Dr Ross answers: Ian, the bike is running lean at that throttle setting. Mostly you would never notice this in normal off-road use where the throttle, gear and load is constantly changing, but when you ride on the road at a constant throttle and 90km/h, you probably only have it at quarter-throttle. These bikes where not made to be ridden this way and that is your issue. Vary your speed and throttle openings more and never think of it again because chasing it around with jetting will not be a fun task.

Dr Ross answers: Rhys, if your wheel has more than about 2mm run-out, you should really have it straightened out by a professional. Truing wheels is as much an art as a science; your local bike shop will be able to help.

Dr Ross answers: Daniel, the '06 KTM 250SX is a monster power-wise, and, if it is feeling unexciting, it must have a problem. Check the reeds for chipping and make sure the power-valve is operating correctly.

Dr Ross answers: Rohan, having owned a '00 KTM 380EXC myself, I find it surprising that you are having trouble with the jetting as those issues were more of a problem on the earlier 360s and the first 380 model. This was largely due to compression that was too high for our fuel, and the tailpipe of the exhaust being too small. With your '00 model, I recommend you go to a 175 mainjet, 42 pilot jet and a DEL needle from Show and Go in SA on the middle clip. The FMF Fatty and matching muffler are also the go.

Dr Ross answers: MX Boy, you need a working headlight, tail-light, brake light and horn to qualify for an "off-road" or "rec" rego event. The requirements and limitations differ quite a bit from state to state. It is best to contact the organisers of the event to get the low-down on the local rego requirements. This year, the event is in the Gippsland region of Victoria, and you should be able to contact the organisers through Motorcycling Victoria's website http://www.motorcyclingvic.com.au/

Dr Ross answers: Sorry Valenzua, your XR100R will never be a match for a CR85 around a motocross track, and trying to upgrade it to be competitive will break the bank. Trade up to an 85cc because this is one dead-set case of ‘if you can't beat them, join them'.

Dr Ross answers: Troy, the black soot is actually a layer of burnt carbon that has been vented through the exhaust system. It's normal for a thin layer of carbon to cover parts of the engine and exhaust that come into contact with it. Normally, carbon does not present a problem. But, through the introduction of contaminants, such as oil or overly rich air/fuel ratios, carbon build-up can become excessive. This will reduce engine performance and require costly service or repairs. If it is just a layer and isn't building up, you don't have a problem.

Dr Ross answers: Adam, your 525 is only fitted with a fairly small 9.5L fuel tank and, to make it worse, the EXC range has a decent-sized reserve, too. Most of the guys tell me they are getting 100-110km before they go dry. Some riders have fitted a leaner needle and one size smaller mainjet and report an improvement in fuel range. I would suggest you run a 182 mainjet, 42 pilot, OBDTR needle on the fourth clip from the top, and ride close to the car.

Dr Ross answers: Pamela, the trouble is you're starting the KLX in extremely cold conditions. At 7-odd degrees you are pretty close to freezing and the fuel is icing in the jets. Some street models have their carbs fitted with a heating circuit to cut down on the problem. Next time it is really cold, keep the bike inside the house overnight and start it as soon as you wheel it out into the cold. My guess is it will start easily. The only real cure, other than keeping the carby and fuel warm, is to try running Avgas which has additives mixed into it for cold weather operation without icing.

Dr Ross answers: We've had plenty of experience with the 250EXC-F, and fitting the Akrapovic system with the long header pipe works well. We ran this set-up on Ben Kearney's Shift Motorex KTM race bikes. Replace the air filter frame with the one from the two-stroke model and you will find the power broader, smoother and more responsive.

Dr Ross answers: Dylan, your PeeWee's carby probably has some wear or dirt in it. Strip down the carby and give it a thorough clean. Then blow it out with compressed air and check the needle and seat for wear.

Dr Ross answers: Angry, the DT230 has a similar motor to the older DT and WR200s, but the pipe is quite a different shape. Some pipes are available for the 230 in Japan (such as the YSR brand), although no one seems to distribute them here. My advice would be to find an English-speaking bike shop in Japan and see what they can do for you. Alternatively, getting a Pro Circuit WR200 system, and having someone modify it to fit your DT230,
will also liven your bike up quite a bit.

