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Author Topic: I hate four carburettors!(help needed with cb400f)  (Read 1735 times)

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Offline stay youth

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I hate four carburettors!(help needed with cb400f)
« on: September 13, 2009, 01:18:34 pm »
ok so my bike has been sitting idle for some time, but i want to get it back up. i'm running an mc-again exhaust and pods. i have increased my mains to 85 and pilots to 38 and one notch higher over stock on the needle. my timing is correct and my clearances are correct. When i try to start it is just winds over and does not fire. My plugs were rich but put new ones in and still does not fire. When i check the spark its seems to be weaker than what i remember in the past. Does anyone have any tips or suggestions?

Thanks so much
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1976 cb400f

Offline kslrr

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Re: I hate four carburettors!(help needed with cb400f)
« Reply #1 on: September 13, 2009, 01:38:01 pm »
With pods and a custom 4-1 farely open exhaust on my CB350F, I am still running the stock 75/35 jets with the needle clip at the bottom.  Maybe your way too rich, though I can't say that my setup applies to the 400.
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Offline Hush

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Re: I hate four carburettors!(help needed with cb400f)
« Reply #2 on: September 13, 2009, 02:20:14 pm »
Are your plugs wet looking when you pull them? Could be you have over compensated for the pods/pipe and she's drowning in a pool of gas. :)
Battery fully charged?
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I think the thing I most like about motorcycling is the speed at which my brain must process information at to avoid the numb skulls who are eating pies, playing the ukulele, applying make-up etc in the comfort of their airconditioned armchairs as they make random attempts to kill me!!!!!!!

Offline stay youth

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Re: I hate four carburettors!(help needed with cb400f)
« Reply #3 on: September 13, 2009, 02:44:45 pm »
hi all

thanks for the quick responses. my plugs are not wet, they got that dry sooty look. Now maybe i did my clips backward im thinking. But being just one clip away from stock seems like it would still at least fire???? Do I drop the clip down a notch to lean out?

Thanks again for the help!
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1976 cb400f

Offline CrashBar

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Re: I hate four carburettors!(help needed with cb400f)
« Reply #4 on: September 13, 2009, 07:17:24 pm »
+1 on making sure you have a STRONG battery.  I recently resurected a 78 550K, no joy until I jumped it off the big battery from my K1100.

Also, try some starting fluid.   If it is an ignition problem it wont matter, if it is a carb problem it will probably fire up, at least for a few seconds.  Try not to have it backfire and light you in fire.
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Offline stay youth

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Re: I hate four carburettors!(help needed with cb400f)
« Reply #5 on: September 13, 2009, 08:19:03 pm »
well i did just charge the battery, but i have had to recharge it a few times. How many times can i recharge the battery before replacing it? Also where should i squirt the starter fluid in?

Thanks again!
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1976 cb400f

Offline CrashBar

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Re: I hate four carburettors!(help needed with cb400f)
« Reply #6 on: September 14, 2009, 12:44:06 am »
Starting fluid - just spray it in the intake.

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2017.5 BMW R1200GS
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Offline stay youth

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Re: I hate four carburettors!(help needed with cb400f)
« Reply #7 on: September 14, 2009, 08:44:51 am »
ok thanks, how about my battery would it be worthwhile to get a new one?

thanks
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1976 cb400f

Offline Bodi

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Re: I hate four carburettors!(help needed with cb400f)
« Reply #8 on: September 14, 2009, 10:13:17 am »
Recharging a battery isn't bad for it, that's what it's made to do after all. Problems arise if you let it drain flat dead, and/or use a high amp charger (2A should be maximum for these little batteries).
There are lots of other ways to destroy a battery but if you've just recharged it with a safe size charger a few times there should be no problem.
Generally if you get 3 years life from a battery you should be pretty happy. After that, sooner depending on how it's treated, and a new battery is part of the price of riding a classic.
The 400F has a weak alternator and consequently the battery as discharging whenever you're below 3000 rpm (or so). Adding a higher wattage headlight or other electrical accessories is not advisable.
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Offline Hush

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Re: I hate four carburettors!(help needed with cb400f)
« Reply #9 on: September 14, 2009, 03:54:59 pm »
In answer to your needle clip question, yes, dropping the needle down a clip lowers it into the main jet emulsion tube which narrows as it gets closer to the main jet so lowering the needle blocks it more thus reducing the amount of gas you are feeding the motor.
Alternately raising with richen your mixture.

