IT 400- Part 1
By Rick Sieman
IT 400 – PART 1
By Rick Sieman
This particular project started because of complaints from readers was that all we did was motocross bikes. Upon review, we double checked and they were mostly right.
Yamaha had a stranglehold on the enduro market in the 70s and 80s, but were usually beaten by riders on expensive European bikes for the higher trophy places.
People really liked the DT series of enduro bikes. Sure, they were heavy and had a “adequate” suspension at both ends, but they were reliable and very, very affordable.
In the mid 80s, Yahama decided to get serious about enduro bikes and introduced their IT line. They wanted to build bikes good enough to not only win local events, but international events as well. They also wanted keep the cost low.
With the bike you’ll see here, the 1978 IT 400 was that exact bike. Not only did it turn out to be a trophy winner in enduro competition, it also proved to be a killer
desert machine and a Grand Prix threat most anywhere.
The latest version of the IT 400 is E, the 1978 model. It still favors the same basic style as the earlier models but has some changes. This new model has long travel forks and equal amount of travel in the rear and. The earlier IT’s had less fork travel and this change was very welcome.
As we remember testing the IT, the ride was very smooth at higher speeds. The rear did have a tendency to move around a bit, but over whoops it was very stable. On hardpacked terrain, it was all that you could ask for. Getting the bike into a controlled slide was fairly easy. Most of the test riders called for a bike a little lower and 1 or 2 inches less on the seat height would be appreciated. We plan to address this during this resto.
When you took the IT through tight woods, all the rider had to do was stand on the pegs and carve around the trees. For this type of riding, the motor brought plenty of the correct type of torque. The rider could let the revs really drop down low without worry about stalling. The engine is basically the same as on the C model, based on the YZ 400. The new pistons are 5 mm longer than the original 400 and claim to have a longer piston life. Luckily, our project bike had a good strong fresh top and. Horsepower according to Yamaha is 40 BHP at 7000 RPM. Maximum torque is at 6000 RPM, measuring 30.9 pounds of torque per foot.
A rather large 38 mm Mikuni carburetor is used, but starting is very easy, hot or cold. Compression ratio is 7.6 to 1, so there’s not that much resistance in the kick starter. Naturally, the IT uses premix at a recommended 32 to 1 ratio and also swears by Yamalube R in the owners manual. Side note: we’ve had good luck with that oil.
The ignition system is a CDI and this has been proven throughout the years. The headlight and taillight are charged from the flywheel magneto; we won’t be using them.
The five-speed transmission is not perfect. It had the same middle three gears as the YZ 400, but first gear is substantially lower and top gear is a bit higher. Ideally, first and second could be closer together.
The stock saddle has a bit more padding than earlier models is more fitted to the riders bottom. Like we said, the plan is to cut the saddle down a bit and while we are at it, we might as well get rid of that big tool bag on the back. It tries to catch your foot when you go to sling it over to start the bike. With the stock seat height of over 34 inches, it’s almost mandatory to have the side stand down when kickstarting the bike. Of course, taller riders wont experience this.
We got the bike from Paul Brady, Sidney Texas; the man had a whole bunch of vintage bikes already. The bike was all apart in pieces at his place, and he was kind enough to put the bike altogether in one piece for transportation. As you can see, we had to take the bike apart again to get in our Dodge Journey.