Ghost, very nice. Looking very much like the big wheel I raced.
I had mentioned earlier two of the "milestones" during development, the pipe and the frt. disc brk. and your pics recall them to me.
Also, as I mentioned, my pipe was Hyrdo-formed by a fellow racer. The funny thing is, when I asked him to build me one, I half expected him to ask me all sorts of stuff, like bore and stroke, carb size, etc, and to get out a tape measure and start going over the bike. He did none of those things and simply told me he would have it the next race.
When it showed up, i was surprised. I had expected it to be a "fatty" pipe, as was the trend back then with the MX bikes. But no, it looked pretty much the same as the YSR pipes[and the one installed on your bike]. How he made it to fit my NS perfectly[which it did], I have no idea.
I remember well how the frt brk. came about.
I was fortunate enough to be sponsored by Star Cycle in Tucson, an independent shop with one of the largest MC boneyards in the US. I went with a late '80's YZ80 system as it was small and powerful and the machinist at Star[Thanks again Jimmy]only had to make a bracket to mount it on the NS fork leg. But the rotor was another story. I rummaged and rooted though boxes after work for a week and nothing was even close. Finally, just when I was ready to give up, I stumbled on a disc from a '70's Honda CB200. It was a rare set-up from Honda, a mechanical disc brk. system that in all fairness, didn't work well on the heavy street bike. But a disc is a disc and it bolted up to the NS hub and was the right radius. I was very lucky on that one and on the track, it had plenty of power. I would have called it a "two-finger" brake.
The tires I ended up using were much smaller though. I'm not sure, but I think the Michelin RS125 frt slick was something like a 85/65-17
Back to the engine-I have already mentioned the connection I had found between the NS 50 engine and the air-cooled CR80's of the mid '80's, but at that point, I didn't have a piston. So I got a Weisco cat. and started pouring over piston dimensions, specificlly bore size, piston pin size and location. When I got to the KX 60 piston, it jumped off the page! A perfect replacement. Same installed height! Huge! No need to remove material from the top of the cyl. And while it only increased the displacement by 8cc's[49 to 57cc], it was slightly domed, but best of all, it was an ART piston
I guess a little back-round is appropriate here, to explain what an ART piston is and why it was so important to me.
ART, is an acronym for a huge Japanese manufacturing Co. that makes all O.E.M. pistons for the Japanese Big Four{or at least they did in 1990].
Why that was important can best be summed up by a common pseudonym of the day we used for Weisco, we called them Seizcos. In 1990, nobody could make a piston of the quality of the Japanese O.E.M. pieces and the thermal expansion of aftermarket pistons required fitting them "loose" in the bore. One only had to hear a Weisco equipped 2-stroke to know what was in there. They rattled.
Boring out the NS cyl. several milimeters presented no problems, but great care was taken with the fitment. Since the engine was liquid-cooled and I was using an O.E.M. piston, piston to cyl. clearance was a very tight .001" to .0015". It was installed, run though a heat/cooling cycle two times, sanding down any high spots on the piston skirt both times before the engine before "break-in" was even started. It was this top end that was used for several seasons[over 40 races and practice and even an ocassional endurance race]with nothing more than replacing the rings
once every off-season. As I recall, I used the standard NS small end bearing. Simply amazing reliability and longevity.
The KX 60 piston also had a lot to do with the direction I ended up going, and in this, I primarily mean the cyl. porting.
So I am looking at the cyl, wondering what I'm going to do and I take review of what I have.
I have CR80 ign., transmission and intake system and what is starting to look like a KX 60 top end, well, at that point it didn't take much brains go ahead and "turn" the NS into a KX 60. After all, there are worst engines a mini racer could end up with, the KX 60 was a well known rocket and some of the smaller MX riders were racing them in the 80cc class.
I was able to get a hold of a port/area map for a KX 60 and I scalled it up to NS cyl size, overlayed it on tracing paper and scribed onto the NS cly. I never took notes, but I remember it was nothing too radical. The transfers were widened a m/m or two, as was the intake and the exh. was raised probably several m/m's and opened up as much as possible. Finishing touches were techniques I had been taught during my RD modd'ing days. The exh. was polished, but everything else was left rough. Special attention was payed to the transfer "roofs"[or floors, depending on one's perspective]. They were carefully shaped to almost a 90%. Once enough time was on the motor, the head was removed to check the pattern of the Schurle loop etched in carbon on the piston crown[it was very good from Honda]. There was no cc'ing of the transfers nor "matching" to the cases, such as was my confindence in Honda quality.
The rest of the aux. components were pretty much standard, standard NGK plug, Boysen two-stage reeds and Bel-Rey MC-1 mixed with a 50%/50% mix of Trick Racing and pump gas.
At the time[and even now as far as I know], there were only two accessories offered by Honda for the NS, the Fairing and the mechanical tach. and I bought them both. The fairing turned out to be too heavy and I replaced it with an universal clubman piece that looked like this;
- U903-4.jpg (29.47 KiB) Viewed 8604 times
The tach I kept, but it couldn't keep up with the engine and there was no time to look at it anyhow. I do remember that I could bury it[15,000 rpm]on a long straight].
One thing that bothers me is that for the life of me, I can't remember which wheels I used. I'm assuming the stock ones, as I don't remember lacing up any special wheels. That, plus I do remember the bike always had a drum brake on the rear. It was all that was needed for racing, as the rear brake is used more for "loading" the chasis than actually stopping.
Above, I touched upon the weight of the optional fairing, but the whole bike was heavy by todays standards, but then again, YSR's are heavy too.
It was only later, as a small wheel, using the beautiful aftermarket spun-alum YSR wheels and an alum. fuel tank that my mini racer could be considered light.
That's about it, but there might be more later.
When I quit racing, I gave the NS to a racing buddy who had a place near Tombstone Az. We've been out of touch for years, but now that I am retired, I'm moving back to Az. next month. I'm going to try and track old #55 down. I wouldn't be suprised if it isn't sitting in a barn somewhere in Cochise Co.
-can anyone spot the very special part I added to my NS's engine that is a big "power adder?"- 
jon
we're not worthy! 