If the bike has been sitting for some time it may pay to check that the very tiny holes in the emulsion tubes have not become blocked
If it is a gas supply problem as Crashbar said, pop off a pod filter, lift the carb slide with a screwdriver and squirt some starter fluid (which is mainly ether so go easy on it) into the body of the carb, kill switch off, igniton on and hit the button, if it doesn't even burble then there is something else wrong, I wouldn't run it too long like that though as damage may occur.
Just another thought, as you've been playing with the carbs/jets etc check that the slides are not actually totally closed at rest.
« Last Edit: September 14, 2009, 04:02:40 pm by Hush »
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I think the thing I most like about motorcycling is the speed at which my brain must process information at to avoid the numb skulls who are eating pies, playing the ukulele, applying make-up etc in the comfort of their airconditioned armchairs as they make random attempts to kill me!!!!!!!

Offline stay youth

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Re: I hate four carburettors!(help needed with cb400f)
« Reply #10 on: September 14, 2009, 05:01:22 pm »
hi all thanks for all the helpful tips hope to get in the garage tmrw night. will keep you posted

thanks
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1976 cb400f

Offline stay youth

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Re: I hate four carburettors!(help needed with cb400f) updated 9/20
« Reply #11 on: September 20, 2009, 10:54:58 pm »
ok so today i tried spraying some starter fluid into the intakes and it did idle for a few seconds but then quit. I also got a new fresh charged battery. I'm really stumped here can anyone offer some advice?

thanks!
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1976 cb400f

Offline Hush

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Re: I hate four carburettors!(help needed with cb400f)
« Reply #12 on: September 21, 2009, 12:20:24 am »
"It started and idled for a little bit"
You just analised your bikes problem, gas supply!
Either the emulsion tubes are blocked, the float valves blocked, tank has rust blocking the gas tap.
There's just a few of the possibles.
Favorite for a bike that has sat for a while is crap in the gas tank blocking the gas tap, it moves and blocks the fuel lines.
Easy way to check, open the drain screws in the bottom of the carb bowls, if you get good gas flow from all 4 carbs then it maybe something else.
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I think the thing I most like about motorcycling is the speed at which my brain must process information at to avoid the numb skulls who are eating pies, playing the ukulele, applying make-up etc in the comfort of their airconditioned armchairs as they make random attempts to kill me!!!!!!!

Offline matt s

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Re: I hate four carburettors!(help needed with cb400f)
« Reply #13 on: September 21, 2009, 06:28:02 am »
Quote from: Hush on September 21, 2009, 12:20:24 am
Easy way to check, open the drain screws in the bottom of the carb bowls, if you get good gas flow from all 4 carbs then it maybe something else.

+1

I was banging my head on the wall for days and having the same king of problems you are having until I did this.  There was a little fuel in the bowls, but none coming from the tank.  Switched to reserve, and she fired right up!  Felt like an idiot but that feeling wore off when I got on a rode her around!
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Offline stay youth

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Re: I hate four carburettors!(help needed with cb400f)
« Reply #14 on: September 21, 2009, 07:59:10 am »
ok great, i will give that a try tonight

Thanks!
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1976 cb400f

Offline fmctm1sw

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Re: I hate four carburettors!(help needed with cb400f)
« Reply #15 on: September 22, 2009, 04:46:56 pm »
Quote from: kslrr on September 13, 2009, 01:38:01 pm
With pods and a custom 4-1 farely open exhaust on my CB350F, I am still running the stock 75/35 jets with the needle clip at the bottom.  

+1 except for I have the stock airbox.  Still black plugs.  I actually bought 72 main jets from sudco and only those because they didn't have 70s...
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This is not a pod thread
This is not a #$%* on my vacuum gauges thread
This is a help or GTFO thread.

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Offline 750Caferider

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Re: I hate four carburettors!(help needed with cb400f)
« Reply #16 on: September 24, 2009, 07:38:51 pm »
If push comes to shove, you could always take it to a reputable bike shop with a dyno.  I love pods and a hot exhaust but combining those and getting everything set right can take a lot of time.  I will hopefully be doing pods and 4 into 4 soon, I'll do the work myself but I think I'm going to save the headaches and have it tuned on a dyno by an old pro.  I'm fortunate enough to live in a town that has a couple of really great shops.

Cheers.

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Offline BVCB650

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Re: I hate four carburettors!(help needed with cb400f)
« Reply #17 on: September 25, 2009, 05:36:23 am »
Quote from: fmctm1sw on September 22, 2009, 04:46:56 pm
Quote from: kslrr on September 13, 2009, 01:38:01 pm
With pods and a custom 4-1 farely open exhaust on my CB350F, I am still running the stock 75/35 jets with the needle clip at the bottom.  

+1 except for I have the stock airbox.  Still black plugs.  I actually bought 72 main jets from sudco and only those because they didn't have 70s...




Hotter plugs can help in over jetting.....
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1979 CB650, 25K miles, recently refurbished
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