Yet Another 76 YZ400 Project Build

Last Friday I put the trans back in the case to get ready to assemble them.



I ended up making a crank installation tool out of some steel pipe to pull the crank through the bearing instead of pounding on it.



After 45 minutes of assembling the cases, it took longer than I thought. Lining up the trans parts I thought would be the tough part. It wasn't. Pulling the crank through was a major PITA. All together.

I worked most of the day Saturday putting the motor together. Got this done before noon.



Used the old penny in the gear trick.



Cleaned up the side cases. I took them all down to the condition of the chain guard in this pic and sprayed them. I then put them under a heat lamp to cure the paint.



While I was waiting for stuff to dry I sprayed the manifold with Plasti-Dip. I had very minor surface cracks and this stuff fills them up and creates a nice smooth finish. I have used this on a few manifolds and it works great. 3 or 4 coats and you are done.

I did a bit more painting of the center cases. I masked everything off and sprayed it. I had painted the cylinder and head previously. I had been looking all week at bolt kits from Stainless Cycle and Spec bolt, I wanted to get this thing assembled and I was contemplating just taking the wire wheel to the bolts after I sprayed it.



I ran down to the bike shop and picked up most of the bolts I needed. The rest I will have to order. The motor with some more bits installed on the drive side.



I went ahead and wire brushed the clutch side cover bolts and mounted the cover. I will have to order up these bolts also.

Me and the dog decided it was time for a break.



Pop a frosty one and watch some Daytona short track.



While working on the reed cage.

Got the reed cage all put back together and decided I can do a little more this afternoon. I really like the black cylinders on the Yamaha's. I also like shiny looking fins on the edges. Out comes the dremel with a drum sand paper attachment. I had bought some cheapo sanding tubes from Vatozone and they are cheap. I went through about 5 of these things to do the fins. They kept exploding on me. Do not buy these things, period.

It came out pretty cool.



I set the barrel on the motor to see how it looks. Mighty handsome I might add.



While I had the dremel out I took the paint off the engine mounting points so it will ground later.



I still had some dayllight and pulled the chassis out of the garage and washed it. The bike has not been outside for a couple of months and it has dust, and soda dust all over it.




Now I am caught up on the build. There will be more to come soon.

That Plasti-Dip is a great idea! My intake is intact but cracked and old looking. I will give it a few coats of Plasti-Dip. Thanks!

Read the instuctions. It has to be real clean to make it work.

Scooter, do I need a puller to get this flywheel off?


If so, what kind do I need to buy? A flywheel puller?

I posted a comment in your thread. DO NOT loose that nut. Yamaha won't have any till the end of May. Ask me I know.

So I went ahead and got the piston in the motor.



It turns into a blur from here. For some reason I turn the crank and it won't move. WTF. I am freaking out big time. I am thinking the thrust washer on the crank maybe? Not it as it spun until I put the clutch cover on. I took the cover off and it spins freely. I pulled the clutch off and re- installed it and for some reason it wasn't seated all the way. It was hitting on the cover. I spun the basket and it works fine.



Made sure the plates were lined up and the pressure plate aligns with the arrows on the basket, and buttoned up the clutch cover.



All fixed................I think.

We are havin some things now. It spins freely. So I put the clutch back on. The next day I figured I would check the shifting and operation of the motor to see if it spins freely. Problem #2........it won't shift properly.

Off comes the side cover and clutch again. I spend about 2 hours trying to get the shift drum and the shift linkage timed. The Haynes book I have is of not much use. It tells you to time the linkage but not where to align the shift drum. Now the damn thing works.

It is craydds' fault. He jinxed me in his 400 build thread. I just know it. No Anchor Steams for him from me.

Last couple of evenings I worked on getting some other things done. Installed the head and gasket and proceeded to clean up some trinketts.





Put the intake together and installed the automatic compression release. I am not so sure if I will keep this on or not.



Motor is starting to get there and almost time to put it in the frame.

Figured I would have a couple of refreshments and relax a little before continuing. Got out the dremel and cleaned the paint of the engine mounts to ensure a good ground.



I went to put the flywheel on and discovered another minor problem. I changed out the stator backing plate phillips head bolts with allen heads. They hit the flywheel just barely.



I chucked one up in the lathe and am going to take of about 50 thousanths off and see what happens.

I am hoping to have the 400 parked next to this one by the end of April. They should look good on my sun porch.

Ah man I love that bike...too small for me but I still want one and kick myself everyday for passing on one.

And pretty quick progress on the 400... When at you gonna start on that TY.

Thanks for the compliment on the bike Jeff. I have tried to condense this build into the last couple of weeks. I am now into the YZ 400 about 6 months. The TY could be fun unless I sell it. We will see. Do you want it?

I've been wondering about the same thing. Why not remove that compression release? How hard is it to kick over without the compression release? I have s strong right leg and a weak mind.

Luckily, I get to see how a real pro does his build. Looks like even the pro's can have difficulties. My motor started up when I got the bike, so I'm thinking my tear down will be minimal, just enough to inspect and clean things up, I hope. If it gets more involved I will send the motor to Scootern29 and buy him three six-packs of Anchor Steam for the rebuild.

I really hate to burst your bubble craydds, I am no pro at this stuff. I am a home garage hobbyist. When you get into Curnutt Shocks, then I would consider my self a pro at them. I was their last employee before they shut down the M/C shocks. I did every facet of the factory. So don't even think of sending me your motor, Anchor Steams, OK, but I limit myself to only a couple. The last time I drank a number of them.............I ended up in the hospital. :eek1

Last night I machined the allen head screws down. It only took 40 thousants to clear the flywheel and leave enough meat in the head for the bit. Got the flywheel mounted.



We will see what I get done tonight. I may leave the side cover off till I check for spark. That would be the smart thing to do.......but...........stuff happens.