I have been looking at street legal dirt bikes and I'm probably going to get a DRZ400SM but I have a question.

How hard would it be to install a big bore kit on a older oil cooled big thumper? From the brief research I've seen on big bore kits for the DR650 and XR650L they look interesting and promising. Good gain in horsepower and decent torque along with what should still be excellent reliability.

If it is not terribly hard to do on the DR650 or XR650 I'm tempted to pick up a high mile bike cheap and put a big bore kit on it.

Bad idea? Should I just get a DRZ400SM and have fun modifying it?

I had an XR for years. Very capable bike. A pig in sand though. And it ran like crap until I plugged and removed all the Kalifornia smog crap off it. So if you go XR, shitcan all that stuff and it will run great!

quote:

Originally posted by stickman428:
I have been looking at street legal dirt bikes and I'm probably going to get a DRZ400SM but I have a question.

Can't speak to the big bore kits, but a few years ago I rode a friend's slightly modded DRZ400SM, and it was about as much fun as anything I've ever straddled. (Maybe I should have phrased that differently. ) Not sure upping the displacement would positively impact just how good that bike is in semi-stock form.

I owned a DR-650 for years. It was very reliable but rather bland on or off road. It was more for the gravel 'fire road' type driving, that real dirt. 1st gear was geared high too.

Since I was on pavement 99% of the time I changed over to a CB-1100.

Those 'Adventure' type bikes look interesting, for those that will be on the street a fair amount.

I currently have the S version of the DRZ and it is about as much fun as you can have on road and off. I rode a loop through North Georgia last year that included 110-120 miles on road and another 30 or so on rough forest service roads. It handled it all with ease.

I don't think the bike needs much power outside of a simple 3x3 mod and the MRD pipe. I have 3 different sprocket setups and 2 different chains that I use.

When was looking for my bike, I looked at the XR, DR650, and KLR, but didn't really like the extra weight for a minimal, if any, horsepower gain. I also liked having a water cooled bike instead of air cooled.

I dunno how much a big bore will gain you given the cost, reduced resale, and potential nick in reliability? What about just finding a used KTM?

Procycle's big bore kit for the DR650 puts down impressive numbers and it isn't really all that expensive. ($660)

After doing a bit more research it doesn't look all that hard to install a big bore kit. I guess it will come down to whether I can find a good deal on a DR650 or XR650L.