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Discussion Starter · #1 ·
Alright, I fixed the exhaust leak and the carb fitment problem on my 73 CL350, and now it runs like crap!! So a rejetting of my 450 carbs is in order. The only mods I have made on the 450 carbs are the Uni Filter foam socks. PLEASE give me some type of guesstimation on jet sizes. I know its trial and error but its a pita to remove that exhaust!
 

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Why don't you start with stock 350 jetting and work from there?
 

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Sensei
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I'm afraid "runs like crap" is not specific enough... Are you too rich or too lean?
Too lean might mean you don't have enough oil on the air cleaner.....

You might try mathmatically comparing throat area (old carb vs 450 carb), and factoring the original jet size.... Should give a decent "start point" anyway....
By this method, a 90 main in the 350 carb would require a 148.5 main in the 450 carb to be feeding the same fuel/air percentage mixture (at WOT)...However, displaced volume and compression ratio's and valve open time also factor in as CV carbs rely on the created vacuum to determine the amount of that mixture pulled through the intake. There are a ton of calculations involved.....
Buy a box of plugs, you'll be taking lots of "plug readings".....
 

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Oh, man - a 150 main is too rich for even most 450's........
As Steve indicated, there's probably no way to "calculate" this, you'll have to do it emperically.

Like Steve said, buy a box of plugs, you'll need them.
 

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Sensei
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EXACTLY...
But we'll need to know too rich or too lean now to even venture a "best guess" of which way to proceed..........Knowing what jets were/are in the original 350 and current 450 carbs couldn't hurt....

Factoring in as many POSSIBLE variables as I can think of, a 90 main in the 350 carb becomes a 125 to 127.5 in the 450 carb, an original 100main in the 350 carb roughly converts to a 130 to 132.5 in the 450 carb.....Personally, I'd start with a 130 in the 450 carbs, and go from there....
THIS IS JUST a "best guess" based on many loose assumptions about how major or minor the differences in the two engines/carbs are...
..WE ARE ACTUALLY COMPARING APPLES AND ORANGES....
If possible, ERR on the rich side...Better to foul plugs than burn valves/pistons
 

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Just throwing my $0.02 out there, my CB360 has CB450 carbs on it as well as Uni's and aftermarket pipes. I have #35 slow jets and #140 main jets. It runs a tad rich, but with #130's I can't go faster than ~60 mph.
 

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Sensei
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Based on Kruk's info/experience....try 137.5's.......
 

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Sensei
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Solder and number drills might be the way to go until you DO find the exact size you want/need...... Borrow some CB pipes for the testing, put the CL's back on after

(Nevermind, too many other changes would be required running the CB pipes.....)
 

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Lemme know what you find. When I had a dude tune mine, he couldn't find any so he just drilled out my holes to the right size.
 

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Sensei
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Yes, if done correctly on clean parts... I have jewelry experience, so I annealed and pickled mine to clean them, then hardened the brass and silver solder "plugged jet" before drilling...... Not hard to do, to anneal you just quench it hot into the pickle....Once it's filled with solder, slow air cooling (just set aside to cool) will re-harden the brass (and solder)....
 

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Discussion Starter · #15 ·
Do you think lead solder would work as well as silver? I've soldered onto brass countless times with lead but never with silver before.
 

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Sensei
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As long as you use a metal-mending lead/tin mix and acid flux, you should be fine... You are just making "plug" , not a structural member....
 

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i've got some feelers out on other posts here about this topic so i'm sorry if i sound redundant here. i'm pretty sure i need to rejet after my jc whitney megaphone muffler and k&n pod upgrades to my 450. last night bike wouldn't run without choke open. some flames here and there too. what do the flames indicate? timing is pretty close to perfect(strobe) and carbs- well they aren't spotless, but they got the bike running(they are now as i type this, busy night). air/mix screws about a full turn out (maybe a little more) and idle screws about 2 full turns. so i'm just looking for a place to start to rejet. 130/38's now. AS STILL A TOTAL NOOB, i'm guessing i'm going up in size? i thought they incremented in 5's so 135 main, and what about the slow jet? are those the ONLY to pieces of this jet puzzle upgrade i should be paying attention to?

many thanks in advance(again),
seth
 

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