building and tuning the KR-i and

KR-iS so that all the information is

together in one place. I’ll update it

all too, where needed. Firstly, I have

always been an admirer of the KR-i

and lS. When they first came out we

saw their potential and did a huge

amount of development for produc­tion racing and Supersport 400 rac­ing resulting in hundreds of race

wins and many championships. Un­like today, where there are only Su­persport 600 and Superbike classes

in the British championships, dur­ing the 1980s there was also the Su­persport 400 British Championship

which was incredibly important to

the manufacturers’ small bike sales

and up-coming riders. Noticing the

success I was having in Production

racing with the KR-i, Kawasaki

contacted me to prepare the works

KR-l Supersport racers, the Stan

Stephens/team Green race team was

formed and rider John Reynolds so

very nearly won the British Cham­pionship. At that time the rules for

SS400 racing were for 25OCC two-

strokes and 400CC four-strokes; I

proposed to the ACU (the sport’s

governing body) that we should be

allowed to race 400CC versions of

the current 25OCC two-strokes. The

ACU asked me to build one so they

could evaluate it. I built a 40OCC KR-

lS and what a missile it was! Need­less to say it was too quick and the

rules stayed at 25OCC two-strokes.

The 400cc KR-iS was what

not available but there are good pat­tern ones like the Mitaka kits. Check

the cylinder bores for any damage to

the Nikasil plating, look for any

seize marks or

KAWASAKI KR-1/SStan Stephens on part one of a resto/tune up of this stroker.

V

Classic Motorcycle Mechanics 16 Jan 2017 +1 more WORDS AND PHOTOS: STAN S

Blistering, also check for cracks be­tween the exhaust ports and the ex­haust boost ports. Any problems,

get them replated - never, ever

have liners fitted! Next step is to re­move the clutch cover and strip out

the right-hand side of the engine. If

the gear oil is white and soupy, this

is emulsified. It is caused by water

entering the gearbox, usually

through a damaged water-pump

seal; check the water pump impeller

shaft - if there is a wear groove in it

the impeller and the pump seal will

need replacing. When stripping the

clutch, check for broken fibre plates

and/or blued steel plates. If you

have any doubt about the fibre

plates, replace them. If the steel

plates are blued but flat give them a

rub over with emery or get them

bead-blasted. Check the fingers of

the clutch basket for excessive wear,

although the KR-iS clutch is very

good and I have never seen a worn

basket on one yet. With the clutch

removed take out the kick-start

mechanism and the idler gear and

the circlip at the back of the clutch.

The gearbox is now ready for re­moval. The KR-iS gearbox is a cas­sette type which basically means it

can be removed complete without

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KR-1/S Masterclass!www.frost.co.uk

01706 658619 QUlPNik.

Kawasaki should have built. When

stripping any engine it is important

to diagnose any problems and to do

some detective work. The first thing

to look at on the KR-iS is the KIPS

valve linkage. A little wear and tear

is acceptable but if the linkage is

falling apart (as most are) there is a

problem, as most of the KIPS parts

are discontinued. Be careful when

removing the linkage from the KIPS

valves themselves because the

valves are very fragile. They are

made from hardened alloy, the

spindles are only about 7mm thick

and there is a flat on them which

leaves about 5mm thickness and

then there is a threaded hole

through it, which doesn’t leave a lot

of metal left. Remove the cylinder

head carefully because the KIPS

valves usually stay in the barrels

and once again, they snap easily.

Inspect the head for any damage

which would give clues to any prob­lems. Check the head face and the

barrel faces for any signs of the

head gasket blowing. Don’t take any

chances with the pistons - just re­new them. The genuine articles are

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Here we are loading the cassette gearbox.

Editor Bertie received an email from

a reader in Australia, telling him all

about the classic racing scene out

there. The guy said there was a lot of

interest in the 25OCC production

class, in particular the Kawasaki

KR-l and KR-lS, and he wanted

CMM’S help with tuning them. As a

result, Bertie asked me to write an

article explaining the tuning work

we carried out back in the day. To

begin with, before tuning any en­gine, it needs to be in good condi­tion and set up properly. What I am

going to do is amalgamate articles I

have written about stripping, re-

the balance shaft timing mark in the

correct place. The problem with the

KR-iS crank is that Kawasaki never

sold parts for the cranks, only com­plete cranks and they were horren­dously expensive and have been un­obtainable for years. The con-rods

and big-ends can be replaced with

KX125 moto-cross rod-kits; the

left-hand and centre main bearings

are the same as TZR250 mains and

the right-hand main is the same as

a 350 LC right-hand main. The seals

are obtainable from Grampian Mo­tors in Liverpool. Quite often the

mains work loose and wear the cen­tre shaft, I have had some new ones

of these made. The major problem is

if a big-end has

always check that everything oper­ates properly at each stage of the

rebuild; don’t wait until it is fin­ished. By this I mean when you bolt

the crankcases together, check that

the crank turns smoothly, fit the

gearchange shaft and go through

the gears and check they are correct.

