I still get calls about Honda XR650R's. Thought I'd put all the details down before dementia hits and I can't remember a damn thing. I was working for Ballards/XR's Only when the 650 came out.
The XR650R was the bike Honda used to replace the legendary XR600R. We started hearing about it in '94. The XR600 was almost unchanged since 1986 and we kept getting whispers of Johhny Campbell and Scott Summers testing the new bike.
There was so much hype about how good the XR650R was going to be that when we received one of the 5 pre-production bikes in January 2000 we all stood around and wondered what on earth Honda was thinking! It looked really heavy. Geoff Ballard rode it at an ADB test and dismissed it as a pig. We had been racing WR400's and XR250's so the 650 was a bit of a shock! Part of my employment agreement was I got a bike every year. GB gave me the 650 as he didn't want to ride or race it.
Slowly over a few weeks I pulled off all road gear, put some normal gearing on it, grafted on a reverse cone FMF Megaphone pipe from an XR600, did some suspension work and went for another ride. Big surprise. It was fast! Pip from Honda gave me a few tips and GB asked for a ride on it when we were out practicing one day. He liked it.
Since then we've raced the 650 in Thumper Nats, Geoff Ballard won the over 35’s title on it in 2000 and 2001. I built the engines for the official Honda Safari effort from 2001 to 2005 (Staintune Honda GHR Safari Team) and grown to love the bike. It’s now ended it’s production run quite a while ago, but will be a very good desert / long distance / supermotard / trail bike for many years.
- Tyres. The stock IRC’s tyres are 80% road, 20% dirt. A 140 rear works well on the 650 and replacing the rear rim to 2.5 is a good move too.
- Exhaust. Pull the sleeve out of the stock muffler. Hopefully the dealer did it for you before you bought it. You can still buy the Canadian tip for the stock pipe, it is the same as the HRC tip. Stock muffler is light and not too bad. If you want to get serious however, the pipe you want is a reverse cone megaphone. No one makes them commercially. I used to have a guy make them for us but he's disappeared. They make 5hp over anything commercially available, but they were $2500 for the set (headers and muffler) plus it’s about 105db. Look on a MotoGP bike and you’ll see what a reverse cone is. Your 2 stroke exhaust guy might be able to do it if he can roll cones. Similar to making a 2 stroke pipe. All the dimensions are freely available in the Honda HRC book that comes with every HRC kit. I’ve been told someone published it on the web, should be easy to find. The stock Staintune doesn't make much more HP than stock, the big header sizes make the bottom end weaker too. The exhaust the Staintune team uses is better but not as good as the reverse cone. I’ve never compared the off the shelf Staintune and the GHR one, it was just a case of try the off the shelf pipe, ask Staintune to make it work better, send the old one back, and the new pipe turned up. Looked bigger in the intermediate pipe and in the muffler core. Staintune can still make the race pipe, they call it the desert pipe or something like that. You have to beg as it's a pain for them to make it. No exhaust manufacturer will admit to a reverse cone working as they don’t make them/can’t make them. (XR's Only in the US still has reverse cone pipes as of 2014). So 60hp was it for the safari bikes. I’ve heard 75hp from guys in the US, but they also say they can only just keep with the 700cc KTM factory bike. Our bikes keep with the KTM so perhaps our 60hp is conservative, or their 75 is bullshit. I’ll let you mull it over. Bear in mind the Baja race bikes do 115mph and our safari bikes do 112mph. Interestingly enough I tried a reverse cone pipe on our original 650 in early 2000 and kept bouncing off the rev limiter with stock headers and cam. But we never raced with it as we were sponsored by FMF at the time and had to use their power core 4 or whatever it was. Killed the power.
- Jetting. Our jetting works for us at just above sea level, so this is only a recommendation. 65S pilot (stock) 1¾ - 2½ turns out on the mixture screw middle clip position 162-165 main (stock main is 175, way too rich). If you use the HRC air box mod you will need to go up a size or 2 in the main. Remove the choke butterfly.
- Bars. Stock are very swept back, go for some good quality 7/8 bars in a bend you like. KX high bend works well. Buy an Applied top clamp, it's a must or a BRP with a Scotts damper.
- Gearing. For typical Aussie bush work 14-48 works well. 15-42 is stock. Add a few links to the chain or buy a new one. The OEM chain is actually good quality.
- HRC Airbox Mod. This makes the air filter breathe from the low pressure zone behind the riders leg, making the distribution of dirt on the air filter even and stops the filter from loading up in one place. It also does a lot for performance.
- Porting. No head flow figures, I don’t do it. I built the engines for free, no budget for flow benches. Just raise the roof and smooth out the big lumps.
- Valvetrain. Keep the stock valves/springs, they're fine. Stock cam is OK but goes flat at 6000. The HRC is a great all round cam and the stage 1 Hotcam is almost an identical copy of the HRC. The stage 2 Hotcam is a rocker arm breaking, high revving waste of time. I made a cam a little bigger than the HRC and used it to great effect in the Safari in 2004. I'll list the numbers when I find them. Stock timing chain is OK too, the HRC kit is overkill.
- Ignition. You need a Vortex with a modified flywheel. Nothing else is any good. XR400 ignition modules are a joke. Stock rev limit is 8150rpm. XR400 is 8350rpm. I initially set the limiter to 9200rpm in Thumpers but GB was bouncing off it so I raised it to 9600. Stock total timing was 33 degrees but the Vortex lets you have another 10 degrees, up to 43 degrees. If you ever want to build a top XR650, its probably too late, because they're no longer in production.