Carburation

This area is dedicated to the carb.

By reading the Engine tuning article, you can put all the information together.

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.

Reference documents

• Calibration Chart for FCR, CRS, PKW, PJ, PE
• FCR, FCR-MX Jet Needles

Fuel deterioration over winter

Letting fuel sit in the bowl for 3+ months will allow the fuel to evaporate, plugging all of the jets, unless you have the tank taps open and the right preservative in the fuel. This situation is made worse if the gas has alcohol in it like in the States.

Use 1.5 fl.oz. per gallon: of LUCAS upper cylinder lubricant to help lubricate the exhaust valve guides and keep the fuel from drying out to a hard lump. Also use 1 fl.oz. per 16 gallons of STARTRON enzyme fuel treatment when it looks like the riding season is over.

The STARTRON is formulated especially for the modern USA type fuel now used. It prevents and reverses E-10 ethanol enhanced gasoline problems. STARTRON is made by Star brite in the USA at www.starbrite.com

Tank discolouration

It used to be a big problem with pre '02 fuel tanks that any fuel left in for a long period of time would discolour and 'suck out' the pigment of the tank. Try to leave in the dark, covered by a cloth etc for the winter and to either leave with a full tank or an empty one with the above precautions in mind.

Carburation related subjects

This section is dedicated to the carb. All other parts of the engine are set to facts and that is that, but the carb is set as a result of all the other settings, according to dampness, humidity, altitude, to temperature. It's set in reaction to an exhaust system or a cam. Very few vehicles are the same BUT they are all close on the Husaberg. We'll start by referring to the Keihin FCR and then at the bottom; the Dell Orto.

The art of Jetting

When a bike comes to you it hasn't been set for your weight and riding area (suspension), gearing to your wishes and finally the jetting for your climate.

Firstly, if a bike is set rich and you ride in a very warm climate you may be raising the temperature of the engine by getting the jetting right. A rich running engine will run at 500F, correct jetting is 800F and lean is a colossal 1,300F! But you should aim to jet correctly and deal with temperature issues later.

Because we don't have rev counters the easiest way to describe the area of revs is to describe you accelerating with neither revving out or short shifting. As we get faster we change gear later and rev further in each gear. Therefore 1st and 2nd gear area is Idle, Pilot jet and some needle. 2nd, 3rd and 4th gear can be on the needle and 5th and 6th the transition from needle to main jet.

The Keihin must be set from the top down. So MJ, then needle, then PJ, then needle straight. All along, the PS will need tweaking to get 'snap' back.

If you are serious about your tests you can remove the radiator cowls and block one fuel tap/line(left) and this makes quick changes really easy. Another thing to do is make testing the reason for a ride and get it sorted! Take the few tools you need.

Write down all the results at the end. The most changes you'll make are say 6-8 in a session. On getting in the Car or, going home, write down how each change felt and on another sheet make a grid across the page:

Under 'others' i would write those things that change with a blue moon such as 'choke jet #85', 'FX tailpipe' or 'LX2 cam'.
In the description you might write:
Test 2: MJ 160 > 155. Bike hesitated at low revs but went faster in 5th and 6th.
Test 3: Needle C3 > C4 hesitation is now gone, no loss at the top.
Test 4: PS adjusted 1.5 > 2. better snap!

So now you've got a faster bike at the top end and dealt with the resultant issues! you may now call yourself a JETSETTER !

Keihin FCR

It can be bought used from e-bay or a breakers. The 39mm are ideal for the 400/450 models. It provides better starting, sharper response at low speeds and smoothes the engine out so much it's almost unsettling compared to dell orto! ('98-'00 WR's, '98-'99 YZ's as well as DR E's and KTM 400s use the Mk1 carb @ 39mm.) On a used carb you will need an inlet spigot from Keihin dealer. Also as below-a 2-into-1 union for your fuel pipes.

