Engine strip and rebuild

All items are for the 400/450, they may also be for the other models.

To confirm differences check out your bike's sector at the bottom.

Light blue for 470/501, light yellow for 550/650.

Also see Year recognition and changes and Common faults
to incorperate any chnges into the rebuild.

Husaberg 400/450 Models

Plan of action

If a complete stripdown is required it can be as easy to remove the rocker cover and head in sits as well as all the left cover etc making the engine easier to lift out. Stick a shaft through the S/A and frame so the bike can be wheeled about.

When rebuilding it's advisable that the entire engine is built and sealed (so spark plug in then!) because muck and grime among the electrics will find it's way into the engine. Also the kickstart mechanism ONLY JUST fits on the crescent and the slightest knock and it'll unwind necessatating removal of the clutch AND the possibility that it will happen (if the engine is upright in the frame and the frame upright on the bench) again and again. And if the left cover is closed, you don't want that silly camchain falling right down the bottom now do you!!!!

Strip!

Clutch cover removal

There are three lever tabs around the outside. Turn the cover over and file a gradient gently to allow a lever in and aid leverage.

Checking the mains

Put here because you can't check it when the engine is all stripped! Stand on the opposite side of the bike to the side you're going to try. Lean over the frame and grab the end of the crank with both hands as best you can and then try to push and pull; feeling for the clonk of a main bearing thats gone.

Measure crank float-NOW!

Crank axial float is vital and many engines have too little. Measure the axial float now and you can then make a decision as to what to do. Axial clearance is in 'blueprinting'. I have always whacked the end of my cranks left and right and measured using the heel of a vernier gauge what the float is. Tool of choice is a 'dead weight' hammer. Simply move the crank one way and mount the vernier heel on the crank and the tail on the bearing to measure. Move the crank the other way and measure again.

Breaking the cases (open!)

Undo all the screws to the cases and then replace two cylinder studs in the right-hand half. Use a hammer initially to tap upwards on the heel at the back of the cases. Then tap back down the end of the crank and both gearbox shafts. Use a drift and hammer on the input shaft - be gentle. Tap upwards the base of the two studs lightly and look for other excesses on the right-hand case that will allow a tap.

A thin screwdriver shouldn't be used unless as a last resort and go again to the swingarm boss area and the frame bolt holes on the front of the engine as the cases are very broad at these points. If the spigot area is difficult try to put a lever in halfway and tap down at the back to tilt the top - up! Remember that every little lift of the case must be accompanied by taps to the end of the three shafts....

Bearing removal

Gearbox output: The best way is to slip a gearbox bearing through the outside of the case while holding the inner race in the roller bearing. The inner race keeps the rollers OUT and the gearbox bearing just presses it all out like A.B.C!

Input, right-hand bearing: Easy

Right-hand main: The gearbox bearing next to it should be pressed out first and then it presses straight through the seal housing onto the right-hand main. Jobs a good un!

Left-hand main: Press out with gearbob bearing through the seal housing.

Top end rebuild only

When doing this the one thing difficult to check is the cam chain condition. If the sidecover isn't coming off then having removed the tensioner completely, feed another old chain on and remove the current chain. Measure the chain on a bench and then make your decision. The split link can be used without the sideplate or the spring clip. The link won't come out.

Stuck woodruffe keys!

When stuck there are two ways out. Firstly, tap one end down exposing the other and with good purchase by mole grips they will come out. Secondly, try drilling several times with 1-2mm drill bits being careful to get the centre of the key and not the shaft. This will loosen the key as it loses it's strength.

Diagnosis and preparation

Cleaning out the crank pin

It is known that the crank has just a small 0.5mm hole through which the oil feeds the big end. So blasting air the traditional way could be a bad move! Below is a system for reverse cleaning the crankshaft.

A peice of plastic tube runs across the end of the crank which is submerged in a bath of cleaning fluid

The air jet blasts along the tube and into the catch can. The run across the top of the crank sucks fluid up

Pin hole in crank. Block this for cleaning with a Dentist's pick

With this squirting oil, balancer falures are a thing of the past

To finish, bath the crank in oil!

Skim the barrel/block

Raise compression or for warpage. See this UHE Forum Thread. The spigot should be flush with the block or can be proud by up to .005" (Lineaweaver). It may pay to have the spigot and crankcase machined separately.

Drill funnel type hole

The right hand cases on the '01 -'03s have a small drill hole for oil to drop down the back of the main. 'Kiss' with a 12.5mm drill bit to create a funnel effect to collect more oil. Clean BEFORE you fit the right-hand main.

