RD400 - Back from the Dead

Bit more digging, found my air/fuel screw O-rings were completely shot... got some new ones on the way.

Also got my cylinders back from the machine shop... they look amazing. Pics to come.
 
Top-end came back from Supertune1. Amazing quality of work. Jugs and pistons installed no problem. Chuck had mentioned he noticed a lot of grit in the cylinders, I thought it was from the honing blocks I used, but upon closer inspection there was SAND in my air box...

I completely disassembled the air box, washed it out with dish soap and simple green, and hit it with a scrub brush. No more sand. Really concerning... Hopefully it was just something I missed during the first go-around.

I was able to get the engine back together, checked and re-checked the float height on the carbs, re-synced and re-cleaned... I'm just waiting on new air-screw o-rigs... should've been here Saturday, but looks like Monday/Tuesday now. They're literally the only thing I need to kick it over and start break-in.

Here's some pics of the progress.
 

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Glamour shots with the new mirrors...
 

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Glad you have it back together. Sand eh?...bad news for any engine, but especially a two stroke...I hope it didn't get into the main or con rod bearings. :eek:
 
I washed out the crank case about 5 times with mineral spirits, then a little ATF, then more mineral spirits... each time the spirits came out more and more clear. I would spin the crank with a drill on the stator side with cardboard taped around the cylinder studs and rubber bands through the wrist pin holes to suspend them in the center of the 'bore'.

There is zero gritty feeling on the crank. I think if anything made it into the crank case of the 15-20 mintues this bike ran it either blew straight out the exhaust, or was in the base of the crank case.

I went through after with a can of brake clean and the air compressor. Then quickly hit everything with some dino 2-stroke oil.
 
Screws came with the right o-rings... she fired on the 1st kick and smoked me out. SUCCESS!


She runs like a sewing machine! Warmed it up, rode it for 5 mins, let it cool down.

Going to check the head bolts and start the break in process. Shes PEPPY!
 
Ran into another odd-ball issue.

It fired up and ran great about 4 times in a row... then on the 5th time (this is after significant cool-down between start-ups). It would backfire. I had the tank on "RES".

I went chasing electrical thinking it was the points, maybe a bad switch, but no... everything was working perfect. Big, fat purple spark on both plugs in both boots... so not the coils.

I decided to pull the fuel hoses and check the petcock for flow.

On RES, I had barely a trickle out of the outlet going to the LH carb... the RH carb was fine.
On ON, I had full flow.

I looked in the tank and the fuel level was about an inch below the "ON" pickup. WTF?

I took the bowl off the petcock and a bunch of sediment was in there. Which is odd, because I soaked the tank in vinegar for 3 days in all different positions and rinsed it out VERY well with distilled water and baking soda, then again with some 2-stroke gas.

There may be some cancer inside the tank I can't see that's causing this.

ANYHOO... cleaned the petcock, added fresh gas, then it fired right up and I took it for a ride... all was normal.

Looks like some Kreem is in my future, but for the time being a couple of 90-Micron screen filters and an extra tank flush will have to do.

This was the result of 2 cups of fuel run through the petcock. I poured most of the fuel off... but there's a good amount of jet-clogging junk here.
 

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Remove your petcock and make sure the screen over the reserve inlet is ok. Then make sure the screen that covers the sediment bowl is ok. You shouldn't need anything but these two screens. Take off the sediment bowl regularly and check for contaminants. After you run through a few tankfuls things should be fine. Don't use any sealer on your tank unless it leaks!!! Especially kreme, which is the worst thing you can do to a tank.
 
I'll second that..DON"T use Kreem! There is always some corrosion sediment/ flaking after you clean a tank, it will flush itself out over time. If you MUST line it, use something like Caswell or POR 15.
 
After a flush the sediment is gone... i wont Kreem... but i did find a pinhole leak by the air box on the left hand side on the bottom of the tank... i think it can be welded. ::)

Found my screen in the petcock was backwards so on was res and vicea-verse...

Lastly, i was still getting bad backfires so I threw in new points and plugs.

She runs better than ever now! Timing set at 1.95mm and both cylinders read 205 degrees after blasting around the neighborhood a bit.

NOW i have enough confidence to break this thing in out on the road...
 
I suggest you try solder rather than weld on that pinhole...a bit of acid flux and a good hot soldering iron. No flames, no boom! :D
 
I agree. This winter I'm going to chem strip the tank, glass blast any rust pits, and then do a pressure test to see where she's leaking... I'll rinse with alcohol and air-purge before hitting it with the iron.
 
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