Take 5mm off the original inlet rubber stub, which keeps the MK1 carb forward, the lip in the groove and the bottom of the carb off the starter motor. Block off the TPS: I used an old suppresser from a fluorescent light (UK). Do the "Taff mod" to the (Mk 1) carb using a wheel collar or block connector on the APJ. You'll need throttle cables from the '04+ Husey. or order these parts: Suzuki Goose.

"Suzuki Goose" adapter for the Keihin carb. If it has "33F" stamped into the side, you've got the correct one. (Kzoo)

FCR 41 Filter adapter KE 021-212. Adapter O-ring Kawasaki 920-55-1492 (Lineaweaver). See Useful part numbers and non-OEM equipment for Yamaha part #. Then purchase the jetting that is recommended below as well as a 'pilot airscrew' (PAS) to replace the PAJ. This gives variety at the turn of a screwdriver to your pilot jetting settings.

The FCR's fuel inlet was against the pipe and boiling gas, so what do you do? You move the inlet to the other side, using a home made fuel plenum... One problem solved. (Kickaberg2)

Cover reinforced, epoxied and tapped for AP adjuster. (Puggy)

Carb mounting collars in place, nearly done, yeah right. (Puggy)

Guidance

Here's a nice article on understanding the carb, The graph is of the Keihin FCR (Sparks). And here is the well known feature by Patrick Burns.

Taff Mod or BK mod

Reducing the APJ pump squirt

For both mods the idea is an immediate start and early stop. It is only useful for jumping logs from idle or wheelies etc. The rest of the jetting should be set with the Accelerator Pump Jet (APJ) closed off completely. At the end of each day it can be re-connected: otherwise it can confuse results. Remember: A CLOSED APJ OR AN OPEN ONE - NEITHER ARE RESPONSIBLE FOR "THE BOG".

MK1 Carb - Taff mod

Where the pump arm enters the side of the carburettor body a toy axle block or block connector (UK and Commonwealth)should be fitted. Make sure that they fit under the rubber gaitor so that water stays out of the float bowl. The block connector needs the plastic removing, a screw and the other shortened so it is down to the block. The rod wants to plunge just .6mm or as the carb gets older and the pump action a little poorer perhaps 0.8mm. This gives a short sharp squirt of fuel ONLY from a closed throttle in either first or second gear as a rule.

Mk1 carb from the right. This is the block connector fitted. Picture: Charles de Bolt from TT. Cheers 'Lightfoot'!

Mk2 carb from the right Acclerator pump timing (DaleEO)

MK2 Carb - BK mod

Under the right cover is a screw which allows the squirt start point to be altered. It should be set to start as you touch the throttle. There is also another tab cast into the body which you will note: a drill could be used and the 'tab' threaded to allow a similar screw to be fitted as well. This screw would then stop the squirt from continueing.

Balance of carb and areas that jets work

If you jet down 10 on the MJ the needle will need to go up around 1 to 1.5 clips to keep it the same mixture ratio as before. This is because the MJ feeds the needle area. Since I started testing, the MJ has come down from a very safe 170MJ to what is now a 145MJ. That represents a drop of 10 jet sizes and the raising of the needle 4 clips. This represents roughly a clip to every three jets.

Main air jet

This is only to be found on the Mark 1 carb so if you don't have the external plunger rod on the right: you haven't got one! It sits in the open face of the carb at the bottom, next to the PAJ.

It's dead easy to play with as a 180MAJ is a 1.8mm drill bit! and again like the PAJ it isn't as critical as the MJ which it serves. The jet lets air through to mix with the MJ fuel as it rises up the emulsion tube. The higher the revs, the more it gets added to the fuel leaning it off! It is most effective at maximum revs - the redline - and can therefore be used to lean or richen the mixture from say 8 - 11,000rpm. It will only slightly lean at peak power (8K) but then as the pulses join and it becomes richer the MAJ is there adding air to lean it off! What you need to know is - by how much?

I ran my jetting down to a 145MJ and a 200MAJ, i went to a 155MAJ and this made the bike richer to the red line and also quicker, so then i had the right curve of fuel i now just needed to check the MJ and in tests the 145MJ was better and now not just to peak power but all the way to the redline. It's all about a fuel curve.