Re-using gaskets

In order to continually re-use gaskets (except cylinder head): try smearing them in copper grease before fitment, the rocker and WP gaskets will be re-usable many times but extreme caution should be taken with the sidecover gasket as half will stay 'down' on the dowels and half will try to come away with the cover!

Re-using the headgasket

This is especially feasable with the blue-lined gasket. Don't just leave the gasket on the head, remove and clean both surfaces as well as the gasket or they WILL leak. Renew if you're not a cheap-skate!

Case and Cylinderhead screw tightening

Tighten the case screws lightly, then the head lightly, then tighten the case screws, then torque the head down. The longest screw goes into the middle of the cases whilst the four shortest go each side of the top of the 'block'. The rest go where the rest of the holes are!

When fitting new mains - at home!

Tape the old pair together and lay on the workshop floor under the outside of the crankcase half. You'll also need a small piece of wood for good support at the back of the cases-get this right before the crankcase comes out of the cooker!

Also put the cases in the oven and the bearings in the freezer for a long time before doing this. This allows full expansion or contraction of items.

Big-end play

To check for big-end play fit a feeler gauge down the side of the piston and THEN try pull/pushing the con rod.

Wear limits crank

Another good way is to hold the assembly by the little end in one hand and slap up the crank from below. this will produce a clonk if worn. A well oiled crank will disguise this.

Screw jet on end of crank

Although it looks like it is part of the crank, there is a screw in the left hand end of the crank that can come loose. It has two flat faces for a small 9mm spanner to tighten with thread running in the usual direction.

Crankend screw

Wash crank gallery

If just stripping engine to replace the big end bearing or for inspection always try to wash the oil feed gallery through the crank out using a pressure engine cleaner/degreaser. Work from both ends and be thorough. The restriction points are the above mentioned screw in the right-hand end as well as a fine hole into the big end. It's likely that these two small holes have been blocked and been the ruin of many an engine...... From '04 you'll also find a very, very fine hole in the left-hand crank cheek on the opposite side to the big-end, this feeds the straight to the counter-balancer bearings.

Big-end sidefloat

Impossible to measure as the big end bearing is recessed into the flywheels.

Pressing the crank together

Some info here. The clearance is in the book but here is another way to measure, Problem is IF IF it has a wider rod.

Measure across crank wheels (micrometer) (Neil_E)

Gearbox - erratic selection

The hardening can come off the teeth, dogs wear at the edges and gears are missed and jump out. It's normally the gears on the secondary shaft that get it. Unfortunately, with their oval end profile they can't be saved. Any shinyness here on the corners and corners that are more rediused then you'll see elsewhere mean that the selection is going to start breaking down.

Hardening gone off 5th gear. (Weed)

Little end/wrist pin bush

The 450501/550/650 little end/wrist pin bush will spin in the rod-nothing will stop it . The little end bush can be delivered loose so order another and another until one arrives that's 'nice' (Lineaweaver). Look for spreading. A worn little end will be wider at the bottom of the hole than the top and sticking out of the rod's eye.

Piston scoring

If you find signs of piston scoring on the thrust faces-don't touch but leave-as this will reduce the diameter of the piston.

Rings

The rings are Chrome in a niksail bore which isn't ideal and makes it two VERY hard materials. The rings should be replaced not because they wear - they don't! but because they lose their strength and flutter in the bore (on some pistons). The factories end ring gap is certainly a minimum. Change them each season if racing.

Spigot ovality

Not as rare as you think! It really might be that the barrel has lost it's shape so check. Possible to go to 101mm KTM piston to get over the ovality. A simple way to check is to hold the spigot on the rings and then turn the spigot around. if it goes hard-easy-hard you know the answer!

Wear limits piston

If you lack an internal micrometer a simple check is to fit the piston complete with rings and then turn the piston in the barrel. Easy, hard, easy, hard means oval. You judge...

Honing the spigot

This can be done with alacrity as the bore is well safe. It will show up low spots and remove a lot of rubbish. Spigots can be saved if mildly chipped but welding on the bore is a no-no except for the 400 which has a bit more 'meat' on it. A proffesional engine reconditioner should be used to hone the spigot because it's at the bottom, around the cutaway that the proffesional equipment can do a better job than a 'home-hone'. Worth the money.

Clear oil ring marks. So how will YOU! hone this out Mr DIY man?

