ZR750C Moriwaki Endurance Racer

QA

You say it's an endurance racer; With that massive rear swing arm; have you considered monoshock conversion?

I did that for my 1977 kz400 I kept in India.
The rippled road surface there, combined with high ambient temperatures and my exuberant riding style, would kill shocks in a couple of seasons and I had to bring them in my luggage from Europe.
Indian made ones would only last 3 weeks before the bike would be twisting down the road due to imbalance.

So I ordered a custom shock from WP, welded some extra bracing to the original swing arm, and that one lasted 10 years until I stopped going out there.
I also had to replace the bushings with needle bearings.

Hi Mark,

Yeah it's an endurance racer, but will only see occasional track days. I like the classic twin shock look, so will keep it that way. Will look to get some racetech shocks custom made for it, as the ones on there now aren't adjustable.

Funnily enough I live in India currently. Never seen a KZ here. I have an Enfield 535GT which is hugely disappointing, and combined with the roads here makes me lust after the Australian twisties. Some great rides to be done here, but the roads are too unpredictable in terms of surface to fully commit to spirited riding. What ever happened to your KZ?

I sold it, or rather had someone sell it for me. I hardly got a thing for it; it was 25 years old by then and the new bikes were coming out.
Someone on a new Honda 150 even gave me a good run; ok, I had a passenger and he didn't, but a 150 against a 400?
Maybe I was already getting old and it was time to lay down my mantle.
I ruled the road there with my KZ for 20 years! Everyone thought it was huge.

Enfield; I don't know about the new ones, but back then they were really rolling junk. I could never manage to keep that opinion to myself, which made me very unpopular with other expat motorbike people there, who all inexplicably loved the things.
They sound good though; I'll give them that.

I also had an Indian made RD350, that was a good beast. no brakes and no suspension, eats fuel like it was 1972, but yippie! sure was fast.
They had trouble with rats eating the air filters in the warehouse, so they started fitting steel scrubber things where the air filters should have been.
Dust induction system I called it.
The dust ate the bearings all the time, which gave the model a bad rep in India, but mine ran good and strong for 18 years [with oiled filters], standing in for the KZ when it was out of commission.
There are lots of bikes for sale there if you look; repairs and parts are difficult. I did my own repairs and brought all parts from Europe or the US when I traveled.

Things are moving. Engine is done (pic is before the head went on, just waiting on frame paint etc. Got a few bits back from anodizing too

Mate awesome. Would love to hear more India stories. What were you doing here?

I looked at the RD's and also the Yezdi roadkings (rebadged Jawa's). I love a smoker as much as the next guy, but decided (perhaps poorly) to get the RE.

I spent the winters there for many years; I could rent out my place in Europe for nearly enough to cover the entire thing. But economy changed and so did the cute village I used to live in. It's now a very notorious tourist / druggy trap. The fun went out of it and it was time to give it up.

Those Yezdis were the absolute worst! If you took the tin off, you'd find a frame more like a bicycle than a motorbike. The 2 stroke 250 motors had good pickup and they had integral racing shifters that no one seemed to know were in there; if you hit the shifter it would disengage the clutch until you released it, shifting up or down.
The front tubes were like paperclips, and had so much stiction that the front end would go solid if the brake was used; which was rarely a problem since they didn't work anyway.
The flexible things would twist and wobble down the roads with terrible speed. I used to borrow one when I was a kid there in the 70's; it was missing the clutch cable and no one else could ride it.
My dad was recruited by the Jawa factory to ride their bike on a circuit in the Boston area back in the 50's; he told me he rode it one lap and gave it back to them, refusing to get back on again.

I turned the RD350 into an enduro bike, which was a lot of fun because there were no enduro bikes there. Eventually the novelty wore off and people started to get pissed with me for riding through their fields and things. I grafted big rear shocks onto it and a Honda 550 front end. the only part left unmodified was the handlebars and engine.

