very nice.


IMG_2484.jpg

Next steps - spring time lifter adjustment and timing check. get some long distance riding in - a little camping in the high country to the east - and dig into that shift stopper project when the weather is a little warmer.
 
Congratulations. You've now graduated to journeyman since you've acquired that sense between almost right and right. It's just a sense you get when something isn't quite the way it should be but there's no solid symptom to diagnose from.
 
Congratulations. You've now graduated to journeyman since you've acquired that sense between almost right and right. It's just a sense you get when something isn't quite the way it should be but there's no solid symptom to diagnose from.

Yep, it's like that "feel" for tightening 6mm bolts... takes time and practice. Journeyman status achieved.
 
Congratulations. You've now graduated to journeyman since you've acquired that sense between almost right and right. It's just a sense you get when something isn't quite the way it should be but there's no solid symptom to diagnose from.

Well there's a compliment not taken lightly. Thanks guys.
 
IMG_2507.jpg

Just swapped out the jets - opened the petcock to check for leaks - found a crack in this left side float bowl.

JB weld from the inside - or on the outside? Other suggestions welcome.
 
I have a spare bowl, although not sure for which side carb.... Would hate to go through customs hassle and it be wrong.....Give me until Monday to dig it out.... it will fit of course, but drain screw may be on wrong side......
 
Spare 14H set - jetting for K&N

I have a spare bowl, although not sure for which side carb.... Would hate to go through customs hassle and it be wrong.....Give me until Monday to dig it out.... it will fit of course, but drain screw may be on wrong side......

Steve - I have another set of bowls - the drain screws are buggered though - I think the last owner used a sealant on them. I had to use vice grips to get them out. The heads are toast. I was going to chase the threads in one of those bowls and see if the good screws will fit. These are 723 bowls - the other bowls are 14H’s. Let me tinker before you go to any trouble.

Also - I was under the impression the carb bowls are identical - not an issue which side is scavenged from. Correct me if I’m mistaken here. Haven't checked the parts fiche, but all four bowls I possess drain toward the port side of the bike. Which makes drain screws on a bowl installed on the starboard side kind of useless.

Again - this may be previous owner improvisation (I no longer have much of a handle on what is and isn't stock on this machine. Lol)
 
Chased the threads on one of the 14h bowls (#6 - 0.75 if anyone is wondering) and the best drain screw I have for it. The 723 screws are a different configuration so I didn't swap them out. The 14H uses a metal crush washer - the 723's use a rubber grommet.

It looks like there may have been a repair inside - hard to tell but there's a lot of corrosion.

IMG_2510.jpg

And it's impossible to see a crack, but microscopic is all it takes for fuel to find its way through.

I replaced the left side with a 14H bowl. Mismatched float bowls is a non-issue on a Frankenbike. No leaks though - which is my goal.

On to the next surprise whatever that might be - glad they're minor ones.
 
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