Aaron/Dan,

I know you are not into giving your trade secrets out, but I have a question on modifying XR-1000 heads.

On your LSR bike, did you re-port the heads or re-port and install larger valves? If you installed larger valves, was it the intake, exhaust or both?

Specifics would be nice, but if could give me some generalities, I can figure it out from there. Thank you for all your help on this.:)

Jesse,

The heads we used on that bike was a set of the late model, oval port jobs, and yes, they were heavily prepared. In fact the ports were so wide they had sleeves in the head bolt holes, and one rocker box hole screw hole broke into the intake port on each.

Valve sizes were stock XR750 believe it or not, not the 1mm bigger XR1000 valves. The 58 degree included valve angle on those heads makes it very difficult to use big valves and/or lots of overlap, the valves love to get together. And the head hates to have it's valves sunk, we tried that once, trying to get more overlap into the motor, and it was a disaster.

Don't quote me on the valve sizes because it's been several years since I did that project and I don't have my notes in front of me, but I seem to remember 43mm intake and 37mm exhaust? Is that right? And then the XR1000 got 44mm & 38mm?

In any event, I tried several combinations on that deal before I got it to work right. Different cams, heads, and pipes. It wasn't a simple development at all. The oval port heads were worth a ton of power over the old round port heads. Dual plugging was worth a bunch as well. Oiling system mods helped the power too. The pump was just putting way too much oil into the motor, and getting it to scavenge properly was quite a trick.

As well as we did with that thing, I wouldn't do it again. That motor is an antique and it's got some major weak points. The cases are entirely too weak, and the insert on the sprocket shaft side loves to come loose. Plus they love to develop cracks between the pinion race and the cam bearings. Also, you have to carve the bejeezus out of the pinion race area in the cam box to get even modest sized cams into the thing. Stock motors also don't have a woodruff key on the sprocket shaft, where it goes into the flywheel, and they love to spin at higher power levels. Just overall a very, very difficult motor to hot-rod and entirely too fragile. XR1000's are best left on display somewhere, they look cool, but that's about it.

I had an '83 1000. It was a dream bike until I owned it for awhile. All of the above problems and more were experienced,at great cost. The XR-1000 is a great collector piece. It IS NOT a well engineered bike. Basically an ironhead with short rods and enough added breathing potential to destroy itself regularly. I thought it was fun for awhile. I also had an XR-750 for several years and despite being tuned for 90+ ponies and 9K rpm was totally trouble free. The famous Lucifer's Hammer XR-1000 of BOTT fame used 750 cases, superblend bearings,etc. The parts are so scarce for 1000's now that it makes little sense to put the spurrs to such a valuable piece of H-D history. If one really has the XR bug-and deep pockets- Sundance has your motor.