The problem is that all bikes are jetted rich and therefore shouldn't have an overrev because there they are hopelessly rich! So all manufacturers put in the biggest MAJ they can to lean them to the redline - so that's a 200 then!

The tube through which the MAJ bleeds is some 2.3mm in diameter which means that any MAJ can be drilled to 2.3mm for a #230 IIIFFF this is the way you want to go.... after that you would have to physically drill the passageway of the carb.

Yamaha FCR parts

Yamaha needles are coated to stop them wearing out whereas those supplied by sudco/allins etc are brass and not quit so durable. Also, Yamaha supply a range of choke (named 'starter') jets that you can't buy from Sudco/Allins. Needles: EKQ = 5JG-14916-E1 DRQ; 5GS-14916-R1 *DTQ; 5BF-14916-D1 DUQ; 5TJ-14916-D1* CVQ; YZ450 part?

Starter/choke jet codes all start: 3TJ-1494F-21 (21 is the example) and then as follows:

Lineaweaver FCR needle

This is a combination of the 'D' and 'E' series needles and is worth it with a clear kick at the top end if you ran a 'D' and at the other end if you ran an 'E'. I'm not saying it's good-but he wants it back when yer done!

Needle codes

The first two letters on the needle are either OB or OC. OB needles are produced as an order by a bike manufacturer for their bikes and are cadmium? coated and silver in colour. The OC needles are brass, brown in colour and produced by Keihin for their dealers to sell. So OC: EMT, DMS, EMR will come from Sudco/Allins and OB: DVR, EKQ, DTQ, DVP will come from Yamaha. Also check out this document: FCR Jet Needles.

Honda needle - NCVS

Honda make two needles coded: NCVS and NCVR. Against the trusty OB DMS, Gokia134 found the NCVS to be better off the bottom. Setting: 162MJ, 40PJ, 80PAJ, NCVS needle on C3. At present, i'm not sure of the needle profile.

FCR 41mm Carb

It benefits all models over the 39mm (Lineaweaver). I have found only a small gain at the very highest revs (SOTP) on the 400 but bigger engines will have better results. Next test is to fit a proper belmouth.

Cookeye and I have bored our's out!

42mm - or more

The carb should infact be suited to 42mm as the boring out will create a smooth entry into the carb. We have had a member bore the carb to 44mm by using a thin steel ring in the middle.

Belmouth

Dr. C and Lineaweaver have used an alloy spigot but Takis went to great lengths to get it right and tried many air filters and belmouth lengths, shapes and curves. I have done this mod and it really improved 2nd gear low rev roll-ons in switchbacks etc.

The carb complete with belmouth and spacer ring, fitted in the bike, with the filter. It just kisses the back frame brace and the underside of the old 'sock' mounting point.

Motion Pro high dispersel jet

The FCR emulsion tube is solid and doesn't allow air to break up and aireate the fuel. However the Motion Pro tube has 8 tiny holes drilled up two sides and adds air particularly at low revs and buzzard's view here.

The tickover/idle

It stands to reason that when you start the bike from cold that the bike needed choke. So that's a rich setting: to run correctly. As the engine warms we lean it off by reducing then removing the choke. None of us would presume that at the moment we do this that the bike has perfect jetting I hope? We know that without the choke it is slightly lean. A minute later as more heat goes through the engine we trust that at last the jetting; the mixture, is what was required and the bike jetted and designed for. So it stands to reason that the warmer the engine gets the leaner it needs to run compared to moments before. Therefore, like the choke tests below, we can listen to the engine for two things: the first is the daga, daga, daga noise that tells us it is too rich here.

The needle straight should be enlarged, say from an R to an S.

The second noise is more likely to be the raising of idle by just as little as 100 revs. At last the engine cries as the temperature soars: the right jetting! But the engine is now past the optimum temperature and fuel may well vapourise rather than atomise so we need to richen it slightly. Richer is cooler and this will reduce the chance of a 'splutter' when opening the throttle.

