Vintage Dirt Bike Q & A

I purchased a 74 mt 250. It keeps dripping gas out of the carb overflow tube after I take it for a ride. The dripping eventually stops after a couple of hours but it makes a mess and stinks up the garage. I rebuilt the carb with new seals and jets with the thought maybe the float was sticking. Before the rebuild it would have a steady stream of gas out the overflow, now it is just a drip ... Any advice?

This seems to be a common MT250 problem. The same carb is leak-free when using premix (I have a theory about this... ) but at any rate... did you try replacing the float needle and needle seat, then setting the float height to 20mm?

Here's a good rebuild kit - it's got a bunch of stuff many kits lack:

http://cgi.ebay.com/ebaymotors/HONDA-MT ... 336bb4e7ec

Here's a link to the service manual - the float height setting procedure is on page 61:

http://alp-sys.com/honda-elsinore/manua ... 5mt250.pdf

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

Thanks for the advice. I actually used the Keyster carb kit. I changed everything except the Jet needle. I even have the official shop manuel from Honda and I followed the manual very closely. Could not changing the jet needle cause this. What would a old needle cause? I was pretty sure about the float hight... Thanks again.

Changing out the needle won't affect the drip, but you might want to try it just to see if makes the bike run better, especially at 1/4 to 3/4 throttle.

It's possible that fuel contamination could be causing the float needle not to seal properly. An inline fuel filter would be easy to install, and a good idea in general. It's also possible the needle seat is not sealing 100% to the carb body or that the body has a crack in it, but these are unlikely.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric