We were able to get this one made on the assumption that the DT360 and SC500 were essentially interchangeable with the exception of head pipe diameter. He built the pipe to fit his 360 with a neck down at the cylinder to fit the 360 flange. Then he chopped off the 360 sized portion and welded on a 500 sized inlet. Pretty slick.

Ordinarily you have to have the bike there to make a new pipe. You might check with Jemco, there is a chance they have a jig and a design for your bike already.

I got some video today, figured it would be a suitable final update for this. Bike is probably going on ebay in the next few months. I've got eight in the garage right now and it's time for some to go.

It's got around 1200 miles on the 500 motor, maybe 50-60 hours. It's been great. No problems, no additional noise or power loss. I suppose keeping the revs under 7k helps tremendously.

Here's some 0-60 pulls:

Way flat.
Down 20hp guessing.

cliff

Wow, that's an interesting take.

The original SC dyno'd at 39hp:


Period tests have it running a roughly 7 second 0-60 and 15.4 second 1/4 mile:



It is missing about 20% at my altitude, so it's effectively running like a 400 would at sea level. It's also geared about 20% taller than the stock SC, which is the only way I can keep wheelies manageable under full acceleration.

I would estimate actual rear wheel horsepower to be in the mid 40's. It compares favorably to a modern 250cc two stroke. It will piss all over my RD400, which is running quite well with high compression heads, cleaned up porting and a Y boot intake. Not even close in terms of acceleration.

If you think that looks like it's making less power than s stock DT360 I genuinely don't know what to tell you. Come out and ride it, then try to tell me it's down 20hp.

What it "sounds like" to me is PERFECT.  Plenty of power and it's still running strong after quite a while!

I raced a lot back in the day...  and yeah...  you can tune until it's running nice and crisp...  20 hp more sounds like a stretch but you'll definitely get a few ponies and maybe even the holeshot at the start of the race! 

In my experience, guys that tuned the old air cooled engines (especially the big bores) "crisp" tended to be the same guys that would tell you a two stroke will blow up if you hold it WOT too long...  and the guy that got the holeshot that way would probably be parked before the end of the race with a blown engine.

I raced both short course and desert...  100 mile plus desert races.  I won a 24 hour endurance race in the desert with a 500cc (I think it was actually 488cc's) air cooled two stroke.  Half the course was very deep sand and we ran WOT probably 80% of the race...  My average lap speeds in daylight over the 10 mile course loop was just over 50 mph...  I was clocked at just under 100 mph with a radar gun in the long sand wash...   that wash was nearly 5 miles of solid WOT under heavy load...  lap after lap for 24 hours.   Never missed a beat. 

I learned to tune just slightly leaner than "four stroking" at WOT...  could lean out the main jet 3 or 4 more sizes and it would definitely gain power and sound better.. for a few minutes.  But it would never have finished the race, 

I'm impressed Turbo Dan. 

Sorry, just going by the sound and short shifting.

Did not know about the highway gearing.

Yes I had 2.
Worx '74 and stock '73.

cliff

And Turbodan blasts off into the distance leaving a lonely beer bottle on the side of a long dusty road, the exhaust note fades, the light finally fades and a whole new life awaits the grunty 500!

A worx "74 would be frightening. An every day SC500 still gives me nightmares lol.