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Discussion Starter #1 (Edited)
Looking for some help with my 900.

For work and travel reasons I have been riding my bike every other year or so. When I do take a year off from riding I keep fresh fuel in the topped up tank and I refresh the oil. I will start and run my bike several times in the season just to make sure she’s still alive.

Late this summer I noticed a couple drops of oil under my bike which I would say is unusual as she does not really leak at all. A few weeks later it was a small puddle. I thought maybe the gasket in the case had gone south, really I had no idea why this was. Last week as I was putting the bike to bed for the winter I decided to start it to warm up the oil with the intention of changing it.

The bike flashed up after a few tries as normal but almost immediately I noticed, what I thought was water, sputtering through the oil breather and shut it off. I quickly realized that it was fuel that had backed up into the engine. WTF??!!! As it was still summer, I had not shut the fuel valve off which I normally do over the winter.

I unscrewed the drain pug and a fuel/oil mixture came pouring out. So may questions. I have Keihin FCR 41’s on my bike. How does the fuel drain into the flat slides and then get passed the cylinder into the engine case? This has never happened before so I have no idea what to do next.

My flat slides had been operating without issue before this. Does this mean that the flat slides did not shut close properly the last time I ran the bike? Do they need to be taken apart now?

What does this mean for my engine regarding the fuel that has run though it? Can I simply refill with oil and start it up?

Any advice would be greatly appreciated. I have not idea how to proceed.

Thanks in advance.
 

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Look around the forum for SuperSports for topics on float bowl stuck - for what you have experienced is quite common. And dangerous to work on so have plenty of ventilation or do it all outside. No smoking!

Drain oil completely. clean or replace the oil breather.

Install an in-line fuel shut off you can easily reach each time you shut the motor off.

Fill with new oil and filter that you are going to toss in an hour or so runtime - have to get the motor hot. It is a good idea to put some fuel cleaner in the tank, I use Seafoam.

2nd oil change and new filter with whatever brands you prefer.

Run the motor, if it sounds rough, replace the plugs. One of the cylinders was full of fuel at one point (and probably part of your exhaust pipe). Shut off the fuel at your newly installed tap while the motor is running and let it die from fuel starvation.

Leave it overnight, shake the bike a couple of times, both forwards and backwards and sideways. With no fuel in the float bowl it might just work its way loose from whatever muck it is/was stuck on.

Next day:
Now, if you see fuel still coming out the overflow pipe on the carbs you are going to have to rebuild at least the float part of the carb.
If you don't see fuel flowing out the carb overflow pipe, it still might do it one day anyway but only if you forget to shut off the fuel tap when you park the bike each time. It won't do it suddenly on the road. It is more likely to happen on bikes that are not ridden often/daily.

The only good thing to come out of this is I found my transmission shifts smoother after the bath in gasoline.
 

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The reason the fuel flowed to the intake valves instead of the over flow pipe is probably due to the flow rate from gravity exceeded the ability of the little pipe to expel it. More so if the bike was leaning left on its stand.
 

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Discussion Starter #6
What I’m not understanding is why, after an extended period of time with no issues, did this take place? Is it possible that after running the bike the last time, in June approx (I did not put it on the road this year), one of the floats was stuck open and then fuel trickled past the cylinder and into the engine?

Previous to 2011, I rode my bike a good deal every season and I’ve owned it since approx. 2000. In all that time I haven’t had any issue with the flat slides and have not had to service them in any way. I guess maybe it’s just time to give them a once over?
 

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I normally have very little problem with my carby bikes but this week I did and so did a riding mate with a Pantah.
After a weekly ride we both shut the fuel off and run the motor till the carby bowl is dry.
Sunday I turned the fuel on my bike and it absolutely poured out the fuel bowl vent.
Investigation showed the residual fuel in the bowl had turned to s shitty brown paste and has stuck the floats to the bottom of the bowl causing the flooding.
My mate has the same crap in his carby's and as we get our fuel from different places the only common factor is BP Ultimate which we both use.
It's supposed to be ethanol free but that brown crap dissolved in IPA but not petrol or acetone so it's pretty obvious it is water based so it sounds like they are mixing ethanol in that fuel.
I've tried contacting BP Australia but non of their contact links on their website are working.....
Dscn8211.jpg
 

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Yep, DAVY.J has the the pic to show what could be in there and it is my personal opinion it comes from ethanol fuel as well. Someone pointed out on this forum that it happened to them on real gas but only after trailering the bike for a long distance. He speculated the bouncing motion kept opening the floats, rather than being stuck.

And yes, when rode last at least one of the floats was stuck and while there may be more than one cause of that, the end result is exactly what you have now. If the engine happened to halt with both intake valves closed, then at least one exhaust would have been open which would have filled your exhaust with the contents of your gas tank. It would also hydrolock that cylinder, but may have evaporated out after long storage. In your case, an intake valve was open which filled your engine case with fuel.