Rocker pads - concave

The pads must be checked for 'cupping'. Cupping will ensure odd valve opening as they move about - especially if the arms have too much float! View by looking at the reflection of light in them. They're relatively cheap to replace.

Badly cupped tappet pads

Cam follower bearing check

The inlet bearing can be checked in situ but the exhaust rocker arm MUST be removed for a proper check. Be careful to push pull in line with the contact with the valve and not laterally and the most important area to check is in line with the valve stem as the underside of the pin wears that faces the tip of the valve. Any looseness detected, tap the pin out and check the condition. The walls get scored and ditched but can be filed flat. If you ever replace a CFB, always keep the little blue spacer to help do this check the next time - it'll keep the needles in place. If the pins are partly out, they must be pressed back in and the shoulders (not the pins) punched to secure.

Tuliped valves

Always check the Inlets, they're usually tuliped if any high revs have been used. They can be cleaned up and their total width reduces as little as by 0.2mm but on average around 0.5mm. The seats on some Husabergs are very narrow, in which case new valves will be required. The 37s are more prone to it and also more expensive!

Rocker shaft wear

With the '01 - '03 heads the pins can be turned over if money is short. Wear is on the underside of the shafts. Best to make a note when removing of course! The bushings in the rocker arms are very hard and last better than the shafts.

Wear limits head

Rebuild

Counterbalancer retention

This is a major decision as they can fly to bits. If removing, simply knock the centres out of the ball races and refit the inners to space the crank.

Present only the crank initially

Below is a description of how to press in the crank but do try to only fit the crank initially and check side (axial) float as well as the fit of the bearings both in the cases and on the crankshaft. Husaberg's main bearings are far too tight a fit both into the cases and the crank's fit into them. If they are a really tight fit the mains feel notchy. Check "Blue printing" for correct tolerances and how to achieve them.

First fit the...

Not the most obvious choice but fit the intermediate gear shaft first in the left case. The reason for this was that the shaft has no circlip to keep it out while the sprocket and gear are pressed on. Support the shaft from behind as they are fitted and then tap the shaft right out to finish. NOw fit the small woodruffe key, sprocket and the gear before adding the nut - locked up or otherwise. Its vital that you 'DRAW' the WP shaft back out again as it will have moved into the engine.

Fitting and timing the balancer

The timing mark on the W/P shaft gear is a very large and clear punch mark, on the balancer it is in the bottom of a tooth and if still covered in oil will be invisible! Mark the end of the balancer plate with a felt-tip pen, firstly on the end and then behind the balancer. Thats right - behind! Having fitted the crank into the left cover you can look through the crank's drilled holes to view the balancer and the gear. It is possible to make last-minute adjustments through here. You can even tap the balancer down to engage and then tap the crank to catch up!

Dot on drive gear to balancer	Dot on the balancer gear close-up. Now mark the end face and then carry the mark on around the back!	Balancer drive gears meshed. Note the felt-tip mark on the end

Pressing in the input right bearing

This is the bearing that can go right through the engine! traditionally you would press this bearing like all others in from the 'inside' but because the outside of the case has about three levels it is actually best to rest it on the inner face and press in the new bearing from the outside!

Inserting the crank assembly

One need's to have a true crank to start with, install a chisel between the flywheel cheeks with big end pin at bottom, insert crankshaft assembly into left-hand side with crank seal greased.

Then press the crankshaft assembly till lightly seated! keeping a good eye on your timing marks on the waterpump shaft and balancer, does the left-hand side spin freely? Piston is now ready to install so a circlip must be installed on the left-side of the piston, slide down on rod as an assembly insert piston pin and other clip. Now fit the spigot and then the right side cover should now fit smoothly or some heat must be used on bearing! (Brother Boss!)

Second version: Place the counter-balance down, meshed with the WP shaft gear. This should lay upon any previously agreed shim. The crank assembly should consist of the crank,rod, fitted piston c/w rings and already inside the spigot and on the spigot should be the 3 spigot rings covered in a light silicon film. Drop the crank in whilst trying to see the felt-tip mark etc as the crank goes through the balancer assembly etc. Fit the R/H cover and as it is gently 'closed-up' tap the top of the spigot down.

Tiny crankcase 'O' ring

The 'O' ring for the cases and also for the head to rocker interface is often missing from gasket packs. In the absense of the correct parts simply coil up some 1mm solder into the correct shape. Sometimes there isn't a machined recess for it either.

Piston circlip fitment

Place the piston circlips in with the 'C' facing down.

