Dead RD400 resurrection

[JBeasty]

SoCal, I'm in NorCal. Solano County, about 30 miles NE of San Francisco. It "only" cost me $80 to put it in my name. No telling what they'll charge me when I go to get it registered for the street. Hope they don't try to get me for 25 years back fees...

[AAAltered]

Non matching numbers and a Daytona head.  What’s the prefix on the engine serial number?  Is it a Daytona engine?

[Alain2]

Get some plastic bins, ziplock bags and a sharpie to label the parts you disassemble, you will thank me later. I believe the only way to budget your build is to disassemble everything to identify what can be repair and what needs to be bought new. I have seen bikes sitting with new paint job because they had no $ for ignition.

[JBeasty]

Non matching numbers and a Daytona head.  What’s the prefix on the engine serial number?  Is it a Daytona engine?

1A1 is the prefix on both the engine and frame. The guy I bought it from said the carbs are oversized (Mikuni 32-34mm?), and it has S&W shocks. Various stickers on the seat pan: Boyesen power reeds, Eibach springs. Does anybody recognize these chambers?

[JBeasty]

Get some plastic bins, ziplock bags and a sharpie to label the parts you disassemble, you will thank me later. I believe the only way to budget your build is to disassemble everything to identify what can be repair and what needs to be bought new. I have seen bikes sitting with new paint job because they had no $ for ignition.

I'm coming around to the total disassembly first approach.

[m in sc]

looks sort of like my pipelyne chambers. those do sort of  look like vm30 or 32s, (stuffed in stock intakes) motor is probably ported and yes, thats a 2v0 head for sure. Its def a period built piece.. 80s/early 90s maybe. its neat for sure, sombody def spent some time on that bike.

def consider not running that type of airfilter, they do NOT do well on reeded 2 strokes. all foam unis are probably your best option. .02

[AAAltered]

Interesting.  I don’t see those exact pipes in the Pipe ID thread.  The riveted cans look different than anything posted….

[m in sc]

mine are riveted to the outside. (by a po). like said similar but ? and  loud.

[JBeasty]

mine are riveted to the outside. (by a po). like said similar but ? and  loud.

Bummer, I was hoping they aren't obnoxiously loud (but then I have neighbors with Harley's). The innards look like they might be somewhat baffley? They have two seams down the length of the pipe, so two halves welded together. Probably cheaper/easier to make? The headers look dangerously close to each other. I imagine that would make quite a racket.

[JBeasty]

Probably easily fixable.

[m in sc]

the headers being close isn't uncommon.

mine were modified at some point int he past, so i cant comment on the baffles you have . the id seems really small. winder if they are possibly for a 250? doubtful, just spitalling as i don't know 100% what they are.  dunno.  eventually when you get it running see where they are, it obviously ran on them in the past. .

[JBeasty]

So the tear down has begun. Pipes are off, they are a little banged up and a lot rusty. One of the studs was actually a bolt - but it threads in and out fine, so I should be able to replace it with a stud. Chucked the pod filters. Got the battery box out. Oil tank is out. Carbs are next.

[JBeasty]

I'm using the Haynes manual, finding some minor errors, and not a lot of pics, but it should suffice? It has me doing some of the engine disassembly before actual engine removal, so that's what I'm doing. Found some bad stuff: the splines on the shifter and shaft are worn bad, the oil pump and surrounding area is covered in rust. Also the clutch operating arm and linkage has oblong holes, and the pin has a deep groove in it. The "generator cover" has a crack near one of the mounting holes. And it's missing 3 of 4 side case dowels.

[JBeasty]

Clutch arm & cover

[pidjones]

First, throw the Haynes manual as far as you can. Then, seek and download a Yamaha repair manual and a parts manual for your year (graphics seem to be for a '77). Then, purchase a good JIS (Vessell) screwdriver before doing any more disassembly. Many of the parts mentioned are readily available (dowels, etc.) There are vendors online for many parts (Economy Cycle, Yambits, many others). You just need to do the "leg work" to find them. More major parts like the cases/covers will need ebay searching, forums searches, or finding a good welder to repair.

By the amount of rust in the oil pump cavity, I would guess that the bike has been in a flood and never drained after (in that case, the crankcase is probably full of rust, too) or left outdoors for rain water to fill the cavity - for quite some time. Remove the pump and closely inspect it. If no pitting, I would clean the outside and send it to Arrow for a rebuild. If any water made it to the crank area, it will probably need rebuilt.