Motorcycle Repair: yamaha rd400 carbs, yamaha rd400, diesel mechanic

Question
i recently received a 76 yamaha rd400 from a friend that has been sitting for a long time.i got it running but it dies if you release the choke.i can wire down the choke lever but can still only ride it for about 100' before it loses power and wants to stall.i contacted a local repair shop and they told me to tear down the carbs and clean them.if this is correct,do you have a blowup  or diagram i could access for this task.thanks in advance for any help,new rd400 owner terry.ps i am a diesel mechanic so i am capable of this task.

Answer
Terry,
 Be sure the choke is operating correctly.  It should stay put in any position.  Assuming that the bike runs at start up w/ the choke closed until it warms up (about 30 sec.) and then dies upon opening the choke, you may be dealing with a carb problem.  Here is the procedure to cleaning and setting carbs:

Disassemble, clean all jets and orifaces with solvent and COMPRESSED AIR ONLY, use NO wire or picks to clean holes/airways. Rebuild carbs with new gaskets and make sure your floats are set correctly. . Do not overlook the float level, be very sure you are not starving for fuel or allowing too much to enter, the spec is just under an inch, about 15/16"+/- 1/16" from the flange surface to the "top" of the float (when holding the carb upside down)  Bend the tab at the center of the floats to adjust.  Inspect the needle valve for smooth operaration and any wear and debris, be sure it is not getting stuck in the closed position stopping fuel from entering. In relation make sure fuel flow is unobstructed and use a good in-line fuel filter from the tank to the carb. Even tiny particles in the fuel can get logged in critical areas and cause havoc.  Main jet needle should have it's "e" clip set at the 3rd grove from the bottom if everthing is stock.  Air to fuel ratio screw is typically set at 1 and 1/2 turns out from seated.  After all is said and done, reassemble, turn on fuel and run.  Finally set the idle screw.  Be sure your reed valves are plyable, not stuck shut and not cracked.

Hope this helps, give a letter back if you run into problems.

Mike