With a few old pics of my own
If anyone knows what kind of Yamaha this is, I'd like to know. 80cc
First real dirt bike. I mowed about a million lawns to save the $800 for it.
Being a dad now, I don't know what mine was thinking encouraging me to jump for the pictures.
By now Im sure all of you are banshee and Rd built up crank experts. This week we will be truing the crank. With the assembly being built up of 6 parts there are plenty of places for it to be out. The spec we will be shooting for is .02mm or .000787 in, thats seven hundred eighty seven ten thousandths. There are three places to check this “trueness”, on the two ends of the crank and in the center bearings. If you paid someone to do this this is where money all went. We will support the crank on the center bearings and take our measurements with a .0005 dial indicator mounted on a magnetic base.
First we set the crank on the V block and spin it through supporting the rods and making sure there are no hang ups. After you establish that you spinning free its time to put the indicator on it and establish a baseline as to where its out . As you can see from the drawing below there are 4 planes we are checking in. We’ll call the crankpin 0 then 90 degrees going around the crank, 180, and 270 respectively. 
Rotate the crank checking all these and see the chart as to where you should hit to correct it. Don’t be shy at first, my crank was over .040 out when I started and it took a good while to get my arm calibrated on how hard to hit it. Check all points after each time you adjust he alignment. As you get close you will want ease up and just lightly tap it to bring it home. It took me about 45 min to get it within .001 and an additional 30 min to get it to .0005 where I left it. Well within spec and at this point Don’t breathe around it as you might just throw it off a few 10 thousandths. 
-DAN
For a long time now Ive been wanting a Yamaha RD350-400 but just couldn’t justify the cost of buying one with all my there current projects. I bought a fancy app for my phone that searches craigslist for you under the search criteria you want. It cost the same as a good cup of coffee, best 2.99 I HAVE EVER SPENT! At work this past week this modern marvel of technology lets me know that there a pair of rd’s for sale in upstate NY for $100 with title. Called guy and he gave me the story, been sitting since 81′ was the fastest bike he has ever ridden etc. After getting off the phone I felt an immeadate call outta work sickness coming on. Me and Cleo Dog took the 10 hour ride there and back through the fall leaves and countryside.
Lately Ive been rather disapointed in the amount of time I’ve been getting at the shop. This project will be done at my house only like old times. Get to put a few hours in after the kids go to bed. 
So Simple and well designed, no wonder the brit's went out of business
This will be kind of a super bike build. Lots of fiberglass, the bike stock weighs in at 351 lbs dry, pretty light to begin with. Im going to try to shave at about 50 lbs off it. I split cases and crank the other night, The build sheet will include new bearings throughout, rods, pistons, banshee reed cages, yz125 reeds, boost bottle, updated brakes and shocks, and aluminum rims. Stay tuned.