Building a drag bike

**PurplePeopleEater** · 03-01-2011, 11:03 AM

Very exciting. How long until we see you taking someone's 'Busa home on Pinks?

**Brian P** · 03-01-2011, 12:46 PM

Hah! Fat chance of *that* happening. I'm too heavy and the bike has zero power adders. Just something to play with on test-and-tune evenings.

**PurplePeopleEater** · 03-15-2011, 09:09 AM

Hey Brian. I met your buddy Drew the former top fuel bike racer on Sunday. Small world.

**Brian P** · 04-13-2011, 05:09 PM

I just took the beast for the first real ride that wasn't just a trip around the block.

One of the objectives was "remain streetable". That, it is. It takes a little more effort to get it turned (the steering is a little heavier, but it still feels reasonably neutral - doesn't want to stand straight up, doesn't want to fall into the corner) and it's still possible to chuck it around on twisty roads. Acceleration is violent

just the way a 1st-generation ZX10R is supposed to be, but even more so

and it stays rock-solid stable when doing so ... which wasn't the case when stock. This is going to be entertaining!

I think the amount of extra wheelbase is pretty close to right for the gearing. There is enough weight transfer so that it will accelerate hard in 1st gear without spinning the tire and without having to do a burnout first. (Go too long and low, there won't be enough weight transfer, that's when it'll just spin the tire.) At the track with a properly hard launch, it'll probably still be possible to pick the front wheel up, but it should come back down again without having to back out of the throttle (this was a big problem with the stock wheelbase and ride height). If needed, burnouts are ridiculously simple ... it will light up the tire at 3000 rpm if you ask it to ... Had to try this just to make sure

Never thought a stretched bike could work so well. Very happy with this as it stands right now.

**FiReSTaRT** · 04-13-2011, 08:01 PM

Great news. Now she's almost as fast as that CBR125 of yours

**Brian P** · 06-04-2011, 12:27 AM

I finally got to run this - just got back now. Best run was a high 10.7 at 136-and-change mph, which is 0.3 seconds quicker and about 5 mph faster than before, and a whole lot more controllable, and there's more in it yet after I figure out how to launch this thing better. And that's having ridden the bike to Cayuga and having to ride it back afterward. Remarkably, this tank of fuel is at 220 km and the low fuel lamp hasn't come on yet, and that distance includes about 10 runs down the strip.

Tire wear is going to be an issue ... I did the first few runs without a burnout to get a feel for it, but then had one with major wheelspin, and that was the end of that.

**Brian P** · 12-27-2011, 05:14 PM

Christmas holidays - Back on this project. Got called by tech inspection for a chain guard being too short ... apparently it's supposed to extend 1" past the axle centerline and I was just using the stock one. (Would be nice if the requirements were actually written someplace that is easily findable, but whatever.) Looking around for a longer chain guard online turned up some shiny polished bent sheet metal bits in the shape of a chain guard, which they wanted 90 bucks for, and which I didn't really like anyways. Meanwhile, there was a piece of scrap thin gauge sheet metal that was about the right size sitting in the odds and ends shelf in the shop, begging to be made into something.

The stock chain guard isn't a very complicated shape, so I first cut out and bent a cardboard template and got it shaped about right, then transferred it to metal, cut it out, bent it to shape (including bending a lip over the edges to stiffen it and also so that there is not a sharp edge along the length of it), hit it with some primer then some black paint, and I'm waiting for that to dry before installing it on the bike. Free beats paying 90 bucks any day.

Also, realizing that this will no longer be a touring bike, I took the Helibars off and went back to the stock handlebars. The grips are worn out (67,000 km on the bike), will probably grab a set at the bike show.

The other issue is that the quick-shifter proved to be irritating on the street. I'm thinking of rigging up a switch to detect whether the clutch is pulled in or not, and disable the quick-shift if I'm using the clutch.