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1975 Yamaha DT 400B Yellow/Grey (None)

Last updated May 2, 2010  

Photo of a 1975 Yamaha DT 400B Yellow/Grey (None)


Sorry about the bad picture, I only have a cell phone camera. I bought this motorcycle 5 years ago not running missing signal indicators and a few other parts also had no keys and no title. Whoever use to ride this bike hit something because the rim and front forks were slightly bent and the fender was not the correct fender I think it was from a DT 100 and its bad because they must of crashed AGAIN pretty bad because the DT 100 front fender was broken too. I got the correct turn signals for it off of ebay replaced the other missing parts and had keys made for the gas cap lock, fork lock, seat lock, and ignition switch. When I bought the motorcycle I did not realize that the laws recently changed in New Jersey for acquiring a title for a vehicle without one. It ended up costing me over $600.00 when it used to cost about $150.00 to get a title for it so I was not very happy about that. If I knew then what I know now I could have got the title on my own but it would still cost me around $175.00 and it is a pain.

I cleaned up the motorcycle really good and also cleaned out the carb. I got it running good and after riding it for 100 miles all off road the piston exploded (don't know why) possibly the previous owner ran it out of oil a lot and weakend the piston. I got it rebuilt at Town and Country. They sent out the cylinder and it came back .30 over bore and a new Wiseco piston and rings. Put it back together with a major problem excessive piston slap. I just rode it anyway for 4,000 miles like that until one day the bike had no spark. I figured while I was working on the spark problem I better get the engine redone before something comes apart plus the base gasket kept leaking after every 1,000 miles I guess from the piston slap causing excessive vibration and causing the cylinder bolts to loosen (yes there is a TSB out on this bike for the cylinder bolts coming lose but I made sure I had the special washers installed). I ended up bringing the cylinder and piston down to Kawasaki/Yamaha and I told them where I had it fixed and they said they use the same machine shop that the other place does, I was like o no, I said you better tell them they did not measure correctly and make sure it is done right this time. I got the engine back put it together but I could not figure out why I had no spark. This motorcycle originally comes with CDI ignition and the problem ended up being the pulser coil and guess what they are really hard to find. So I ended up doing a lot of research and I found out that I could use the conventional ignition from a 1974-1975 DT 250 which includes wiring harness, magneto, stator, and ignition coil. I hate changing original stuff but I did not have much of a choice. Got everything off of ebay but when I got the stator the coils were damaged so I had to get them fixed but the place that fixed them messed up the lighting coil and the source coil and I ended up blowing out my headlight indicator lights and ignition coil. I searched around and found NOS Yamaha Lighting. charge coil and source coil. I installed them along with a NEW ignition coil and now everything works great. It now has points and condenser ignition system, I guess I went back in time. I also needed a rear sprocket and that was a nightmare (one place said they had it so I ordered it and it ended up being for the later MX models. They would not give me my money back so I had to go through the credit card company to get most of my money back.) ended up having a problem getting one but found a place called sidewinder sprockets and they had them

My next step is inspection of the clutch and a new trials rear tire



Overall Length: 85.8 ins

Overall Width: 34.3 ins

Overall Height: 44.9 ins

Seat Height: 32.1 ins

Wheelbase: 55.5 ins

Min. Ground Clearence: 8.7 ins

Weight (Net) 273 lbs

Weight (Gross) 292 lbs

Engine Size:

24.22 cu. in. (397 c.c.)


21 (I think)


?? (unknown, but I would guess it to be up there)



1/4 mile


Top Speed

84 mph (with original sprockets)


Factory Options

None, but it could have come with a right side mirror


1.Folding rear turn signals
2.Front fender mud flaps

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