Dr Ross answers: Jeff, it would be advisable to get the head off and replace the gasket. If you are losing coolant, you are risking further engine damage through over-heating. If possible, have the head and cylinder gasket surfaces checked to make sure they are still flat. A sheet of glass and some wet-and-dry 600-grit sandpaper should do it.

Dr Ross answers: Brett, with the road-going component of your planned riding, I would recommend a used KLX250 or 300. They are decent both on and off the road, and there's plenty of them around in your price range. A Yamaha TT-R250 or Suzuki DR250 would also give great value and are surprisingly good on the trails.

Dr Ross answers: Peter, it sounds like your CRF isn't charging the battery. This could be due to a broken connection or a poor earth. First check that the battery is earthed correctly and then, with the bike at a high idle, put the battery on a multi-meter and check that the reading is over 13 volts. If there is no change in the reading after you've switched the bike off, your problem is with the generator or regulator. Best way to fix that is to drop it into the bike shop.

Dr Ross answers: Ramiro, just about every method of raising the little TT-R up will cost you money, and adversely affect the handling. I wouldn't recommend anything more than raising the seat height with some extra foam. A local upholsterer should be up for the job, or check out: www.australiancumfymotorcycleseats.com.au

Dr Ross answers: McNamara, I would get at least one of those slabs back as you've been grossly overcharged! Take the re-possessed beer and the bike to a bike shop and get them to check the stator and coil.

Dr Ross answers: Mike, two-strokes will always have a bit of oil around the exhaust and possibly leaking from the cylinder and silencer joints, too. It is nothing to be worried about. With the poor quality of pump fuel at the moment, fouled plugs are a common occurrence. The ratio you mix the oil at is different for each of the oil brands out there, and it's best to stick with what the oil company recommends. If the fouling continues regularly, you may need to lean off the jetting.

Dr Ross answers: Peter, the jetting sounds fine for your YZ, but you might want to check out the condition of your reed petals to see if there are any cracks or chips. This could affect the starting. If it was running fine before the rebuild, you might find the increased compression to be a factor in the hard starting.

Dr Ross answers: Pudds, you say you fitted a new set of rings 40 hours ago? 40 to 50 hours is a long time to run a piston in one of these racing four-strokes. If you are riding the bike hard, pushing it to that many hours is very risky. I'm afraid you will have to have the motor stripped down to find the problem before I can offer you much additional advice.

Dr Ross answers: Matt, you should pop into your local auto electrician and get them to load test your battery, as it's quite common for them to show a full charge and still not be up to the task of starting the engine. Many bikes a few years old, like yours, are fitted with aftermarket batteries that have lower amperage than the original specification, and in cold weather, or after a few months, they just can't cut it. If the battery checks out okay, it might pay to check the exhaust valve clearance, as having them set too wide can stop the auto-decomp from working properly.

Dr Ross answers: Peter, your mechanic is right; the most likely reason the piston would have broken the skirt off is from excessive clearance due to wear. A 125cc two-stroke race bike like yours needs a new piston about every 20-30 hours for the average rider. After six months you've probably ridden the bike for a lot longer than that. I recommend you fit an hour meter and inspect the condition of the piston and rings regularly.

Dr Ross answers: Thomas, the noise limit has been this low in Europe for some time and any of the European pipe brands should be a safe bet for a performance boost while still being under the limit. I have been using the Akrapovic systems for several years now, both at team Kawi and here at KTM, and recommend them highly.

Dr Ross answers: Visser, most off-idle cough problems relate to the air/fuel ratio being too lean although, just about any bike can bog if you turn the throttle fast enough. You should adjust the air/fuel screw on the bottom of the fuel bowl, winding out the adjuster to richen up the mixture. This screw should be at 1.5 to 2 turns out. If you have the best throttle response at more that 2.5 turns out you should fit a larger pilot jet and start again with the screw set at 1.5 turns out. You can also get better response by adjusting the pump. There is a small screw on the right-hand side of the carby under the black plastic cover that changes how much the accelerator pump is depressed. By the process of trial and error, you should be able to eliminate your bogging problem.

