1970 XR

1970 XR-750

Links

X-R 750 as produced

My 1970 X-R
(Click for more pictures)

I own the X-R and a "Big Twin" It's kinda like having a sports car and an Old's 88. If you want to lay back and cruise, then take the 88. If you want to really enjoy then take the sports car! So follows the history of my sports car.
In 1969 Harley Davidson produced their only "Iron Head", overhead valve, competition only, 750cc flat-track racing motorcycles.

Dubbed the "X-R", they replaced the Flathead "K-R" and were used during the 1970 and 1971 AMA racing season.
To make them official "production motorcycles" so that they were legal to race, 200 Iron head X-Rs were built by the factory race department but only 100 were released. A few were used by the factory race team and the rest were offered to privateers.
With the release of the dual carb "Alloy Head" X-R in 1972, the remaining 100 Iron X-Rs were destroyed by the factory for accounting reasons.
Only about 25 1970's are known to still exist. Just for my own curiosity If you know of one, please E-mail me. @Flattracker

As produced, they had no battery, charging system, lights, kick starter, side stand, front fender, or brakes, and weighed only 315 lbs. (mine now weighs 390 lbs.) I talked to the guy that was the tuner for my bike , he "claimed" (I find it hard to believe) that by the 1971 season they were getting 90+ horsepower from it on an engine dyno at AirFlow Research. He said the flywheels had so many lightening holes drilled in them that they looked like Swiss cheese and had a very short life span because of it.
I bought it in 1981 for $1000. It had originally been flat tracked up and down the West Coast and in Texas. As near as I could find out, the last time it was raced was around 1974 in a road race at Seattle International Raceway. The factory race department had given the owner a set of flywheels to make it 900 c.c.'s (X.R.T.T.?).
I got it after the owner's garage burned down around it. The tires, fiberglass tank, fiberglass seat / rear fender and the oil bag were melted as was the carburetor. Everything that wasn't melted was covered with fiberglass soot from the boat he had been building in his garage.
When I took the engine apart the crank pin was pitted so bad I couldn't use it as it was. The bearing cage was broken and the rod races were as bad as the pin. I spent along time trying to find someone who had some good ones but came up with zero. My choices were to try to repair what I had or machine the flywheels to accept a Sportster pin (about half the diameter of the X-R's) & rods, I decided on the latter because I had no intention of racing and if I had problems in the future, I could easily find parts. The cams run on roller bearings instead of bushings and it uses a one quarter speed oil pump because the engine normally ran at 7000 to 8000 RPMs.
I had to bore the barrels to .060" over to get rid of the windows in them. The new pistons had the wrong pin location (or the rod length was longer, I don't remember any more) for the shorter X-R barrels so I had to space the barrels up .250" to keep the pistons in.
I put all of the parts in so it would have a kick starter and bent just about all of them because I still had the original 19 tooth motor sprocket. It now has a 34 tooth for a little more mechanical advantage so the kicker parts will live. But it doesn't pick up the front wheel anymore when you roll the throttle on in third gear because of the higher gearing.

Click on Picture for slow loading, but high res picture that can be enlarged for good detail. DSL or faster...

I had the Barnes quick change rear hub laced to a 6" wide wheel. Both the sprocket and Airheart rear brake rotor have splines on them and are held on the hub with a big spanner nut on each side. I would sure like to find a larger Barnes wheel sprocket to replace my 44 tooth (mile track gearing, I think?) so I can gear it a little lower. Know of anyone with one?.

They came with a magneto in the spot where a shovelhead Sportster had a generator. I didn't have the original short shaft horizontal magneto so I machined the cam cover to accept a gear to drive a generator in its place and then put a vertical mag. on the side. I use an Accel regulator and battery eliminator, so I don't need a battery.
I needed foot pegs and a side stand so I found the stock piece off of a Sportster, cut it in two and put it around my frame and then welded it back together.
Mounting the Performance Machine disc brakes on the Ceriani fork legs was probably the hardest part as there is almost no clearance between the calipers and spokes and the rotors and the fork legs but clearance is clearance and a little is enough.
I'm still not sure why the original tin clutch cover won't fit over the clutch drum so I have to use an after market one that is a little deeper. I was told that one of the little tricks the racers used to lose a little more weight was to mill off the clutch drum and the side of the engine case the thickness of about two clutch friction discs and then run with less discs. I used a Sportster drum with the kicker gears on it, so that might be the problem.
I don't ride it as often as I used to anymore because it has become too valuable and I hate that, then there is also the fact that after 50 miles on it I feel about the same as after 300 miles on my FXS. However, whenever I do ride, it turns heads. I can't ride Teri's Sportster anymore because I just don't look good in pink, so I am looking for a deal on a 1200 Sporty so I can have a sports car again.
It is like driving a sports car, you can feel everything, which is both good and bad. No creature comforts what so ever, just sort of man and machine. A real rush!
To any purists out there, I apologize for defiling the motorcycle by making it street legal. Then again on the other hand, it's mine not yours!