1976 RD400c restoration

rd400canuck · October 30, 2019, 02:47:59 PM

Hi everyone,

Figured I'd start a thread here to document the restoration of an RD400c I found in Toronto.

I've had two-strokes in the past...a couple RZ350's and an RD400g. I got out of messing with these old smokers around 6 years ago because I got fed up with the money pits they can easily turn into and the constant issues they seem to have. Endless jetting and ill running being the biggest headaches, of course.

Yet, here I am again! I saw one for sale and I wanted it so bad. I love the character of these bikes an riding them gives me a joy I dont get on newer bikes.

I told myself if I could get the asking price to a point where I was comfortable I'd get the bike and put it back to stock and pray that in stock form the damn thing would run properly and be reliable. I told the seller I knew I'd have sink a couple grand into it just to get it mechanically sound and he agreed and dropped the price for me after it wasnt selling for more than a month. I always wanted a completely stock bike with the original intake and exhaust system because I love how much torque these bikes have when they arent piped and 2-into-1'd and ported to death. In my mind a bike like that is nothing more than a pain in the ass to drive around town from light to light or go on nice relaxing rides with. The loud silencers and intake drone got old real fast for me. Once I put the stock airbox and exhausts on the RD400g I had I was stunned with how wonderful and torquey these bikes become. Plus I love the sound of stock pipes.

Here is the bike I bought and the last pic is what I intend it to look like. It's an R1/R6 blue not one of the original blues but I love it. Everything is there so I am happy. All the chrome is in good shape, too. Only things I see are the front rim is gold and not orig (unless someone painted it) and the seat cover is aftermarket with the yellow piping to match the paint someone did in the past. According to the ownership this bike was black when it arrived in Canada in 1976. The important thing was the bike was all stock and had everything it was built with and this one was very close.

rd400canuck · October 30, 2019, 04:44:25 PM

So the motor is out and I already started the inspection process to see what needs to be replaced.

As you can see from the pictures of the two exhaust ports one of them is butchered. They ground right up into the hole on one side. The exhaust ports are supposed to be 35mm but mine are 32 and 28! Good grief what a freaking hack job! To think on one side they raised the port by 7mm. The only way I could even tell these were actually RD400c/d/e cylinders what that the transfers are 51mm down. There are no markings on these things to tell me what they are from.

The pistons looked ok to me... no blowby and no scoring but as you can see on the top these are 0.80 over and that's the last overbore. The people that are going to rebuild my crank said they have wosner pistons 1 and 2 sizes over the .08 or could even re-sleeve them for me... but since they are so hacked up Id be a fool to put any money into them.

I found a fela on ebay that has cylinders at 1mm over freshly bored. He also has brand new pistons/rings/bearing as well. The important thing was stock port heights.

rd400canuck · October 30, 2019, 05:12:49 PM

And here is what I ordered from my new friend... they look awesome. As long as I live these cylinders will never be ported.

rd400canuck · November 14, 2019, 05:48:57 PM

Parts are rolling in now.

HPI ignition looks like a clean piece of kit. Very small and light rotor I can't wait to blip the throttle... should spool up quick!

SUPERTUNE · December 05, 2019, 08:42:22 AM

On the HPI, I would do the charge coil mod as Mark said, disconnect the charge coil ground and connect to a new wire lead to run out to REC/REG as a 2nd charge leg. I think they come too close to being enough charging as they come out of the box with only a single charge wire setup.
Chuck

SUPERTUNE · December 07, 2019, 01:19:21 AM

Quote from: rd400canuck on October 30, 2019, 05:12:49 PM
And here is what I ordered from my new friend in Texas... they look awesome.
As long as I live these cylinders will never be ported.

But once you do find the right engine builder to port them and get all the goodies to support porting you'll change your mind rather quickly...
C

rd400canuck · December 10, 2019, 09:58:50 PM

Quote
But once you do find the right engine builder to port them and get all the goodies to support porting you'll change your mind rather quickly...
C

Ha ha! It' possible... but I think Ive had my fun with modified two-strokes. A couple rz's and an RD400G. It was actually intake drone that forced me to find a stock airbox for the RD400G and that's what set me on the path of loving these bikes more when they are stock. After the airbox I was compelled to get rid of the DG's in it and find stock exhausts and after that I was sold. Nice smooth torque from idle.. and my head wasnt getting split open from noise. Chasing jetting on modded bikes got old, too.

This time I'll keep it to just one stock bike.. aside from the ignition that is.. points had to go.

rd400canuck · December 10, 2019, 10:05:02 PM

Quote from: SUPERTUNE on December 05, 2019, 08:42:22 AM
On the HPI, I would do the charge coil mod as Mark said, disconnect the charge coil ground and connect to a new wire lead to run out to REC/REG as a 2nd charge leg. I think they come too close to being enough charging as they come out of the box with only a single charge wire setup.
Chuck

Can you point me to where the mod was talked about?

SUPERTUNE · December 11, 2019, 12:32:57 AM

Mark made a post on the 'HOW TO' HPI Install.
I think it's at the bottom of page 4.

All I think you have to do is un-ground the charge coil lead on the backside of the stator and connect a new wire lead to run up with the rest of the wires and use it a for a 2nd input lead at the rec/reg so you now have 2 ac wave leads instead of 1 like I did on Mikes setup.

If you see in this pic 2 leads off the rec/reg are tied together as a purple and a yellow then connected to the single yellow lead the HPI came with.
Now that you just ran a 2nd lead, now unsplit the tied in purple wire and connect to the new lead you just made and now you have 2 ac leads into the rec/reg. Simple I think...
DC diagram on the left is the one your looking at.
Chuck

rd400canuck · December 11, 2019, 07:41:22 AM

not sure why but the pic isnt showing up for me.

SUPERTUNE · December 11, 2019, 07:11:06 PM

I'll try a smaller one...
Who else can't see it?
Chuck

big one again...as a link instead.

https://photos.imageevent.com/supertune/mikemrd350/large/20191028_124613.jpg

rd400canuck · December 11, 2019, 07:54:27 PM

sorry... it must have been my network at work preventing me from seeing the first one.

rd400canuck · December 12, 2019, 01:36:24 PM

I'm learning this is a single phase and not a 3 phase stator and that it's basically the yellow wire, through the windings then right to the ground post in the unit. So unhook the end of the winding wire from the little ground post... extend it will some wire and connect it to the other pin on the rr. (does it make sense to just attach the second r/r pin to ground instead? It seems like the same thing to me)

I'm curious... what does connecting both the pins on the r/r like they suggest do exactly?

You mean like this essentially?

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1976 RD400c restoration