When checking the gear selection,

get someone to help. This is because

one has to change gear while the

other holds the output shaft and

turns the input shaft so the gears

will engage. When fitting the kick-

start shaft, make sure it works and

that it returns. When you fit the

clutch, turn it to make sure it is not

tight. Continue checking everything

as you fit it. With a nice clean bench

you’re ready to start the rebuild.

Unlike most two-stroke twin en­gines, when assembling the KR-iS

crankcases the crankshaft is loaded

into the top crankcase. With the top

crankcase on the bench upside

down, fit all the bearing locating

half rings and most importantly fit

the gearbox right-hand input shaft

bearing. Lower the crankshaft into

the top crankcase and locate the

bearing pegs. Make sure you have

the case dowels fitted. Smear the

bottom case with sealer, I always

use Yamabond, carefully fit the

lower case and fit the eight 8mm

bolts (12mm heads) and the four

6mm bolts (8mm heads). Torque

down the 8mm bolts and tighten the

6mm bolts. Next fit the balance

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v;Here we have the engine stripped. What so many KR1/S engines look like

now! And now the bottom case fitted.

stripping too much of the engine.

The gearbox is removed from the

left-hand side of the engine. Take

off the gearbox outer cover and re­move the gearchange mechanism,

then remove all the screws holding

the outer casing on. Be careful -

some of the screws are hiding! The

gearbox can now be slid out com­plete. Check all the gears for any

damaged or worn teeth or dogs.

Next, remove the ignition flywheel.

This requires a special but readily

available puller. Then remove the

ignition stator and the back-plate.

Turn the engine upside down and

remove the bolts holding the bal­ance shaft casing. Remove the cas­ing and the balance shaft. Remove

all the crankcase bolts, the 8mm

bolts (12mm heads) and the 6mm

bolts (8mm heads). Remove the

lower crankcase and take out the

crank. To strip and rebuild the

crankshaft is a specialist job and it

has to be rebuilt on a special jig to

ensure the big-ends are set at 180°

and that the centre gear is set with

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Gone and has damaged the crank-

pin which is part of the flywheels.

When rebuilding a classic engine

whether for road or for racing I pre­fer to have the crankcases aqua-

blasted and all the nuts and bolts

zinc-plated. Whenever you have any

parts bead-blasted or aqua-blasted,

always blank off any threads with

old bolts but when you get the parts

back still thoroughly wash all the

parts off and blow out all the

threads with an air-line. Be pre­pared to run a tap down all the bolt

holes if there is any doubt (tap as in

taps and dies, not the kitchen tap!).

A few golden rules when building an

engine; always fit new engine and

gearbox seals, always use new gen-

Thc top-case with crank and gearbox

bearing fitted: we've got a long way to Balance shaft timing marks on crank.go.

shaft, align the timing mark on the

balance shaft gear with the mark on

the crank gear. Locate the bearing

pegs and shields and fit the plastic

oil feed in the end of the shaft. Fit

the balance shaft casing and torque

down the four 8mm bolts(l2mm

heads) tighten the six 6mm bolts.

Make sure to use a counter-sunk

screw at the front casing bolt-hole

or the water-pipe will not fit prop­erly. Fit the steel water pipe with

new greased O-rings and fit the

large rubber water-pipe. Time to fit

the gearbox. Turn the crankcases up

the right way. There are no loose

uine gaskets, always use new lock

washers, always grease inside seals,

always oil all moving parts. Thor­oughly clean all the parts and espe­cially clean/blow out all thread

holes and clean the threads on the

bolts. I clean all the threads on a

wire wheel. Remember if you are

putting the crankcases together and

use bolts with dirt and grease on

them, as you screw the bolts in the

dirt comes up the threads and is left

between the crankcase faces. Don’t

grease the threads or the same thing

will happen. Another golden rule:

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shims on the gearbox; the only shim

which looks as if it should go on the

input shaft goes on afterwards be­hind the clutch. There is no gasket

on the gearbox - use the Yamabond

sealer. Check all the selectors etc.

are located still and slide the cas­sette gearbox in. Fit and tighten all

the head and then fit the KIPS valves

to the head m.* -

(All four valves are the same). The

barrels only have one dowel per

barrel but the head has two dowels

per barrel so when you fit the head

and KIPS valves to the barrels be

very careful and pivot each barrel

about slightly until all four head

dowels line up (this is why we didn’t

tighten the base nuts). Now lightly

nip the head bolts down and evenly

tighten down all the barrel nuts,

then torque down the head bolts.

