Kawasak F5 and F9 Big Horn speed secrets
Performance mods and "hop up" tips

Below are scans of an article on how to make the Big Horn Hotter.  Some of the tips and tricks outlined are obviously geared more to making the F5/F9 Big Horn into a flat track racer so not all of the techniques will apply to your F5/F9 Big Horn, also 30+ yeas of knowledge later has shown that some techniques are maybe a bit questionable.  However it is a unique look back at some performance tricks for the Kawasaki Big Horn. Check out my videos for general performance tips and specific tips related to my performance F9 Big Horn build.  Use the below information at your own risk.  I also have all the information from the Factory "Speed Kit" on another page.  It contains all the specs, parts, and instructions to modify your F5/F9 Big Horn.  
​                                                                Below is a playlist of my Vintage MX performance bike build

Need to replace that leaking vacuum operated fuel tap (petcock) on your Big Horn (350cc) or Bison (250cc)?  

Try this replacement fuel tap that fits 1975-present Harley Davidson Sportsers HD p/n 62163 OR Biker's Choice p/n 49-2599 it has a straight outlet and features 22MM threads that fit any tank with 22MM threading.  This will fit F5,F9 and F7 (175cc). Can be found on Ebay and various sources.

Suitable replacement fuel cock for the Big Horn (F5,F9, will fit F7)

Making your Big Horn hotter

Improving the F9 Big Horn's handling

Improving the lubrication to the big end bearing on the F9 crankshaft

Cleaning up the cylinder ports will help flow

This is another one that is questionable, as using two or three gaskets will lower compression and help prevent detonation, however it still doesn't fix the issue of the head not having a proper squish band. Klemm Vintage has a good picture of this on his website.

See Speed Kit manual for exact specs and how to cut the valve

More of a quality control issue here, check yours and weld if needed

F9 clutch replacement uses expander rings which is somewhat unusual

Follow my videos for jetting tips. Each situation will be different.

I am not sure what a "filtron cap filter" is, but find the carburetor cover intake for an F81M or p/n's 14065-003, 14063-002, 92065-074 or make a filter out of bulk filter material

Special socket required to remove the oil pump pinion gear/nut on the F5 F8 and F9

Below are pictures of the rare F81M button mag, magneto and lightweight flywheel setup that came stock on the Kawasaki F81M (250cc).  This is/was a popular upgrade from the heavy stock F5/F9 flywheel (almost 3 lbs!)  This will really make your F5/F9 (350cc) spin up quicker.  This also fits the F11M.

Making the Big Horn Hotter page 1

Simplifying the Big Horn's wiring for racing

Improving the seat on the Big Horn for racing as the stock F9 seat is hinged and uses the ignition key to latch and lock it down which is unnecessary for a racing machine.

The lighting coil can be removed for racing and simplifying the wiring on the F9

There is conflicting opinions on if this is a good idea from a performance and reliability standpoint, remove piston ring at your own risk. Some people will argue that the ring groove will alter exhaust port timing and or disrupt flow. However others will dis-agree stating that the 3rd ring only adds weight and friction and is not needed, a valid argument. The factory service manual states the reasoning for the 3rd ring is for heat transfer and cooling. The "Speed Kit" piston only has 2 rings but is of a slightly different design and is lighter, which begs the question why the "speed kit" piston didn't become standard equipment in the later F5A and F9? This suggests a possibly long term reliability issue in a non racing application.

Using a different spark plug is a good idea

This is more a general tip on reassembly

The F9 clutch, follow the tips in my videos to improve the clutch (see the video pages)

Another source of debate, personally I would still run the oil pump to ensure good lubrication to the main bearing. The Speed Kit manual recommends unhooking the cable but still using the oil pump and mixing at 15:1

Again, this will vary by altitude and situation see my videos for more

"Molly" sure looks like a decent flat tracker and it would be nice to know what exhaust is on that bike. Use the information above at your own risk.