Vintage Dirt Bike Q & A

I bought a 1975 DT400B a month ago and it wasn't running. In fact, it had a huge hole in the piston, but that's all under control now. I'm trying to figure out the jetting now since the stock airbox is long gone and it was never rejetted. My question is, is the choke on or off when the lever is in the up position? It's hard to tell when it's not running very well to start with.

My other question is, does anyone have a scan of the factory service manual that I can download free of charge? I've seen it on ebay, but the bid starts at $10... too much in my opinion. I've found a copy of the DT250A-360A service manual, but I'm not sure how similar it is.

the choke is off with the lever in the up position.the dt360a is very similar in spec to the 400.the 360 has a 80 mm bore and the 400 has a 85mm bore and the clutch has one less plate on the 400 than the 360 does.those are the two biggest differences between the two.of course the jetting on the 360 will be different than the 400.the dt360 has a 30 mm carb and the 400 has a 32mm carb.

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(2) 1968 DT1 1970 RT1M,1970 DT1C 1971 RT1B Enduro 1974 MT250 1974 DT250A (2) 1975 DT400B 1974 DT100,1978 DT175
1975 CR250M1 1979 CR250R 1979 Kawasaki KZ400H1 Jesus is Lord!!

thanks a bunch.