Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: RGP750 on July 04, 2014, 07:48:53 PM
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Slight hold on last post. I ran a short ride night before last and limped home on 1 and 2 cylinder.
Traced problem to no fuel coming from the Tap tube feeding 3 and 4., Tank off Tap off clean everything
blow out everything, put on new fuel pipes,(in case a spider was left in the original pipes).
Ran ok ,only in drive way,but of course bowls were full, same problem tonight only 1 and 2 cold ,i had switched the pipes on the tap..
Just taken tank off again ,this time put tap on reserve and fuel isn't coming out of the front pipe,if i put my finger over the back one with fuel coming out fuel then flows from the front pipe si it isn't blocked just seems to be some sort of vacuum being formed.
If no one has any idea it looks like DS will be getting another £50.
Cheers Rich :-[
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I think these tanks vent through the cap if you open it does fuel come out of the tap then
Mick
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Hi
Yes tried that and it's fine.
it's only one of the tap outlets that wont seem to work for some reason.
The weird thing is it was fine for 12 miles the night before last then suddenly
just cut out and only fueled 2 carbs.
Rich
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How is the packing valve behind the tap part 4 schematic I think it works in similar way to the valve in my airless spraygun any damage or deformity it stops working
http://www.cmsnl.com/honda-cb750k2-four-england_model14363/partslist/F11.html#results
Mick
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Yes the rubber seems ok. I can't get my head around it stopping working.
Just taken it apart again, the rear tube has the direct flow from the tank so will potentially
have priority over the front tube which has an internal 90 degree drilling from the rear tube.
Whichever pair of carbs is supplied by the front tube is starved of fuel,very weird.
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Neither should have direct flow from tank, fuel should go from tank via tap and filter screen to bowl then to outlets, which is why if the washers are duff you get fuel to the carbs all the time as it comes down the screws and bypasses the tap
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just a quick thought,I recently had to drain my tank,(CB500-4) the fuel tap did a similar thing,full flow from one outlet,dribble from the other,this made me think,a very rare occorance !
is the fuel taking the line of least resistance?
in normal use,it fills each pair of carbs,guessing the full flow fills faster,when that is full it means the only out of the tank is by the "slow"
pipe ?
as both sets of carbs will normally use the same amount of fuel,it is likely to happen after maybe a dry start ,were the carbs are empty,
or if it runs onto reserve,
this is not a sure cure,but something to ponder on,
try putting your finger to stop the flow,and see if it increases in the other pipe,
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Happy again. It would seem the problem was down to low fuel,i had about half a gallon in the tank.
I put a couple of cans in and all seems well.
Just done a 70 mile ride and pulled to 70 no problem ,lovely to ride. ;D
5 miles from home and it chucked it down with rain so now have a bit of cleaning to do, oh well the
ride was worth it. Roll on the next sunny day.
Cheers to Bitsa for his guidance over the last 6 months.
Rich
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Yup reserve is more than you think!!