Author Topic: 1975 CB400F ONLY FIRING ON 2  (Read 3093 times)

Offline OLIVER1GEORGE

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1975 CB400F ONLY FIRING ON 2
« on: April 14, 2009, 07:14:54 PM »
HI i recently purchased a 75 cb 400f it had been in storage for 10 years, when i got it i gave it a service ie. oil change filter ,plugs air filter gave the carbs a good blast of carb cleaner a new battery and she fired up when i kicked her over but she sounded like a v twin ducati not good any ideas . no smoke at all when she starts but just wont fire on all 4 there is a spark on all plugs can anyone help or give advice many thanks

Offline Dave M

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Re: 1975 CB400F ONLY FIRING ON 2
« Reply #1 on: April 15, 2009, 07:41:46 AM »
The carbs will need stripping and cleaning thoroughly if it's been standing that long.
Dave
Melbourne.

Offline OLIVER1GEORGE

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Re: 1975 CB400F ONLY FIRING ON 2
« Reply #2 on: April 16, 2009, 09:07:52 PM »
had carbs off  give them a good clean blew them through with compressed air put them back on and i was so happy it fired on all four but now i have another snag it smells really rich and white smoke from exhaust its allmost as though it is burning pure fuel any idea what i have done

Offline Dave M

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Re: 1975 CB400F ONLY FIRING ON 2
« Reply #3 on: April 16, 2009, 10:57:18 PM »
Did you take all the jets out of each carb body for cleaning? You may need to soak each one in cellulose thinners before blowing them out with carb cleaner and compressed air and then check visually.

Did you clean the internal drillings in each carb body?

Are the floats OK? No petrol inside them? No leaks?

How about the float heights? All checked and set correctly?

Any leaks from the carb overflows when the engine's not running with the fuel tap on?

Pilot screws set to manufacturers settings? May need tweaking.

Is the air filter clean? Try running briefly without the filter and see if there's any improvement.

Carbs can be so fickle and difficult to fettle when they've been standing for a long time with fuel in.

Good luck.
Dave
Melbourne.

Offline OLIVER1GEORGE

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Re: 1975 CB400F ONLY FIRING ON 2
« Reply #4 on: April 17, 2009, 09:15:11 PM »
i will take um off again and give them a real good going over im so close the engine sounds really tight and nice just running rich thanks for your advice i will get back to you and let you know thanks

Offline OLIVER1GEORGE

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Re: 1975 CB400F ONLY FIRING ON 2
« Reply #5 on: April 20, 2009, 06:43:46 PM »
Atlast my baby is working properly give the carbs a real going over replaced a couple of orings that looked iffy and put them back on bike and started lovley then i borrowed a mates sycnro kit and balanced to within 3mg of each other or as close as i could and it picks up lovely with no smoke thanks for your help everyone.............one happy biker

Offline Dave M

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Re: 1975 CB400F ONLY FIRING ON 2
« Reply #6 on: April 20, 2009, 07:39:15 PM »
Sorted! :)
Dave
Melbourne.

 

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