There were long thin high ridges that ran for miles; the remains of 40,000,000 year old lava flows. I loved to ride along the tops of them. People ran in panic when I came across their illegal alcohol stills.
There was a deserted beach to the north where we used to go sometimes; I went riding across the sand but things had changed. also the tide was coming up. On dry sand, you have to keep moving or you get stuck; suddenly, a wave shot up the beach and there was no where to go except under a thatched roof of a beach restaurant!
Angry shocked faces as I shot through between two tables; shit, I thought, that was bad. Better get off the beach, but then I was bearing down on a film crew.
Actors and actresses, cameramen and gaffers, a director, some sets... everyone just stared as the RD and me roared through their scene.
I got back onto hard ground and back to the road, and never went back there again. There could be trouble waiting for me...
I should have known that once the new bridge was up and it wasn't necessary to take the ferry across the river to get there, change was inevitable.

You build is gorgeous, thanks for sharing it with us.

I already posted this elsewhere on the forum but here's a picture of the modified RD. The tank was hand formed in steel, but weighed 4.5kg, so I had it remade in fiberglass. I designed the expansion pipes and rear cans using info from a book. It actually had pretty good sound for a 2-stroke.
The radical rear fork angle needed a chain guide and tensioner.

kretchman wrote: The engine is coming together. Bottom end done, head assembled. Just waiting on barrels to be bored out and then final assembly. Frame wheels etc at the painter now. Getting close to assembly!

I've got my final parts in, Watsen flush mount LED indicators front and rear, Raceworks oil cooler lines, NGK leads etc.

Here's some shots of the bottom end together.

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I've got EBC heavy duty clutch springs in there, but my builder thinks I may need more clutch to handle the increase in power. He's predicting HP in the high 80's low 90's. What do you guys here run for clutches? Will I be ok with upgraded springs, or do I need new plates too?

Believe it or not but the "heavy Duty" clutch kits are not needed in these. The OEM clutch setup is plenty stout, in fact Kawasaki racing back in the 70's and 80's used the stock clutches in their race bikes. I have a highly modded KZ650, 810 HC kit, big cams, ported head, big carbs, 4-1 pipe, ect.. I have ran the stock clutch for decades with zero issues. I also have a hopped up GPZ1100 engine in my ELR clone and I again use the stock clutch setup with zero issues.

I had a 1972 H2 750; had clutch slip.
I noticed the kz400 springs were the same diameter and length but with heavier wire.
5 KZ400 springs in the H2 needed a strong wrist but it did the job.

The amazing thing was selling the H2 while still alive... what a deadly monster it was.
[cue lots of whooping and jumping up and down]

Springs are all about free length vs. rate [lbs of force per inch of compression] In a given cavity the od will be the same; you can use a little more free length [which will give greater preload] or thicker wire, or higher tempered wire.

I tried to upgrade a diaphragm clutch in a hopped up camper I had by adding 'helper' coil springs around the edge.
It didn't slip anymore, but wouldn't disengage either.
Ah well, back to the drawing board.

Thanks for the responses guys. Engine is complete in all it's glory!



With the clutch, I'll put in the heavy duty springs and see how it performs. This bike has always had clutch issues from when I got it. I opened it up the first time and found the basket had only 4 sets of springs in it! One of the bits of the basket where the springs and retaining bolt go had broken off somehow and made a meal of the inside of the cover. The PO just took the broken bit out and reassembled it with 4! Once I replaced the basket and clutch plates etc it was fine, but the adjustment was always a bit finicky. Couldn't seem to get enough throw out of the lever. The new clutch lever has more of an offset from the bars than the stock lever so I should get a bit more action on the cable that way.

Thanks guys,

A few more pics of the engine rebuild. Overall it wasn't in bad condition. Quote from the engine builder:

"The old pistons weren't too bad but the rings were shot and the little ends were starting to bind. hence the new conrod #2 was seized"









In the last pic you can see the teflon coating on the skirts. Pretty cheap at $40 a piston. Worth doing if you're in there anyway,

Anyway frame is due back late this week and the bike will be back as a roller soon!

Frame and other bits back from the painter. Assembly starts next week