It's happened to me a few times, caught it the last time while it was still filling my exhaust. Removing the spark plugs did allow the motor to turn over shooting fuel out of one cylinder. After putting the plugs back in I had to roll start it down the hill because starter would not turn it over with a plugged exhaust, (I know, that was stupid), and people said flames shot 50 feet behind the bike.

9 years with no carb rebuild along with frequent long term storage? Yeah, your carbs probably look worse than the pics above,...
 

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StaBil 360 Marine ... recommended by some of the best carb rebuilders within our membership.

LINK = https://www.goldeagle.com/product/sta-bil-360-marine/

Quote from info page .... "PREVENT ETHANOL DAMAGE: Protect your entire fuel system against damaging rust and corrosion caused by moisture and ethanol fuels. Provides a protective coating on ALL the metal parts of the entire fuel system and combustion chamber, even when the engine is not running."
 

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When I worked at the dealership in Ohio, 20% of our yearly work was cleaning carbs. Dozens of bikes each Spring. Only 4 strokes. The 2 stroke bikes don't seem to have a problem with it.

We actually had to fix 2 bikes that had hydro-locked a cyl and then bent a rod when the owner went to start the bike. One was an '87 1000 Concours, the other was an '86 1200 Goldwing. They still ran with a slight kink in the rod, but the front of the rod on both was making a little clicking sound as it came around and made contact with the edge of the block.
The owners didn't want to pay to fix the bikes, and they got sold as is. Friends of mine ended up with the bikes afterward, and they put many miles on both of them.
 

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When I worked at the dealership in Ohio, 20% of our yearly work was cleaning carbs. Dozens of bikes each Spring. Only 4 strokes. The 2 stroke bikes don't seem to have a problem with it.

We actually had to fix 2 bikes that had hydro-locked a cyl and then bent a rod when the owner went to start the bike. One was an '87 1000 Concours, the other was an '86 1200 Goldwing. They still ran with a slight kink in the rod, but the front of the rod on both was making a little clicking sound as it came around and made contact with the edge of the block.
The owners didn't want to pay to fix the bikes, and they got sold as is. Friends of mine ended up with the bikes afterward, and they put many miles on both of them.
Same here ... easily 20% of the auxiliary generators we repaired each year were carburetor rebuilds.

Regarding two strokes ... I wonder if that has anything to do with the use of premix fuel? Secondly, I wonder if two strokes that have oil injection systems have dirty carburetor problems since they use straight gas rather than premix?
 

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Secondly, I wonder if two strokes that have oil injection systems have dirty carburetor problems since they use straight gas rather than premix?
I think so...I seem to remember cleaning the carbs on a couple of 3 cyl Suzukis. (380 or 550)
.
 

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My riding mate who also has the same problem does mix a little two stroke oil in all his fuel but still has the same issue so I'm not convinced yet although my Cagiva Mito so far has been trouble free on the same fuel.
 

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The first bikes I found to be affected by the fuel were old British bikes. Apparently the composition of the alloy used in the castings react more than most . I had put original Stabil in the fuel and thought I was doing the right thing . I had run the bikes until they quit but didn’t drain the bowls. When they wouldn’t start, no fuel to engine, I found the bowls were full of something resembling gray paint in color and consistency. That turned out to be the castings dissolving. There were holes in the float bowls. There were holes in the floats. They looked like they’d been soaked in acid. Same thing happened to several other small engines I had, not draining the fuel after running the original Stabil through the carbs. It appears they’ve changed the formula since then, but I can’t confirm that.
 

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The first bikes I found to be affected by the fuel were old British bikes. Apparently the composition of the alloy used in the castings react more than most . I had put original Stabil in the fuel and thought I was doing the right thing . I had run the bikes until they quit but didn’t drain the bowls. When they wouldn’t start, no fuel to engine, I found the bowls were full of something resembling gray paint in color and consistency. That turned out to be the castings dissolving. There were holes in the float bowls. There were holes in the floats. They looked like they’d been soaked in acid. Same thing happened to several other small engines I had, not draining the fuel after running the original Stabil through the carbs. It appears they’ve changed the formula since then, but I can’t confirm that.


StaBil 360 Marine .... totally different stuff .....

StaBil 360 Marine ... recommended by some of the best carb rebuilders within our membership.

LINK = https://www.goldeagle.com/product/sta-bil-360-marine/

Quote from info page .... "PREVENT ETHANOL DAMAGE: Protect your entire fuel system against damaging rust and corrosion caused by moisture and ethanol fuels. Provides a protective coating on ALL the metal parts of the entire fuel system and combustion chamber, even when the engine is not running."
 

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I forgot to mention that the carb damage was over one winter. I still use Stabil in some engines with no apparent issues but I also use SeaFoam at the same time ( I use Sea Foam year round) .
 
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