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Discussion Starter #1
i've found tons of stuff on jetting for 350's but no 400's.

im replacing my crappy cv carbs with some round slides and i just got them in the mail. today i checked tank clearance and made sure it would fit on my intakes, check. next thursday i'll be hooking them up and doing some test runs...as it'll be a three day weekend for me.

the carbs are sudco tuned(fingers crossed on jetting) for a cb360. i heard they were a bit much for cb350s/360s so i figured they'd be(roughly) just right for a 400. the only things that'll affect the carbs are my two into one pipes.

if vm32's are overkill for a 350 do you think they'd be just right for me? i'll find out next weekend but if anyone has suggestions on jetting or needle heights let me know. i want to buy all the jets i'll be needing to try out at once so i dont have to drive back and forth to the parts store, as well as some plugs.

thanks in advance
 

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Did they come with the 190 mains and 35 pilots?

PJ
 

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Man...bums me out hearing everyone having trouble with Sudco. I bought the FSR39's on my SuperIII from them "pre-jetted" and once they were installed the bike spent an afternoon on the dyno for some tuning. In the end we added velocity "tubes" inside the pods but the jetting was a close tp perfect as I could have hoped for. We changed no parts, I think the needles were tweeked a bit and perhaps the idle air.....but I can't remember. Just remember that no parts needed to be changed.
 

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quote:Originally posted by txchainsawgogi

quote:Originally posted by crazypj

Did they come with the 190 mains and 35 pilots?

PJ
sure did...why?
Because none of the VM's seem to be jetted right (unless your running a 1970's two stroke MX bike ;))
Ain't too expensive to change the brass though.
If I ever get round to it I'll make some 'proper' emulsion tubes so they don't run too rich mid range

PJ
 

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What type of 400 is it? I can't remember what type you're working on. If it's a stock-ish CB400 twin, I suspect that the 32s may be a bit overkill. The could be made to work, but 30s might work better. If it's not a stock-ish CB400 twin, then I apologize.
 

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Discussion Starter #10
quote:Originally posted by whiskeysid

What type of 400 is it? I can't remember what type you're working on. If it's a stock-ish CB400 twin, I suspect that the 32s may be a bit overkill. The could be made to work, but 30s might work better. If it's not a stock-ish CB400 twin, then I apologize.
sigh... stockish(engine) for now...and technically a cm400 given the year. minus an airbox and with 2-1 pipes. other than the engine literally everything else is different as it was an ugly fucking bastard when i got her.
 

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I don't know too much about those bikes, but I think they're tuned very mildly. They probably make less power than an old CB350. That's why I say that the 32s may be a bit big.
 

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Discussion Starter #12
if i remember correctly a blueprint stock 68' 350 put out 36bhp and my cruddy little engine puts out 30. mainly because honda felt the need to detune it by using smaller valves.

ive always wondered...if i found a cm 450 engine if i could use its pistons and bore my 400 over. my bike is my daily, but i still plan on getting the most out of it that i can.
 

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quote:Originally posted by txchainsawgogi

if i remember correctly a blueprint stock 68' 350 put out 36bhp and my cruddy little engine puts out 30. mainly because honda felt the need to detune it by using smaller valves.
The way HP measurements were made was different in 1968.
CM 400 is very mild tune but has far more potential, it may have smaller valves but, it has double the quantity-3 valve per cyl head (2 intakes)compared to 2 valves/cyl
Look for a cylinder head and cam from a 'Eurosport' 400, they were good for 110mph, or just 'research' European/British CB400.
Alternatively, get book on Honda B16/18motors, the car engines were developed from the bike

PJ
 

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Discussion Starter #14
sorry i wasnt clearer. i meant my CM is the downtuned version of the 78cb400, but yes i know of the brit cb400...the N model is what i pulled my tank off of. too many similar models in such a short range of years!
ive got a few books on older hondas, and one thats literally the entire history with almost every model in it. very interesting reads.

i learned to ride on my uncles 2003 883r sportster(the orange/black flat tracker), and have riden an old bmw and my buddies r1... but i always feel more partial to hondas for some reason.
 

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Discussion Starter #15
what exactly would a euro head and cam do for me? any specifics on a year?


edit: sorry i was drunk earlier and didnt really think before typing!

do you think if i got a head, cam and valves from a brit cb400n i'd get a decent enough hp increase for the hassle? i looked up the engine blueprints and theyre very similar. the 400N put out 43bhp with a top of 108-110, and i've gotten mine to 101 before i backed down on flat ground WITH shitty carbs. im hopeful to get my 81 cm400 to be badass.
 

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probably want closer to 145~150 main jet and 27.5~30 pilot

PJ
 

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probably want closer to 145~150 main jet and 27.5~30 pilot

PJ
 

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Discussion Starter #20
ok so ive noticed that its going through plugs pretty quick. a lot of carbon build up on my plugs, but also a dead spot at 50mph.

should i back the air mixture screw out and move the needle up a notch? its currently clipped in the middle position.

i wont be able to screw with it until the shit weather clears up here :(
 
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