Vintage Dirt Bike Q & A

The oil drain plug on my 76 cr250 is stripped, what are my options for repairing this? Can I possibly just run a tap through it to clean it up?

Thanks.

Your CR uses the same drain bolt as my Hondas, P/N 92800-12000. It's got an M12-1.5 thread, 15mm long.

If the threads are really stripped, I don't think just cleaning them up with a tap will give you something you could safely bet the life of your gearbox on.

If it were me, I'd either Heli-Coil the threads back to M12-1.5, or drill and re-tap for an M14-1.5 drain bolt (Honda P/N 92800-14000) if there's enough room on the crankcase drain-plug boss for the larger bolt and washer.

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

Good advise, what size drill bit do I need if I decide to re-tap it to 14mm ?

The tap chart below indicates a 12.5mm (1/2") drill bit is correct for an M14 x 1.5 bolt:

http://www.physics.ncsu.edu/pearl/Tap_Drill_Chart.html

I'd probably use a 12mm drill, to get every last micron of thread depth.

Just to be safe, you might want to have the new 14mm drain plug in hand before ordering a tap. I'm 100% positive the 12mm plug is M12-1.5 (I've measured it) and it's very unlikely that Honda would use the same primary part number on a bolt with a different thread pitch, but there's the slightest possibility the pitch is different from 1.5.

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