Panning for Gold

I'm sorry, I have the same impression.. either buy and install stock internals.. which would be a great opportunity to learn, or buy a solid motor and install it.

I don't think the L and R engines are interchangeable. The XR650L is the air cooled version, much less power.

I'd be willing to be that at least 3 times more "L" models have been sold. In watching eBay I've only seen two "R" motors. Both looked much worse than mine from an exterior cosmetic standpoint and were priced at $1400 and $1800. At that point the math doesn't seem to work out in favor of buying an engine.

I started tearing into the engine this afternoon. I can't find anything that appears damaged in the head. I'll still have to mic everything to be sure, but the cam and cam bearings look perfect. Very good news since it's a very expensive HRC cam. The bore actually looks very good as well. It still has a nice crosshatch pattern in it. It will still go to Millenium for a replating but it helps reassure that the chunks of blown bearing didn't have time to tear things to peices before it shut down.

I'll admit that the piston bore is actually bigger than what I was picturing in my head.

I took the piston out and got the bore off. I've decided that the exhause valves were ever so slightly contacting the piston. They have matched shiny spots. I assume that when the bottom end bearing went that it allowed just enough more piston travel that things were making contact. I have a sweet new HRC paper weight.

I've decided that's why it will get rebuilt. Maybe not today, or anytime soon, but as time and money allows I'm putting this thing back together...and it will be better than ever.

What was the HP rating on your motor? I'm assuming you want to stay with that particular bike because of the street aspect?

I was getting 55hp and 44ft/lb at the rear wheel according to local dyno. The bike right before it on the dyno was a supposedly "well built" CRF450 dirt track bike and it made 44hp, I didn't hear what it was putting out for torque but I guarantee it was less. The only way I'm going to gain anymore power on this engine is to upgrade the carb. That's the limiting factor at this point.

The main reason for staying with this particular bike is the maintenance. It was built as a full race bike, raced 534 miles across the desert, lasted 3000+ very hard street miles, and three track days with nothing more than a few oil changes. I could get slightly more peak performance and slightly less weight by going with one of the 450 class bikes but I'd have HUGELY increased maintenance.

I see. I was thinking of the same comparison. The 450’s stock now make about 51. A few year old ones make just under 50 stock at about 32 lbs of torque. For 3k you could get a lighter bike, better suspension, and about the same power. Not to mention the availability/ cost of parts. I’m not really sure about the maintenance/longevity though. My dad has gone through his once in the last few years, and he rides his pretty much weekly on the race track. (all dirt of course, and in the warmer weather) Not that there is a right or wrong way.. just when you said 2k for a motor, the thought just popped in my head.

51 is the quoted crank horsepower if I'm not mistaken. I've got 55 at the rear wheel and quite a bit more torque.

For $3K I could get a well ridden used bike with unknown history and I'd need another $1500 to convert it to a sumo. Since it looks like my camshaft is fully intact the math adds up to about $1500 for the rebuild. I could actually do it cheaper than that by far but I'm going full out with Falicon supercrank and knife rod, piston coating by Swaintech, and bore replating by Millenium. Pretty much ensuring thousands of miles of trouble free riding.

My bike had the front suspension completely done by Precision Concepts and the rear has a three way adjustable shock that was only available to factory riders. Both were set-up for high speed desert racing rather than MXing which make the whole set-up work very well on the street and track for someone my weight.

How many actual miles do you think that adds up to each week at the track though. Compare that to holding it wide open on the freeway for hundreds of miles like I've done with mine, thousands of miles total. All of that after unknown amounts of abuse at the hands of a factory level rider tearing across the desert on it.

In addition this bike already has a lot of other very trick aftermarket parts on it. Probably the most important being the giant aftermarket aluminum radiators that help keep everything running cool for more longevity.

I'd love a 450 sumo if it was just going to be used a short track only weekend warrior but I'm not convinced that any of them can hold up to street use and road course track days.

Oh yeah.. you have to fix it. The thought was more a hindsight comparison.

Yeah - you gotta rebuild it. It's the only good choice.

Wish I could help.

I can give you directions to my place. In all seriousness I've contemplated gathering all of the engine parts and showing up at evls place (he offered), I could just bring them all to your place.

Not at all out of the question. Probably easiest if I just drove down to your place.

Having Evl-Twn present, either virtually or in person, would be a pretty big benefit. He's actually done this before, unlike either of us.

you took it apart you can put it back together, might have some extra pieces but it'll be back together.

Go ahead and bring the engine over, but it might end up with some parts in it from several other motorcycles, or maybe even a small block Mopar.

Shoot, with the size of that piston, new gen mopar parts would be downsizing..