The needle should go down one letter from say an S to a R.

Setting the TPS

To reset the TPS on the Keihen carb the engine has to be idling at manufacture's spec - 1,800RPM. Disconnect the plug from the TPS measure the resistance across blue and black wires it should be 750 Ohms + - 25 Ohms at 20°C or 68°F. (Sparks). There are two readings to be taken, the first is often close to 750 but it's been found to be nearer 1100-1200 instead of 750 at the second (DaleO)

Choke

Identify the correct choke jet

Every change at the lower end of the jetting has creates a problem or change elsewhere and therefore affects the choke jet size.
The dell orto carb has a choke jet that can get bunged up-especially if the bike hasn't been used for a couple of months. It will need cleaning out and should be held up to the light, the hole should be quite large but the trouble is that after cleaning it may be no better. It should appear to be at least 0.5mm.
The jet sizes on the keihin are actually basically only a metric drill size so a 180MJ is 1.8mm etc, that doesn't though make it smart to go around drilling jets though!
The important thing is to LISTEN TO THE ENGINE. This is something that few people do. They bitch coz it doesn't start yet the engine is trying to tell them something!
The reason we have fun with carbs is because it's the LAST thing we fettle. Everything else is set and the carb REACTS TO THE ENGINE and that is the fascination and why it is so hard to help with each machine.
So this is what to look for when starting a bike:

Lean on choke: The bike is a bitch to start and takes 30 kicks. each time it starts it runs a little longer until after 5 minutes it runs-just! But you daren't touch the throttle for another two or three minutes!

Slightly lean on choke: After "quite a few" kicks, the bike starts and judders for anything up to 10 seconds, you daren't touch the throttle before it builds up revs gently on it's own. It then starts to rev like an idiot compared to starting! this bike will never 8-stroke and you can go to the loo/tog up ready, lock the garage - the lot-it ain't gonna stall!

Spot-on: The bike starts after three or four kicks, it runs at medium high revs for at least 30-40 seconds before starting to 8-stroke mildly. It should run straight away at high revs and not build up and the revs should stay the same for over a minute before perhaps 8-stroking mildly and losing revs-it shouldn't stall and or 8-stroke any sooner.

Slightly rich on choke: Bike starts well everytime but you need to blip the throttle almost immediately or the revs might drop and it might stall. There is no chance to even get a glove on. The idle isn't even high - it just runs at a regular idle and then the note of the engine changes oh! so quickly to 8-stroking.

Rich on choke: Bike starts fine but within 1, 2 or 3 seconds it 8-strokes, the engine note immediately changes and the choke can be turned off. Alas, without the choke, you can't touch the throttle so you may even try a bit of choke again or revert to revving the engine before it has really had a chance to warm up. This is bad news for the bike!.

What is 8-stroking? Well the best way to describe it is to write it: When the bike starts and all is good it has a: Br-r-r-r-r-r-r-r noise. As the choke becomes too much this will change to: daga, daga, daga. Then the choke is too rich and it becomes: ga-daga,ga-daga ga-daga. THIS is 8-stroking!

On the keihin carb even the MJ affects starting - seriously! so every mod you make has a knock on effect. Different choke jets are available from Yamaha but you can't get them from keihin for some reason (well it used to be like that!) so Yamaha are the boys!
I have several choke jets and i used to always be swopping them out. Everytime you change the needle straight (very last suffix letter) you will affect the starting. The PJ is only a small part compared to the needle straight and I have estimated it to be 80%/20% needle straight/PJ effect on starting with the FCR.
With the dell ortos, the starting is really just the effect of the choke jet combined with the slide cutaway and PJ. that's why it's a lot harder to understand but not necassarily a problem in itself. So next time listen to your engine!!!!
Quick starting or Easy-to-use starting? From the five grades listed above you may have decided that the 'correct' jetting is the one for you! three or four kicks, gently 8-strokes after a minute or two = perfect!
Well maybe it isn't! If you race, you need to start first time and be gone -after 10 seconds it would normally stall due to the richness but as you move off you are putting heat into the engine, the throttle opens, you feed less air into the choke channal. So quickly you can bend down and flick the choke off and the race is on.
So for me, an enduro racer, a #75 is the correct jet for back home but at the track i choose an #85, start first time, gone!....

