Vintage Dirt Bike Q & A

I am bringing a '75 MT 250 back to life and have a question about the carburetor air/fuel mixture screw: Should there be a tiny o-ring and flat washer at the bottom of the hole after the screw is removed? I have rebuilt a ton of Keihin carbs and every one of them had the o-ring and washer,but I did not see them in this particular carb. It looks like the carb has been apart before so I'm thinking the previous owner possibly lost them. Any info appreciated.

Try this
http://www.westernhillshondayamaha.com/ ... &fveh=3527

_________________
77 MR175, 89 HD Sportster
74 CR125, 00 Kawasaki ZG1000
79 XR185, 56 Cushman Eagle
03 XR650L, 79 Vespa P200E
72 Vespa Super150,
74 HD Z90

Thanks. I already ordered some other parts from that same print from bikebandit.com,but the print does not show the o-ring and washer. I also found the Keyster (sp?) rebuild kit and it does not include the little o-ring and washer. I asked another guy online if the two parts should be part of the carb and he said yes..now I'm confused!

The newer Keihin FCR carb on my '08 YZ250F has the O-ring and washer, but the MT250 Keihin doesn't - it just has the brass air screw and spring. The MR175 uses the same carb body, with a different needle, needle jet, etc.

Ray

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

Thanks Ray..It will be interesting to see if this bike starts. When I took off the bowl,about two tablespoons of a powdery,dirty grit fell onto the workbench..

Wow, two tablespoons - quite a bit! Even half a teaspoon would have me a little nervous (I'm a big fan of fuel filters). Speaking of which... I don't know if you still have the stock petcock, but if so I would definitely unscrew the sediment bowl and pull out the brass screen with needle-nose pliers - might be all sorts of exciting things waiting to be discovered. :>) Come to think of it, my buddy's '74 MT250 had grit in the carb too, and he was always having trouble with the carb leaking and overflowing... hmmm....

My MR175 uses the same petcock, and I had to do a bunch of work to it to keep all the tank rust from clogging up the main/reserve inlet 'snorkels'. I finally got it working OK, but I ended up biting the bullet anyway and getting a Clarke tank.

You might have gotten lucky and all the grit stayed within the carb, but if it were my bike I would moisten a paper towel slightly with gas and rotate it through the crankcase using the crankwheels, and see what (if anything) it picks up. And blow out the carb well, of course, especially all the passages related to the pilot circuit (there's a bunch of 'em) and the passage from the air jet to the needle jet.

Ray

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