RXS100 Carb Runneth Over

[Serendipity]

My RXS100 is once again on the road and running quite well except for a problem with the carb.

It was fine for a few weeks, and then the carb suddenly started overflowing from the breather at the base of the float bowl. The leak stops if the fuel tap is off (no kidding ).

I dismantled the carb and cleaned it all out. I made sure the float was working correctly and that the little piston it pushes was moving freely. Reassembled the carb and tested...

...still peeing petrol everywhere.

Next I took the carb off my spare bike and fitted that to the running bike. Exactly the same problem happens.

Why’s that then? Any ideas?

Cheers
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2016 CBF1000F - Commuter heaven | 1994 CBR600FR - Awaiting defibrillation

[Serendipity]

Forget it. I just dismantled the old carb and found little motes of rusty shite in the float needle seat. I've just drained the fuel tank so I can check the filter in the petrol tap. I'm guessing it's knackered.

Doesn't explain why the replacement carb, did exactly the same trick, unless there's loads of rusty crap coming down the line and the seat got jammed immediately...
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2016 CBF1000F - Commuter heaven | 1994 CBR600FR - Awaiting defibrillation

[Dipsy2]

deleted

[Serendipity]

No namby pamby dribbles here. We’re talking full on gushing!

I’ve just finished stripping and cleaning the original carb and the fuel tap. The design of the tap means that the reserve inlet is totally unfiltered. The main fuel inlet has a cool little plastic mesh filter on it. I guess all the crap got into the carb when I used the bike on reserve.

I washed all of the rusty crap out of everything and carefully assembled it all again. Filled up the tank, switched the fuel tap on and the bike started first kick. Hooray!

I ran it for a couple of minutes while talking to a neighbour before I suddenly realised it had started pissing petrol again...

... Bollox!

Going to sleep on it and have another go tomorrow. Float height is the next check as suggested by Poppy.
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2016 CBF1000F - Commuter heaven | 1994 CBR600FR - Awaiting defibrillation

[27cows]

A gush rather than a drip or dribble usually indicates crap in the needle seat. If it's doing it with two carbs, would suggest a damaged fuel tap filter allowing the shite into the carb.
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The RXS100: vehicle of choice for Chuck Norris

[russeleoin]

Hi Senendipity, I had a similar problem on my YB100. The upshot of it was there were the samllest of holes in the float base. In hot weather( or when the bike got hot) the air inside the float expended and the float got lighter. Then when it cooled down, it would suck fuel into the holes and the weight of the float would rise. It would then not shut off the fuel and therefore I would find a puddle of fuel on the floor. The hard part was derterminng that there were holes in the float. When I handled it, it got warm and off course the fuel expanded and i couldnt see any fuel. So if you think this could be your problem, take the float out, get a glass bowl and fill it with hot water. Submerge the float fully and watch for the tiniest bubbles coming from it. To fix it, use solder, I tried araldite first and it was fine for a year then the damned stuff denatured and started leaking again. I have soldered it now and it works like a charm.
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I love classic merc's but bikes take up less space.
Current ride is a Yamaha YB 100 and I love it! Oooow and now a running GPZ400R!
Next stop, Direct Access hopefully by the end of summer.

[Serendipity]

I’m fairly sure that my floats are still floaty. They’re plastic ones and have no liquid trapped in them.

I think that its chunks of rust from the tank blocking the float needle again. When I dismantled and cleaned the tap last night I noticed that what I thought was the reserve inlet was completely unfiltered. Now looking at this picture from Wemoto:

https://images.wemoto.com/full/FUEL_TAP_COMPLETE/10004593.jpg

It looks like there is a copper or brass tube on the tap, presumably for the main inlet while the filtered inlet is actually the reserve. I reckon that my tube must have vibrated off and I’m willing to bet that it’s rolling around in the tank somewhere.

More draining, cleaning and shaking in my future.
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2016 CBF1000F - Commuter heaven | 1994 CBR600FR - Awaiting defibrillation

[27cows]

Might be worth trying an external fuel filter (which is to say, one between the tap and carb). Can pick them up for next to nothing.
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The RXS100: vehicle of choice for Chuck Norris

[Robby]

Yup, inline fuel filter. Surprised you don't have one already. Go for the slightly more expensive (£2.25 instead of £1.50) paper element ones, the mesh ones are crap. Buy a handful, if there's a lot of crap in the tank you'll be surprised what you see in the filter.

The gushing is down to the needle valve seal. Seeing as you know the fuel coming in is dirty, pop the carb off again, get a new can of carb cleaner, strip out everything (including the idle jet), use the long nozzle on the brake cleaner and poke and spray it into everything (eye protection worthwhile, you'll see why). Let the carb dry out somewhere warm, reassemble to factory spec including setting the float height.

Sorted.

Don't be too rough when cleaning the rubber tip on the needle valve, and if in doubt replace. Despite being a cheap looking little thing they're quite precise and a few small scratches can make them leak. Not gush though, that's down to bits of rust.

[Billing]

I had a very similar problem on my TZR, which has similar looking carb internals.

I cleaned the carb no end of times, checked that everything was as the factory intended and it still did it. I changed the float valve, and that seems to have cured it
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'84 TS50X, '91 TZR125, '89 CBR400RR, '91 VFR400R NC30, '98 R1
"Hey copernicus! Why don't you navigate yourself to the back of the line with your feet and stand there with your shit."
BCF Eastern members map here ---> g.co/maps/2tm8b PM me to be added to it!

[27cows]

Just looked at my spare fuel tap and that has both stubs filtered. So if your reserve isn't, that'll be the problem, I think.
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The RXS100: vehicle of choice for Chuck Norris

[Serendipity]

[Robby]

The in-tank filters tend to get dislodged when someone uses a handful of nuts and bolts to scrape the rust off the inside. They're a fairly delicate connection.

Easiest way to get them out is to upend the tank and fish inside the inlet with some tongs. Depending on the design you might not be able to refit it - I know on my bike I would need to get my hand in the filler neck and down the side to press it into place.

Inline filter. In-tank filters are bollocks, they're a fairly loose mesh and only stop fairly big chunks of rust. If you have bits of rust that big then your tank needs treating before rusts through.

[Serendipity]

The tap filter on the RXS from 1995 is a little plastic tube with a plastic mesh, not unlike the mesh lime scale filter you get on a kettle. It’s very fine so should stop quite small particles while being washed clean by the sloshing of fuel in the tank. The filters should come out attached to the tap as you remove it.

The RXS tank is sort of tiny. I can get a few fingers in the filler hole, but there’ll be no reaching around inside. Also because the neck of the filler extends several centimetres into the tank it’s a bitch to bounce crap out of the tank by shaking it upside down. I can get my little finger into the petrol outlet after removing the tap and can feel the filter brush past my finger while shaking it about. I have yet to successfully trap it, but I’ll get the bastid eventually!

The tank isn’t too rusty inside, but leaving it over the winter with minimal fuel probably hasn’t done it any favours. The visible areas look pretty clear of rust, certainly better than the original tank. Although my bike is a 1986 model, this replacement is a 1994/5 tank.

I’ll have more time tonight to get this sorted. Cheers for all the help so far.
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2016 CBF1000F - Commuter heaven | 1994 CBR600FR - Awaiting defibrillation

[Serendipity]

Right, all sorted now... ... I hope.

I used a few inches of stiff wire to hook the errant fuel tap filter out of the petrol tank. I said I’d get the sucker eventually.

The long bit of plastic is the bit that had come adrift and was rolling around the tank. It was a nice tight fit back into the tap so hopefully it won’t work loose again. This I hope will take care of 99.9% of the filtering duties. It goes back into the hole to the right of the installed reserve filter.

https://i221.photobucket.com/albums/dd227/serendipity_uk/RXS100/IMGP7033.jpg

I took the precaution of stripping and cleaning the tap. Then stripped and cleaned the carb and put it all back together.

Taking the sound advice of Messrs. 27cows and Robby I purchased an inline fuel filter (sadly a mesh, not paper one) and installed it midway in the delivery pipe. I suspect that I may have to shorten the pipe a little to stop the filter rubbing on the side panel, once reinstalled.

https://i221.photobucket.com/albums/dd227/serendipity_uk/RXS100/IMGP7034.jpg


The bike runs perfectly and, so far, no premature moistening of the crankcase. I have rather rashly left the fuel tap switched on so fingers crossed I don’t find a petroleum swimming pool in the morning.
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2016 CBF1000F - Commuter heaven | 1994 CBR600FR - Awaiting defibrillation

[27cows]

There's at least three types of RXS fuel tap, so I suspect it took them a while to get it properly sorted. Mine both have metal stubs with similar looking push on mesh filters. I think the all plastic version is the final one.
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The RXS100: vehicle of choice for Chuck Norris