The Bog

The bog can be caused for three reasons. The first is the PS not being set correctly and the cure is relatively easy. The second is a slightly lean condition when opening the throttle in first or second gear. The third one is because the jetting is too rich. The first thing to understand is this simple rule: if you jet up or down 5-8 you need to go in the opposite direction with the needle to keep the midrange jetting the same. So for example if you are running a 170MJ and C3 you may jet down to a 160MJ but the needle needs richening to C4. So with this in mind here are the three 'bogs'.

Snap wheelie tests - setting the PS

The bog at idle is usually cured by setting the pilot screw (PS) under the carb correctly. To test, you need a small screwdriver that fits and then I suggest the following: jeans with pockets, no gloves on. Warm the bike with a couple of 200M runs and then let it fall to tickover in second gear. Then snap the throttle, the bike should spin the wheel and pull hard. If it doesn't, and it bogs, try turning the PS out 0.5 turns at a time until it does. By writing down 'how many turns out from in/closed' you will now have some more information. Read on...

The lean bog

This is when the slide starts to lift but the straight sides of the needle are still in the atomiser. you need to lift the needle one clip position, this won't affect your MJ and is all you need to do.

The rich bog

This is when there is so much fuel going in that it blows out the spark. Rich is OK but this is more than rich! So you may have to lower the needle or the MJ. Firstly, lowering the needle: normally it will get better after the first drop and then be completely gone after the second drop. Now the MJ: There is also a second reason that it can be cured and remember that 10 down on the MJ is also leaning the needle by around 'a clips worth' so if your MJ is rich and you come down 10 you have EFFECTIVELY ALSO LOWERED THE NEEDLE by 'a clip position'! So 175MJ C4 can becomes 165MJ C4 - bog gone!

None of the above conditions happen when the correct MJ is chosen, they happen when you ride with the OEM jetting which is very rich on Husabergs. Remember, all jetting tests must start with the top end and the MJ, you cure everything after you've got this right!

Paddock stand jetting

There are a few that have tested their jetting and snap on the paddock stand. These sheytheads have tested the bikes for "snap" and when the bike has bogged; have declared the jetting to be wrong. We trust you all know better!

PJ size

A good indicator of the PJ you need can be gained from how far out the PS is set. There are 3.5 turns for the PS and if it is out less than 1 turn you need a smaller PJ (because it is trying to get lean). If the PS is out over 2.25 turns then you need a larger PJ (because it is trying to get rich). On the Mk1 carb there is a PAJ which governs the amount of air that goes through the circuit that picks up the fuel at the PJ. There is a ratio of PJ to PAJ which I developed over at TT in 2002. If you have too large a PAJ it can cause a lean spot just before entering the needles 'zone', also vice-versa so look at this table below for the correct PJ/PAJ. There is a simple rule you can keep in your head and that is 15 air to every PJ. Whilst the PAJ matters little on opening the throttle, it will make a big difference before entering the needle zone and if you happen to snap the throttle right on the wrong point you'll soon find it! So:

Boyesen quickshot

Slightly more technical APJ unit that allows control of amount and duration. I beleive that as the APJ is virtually useless you can draw your own conclusion about the necessaty of this device.

Boyesen quickshot pump (Bergoroadracer)

Tidy those breather pipes up!

This neat little unit is perhaps better for road and SM use.

PC Racing (Bergoroadracer)

Fitting a hotstart button to the FCR mk 1

Yet again Cookeye did it and also, so did Steve!