Fitting the rings in the spigot/linar

No ring compressor - no problem! Get all the ring gaps to the same side as the cutaway in the spigot. Then as you feed in the rings around the back (easy) you can tuck them in around the front as you go. I use the flat face of a flat bladed screwdriver and just crush the rings down/in to the groove.

Spigot 'O' rings

The three huge spigot 'O' rings in place and to seal by putting a smear of silicon around them whilst in their grooves ready for fitment. If you ran the bike without coolant and cooked the engine you must purchase new ones as they will have overheated and lost their rubbery-ness!

Working around the engine without the gearbox flopping out

Just a simple zip-tie will keep the gearbox in place while you work around the left cover or crank etc etc.

Zip tied gearbox

Gearbox noise/whine

It could be you can hear a noise coming from a 'whining' gearbox. This is noticeable at any speed, any gear, any time. If there is too much endfloat in the output shaft gears will rub inside. It's not dangerous but is avoidable at a rebuild. By using thicker shims the float can be reduced from a noise inducing.020" (0.5mm) to .008" (0.2mm). JoeUSA has the answer!

Parts including custom stop disc (JoeUSA)	OEM & custom stop disc, shaft (JoeUSA)	OEM & custom stop disc (JoeUSA)	Stack assembled with custom stop disc. Perfect clearance for retaining ring. (JoeUSA)

When fitting the gearbox

When fitting the gearbox in the L/H case, this is the order; output shaft half in at a slight angle, input shaft straight in, bring left shaft upright and press both down and in. Selector forks fitted, selector rods through forks but not located in cases but separate them as wide as they'll go apart from each other. The single fork needs to rest on the case half. Fit hollow washers on forks, move over into the selector drum which has the drilled hole in the end placed at 1.30pm. This is virtually neutral. Push the fork selector rods home into their recess.

The order of the gears on the bench should be (as if sat above them):

Both 19 and 23 are on one gear and appear to be fittable either way around so be careful. The gear in the parts manual (2001/2) coded #31 is shown as the wrong way around to the correct fitment direction.

Crank seal

Fit crank seal after you're happy that the cases are now closed-for good!

Working in the left side of engine

When working in the leftside of engine, fit the reed valve first so that anything dropped won't go through and in to the centre cases (Simon).

Gear selector

When trying to find neutral, remember the selector drum is clockwise to 6th and anti-clockwise to 1st gear. Turn ACW from 1st a little for neutral, check by holding one shaft and turning the other. Sometimes you can change gear simply with a 10mm socket on a speedbrace. Do this till you are perfectly satisfied that neutral was one gear and a fractoion from the end of travel. Then fit the star with the odd part ready to fit the sprung wheel. Position: The short pin should face the front of the engine for neutral. (Simon). Why not mark a pin when disassembling so that the star goes in the right place and you have the bike in nuetral.

Timing gears

Try and retry to get the single upper dot between the two lower dots as per manual. It's worth pursuing. It may appear 'nearly correct several times. Try using a ruler and closing one-eye! When fitting the two timing gears, the 2-dot gear fits the crankshaft and the 1-dot gear the intermediate shaft. The important thing will be later and the cam timing though....

Here is a diagram of the timing.

When fitting the lower timing sprocket and the intermediate gear

You'll note that you have a choice of two slots for the woodruffe key. You can tell thier old positions upon reassembly by the 'stain' on the shaft created by the 'dummy' groove. If struggling with the woodruffe key infront of the lower timing chain sprocket-just grind the end off slightly. Tightening the nut on the countershaft will draw the shaft right through eventually. You'll have a shorter key but it'll be fine.

Crank and Intermediate shaft nuts - recess face-in

Be warned, the nuts have a recess on them. this should face the gears because the ends of the woodruffe keys are proud of the gears. Fit them the wrong way round and they can't be tightened correctly. 10 hours and the engine will fail!

Kickstart crescent screws and gear selector central screw/post

Vital that these are carefully removed, oil cleaned off and a bonding agent used to keep them in place. They are physically hit from the side which isn't their usual task and are therefore susceptable to loosening. Torq screws are now available at the dealers so a greater tension can be used.

Clutch basket

The reason the clutch basket won't drop in its place is because the plastic oil pump gear needs a 'flick' around! It can be reached through one of the back holes in the clutch basket. Use the wooden tail of a small hammer within the basket around it's cirumference to just agitate the basket down into position.

Clutch plates

Change the outside plates into the middle and vice-versa so as to spread the wear throughout the pack. Split the pack in the middle and simply turn the middles to the outsides and then arrange the friction and steels...

