CB400 bogging

[GeorgeB.]

Hi all,

I've had a bit of an issue for a while with my CB400, where that it'll die after giving it some beans for a bit (or trying to sit at anything over 65 on the motorway). I've discovered that this is because the the fuel cap breather is blocked, therefore creating a vacuum preventing free-flow of fuel

Unfortunately I only worked that out on the M6, 70 miles from home at about 10PM on Sunday night. So, as a temporary fix, I rode home with my fuel cap open (not wide open, it was closed as much as possible without locking it. Problem solved, sat at 90 without even caughing all the way home and would pull me to 120ish without any issue.

However, after a spirited ride to work yesterday morning, the bike started bogging. It's not the same issue as the fuel cap blockage, because that's now fixed. It still accelerates but not as quickly as it should, and the engine sounds weird.

Is it possible that I've managed to get road crap in my tank/carbs? Or something simpler than that?
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Current: '99 Fazer 600 | '99 Range Rover P38 4.6 HSE
Previous: Keeway TX125 | CBF 125 | CB400SF Project Big One
CBT 04/12/12 | Theory 03/12/13 | MOD 1 06/01/14 | MOD 2 13/01/14

[P.addy]

Can you run the bike on PRIME?

Unsure if the CB400 you have is ON/PRI/RES or has an off part... but you might have a busted vacuum line.

[GeorgeB.]

[orac]

drain a litre of fuel strait out of the tank into a clear bottle, if there is water in there you will see it. i get the same issue after the wet winters like we have just had.

once you are only getting fuel out of the bottom of the tank, drain the carbs, check them for water and dirt. prime them up and test ride.

it will be worth while you getting a length uf pipe you can put of the vacuum feed for the fuel tap, gnetly suck on it (yeh that what you said the misses etc etc). you can put your tong to keep the vacuum in the tube without having to constantly suck. please make all the jokes you like of the back of that last paragraph
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Current rides - 2016 Triumph Street Triple Rx, 1994 Suzuki Bandit 400 VM, TGB 204 Classic 125cc
"with nothing left to lose, there is everything to gain. It's not the size of the dog in the fight, it's the size of the fight in the dog"