Engine started before, but not anymore

BikerRay

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9:39 PM
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Sep 30, 2024
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Location
Europe, Baltics
My engine ran fine for many good kilometers and hours. I would say about 5 hours.

Because I had to bend the exhaust to work with the pedals, I burned it to the point where some paint got burned off. I took the exhaust off to repaint it. It stayed off for about 1 month (I was waiting for good weather). The bike sat and has always sat outside under a waterproof cover.

When I finished painting I had to keep the paint on about 150* C for about 1h. The best idea I had was to put the exhaust on the bike and just let it idle for 1h.

So after painting that's what I did. The bike did not start on that day. The engine spins around and has compression. I pedaled it around for at least 500m in total in 50m lengths on a high speed (about 25+ km/h). Before I could start the bike easily at 10 - 15 km/h. It sometimes fires but does not start. In 50 - 80 meters of pedaling, it fires about 1-2 times (but does not start).

I have checked the spark, it has a spark (very good spark). I have checked the carb, looks good. If I take the spark plug out, dry it, put it back into the engine, and spin the engine around - then the plug gets wet again. So based on that, I assume the carb is okay. I have played around with the choke also.

The only thing I see wrong is the fuel. My fuel has turned yellow for some reason. I had the fuel in the tank for about 3 months. 1 month ago the bike was last working. I plan to drain the whole fuel system, including the carb, and replace the old fuel with a new one. But the the same time, I don't think the fuel is that big of an issue. It should still fire up or do something.

Any ideas?
 
The best idea I had was to put the exhaust on the bike and just let it idle for 1h.
That was NOT "The best idea" with a two stroke motor standing still with no air flow to keep it cool running at idle for an hour...Two stroke motors can and do start overheating if left at an idle for over 1 minute, let alone 1 hour, you may have cooked that motor beyond repair by drying the paint on the exhaust by engine idling for an hour.

If you were just riding and stopped at a traffic light for over a minute, your always advised with a two stroke motor to shut it off if it has just idled for more than a minute on these bicycles to prevent over heating whilst waiting for traffic to go by.

The only thing I see wrong is the fuel. My fuel has turned yellow for some reason. I had the fuel in the tank for about 3 months. 1 month ago the bike was last working. I plan to drain the whole fuel system, including the carb, and replace the old fuel with a new one. But the the same time, I don't think the fuel is that big of an issue. It should still fire up or do something.
Three month old fuel can also be a problem when left in a tank with a vented fuel cap for more than a month, let alone 3 months (these 2 strokes are Not sealed ), your fuel in the tank has absorbed moisture via the vented fuel cap as it was also left outside exposed to the damp weather regardless of it having a tarp over it.

I don't think the fuel is that big of an issue.
It is that big of an issue, moisture laden fuel will do just as you described it doing, you will have to do more than just drain it, you will also now have to dismantle the carburetor and totally clean that out now as well as replacing the fuel filter, fuel line, clean and dry out the fuel tank, etc.
 
Thank you.

I think you misunderstood sonething. When I tried starting the motor (after painting) to let it idle for 1h, then it did not start. So it never idled.

Also, when riding does it cool with the moving air? And would a better idea be to ride it for 1h? What is the exhaust gas temp of those engines?
 
Toss the muffler in the oven for an hour. The heat will be way more even, plus do not idle an air cooled engine like that for an hour, let alone 10 minutes. They are cooled by the air flowing through the fins on the engine.

Okay, now for the no start issue. The fuel turning yellow is the ethonal in the fuel starting to spoil. It will eventually turn green and that's when it sucks to clean out. Drain all your gas and get fresh ethanol free gas and clean the jets in the carburetor with carb cleaner. Replace the Chinese spark plug with an NGK BR6HS. And last retorque the head bolts!
 
Toss the muffler in the oven for an hour. The heat will be way more even, plus do not idle an air cooled engine like that for an hour, let alone 10 minutes. They are cooled by the air flowing through the fins on the engine.

Okay, now for the no start issue. The fuel turning yellow is the ethonal in the fuel starting to spoil. It will eventually turn green and that's when it sucks to clean out. Drain all your gas and get fresh ethanol free gas and clean the jets in the carburetor with carb cleaner. Replace the Chinese spark plug with an NGK BR6HS. And last retorque the head bolts!
I can't put it in oven. It will make it unhealthy for cooking food.

I will clean the fuel system. My fuel lines have turned rock solid. What's causing that?

Also, why should I change the plug if the stock one works fine?
 
I can't put it in oven. It will make it unhealthy for cooking food.

I will clean the fuel system. My fuel lines have turned rock solid. What's causing that?

Also, why should I change the plug if the stock one works fine?
Suit yourself, but riding with wet paint is the worst idea. The solidifying lines is also from ethonal fuel. And the stock plugs are junk, and it's been proven several times
 
Suit yourself, but riding with wet paint is the worst idea. The solidifying lines is also from ethonal fuel. And the stock plugs are junk, and it's been proven several times
Okay.

Also, the paint has to dry under normal conditions for 1h and after that, you have to heat it for 1h.
 
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