Wear limits clutch

Later tensioner blade

If you find a yellow one you must replace with black and remove alloy stump off the tensioner. The balde will also need a small amount of shamfering on the top 2" otherwise all the pressure is at the sprocket end.

Rocker arm float

This can be found by fitting the rocker cover and screwing down then undo just the two screws over the end of the shafts. By tapping in with a light hammer the float can be adjusted.

Removing the decomp cables and lever

With the latest decomp fitted there is no need for the: Kickstart decomp assembly Manual decomp assembly Bracket on head Decomp lever The hole can be filled by tapering gently a 6mm allen head screw and leaving inside the head with the nut on the outside. Exactly the same goes for the kickstart decomp, taper a screwhead, add some silicon, pullinto the case and nut on the outside. a rubber 'O' ring can be placed on the bolt shaft and squeezed in the hole for added reassurance.

Inverted screw up into cylinder head

The only upward facing screw is not removable with left sidecover on if you have a 400/470. Change from Allen head to a normal hexagonal head bolt when you next have the cover off. This will allow work on the head without removing the cover.

Cam timing

Perfect cam timing

To perfectly time the cam you need the engine at exactly TDC, then lay a ruler across the two lobes as they both sit up at 11 and 1 o clock. The ruler should be parallel to the cylinder headand can indeed tilt forwards ever so slightly to allow for future camchain wear. To change the timing you need to remove the camwheel completely and rotary file the slots to elongate them.

At the cylinder head

Rotate engine to exactly TDC (TDC is equadistant from the left to right line but repeated to the right of the right line), and have the cam lobes pointing up at 11 an 1 o' clock - they must look symetrical. Fit the tensioner and release it to let the camchain tighten. The cam will rotate backwards slightly so check that the lobes are still 'balanced' and level with top face of head - use a ruler diagonally layed across the lobes. Is it level? It doesn't hurt for the ruler to tilt slightly towards the front wheel. The wear in the camchain is worth 2mm of turn at the outer edge of the camwheel by the end of it's life. This will tell you that the cam timing will 'come right!'.

Cam timing adjustment

Minor changes: Possible to file the camwheel bolt holes oval. In the above, allow the cam lobes to tilt down ever so slightly from level with the head. As the chain wears the cam timing will go from 'leading/advanced' by 2-3 degrees to 'spot-on'. If the camchain link isn't where you want it, turn the engine over 3/4 times until it is. It moves on a bit everytime. Remember, you won't hit the piston if you are as much as a whole tooth out, Husaberg built a generous valve to piston gap into the engines.

Major timing changes

One tooth via the straight cut gear on auxillary shaft (Crankshaft drive, clutch basket ring then auxiliary shaft) will change the valve timing by 11.6 crankshaft degrees. One tooth via the camshaft driven sprocket is ~ 24 crankshaft degrees. (Lineaweaver). See timing diagram above.

Decomp stopper bolt

The decomp weight hits this one. Peen over the threaded bit of the bolt to secure. (Ausberg)

Rocker cover breather tube

These can be loose and be the cause of the front left corner oil dribble! Remove spigot, clean both threads and use a gasket fluid before tightening back in.

Plane the Rocker cover and upper side of head

The rocker cover can be cleaned up and plained flat by simply mounting a sheet of P600 wet 'n dry on a pain of glass and with the use of soapy water rub the cover 6 strokes before turning 90 degrees and continueing. Do as little as possible as the cover still has to press on the cam bearings. The Head can carefully be done either the same way while the valves are out or chasing around the outside with a small but straight peice of flat and plained wood wrapped in wet 'n dry again.

Sealing the rocker cover

Particular attention must be paid to the use of a good bonding agent between the rocker cover and the head. Run it around the cover not the head and then let the agent cure and fit. Best results come by leaving overnight.

Left cover crank oil seal

The seals can be nudged deeper into their housing when fitting the left sidecover. Use a later oil seal with steel circumferencial backing. These need to be nearly driven in and are unlikely to move accidentally.

Crankshaft oil seal, metal vs. OEM rubber. (Bergoroadracer)

Clutch cover fitment over waterpump shaft

590 29 005 010 is a plastic sleeve that is slipped over the water pump shaft, so as you install the clutch cover, the water pump seal is protected. (Fryguy) Another way to do it safely is to fit the sidecover and THEN add the oil seal afterwards.

Losing coolant

If using same headgasket again... May try torqueing down to 60Nm. This is 15Nm above factory numbers on pre '04 bikes which became the standard torque setting from '04 onwards.

