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Discussion Starter #1
Hey folks.
I have a condensation problem.
Bought a 250 rebel earlier this year. It ran kinda ok when I bought it but the choke/plunger was siezed. Also the whole bike looked tired and needed tidied up a bit.
Anyway I serviced it, new oil, air filter and spark plugs. Checked the valve clearances. Removed petrol tank and cleaned it. Repainted the whole bike. Stripped and cleaned the carbs.
First start after all that was no problem. It fired right away. Ran smooth and revved nice n clean.
I took it for a run and it was fine for a bit then started to feel a bit rough. Wouldn't idle and wouldn't rev smoothly.
Back to the shed... After alot of head scratching I discovered water in the float bowl by draining it. So I cleaned the plugs and fired it up. No problem right away and ran sweet.
But after a few minutes ran rough again.
Noticed my carb had condensation on the outside and is also forming condensation on the inside. If I drain the bowl I can see tiny droplets of water in the petrol
I've checked for air leaks with carb cleaner and couldn't find any.
Fuel/air screw is set at 2.5 turns out.
Anyone ever come across this problem??
 

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Condensation on the carb is normal, especially in more humid climates. This is due to natural evaporative cooling of petrol, which cools the incoming air as well.
This shouldn't cause significant amounts of water in the fuel though. I'm thinking that's due to old or bad petrol.
 

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Discussion Starter #3
Thanks for the quick reply. I understand carb cooling is a natural process and can cause carb frosting. I believe the condensation is the stage before frosting.
Tank has been cleaned and fuel is fresh.
The water in the fuel is definitely coming from the condensation build up. I just don't know why it's so excessive that it's causing problems.
 

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Discussion Starter #4
Also when I bought the bike it was just imported from Holland. Could it be a jetting problem due to different atmospheric pressure? Although I have bought other import bikes with no issue
 

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No way you are going to pull enough moisture out of air to show up in fuel imho..
have worked in and around automotive industry for decades.. I've seen carburetor icing in automobiles, snow mobiles, and naturally aspirated aircraft..
Never have I seen water in fuel bowl that didn't arrive by way of contaminated fuel or vehicle submersion in flood waters..

P.S. you can add "Denatured Alcohol" (methylated spirits) no more than 1 oz (30 mL) to tank fill up as a gas dryer.. The alcohol will absorb water which will burn along with gasoline.. Rubbing or isopropyl alcohol will not work..
 

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Discussion Starter #6
I've never seen this before now either. I've been messing about with bikes for over 30 years. Buying/selling, servicing, repairing and rebuilding from frame up. So I know my way around them. But this has me stumped.
As I said I repainted the bike. So the petrol tank is clean. As is the carb. The fuel has no water in it. I've checked. The moisture only appears in the bowl after the bike has been running. I can see the condensation build up on the outside after a few minutes and can only assume it's the same on the inside as when I drain the bowl I can see the tiny droplets of water in the fuel.
 

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As you probably already know, keeping the tank topped off after riding will reduce condensation inside the tank. I live in Louisiana and ride in temperatures ranging from 100+ degrees Fahrenheit down to the high 20's. Humidity here is high. I've never had a problem with water in the fuel, but I do run gasohol (gasoline plus ethanol) in my bike.
 

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i've seen fungus growing in ford diesel pickup fuel tanks that plug up tank pickup sock..
So I suppose anything is possible,,
I'd suspect the fuel tank is experiencing condensation internally with high humidity in area..
 

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Discussion Starter #9
Fuel tank Is full to the top with fresh fuel, so no room for condensation there.
Humidity is around 70% and temp 4°c.
The condensation is definitely 100% being formed in the carb.
I have other bikes that run without any issue in the same conditions and I ride in all sorts of weather.
 

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Also when I bought the bike it was just imported from Holland. Could it be a jetting problem due to different atmospheric pressure? Although I have bought other import bikes with no issue
Did you remove the plastic plug and empty the crankcase breather tube? That tube will fill to the top with water and backup causing excess moisture to go into the airfilter fitting. The tube needs periodic draining as part of routine maintenance.
 

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Did you remove the plastic plug and empty the crankcase breather tube? That tube will fill to the top with water and backup causing excess moisture to go into the airfilter fitting. The tube needs periodic draining as part of routine maintenance.
+1
 

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Discussion Starter #12
Cheers Ron I'll check the breather pipe in morning (2.15am here now so a bit late to be in the garage lol). Not sure what plastic plug your referring to though
 

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The plug is at the end of the tube shown in this thread: Drain/puke tubes | Honda Rebel Forum

It's the crankcase breather drain tube, but is often referred to as the 'puke tube" due to what the contents look like when drained. The contents can be recycled along with used oil.
 

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Discussion Starter #14
Sorry it took me so long to get back to this.
Thanks people i think the problem is solved.
The puke tube was full to the top with puke. This would indeed bring moisture in through the air filter.
But also the separator unit was full of puke, which prevented warm air flowing from the crankcase breather into the air filter. In turn causing excessive carb cooling and excessive condensation.
All that's left to do now is put it all back together. Fingers crossed.
 

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Glad you found the cause and solution.
 

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Glad you found the cause and solution.
Thanks for letting us know the follow-up info. My Rebel's drain tube fills up fast with mostly water certain times of the year which is why i highly suspected that was your problem also.
 

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Discussion Starter #17
Bike is back together and running perfectly now. Thanks for the advice. I love learning something new 👍
 
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