Kawasaki F5 Big Horn speed kit manual
Here it is, the rare Kawasaki Speed Kit manual for the F5 and F9 Big Horn. The Speed Kit (or Power Pack as the brochure calls it) for the F5 was Kawasaki's version of the Yamaha GYT kit that was available for the DT1 (250cc). Interestingly the Speed Kit was only issued or advertised in 1970 making parts extremely rare. Kits and parts were no doubt probably sold in 1971 and possibly later, but the parts themselves had a very limited run. The F5 Speed Kit is a collection of parts and modifications claiming to increase the Big Horn's power from the stock 33hp to 45hp along with making the bike more tailored towards racing by removing all lights and battery. Below are scans from my F5 Speed Kit manual. Scroll for details part numbers, and information contained in the manual itself.
See these performance techniques applied to a Kawasaki F9 (350cc) (link)
See the F9 Speed secrets page for even more performance info
Click the images to enlarge to read the pages.
Kawasaki Big Horn Crankshaft differences from early 1970 engines to mid-late 1970-1975 as follows. (verbiage from the manual on page 4)
"In the case of the (speed) kit parts are used on the old models (before engine number 07268) it is supposed to be dangerous to increase the engine rotations over 8,000 rpm because the bearing on the big end of the crankshaft may seize. In case of raising the rotations over 8,000 rpm us the new type cranksaft assembly, or replace the crank pin and side washer with new ones as shown in Fig 5. (see page 4) machining the points A and B on the crankshaft as the new one's dimensions. The critical engine speed (red zone) is over 9,000 rpm when new type crankshaft is used."
Obviously there is some grammatical translation issues from Japanese to English but basically the crankshafts changed mid year 1970 for durability. After engine number 07268 (mid year 1970 and later) the crankshaft bearings are larger and a new crankshaft was introduced for later engines into the F9.
The new crankshaft assembly will retrofit into the pre 07268 (early 1970) engines. Interestingly the F5 Speed Kit manual is the only place this information is noted. The 1970 service manual does not notify the owner of this nor is there any supplemental information released later about this change for people working on older engines. My thinking is this was a warranty issue and customers were instructed to bring their bikes in for the crankshaft update, however my Big Horn I restored has an engine built prior to the crankshaft change making it an even more rare bike as the original owner did not have the update done. My crankshaft is the "old" style.
Oil Pump information (verbiage from speed kit manual page 6)
"In the case of the F5 kit parts installed. The pre-mixed fuel (15:1) is used. Therefore it is not necessary to lubricate the main bearing con rod and big end. Remove the oil pump cable from the oil pump lever and set the oil pump lever to full closed position. At which flow amount of oil is 110cc / hour at 3,000 rpm."
Because of grammatical mistakes in translation some misinterpretation happens with people thinking that complete removal of the oil pump system is being recommended or is warranted. This is not the case, the manual simply is trying to state that the primary means of lubrication is now premix (in stock form straight fuel is used and the pump varies the oil output via cable attached to the throttle cable) the oil pump system is now supplementary feeding a constant (less than) 2cc of oil per minute to ensure enough lubrication gets to the right side bearing during operation because of the engine/crank design. This is backed up by the information on page 8 under OTHERS stating what parts can or should be removed for a racing application, the oil tank is not listed as parts acceptable to remove. I believe some people have experienced engine damage due to removal of the system entirely not realizing the bearings still need some supplemental lubrication even when switching to premix in this application. You can read my article on the general debate about removal of 2 stroke injection systems here.
Kawasaki F5 Big Horn Speed Kit parts list (page 11-12)
Part # Description