			A remote hot start from Ballard's means that on the odd occasion the Berg decides to stop of its own accord, restarting is easy.
(Cookeye)	Note hot start tube from head. (Steve)	(Steve)

Settings-FCR

Firstly, with the 'E' series needle which is great for top end in fifth and sixth gears.

• 152MJ with std/ FX/FC pipe.

• EKQ needle on clip 4, a 38 PJ: which needs #60 PAJ (3/8 turn on a PAS).

• Reduce pump squirt to .028" or .75 second.

• PS 1.5 turns + or - 0.5 turn.

Also, below are 'D' series needle settings. The 'D' series is excellent in the 'nadgery' stuff, in first or second gear etc. Generally, because the needle is a lot thicker at the tip (thus impeding some of the MJ's flow) we jet up by about 5.

• 150MJ with std/ FX/FC pipe.

• DMS clip 2 needle with 35PJ/45PAJ.

• Reduce pump squirt to .028" or .75 second.

• PS 1.5 turns + or - 0.5 turn.

Also

• Try 175MJ, OC-EMS needle and 48PJ (Lineaweaver).

Acclerator pump, timing (DaleEO)

Air Density Jetting correction chart (DaleEO)

In addition to the Air Density Jetting correction chart check out this handy Altitude Jetting Chart prepared by Gokai134.

Throttle plate cracks

The throttle plate mounted on the back of the slide cracks in a circular motion around the dished depression in the designThe plate cracks because it can vibrate after a very large rubber ring has worn from the fluttering and from then on you can hear the plate 'clattering' likle a a handful of dominos on a kitchen table. If you replace the inexpensive rubber 'O' ring at this point it's a good cure and the plate will last interminably. You can make the plate clatter at anytime by holding your hand over the end of the silencer........!

Dribbles fuel down breather tube

There is an 'O' ring which fits the float valve housing (made of brass and sits in the floatbowl of the carb). The floatvalve 'bobs' in and out of it. The 'O' ring hardens and leaks fuel straight 'around' the floatvalve mechanism completely overfilling the floatbowl. This causes fuel to leak out the breather but can also disasterously pour into your engine. Signs are: poor starting, generally rich running at low revs, tickover must be raised. (DaleO)

Fuel quality

Doesn't appear to suffer in the UK from LRP+ (Lead replacement petrol).

Fuel screw

There is a difference between the fuel screws required for the Mk1 or the Mk2 carb. see here

In water

"Shit in the carb" (how often?!?!). Old joke-still funny! With the mods below deep water isn't a problem! If the electrics are correct, the problem will be the carb injesting mud or water. Try T-piping the black central pipe on the Keihin MK1. Feed a breather high in the frame around the earth carousel and down. The bike will stop in water and upon restarting will suck are in the carb and NOT water up. A 100% cure!

The consumption!

On 14/48 gearing: as little as 3-hours but with Keihin FCR and jetting leaned off and small throttle settings etc: 4+ hours are possible.

Variable Throttle Cam

G2 Ergonomics sells an anodized aluminium throllte sleeve in which you can change the throttle cam out to suit your current riding conditions, they call it their "Throttle Cam System". The system comes with the throttle sleeve and 3 interchangable throttle cams, they also have 3 additional cam grinds that you can purchase seperately. The throttle cams are also anodized aluminium. All 6 different cam grinds get you to full throttle in the same amount of throttle twist and time as the OEM unit does. They change the grind on the first 1/4 of the cam to get the desired effect. The cams are as follows: 050x - Quicker initial power and take-off over stock grind. 100x - Same grind as stock. Cams 200, 300, 400 and 500 progressively ease the power on instead of the quick touchy stock throttle. 200 being the closet to stock and 500 being the smoothest and least touchy and made for tight woods riding.

Fuel supply

The left side supply can be changed to a right-side by fitting a plug on the left and drilling the plug on the right. The screw hole is already there. It has the advantage of keeping the fuel from vapourising and catching the exhaust system.

Pipes abound!

An alternative to many pipes and unions is to make a 2-into-1 connector, as below.