Oil leak from weephole?

Don't forget to clear this out of dirt and filth. Oil leaks from the engine past the bearing in the sidecover. The shaft has an 'O' ring on it and oil passes this.

When fitting a new bearing in the cover make sure the rubber seal hasn't come adrift from the bearing. Also make sure the ditch created for the oil or water to vacate the engine is clear or deepened manually so that it is effective. The Rubber face on the bearing can tend to block the path.

Waterleak from weephole

Drips coming from hole. Not too bad. Trick is to replace with two thinner oil seals. Also newer seals are available with a hardened metal backed shoulder. Easy to fit, they also seem to last well. Remember also that there is a factory tool to aid fitting new seals without damaging the lip. See this UHE Forum Thread.

Check the back of waterpump cover

Many an impellor has come adrift and owners haven't machined flat/renewed the back of the cover. The cover surface should be perfectly smooth.

Waterpump seal

Check that it is located correctly relative to the weep hole. On some models it may be necassary to epoxy the original hole and drill again. The oil seal in the sidecover should have the part numbers facing you.

The coolant 'O' ring in the left cover overlaps with the cover gasket. Cut the cover gasket around the 'O' ring. Recent gaskets have this cutaway already. To keep reusing the same gasket: smear it in copper slip.

Wrecked the gearbox seal? In a panic? Fit the old countershaft bearing and then an 'O' ring as a get-you-out-of-trouble-for-the-day fix.

Engine oil

When fitting the inlet stub, the tiny (moulding) nipple in the middle should be underneath. It looks symetrical but it isn't!

Engine oil

You'll need 1200ML of oil to re-fill from a complete rebuild. But an oil change alone needs just 900cc to bring it to the lower oil window lower level. It's very important that the oil stays at the bottom of the window ass, oddly enough, they are prone to overheating... Oil pressure 15psi @ 3,000rpm (Lineaweaver).

Refitting the engine

Drop the engine into the frame and very loosely fit the front mounting bolts, then the swing arm pivot pin and tighten, THEN tighten the engine mounting plates. If however you have a linkless final drive chain you will need to fit the front sprocket, remove the chain from the rear sprocket and before you push the swingarm onto the back of the engine, feed all the spare chain you have past the gearbox shaft and onto the sprocket. SM engines with 15T+ make it very difficult to fit as there is a recess in the rubber protector at the front of the swingarm.

Fitting carb and airboot

It is best to fit the carb into the inlet manifold, then into the boot and then the boot onto the frame. Now screw the inlet manifold to the head and then adjust all joints for shape and comfort before tightening both clips and the manifold bolts.

Stator wiring

Is as follows; yellow into a double red, second yellow into the regulator (second from the right), light blue into a brown (or earth carousel), black into black and green into green, pink to pink.

Kickstart fitment

Remove the outer gear for now so that you have just the splined shaft complete with 'keyhole' ratchet and tiny spring fitted. The diagram in the parts manual shows the kickstart spring the wrong way around! So you need the straight pointed end to face away from the bike at YOU.

Fit the straight part of the spring into the tiny hole in the kickstart mechanism and then fit the hooked end into the engine case feeding it all in as one. Leave the body of the splined shaft OUTSIDE the crescent and re-fit the kickstart arm. Start winding the unit clockwise until the 'keyhole' shaped ratchet piece goes past the high point of the crescent plate. Now, holding the keyhole 'closed', press the unit down into the case and release both the keyhole and the kickstart arm. The unit will turn itself counter-clockwise and rest against the shoulder of the crescent. Now remove the kickstart arm and you're ready to fit the gear on. Because the keyhole is 'closed up', the gear will drop over!

Spark plug fitment

Apply a light coating of coppergrease to the threads EVERY time you remove the plug.

Ignition timing

Firstly, you need to know that the timing mark on the '01-'03s is always scribed wrongly. The real TDC can be found in 'tuning'. Use a strobe with a timing adjustment knob. Set the timing so that the line on the flywheel meets the mark in the spy-hole with the revs high enough that the advance of the flywheel marks have stopped, you are now at full advance. Using the adjustment knob look for 64 to 72 degrees of advance. Half this figure is your real advance. I.e. you have 72° which means it is 36° advanced. (Lineaweaver) You want 32-36°. This also means that when making adjustments to the timing, a one degree turn of the stator will actually change the timing two degrees at the crank.

Engine cutaway

Engine cutaway. (Grok)