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MT250 stock carb - do they leak?
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Author:  rayivers [ Mon Oct 01, 2012 10:53 am ]
Post subject:  MT250 stock carb - do they leak?
I just finished rebuilding a stock 004A 28mm Keihin carb from a '74 MT250, which dripped gas continuously with the petcock on. Float, float pivot, float needle & seat, needle jet & needle, and float bowl gasket were replaced. Carb body looks nearly new, but was inspected for cracks with a 4X magnifier. Unit held gas perfectly overnight on the bench.

Once on the bike, it started leaking again. The only difference is that now fuel drips from an overflow tube, not the (new) bowl gasket. :(

This bike leans WAY over on its kickstand. Could the float pivot be binding from the angle? I can't test it with the bike straight up, as I don't have the bike now.

I'm kind of grasping at straws on this one, never seen it before. Any help appreciated.

Ray
Author:  Dave [ Tue Oct 02, 2012 1:55 am ]
Post subject:  Re: MT250 stock carb - do they leak?
if it is coming out of the overflow tube this is usually due to a sticking float or a worn float valve or a float level set too high and even though it is rare but can happen,sinking floats.

if it is working right it should not leak at all.


here is a carb kit listed for the 1974-76 MT250.
http://www.ebay.com/itm/HONDA-MT250-Car ... 00&vxp=mtr

all i can find from OEM Honda parts is a listing for the 1976 MT250.there is no listing for the 74-75 models but some parts might interchange from a 1976 carb.
http://www.powersportsplus.com/parts/se ... parts.html
Author:  rayivers [ Tue Oct 02, 2012 4:17 pm ]
Post subject:  Re: MT250 stock carb - do they leak?
Thanks for the info, and the links!

So your stock MT250 carb never leaked at all when the petcock was left in the on position?

Ray
Author:  Dave [ Wed Oct 03, 2012 5:56 am ]
Post subject:  Re: MT250 stock carb - do they leak?
they leak if the petcock is left on while the bike is parked for a day or longer,mine has filled the crankcases with gasoline when i once accidentally left it on a couple of days.the petcock is supposed to be turned off when the bike is parked and only turned on if you intend to start and ride the bike then turned off when the bike is not running and parked.

the carb should not leak if the engine is running.

if it runs fine and the carb does not leak and or flood while running the chances are the carb is ok.

here is a video of my 1974 MT250 idling and running good.no carb issues here.
Image

click the image to play the video.
Author:  Dave [ Wed Oct 03, 2012 6:27 am ]
Post subject:  Re: MT250 stock carb - do they leak?
Dave wrote:
if it is coming out of the overflow tube this is usually due to a sticking float or a worn float valve or a float level set too high and even though it is rare but can happen,sinking floats.

if it is working right it should not leak at all.


here is a carb kit listed for the 1974-76 MT250.
http://www.ebay.com/itm/HONDA-MT250-Car ... 00&vxp=mtr

all i can find from OEM Honda parts is a listing for the 1976 MT250.there is no listing for the 74-75 models but some parts might interchange from a 1976 carb.
http://www.powersportsplus.com/parts/se ... parts.html



this was written in presuming the petcock was turned off when the bike was parked.they all leak some if the petcock is left on for a extended period while parked or the petcock is leaking and does not shut off the fuel completely when turned off.
Author:  rayivers [ Wed Oct 03, 2012 7:25 am ]
Post subject:  Re: MT250 stock carb - do they leak?
OK, thanks again for all the help, much appreciated. The video is cool, I didn't realize you could post them here.

Ray
Author:  Dave [ Wed Oct 03, 2012 1:11 pm ]
Post subject:  Re: MT250 stock carb - do they leak?
you can upload videos or pictures to Photobucket,it makes posting pics or videos very easy.
Author:  mbilder [ Thu Oct 11, 2012 9:59 pm ]
Post subject:  Re: MT250 stock carb - do they leak?
If it is leaking, check to see whether the overflow tube is cracked. The original carb on my 75 mt250 must have gotten some water in it and froze because the brass overflow tube split. For the life of me, I couldn't figure out why it was leaking. I would turn off the petcock; I even unattached the fuel line, but everytime after riding the next morning there would be a small oil/fuel stain from the overflow. I replace the float pin, check and replaced the float. Finally, I happened to pass a flashlight over the bowl and I saw the crack in the tube.

You may want to check.
Author:  mxgirl75 [ Thu Oct 11, 2012 11:19 pm ]
Post subject:  Re: MT250 stock carb - do they leak?
So what happens if your cases fill with gas? How do you get it cleared out? My CR250 might have the cases filled with gas, it has been setting for a 4 days now with no gas going in the cylinders. Carb is off in pieces, waiting for parts. The story of my life right now..
Author:  Dave [ Fri Oct 12, 2012 7:17 am ]
Post subject:  Re: MT250 stock carb - do they leak?
when the crank cases filled up on my MT250 i disabled the ignition system then removed the spark plug,put the bike in 2nd gear and pushed it with the clutch engaged until i saw no more raw gas and vapor coming out of the spark plug hole then put the plug back in and let the gas evaporate and wiped down as much as i could.after the gas was all gone i enabled the ignition to work and started the bike.

you may need to treat it as a flooded engine still and hold it wide open while kicking.
Author:  mbilder [ Fri Oct 12, 2012 7:28 am ]
Post subject:  Re: MT250 stock carb - do they leak?
Same thing happened to my mr175. Take off the spark plug, muffler and carb. Put something to protect the fender from splash, then crank away. I had what seemed like half a cup of gas pump out each crank. When nothing comes out anymore, let it sit for a while and evaporate. Note: do all this outside on a surface you can get gas on.

Later after you put it back together, it may take some cranking, kick-back and backfire, but it should be no worse for it.

Check your petcock with the fuel line unhooked to make sure it doesn't leak with the fuel off, them make sure u turn it off when not riding.
Author:  rayivers [ Fri Oct 12, 2012 7:38 am ]
Post subject:  Re: MT250 stock carb - do they leak?
mbilder,

Quote:
If it is leaking, check to see whether the overflow tube is cracked.

Thanks for the tip !! I'd never have thought to check the overflow tubes. Come to think of it, the carb always leaked from the overflow even when the bowl gasket was also leaking, which was below the level of the overflow tube top - and the leaking coninues long after the petcock is shut off, just as yours did.

This bike spent a long time in an unheated storage container in CT, and surely saw many freezing nights.

+1 on all the crankcase gas-removal advice too.

Ray
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