250 hornet carbs refuse to stop overflowing

[motorbyclist]

long story short, little brother dropped bike and it dropped a cylinder, but it was running sick anyway after a 3 week sit without use.

every person to look at it has had a different set of cyclinders firing, so i had a crack at it: i've even gone and removed, cleaned, and refitted the carbs yet the fuel overflow continues to dump fuel and the motor gets literally flooded and borderlines on hydraulic lock.

fuel (currently) comes from both overflow tubes (one tube to a pair of carbs)

the float valves and seals all seem to be fine. carby bowls all had a bit of sediment in them but that's gone now and no jets were blocked.

any ideas?

[NinjaNanna]

... the fuel overflow continues to dump fuel and the motor gets literally flooded and borderlines on hydraulic lock.

fuel (currently) comes from both overflow tubes (one tube to a pair of carbs)

the float valves and seals all seem to be fine.

Your symptoms don't seem to be adding up to me, if your float valves are ok then unless your float levels are set way,way wrong then you shouldn't be getting this problem. Is it possible that the drop fucked the float levels?

Also I don't see how you can be getting so much fuel into the cyclinder to nearly cause hydraulic lock if the overflow tubes aren't actually blocked and syphoning the excess fuel away.

First thing I'd check is to see if the overflow isn't partially blocked. Then I'd be trying to work out which specific bowls are flooding.

One way that you may be able isolate the bowls is to use the drain screw on one bowl at a time, if the fuel stops coming out of the overflow then it must be that carb that is overflowing.

[motorbyclist]

Your symptoms don't seem to be adding up to me, if your float valves are ok then unless your float levels are set way,way wrong then you shouldn't be getting this problem. Is it possible that the drop fucked the float levels?

doesn't make sense to me either! the floats and arms are all plastic so as far as i can see there is no way for adjustment nor should/could they be damaged.

the valves themselves seal well and have no signs of damage.



Also I don't see how you can be getting so much fuel into the cyclinder to nearly cause hydraulic lock if the overflow tubes aren't actually blocked and syphoning the excess fuel away. dunno if it was a hydraulic lock but the last bout of starting had zero cylinders firing and the motor/starter occasionally stalling.

atleast before i went as the carbs i had 2 of four cylinders - just they were a different pair to what the old man had and my brother again!



First thing I'd check is to see if the overflow isn't partially blocked. Then I'd be trying to work out which specific bowls are flooding.

One way that you may be able isolate the bowls is to use the drain screw on one bowl at a time, if the fuel stops coming out of the overflow then it must be that carb that is overflowing.

good idea mate - i'll give that a go tonight

[R6_kid]

Get an inline fuel filter... my bike was doing the same and a fuel filter is what sorted it.

My guess is that the drop has dislodged shit in the fuel tank, which is now flowing through into the carbs and holding the float valves open. That would be why even after cleaning it you have the same problem.

Clean the carbs out, put the fuel filter in, then replace the carbs, hookup the fuel lines and see what happens. At $12 for a fancy pants cleanable fuel filter it's not exactly an expensive fix!

[motorbyclist]

My guess is that the drop has dislodged shit in the fuel tank, which is now flowing through into the carbs and holding the float valves open. That would be why even after cleaning it you have the same problem.

i'll give it a go, but there is the filter at the tap, inside the tank, which you'd think would catch all this....

[NinjaNanna]

Clean the carbs out, put the fuel filter in, then replace the carbs, hookup the fuel lines and see what happens. At $12 for a fancy pants cleanable fuel filter it's not exactly an expensive fix!

Cycle Treads have the disposable plastic kind in 6mm and 8mm outlet sizes. fairly small specific for bike use as opposed the the big arse things for cages.

If you saw all the shit caught in mine there's no way you'd run an older bike without one.

Also I thought it odd why you'd suddenly get at least 2 carbs playing up - R6_Kid's theory accounts well for it though.

[NinjaNanna]

i'll give it a go, but there is the filter at the tap, inside the tank, which you'd think would catch all this....

you sure its still there wouldn't be the first time one's been removed.

In my wife's Balius not only the filter but also the main/reserve tubes have been removed so the tank gets run totally dry.

Try living that down on the ATNR.

[The Stranger]

In my wife's Balius not only the filter but also the main/reserve tubes have been removed so the tank gets run totally dry.

Try living that down on the ATNR.

Riding your wife's Balius? No thanks.

[NinjaNanna]

Riding your wife's Balius? No thanks.


Hey whatcha talkin bout, I changed the plug caps and the thing goes like a rocket now.

[motorbyclist]

right, well i bought a pack of party balloons and gave the carby a good blow out, including the fuel lines etc etc.

all the bowls are still overflowing, so I'll definitely go give the inline filter a try considering the unknown state of the existing filter.

cheers for the advice

[Squiggles]

I think you should let me play with it :D

[R6_kid]

i'll give it a go, but there is the filter at the tap, inside the tank, which you'd think would catch all this....

That's what I thought too... i even replaced the fuel tap on the CB650 as that was leaking too, the filter on the new tap didn't stop the problem, but an inline filter did.

[elevenhundred]

How does it go if you try to run it without the tank? i.e. just using the fuel already in the float bowls, it should at least remove the overflowing so you can see if there are any other issues.

[motorbyclist]

That's what I thought too... i even replaced the fuel tap on the CB650 as that was leaking too, the filter on the new tap didn't stop the problem, but an inline filter did.

bloody tank filter looks like a non-removable item, so inline it most definitely is!


How does it go if you try to run it without the tank? i.e. just using the fuel already in the float bowls, it should at least remove the overflowing so you can see if there are any other issues.

well first i had to remove all four plugs to relieve the hydro lock.... squirted fuel fucking all over the place.

then i lost interest and had a steak + beer

[R6_kid]

...
then i lost interest and had a steak + beer

You big burly man you!

[motorbyclist]

ok, new inline filter installed, fuel lines flushed until blowing into the overflow no longer sent air/fuel out of the fuel line and started her up.

all seems good :)

will ride her to uni tomorrow and see how she goes

[NinjaNanna]

so how's she going after a good run?

[motorbyclist]

mint! fuel filter did the job and fits nicely under the carbs without having to add any more fuel line - cost all of 8 bucks from cycletreads.

Taking off from two sets of lights i dropped a cylinder. Seemed to come right though (probably after hitting reserve tank). She sits happily at fairly high revs without starving of fuel so the filter hasn't created any new problems either :)


So i took it up SH16 where the gear lever fell off just before wellsford, and then ran out of gas on the way back to auckland cause i left it in reserve after filling it up.... then after the AA rescue i hit reserve tank, having thought it was already on it, so thought it broke again but all good :niceone:

[gijoe1313]

:blink: Crikey, that poor lil'ol'hornet has been a mite sick! Hope that is the end of the dramas and well done for being resilient and presevering through all the trials and tribulations!