TC250 fuel leak from case bottom when running

doug rooney · Post by **doug rooney** » Fri Feb 26, 2010 10:34 am

Fired up the TC250 for the second time yesterday. The first time I did it a few days ago, had a runaway idle of about 5,000 RPM's. Got that settled down yesterday and was running well BUT....now I notice a raw fuel leak when running in the case bottom nowhere near a bolt or gasket. I'm guessing cracked case?? Motor is now out of the bike again. Can it be repaired? What's the best way of locating the crack? Can't really see anything much on the outside so it may not be visible when I get it apart.

I now have it apart and have the bottom case outside with gas in it to see if it leaks. Doesn't seem to maybe because it has to be under pressure and running?? I see a faint hairline crack on the inside under where the right side of the crank sits. That's the area it was leaking from yesterday.
Any help appreciated. Thanks

Could fuel leak out the bottom somehow if the center seals were bad?

Coyote · Post by **Coyote** » Fri Feb 26, 2010 3:14 pm

The best way to find a crack is to have the piece magnafluxed. That can be pricey though.
You might try mixing some color dye in a glass of water. Paint the suspected surface with the water and let it stand about 15 -20 minutes. Wipe it thoroughly dry and give the area a light dusting of flour or baking soda. The water in the crack will stain the powder and show you exactly where the crack is.
Thinking now ..... there should be fuel in the crack. Just wipe the surface clean and dust it with powder. It will show it's nasty self.

doug rooney · Post by **doug rooney** » Sat Feb 27, 2010 8:17 am

Thanks Yote..Will try that today

doug rooney · Post by **doug rooney** » Sat Feb 27, 2010 11:42 am

Upon close inspection today, I now believe it was indeed coming from the carb overflow and through the drain hole on top. Don't think it's a crack anymore.
Thanks all, Doug

Post by **Suzsmokeyallan** » Sat Feb 27, 2010 1:49 pm

Wow that was an expensive and time consuming way to find out one of the carbs was leaking.
I hope it is indeed solved now

doug rooney · Post by **doug rooney** » Sat Feb 27, 2010 2:02 pm

No expense, just time. I make my own gaskets when possible. I do everything 5 times it seems

rngdng · Post by **rngdng** » Sun Feb 28, 2010 1:05 am

doug rooney wrote:Upon close inspection today, I now believe it was indeed coming from the carb overflow and through the drain hole on top. Don't think it's a crack anymore.
Thanks all, Doug

Yep, that could be it. Most bikes have a drain hole to allow carb overflow to drip out the bottom. Good catch...too bad you pulled the engine first, but I'll bet it's getting easy for you isn't it? I've been there, too.

Lane