1978 KZ400-B1 "Spankey the race bike"

You might pick up a few MPH if you learn to tuck in like the flat track racers do. Get your body as close to the fuel tank as you can and place your left hand on the low part of the handlebar or better yet, grab on to the fork tube!!!! Tucking in and grabbing the fork tube on my 400 sure helped my top speed by a few MPH!!!!! 

 

 

I can’t contribute technically so I’ll be the funny guy… There’s always this technique!!!

 

my suggestion would be add a little bottle of nitrous under the seat.

wrote:

my suggestion would be add a little bottle of nitrous under the seat.

Just don't get too greedy with the spray - or else, as the late great Smokey Yunick would say, "you'll run over your crankshaft".  

Also, what rpms do you launch at ?  Your 60 ft times can save you a bunch.

wrote:

my suggestion would be add a little bottle of nitrous under the seat.

 

This is a pretty good video. Yes, they're putting nitrous on a pit bike but they do go into some detail, e.g. dry vs wet systems.


 

Best bang for the buck to improve performance with the KZ400/440 is to advance the cam 1 tooth.


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That pic of Rollie Free suggests some good advice. Loose weight, both bike and rider. Look carefully at the rules to see what you can race without and what you can replace with lighter weight components. Can you skeletonize parts without sacrificing safety?
Streamlining within the rules will help, though I am not sure a swim cap is the best way to go.
If you can loose a few pounds of body weight, that will be free horsepower.

Wow! A lot of great responses. I guess I must not have been logged in when I read the last reply. I'll respond to these posts in order.

wrote:

Advancing the timing will make less power unless you give it more air/ fuel mixture to burn during the combustion phase (bigger carb, bigger valves, longer duration cam etc) there is no easy power gains, everything is a compromise and needs to work together. To be honest tighter fitting clothes would probably reduce your times more than the mods you have mentioned by reducing drag 

I normally do wear tighter clothing. This photo was taken at the first race of the season, and it was still quite cold here in Canada. 

Nerdy wrote:
The dished seat and lower bars would help your torso act less like a sail as you go down the strip. You might consider a small bikini fairing to clean up the aero a little.

You mentioned rearsets. In the action shot you posted, what is supporting your left foot? It appears to be too high for the stock pilot peg and not far enough back to be on the passenger peg.

I'm definitely looking at small bikini fairings. There's quite a few different styles on the market, so I've got decisions to make. My foot is in fact on the stock pilot peg there. It's a real problem as it limits my ability to tuck. I have found a guy who street races one of these who managed to make Yamaha R6 rearsets work in place of the passenger pegs. I think I might give that a try.

gd4now wrote:
First nice stable of bikes you have.  Second, not sure if you have seen this or if it will be of any help to your quest but check out this link with some IMO interesting suggestions. 

kz400.com/racingFrameset-5.html

I have seen that, and read it many times. The voltage regulator killswitch sounds interesting and easy enough to do.

urankjj wrote:
Before you change anything you might simply try a tank full of ethanol free gas. It does burn with a bit more energy than ethanol pump gas. It may give you a few more tenths, or it may not.  Good luck.

I only ever run ethanol free fuel in any of my bikes. Helps save on the carbs when rotating between bikes.

Dragbike_Mike wrote:
Also, what gear are you in when crossing the finish line?  For lowest E.T. you want to be revved out in your highest gear on the top end.  And, make sure that you add enough teeth on the rear sprocket (and/or remove teeth up front) so that you're truly on the top of the powerband.  You don't want to be crossing the line halfway into powerband and still accelerating.  

Every shift is at the redline. I end up shifting the last time right before the finish line. I never have had the wherewithal to figure out if that's a shift into 5th or 6th. I'd agree that going up several teeth in the back should help. Probably go to a 520 chain for weight reduction too.

TexasKZ wrote:
That pic of Rollie Free suggests some good advice. Loose weight, both bike and rider. Look carefully at the rules to see what you can race without and what you can replace with lighter weight components. Can you skeletonize parts without sacrificing safety?
Streamlining within the rules will help, though I am not sure a swim cap is the best way to go.
If you can loose a few pounds of body weight, that will be free horsepower.

If I lost any more weight the bike would have to go down the track without a rider. 

I appreciate all the input folks. Honestly, turning Spankey into a "race bike" just started out as a joke with my friends, but the more I think about it, the more excited I am to do it, if only to see what this little guy can do. It's going to be a slow project as I've been posted to relocate to Ottawa, and the 400 is staying here, so I'll either be tinkering on it while I'm in town, or sending parts to my friends to install for me. I think to start simple, I'm going to swap the bars, then lower the front fork tubes as much as possible, and then replace the rear shocks to shorter to match the front (will help with burnouts, as I'm vertically challenged). The rest will come in time. I still want to shave the seat, but I'll need a new seat or seat pan before I do that, as I want everything to be reversible.

Lookup HondaMan Carl Kneiper.  He's been racing the same 1972 Honda CB350 since he bought it new.  Very fast for a little 350, very consistent too.