The Kawasaki manual does not ex­plain how to fit and time up the

KIPS valves and linkage. I did an ar­ticle in CMM a few years ago on how

to do it - it’s very difficult to ex­plain but I will give it another go!

When refitting the KIPS system no­tice all four alloy pulleys and arms

are different and that two of the

three small connecting rods are the

same length, but the third is a dif­ferent length. Assemble the KIPS

valves in the head with the flats on

the KIPS spindles facing roughly

forwards. Fit the two pulleys on the

centre KIPS valves. The pulley with

open and closed on it goes to the

side with the valve timing pointer

cast in the head. The two outer arms

are different to each other and are

fitted with them facing inwards. The

two connecting rods of the same

length go between the pairs of

valves and the shorter one goes di-

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BSEthe mmmTiming marks on the balance shaft. The circlip and shim behind the clutch.Cover screws including the two in­

side by the gearchange. Fit the

gearchange mechanism and small

spring. Fit the gasket and cover.

Now for the clutch side. Fit the cir­clip on the input shaft (clutch shaft)

and the shim. Fit the idler gear and

kickstart shaft assembly and the

small alloy oil jet. Put the clutch

basket on the shaft and fit the

shim/spacer, now assemble the rest

of the clutch complete but just use

three springs and very lightly

tighten the three spring retainers so

that it is still possible to turn the

plates. Now fit the assembly onto

the shaft and jiggle the plates and

clutch centre so that the clutch plate

fingers locate into the outer basket

at the same time the splines of the

clutch boss line up with the splines

on the shaft. It’s a bit of a fiddle. Fit

a new retaining circlip. It’s best to

fit a new water pump seal. The seal

fits from the outside inwards and

needs pressing out and a new one

needs to be pressed in. If you

haven’t got the use of a press you

can use a large vice and a socket.

Now we've got the balance shaft fitted.

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Don’t fit the water pump cover on

yet because as you fit the large

clutch cover you can turn the im­peller with your fingers and engage

the drive gears. Be careful when fit­ting the cover that the steel water

pipe with its greased O-ring fits

properly and that the O-ring isn’t

displaced. The outer clutch cover

gasket and the water pump gasket

are no longer available, it is okay to

just use Yamabond, the clearance is

sqEe © 0 dfiThe complete water pump assembly.

agonally between the two pairs of

valves. When fitting the counter

sunk screws that hold the pulleys

and arms to the valves, make sure

the flats on the valve spindles go to­wards the heads of the counter sunk

screws. When the KIPS valves and

This is the selector mechanism.

okay. Now the top-end. Fit the pis­tons, rings and small-ends and base

gaskets and the base dowels. Fit the

barrels but don’t tighten the base

nuts yet. Put the head gasket onto

-X IIMOTO GUZZI LEJVIANSlen, B

HON PA C4tBuyer's Guide70s W

PM classic ■ motorcy* mec in

Now for the head gasket, dowels and KIPS

valves ready for the head.ALL THAT'S BEST IN MOD LASS/C MOTORCYCLING

4Os

Here we're fitting barrels over the rings.

KAWASAKI I

Seventies King of cool! m<

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--nj VV * .

A clutch stack of plates ready for assem­bly. cAnd - finally - what the engine should

look like!> % fffl/m

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*FIVEDECADESHere we see the KIPS links correctly as­

sembled.

closed position and check the boost

ports are closed. Remove the KIPS

chambers on the barrels and check

the hole into the exhaust port is

open. If that all sounds complicated,

don’t worry it’s a lot easier to do

than it is to explain it!

HNow the clutch side is ready. OF MODEM CLASSIC

MOTWCrClE MECH1HICS

’190mi Kawasaki KR-1S rebuild. Honda VFR400R

NC30, Honda CBR600 F-X Honda GB500TT. Yamaha

DTI75 and TZ250 S resto 70m: Honda CB750K2, Suzuki Stinger Rmt

Plum: Plastic repairs, electrics, Q&A and your memories!

50 XI

linkages are assembled, check it is

all timed up correctly. Turn the pul­ley to the open position and look up

the exhaust ports to make sure the

valves have opened the exhaust

boost ports. Turn the pulley to the

HIT SINGLE!Honda GB500TT ridden

Yamaha's XSR a*