RD400 - Back from the Dead

DannyMotor

Blood, sweat and beers.
For a mere $200 of my dollars, I was able to snag this gem of 70's blue-smoke from under a pine tree... It had been parked, under a tarp, for over 10-years.

It's 100% there, engine turns over and has good compression, and although it was a home for chipmunks (dear God the smell) it appears all hoses, rubber, and wires are in-tact.

I have had a lot of experience with 2 strokes, and know some of these old "street bikes" of the 70's can catch a fair price if taken care of. SO, I'm going to do a "light" restoration on this one.

- Buff out the chrome.
- Rid the thing of piss.
- Clean up the tank.
- Paint the frame.
- Restore all systems to factory.
- New tires.
- Make it smoke.

I want to avoid painting the tins... but there are some rusty bits on them... probably impossible to find a touch-up that will blend.

Pics are as-picked... then after a pressure-wash.
 

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Wow, that's a NICE bike! And the price was right too! That's in such decent condition (all things considered), I'm sure just a thorough detailing and a bit of maintenance/ repair would cut the mustard. It would look great as a 'survivor', although I myself have a tendency to lean toward the restoration side of the argument. Ether way, I'll be peeking in now and then, please keep us posted!
 
I agree, Goldy. My head says get it running and keep it as is, my heart is screaming "BARE FRAME! CALL THE POWDER COATERS! BYU ALL THE GASKETS!"

Lol... but I think Im going to meet it half way. Or at least attack the build in stages.

Stage 1: Cleaning, mechanicals, maintenance, get it rideable.
Stage 2: Restore chassis, engine, brake and suspension components.
Stage 3: Restore paint, and hunt down NOS parts dow to nuts and bolts to keep it 100% stock.

So far Ive started tearing it down... little rust on the tinwork, and in the tank, but not horrible. The wiring has been chewed, and there is a LOT of shit to clean up. The paint has been eaten clean through in some areas.

Carbs are stuck. Will have to boil them. Brakes are dragging, and front is bone dry. Some dings and dents on the gauges and mounting brackets. Looks like someone tried to repair it with bondo.

Points look new. Pump looks new. Someone definitely took the covers off a few times... stripped 3 of the old Japanese screws. Tempted to swap for allan heads, but dont want to wreck originality.

More to come... just the tip of the iceberg.
 

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As always... we begin with the carbs. Popped them off, and gave them a rigorous boil in lemon juice... So clean you could eat off'em now.

Popped off the reed valves... seems the reeds are a bit slack. Might be normal, will have to check the manual. Then I took the heads off. To my surprise, the pistons look fairly new... both have different gaskets, and both have different numbers stamped on them... could be one is OE? I cant tell.

Some minor concerns started bubbling up once the motor was coming apart... mainly, the pistons are loose in the cylinders... front to back and side to side... about .010 to .020...

Im going to pop the rings off and check them in the bores... also going to read up on the clearances in the manual... hopefully all is well ... ?
 

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Those are 1mm oversized Wiseco pistons with very few miles on them and rocking at the top is not an issue. Pistons have a taper and are smaller at the top than the bottom and smaller again between the ring lands. Check the clearance between bottom of the piston skirt and the bore. Wiseco use different clearance than stock cast pistons.

Reeds tend to do that so get a set of new petals. Call John at Economy Cycle and see what he has for a stock motor. There are a few choices. The only ones I don't like are Boyesen.

With barrels off, you could go ahead and port it and have the heads machined. Chuck Quinzler in FL can advise you what he would do to keep it stock but better in terms of porting. His work is really first class. There are others who can do porting work too.
 
teazer said:
Those are 1mm oversized Wiseco pistons with very few miles on them and rocking at the top is not an issue. Pistons have a taper and are smaller at the top than the bottom and smaller again between the ring lands. Check the clearance between bottom of the piston skirt and the bore. Wiseco use different clearance than stock cast pistons.

Reeds tend to do that so get a set of new petals. Call John at Economy Cycle and see what he has for a stock motor. There are a few choices. The only ones I don't like are Boyesen.

With barrels off, you could go ahead and port it and have the heads machined. Chuck Quinzler in FL can advise you what he would do to keep it stock but better in terms of porting. His work is really first class. There are others who can do porting work too.

Thanks! I can just now see the "1.00mm" stamp!

Can I check the clearance as I would by the manual?

Stock specs:
Piston ring in groove should be <.05mm gap.
Ring end gap in bore should be 0.3-0.5mm.
Cylinder bore clearance piston at the skirt with the piston 3/4" down from TDC should be <.035mm.

Thats pretty much all I have to go by. Are there Wiseco specs on their site?
 
Nevermind... found this:
 

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That's teh place to start. BTW, how did you clean the carbs? What I am really asking is did you check each and every passageway by blasting cleaner through it and comparing both carbs? A dip and boil does not always clean out the tiny drillings causing people to lose their minds thinking the carbs are perfect and sometimes they are not.
 
Potential bad news... Took everything apart... here are my measurements :

Left Cyl:
Bore - 65.05mm
Cyl Clearance - .005"
Top Ring Gap - .040"
Bottom Ring Gap -.040"

Right Cyl:
Bore - 64.72mm
Cyl Clearance - .003"
Top Ring Gap - .017"
Bottom Ring Gap- .018"

So the right is on the cusp, and the left is bunk... probably a lean condition on the left side, or a terrible machining job.

Anyhoo... Wiseco makes 1.50 and 2.00 over bore kits... $300, plus machine shop work... this bike is getting expensive!

Looks like they only have the 2.00 in stock, too... may be the last ride for this pony...
 

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I would get a set of rings, check the gaps and as long as they are big enough put it back together. The difference in bores is a bit wider than I would expect, but not the end of the road. Those numbers are not perfect, but probably closer than many bikes on teh street. Cold it may rattle a little but it's a two stroke, they are supposed to make noise.
 
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