Vintage Dirt Bike Q & A

I have a 1973 cr250 which I was planning on racing this weekend at "The Farm" in Chehalis but I can't seem to get her started. My bike has sat for about 2 months since I last started it. It always had a problem with running rich. I'd foul plugs every day or so. Although once it was running, it ran strong. I replaced the #55 slow jet with a 50. Buttoned everything up but it won't start. I replaced the gas with fresh. I have even tried switching back to the old jet. It almost started this morning but then flooded out. It's got strong spark and gas is getting to the cylinder. It just keeps flooding out. My needle for the slide is on the second from the top. The needle jet looked good. Any ideas?

if its running rich, I'd check the float level. It may be to high, allowing too much gas into the carb, causing the bike to run too rich. Also what mix ratio are you running. Too heavy will cause plugs to foul. I have a 74 CR250M, that I've owned it since it was new, and it rarely fouls plugs. As far as I know (which is very limited), the 73-74 CR250M was not known for fouling plugs.

To get the bike running, 1st put in a new plug. Since you stated the bike seems to be flooding, I'd work with the float height. I don't think the problem is the jet settings. Kick start the bike several times. Now check the plug to see if it is wet. If it is, I'd say the float height is too high, allowing too much gas into the carb. Adjust the float height slightly lowering the level, small adjustments are all that is needed. Keep working with the float height checking to see if the plug is wet with gas. This is a slow process.

Good Luck

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74 CR250M, bought new in 74, still stock, except for the new 36mm Carb, and proform exhaust.

Thanks for your help. I figured it out. The needle valve and seat were worn, allowing it to flood. My eyes aren't what they used to be. Got the last one the local Honda dealer had in stock. It had been sitting back on the dusty shelves for about 30 years. "The Farm" awaits.