This is the 2 into 1 for the FCR that Taffy has supplied, top piece of kit!!!! (Fixerman)

Dell orto

Settings-Dell Orto

• For a 400; 200MJ, DR266, K35 needle on C1, 40PJ, 3.25mm slide cutaway, 45 choke jet, PS = 1-turn = Sea level. After years of reading other jetting settings it would appear however, that a move to a DR272 or Dr274 should have been effected therefore the below jetting would seem better....(Taffy)

• 170MJ, DR272, K51 needle on C2, 35PJ, 4.5mm slide cutaway, main air bleed drilled to #53 (1.5mm), pilot air bleed drilled to #60 (1mm). PS to suit (4,000ft) JoeUSA has a 501 but it's similar and worth a try. See this UHE Forum Thread.

See below for MJ size for 650 only.

• 195MJ, K51, 33PJ, DR274, 4.5mm slide cutaway, from factory mechanic (HeimarBardison).

• Lineaweaver will take your Dell modify it and convert the guts to Keihin, we've had great reports back about this work!

Modified Dell Orto slide

Try this below if you are getting the 'reversion' that Joe talks of in the above link. Attempted this with great and measured the work as you go. Perhaps a machine shop would be safer!

The pics show a slide modified by JoeUSA from 4 to 4.5mm cutaway.

Dell Orto choke lever

This can be remounted on the left of the cam cover near the cam cap. Just use an extra long allen screw and a dowel to clear the choke mounting bracket away from the head so you can get the right angle for the cable run. Allows choke to be turned off without holding up the entire field as you enter the woods for the first time!

Missing CD jet?

Some Dell Ortos may be missing this jet tube.

Checking the Dell Orto through

The carb must be pulled apart, all orofices blown out and the following checked very carefully:

• The float should be laid on a table and checked for flatness in three dimensions.

• The atomiser must be removed and checked for wear and ovality by holding up to a light and visually checking. Another way is to put the needle in and seeing if the ovality can be seen this way?

• Next, check the needle for abrasive wear and ring marks around it's waistline. Roll the needle on the bench and check for being bent or similar damage.

• The choke jet as well as others: is always getting blocked and can be cleaned with a combination of 'carb cleaner aerosol', a wire brush's wire run through and coca-cola!

• The slide can have bad wear on all faces and should be checked in the carb for looseness.

• Check that the Fuel screw has a washer and a tiny rubber 'O' ring on the end.

• Try and use an airjet that has a sports ball type needle in the end so you can get right in the eye of the air galleries.

• Check the slide height, write this down as well as clip position, needle code and jet sizes.

• If air bubbles can be seen leaving the carb to rise up to the tank you have a blocked fuel filter screen at the entrance to the carb.

• Floats can stick so have a good look for a poor run for the pivot needle, wear and detritus on the fuel valve itself and floats being a bit out of position.

• Also check if your carb is meant to have a fuel anti-shake around the MJ area.

Firstly, how old is the plug? has it had to run under harsh extremes of hot/lean or cold rich all in one ride? Get a new plug! Have you ever checked the ignition timing with a strobe? Husaberg timing can be out because the timing marks are wrong... It's a possibility! Check out the Electrical section to get this right FIRST!!!

Try and get the bike running and then set up the fuel screw for best running at idle, next, do some throttle response tests and if the bike is flat - adjust the fuel screw until the hesitation disappears. Did the screw need more fuel by turning it anti-clockwise? Or did it need leaning off by turning the fuel screw clockwise? Record your results simply on a sheet of paper with a note of how it felt to ride.

Next, having got the bike idling correctly and accelerating correctly: try stalling it and kickstarting it. From this you can learn more: a rich running bike is a sod to start. A lean running bike is easier. All the time you are building up a bank of knowledge as to what may be wrong with your bike and how it may be cured.

DNA air filter

More air into the frame. (Bergoroadracer)

Modified seat

Use without filter for more air. For streetracing! (Bergoroadracer)

Gas analyser

Lambda sonde (Bergoroadracer)