Dr Ross answers: Aaron, your KTM is most likely running too lean on the pilot jet, which would make it harder to hot-start and also cause you to excessively crank the engine, which would be why your battery is going flat. We fitted a larger pilot jet and have been able to run all the Motorex KTM team bikes with the small battery all year, even in winter. On extremely cold mornings it could be worth having a jumper pack on hand and you can buy these for about $70 at discount stores like Supercheap Auto. As to why the battery would go flat while the bike is being ridden, it could only be either a faulty battery or a problem in the charging circuit. Your dealer should be able to diagnose both of those if that was the case.

Dr Ross answers: Matty, the best and safest way to lower your WR400F is to have a competent suspension tuner lower both the fork and shock to suit your height. I know several shorter riders and female racers who have lowered their machines by as much as 30-40mm. Most of them simply can't believe how much better and more confidence-inspiring the bike is to ride when you can touch the ground. The mod isn’t cheap but the pay off will be worth it. Race Tech dealer Shock Treatment charges around $400 to lower both ends.

Dr Ross answers: Ian, if the bikes are in good shape they both will make the trip. Just keep up the oil changes and look after the air filters. I suggest you get damped rear hubs fitted to each of the bikes if you're going to be on the highway for any great distance. Also, fit a long-range tank to both bikes. The secret to making these type of trips is planning. Make sure you have the gear for the trip organised in advance, particularly oils and spares. Knowing how far apart the fuel stops are and how far your bike will run on a tank of fuel is essential. Every day should be totally planned so you don't find anything out the hard way! Gary Williams from Wombat Motorcycles out at Windsor, NSW, has prepped plenty of WR-Fs for rides like this, so give him a call. Good luck out there!

Dr Ross answers: Webby, converting the 250cc to 300cc is a snap and totally reliable. The 330cc kit could be pushing it too far. Give the guys up at Newcastle Kawasaki a call. They are the Ballard's of the green team and have all the good mods worked out for the KLXes. You can also check out ADB's story on the 300cc kit in the September issue.

Dr Ross answers: John, your CRF250R is one of the few bikes on the market that separate the gear and motor oils, so you can run the two-stroke gear oils in the CRF's gearbox.

Dr Ross answers: Peter, you can remove the bottle and re-route the hose down the front frame tube to the bottom of the frame near the front engine mounts, with the help of a few zip-ties. This is how it is on the YZ-F models and the only drawback is that the expelled coolant is lost and there will be a need to check the level more regularly. If you regularly overheat the bike it might be best to leave it on.

Dr Ross answers: Mike, the thread is normal direction-wise. The nut should have been thread locked from new and the Loctite used for this is pretty strong, which could explain the tightness on the shaft now. If the shaft is damaged, you're going to be in for a big repair bill to strip the motor down and split the cases to replace the shaft, so hopefully it isn't. The tightening torque is quite high on this nut and most issues with that particular item on the KX450F relate to not being able to get them off! I have seen a few that refused to come off easily. You should get the nut off and inspect the shaft for damage. If the shaft is okay, replace the O-ring that sits behind the collar. Also, check the sprocket for damage and replace if necessary, re-fit the nut (use a new one if there is any sign of damage) and tighten to 93ft/lbs with fresh Loctite and all should be good. Don't forget to check your oil level, too.

Dr Ross answers: Stuart, your 18-year-old DT most likely has some worn out gears. To have the motor removed and cases split to diagnose and repair the problem is going to cost you at least $400 plus parts. I would be putting aside $600 to $800 for the whole job.

Dr Ross answers: Shawn, you can ether tap out the thread to a bigger size or fit a heli-coil. Make sure you put a bunch of grease on the tap when you cut the thread to catch the swarf, and be careful to flush the hole with some motor oil before you finish, and you should be okay.

Dr Ross answers: Alan, short of fitting additional fuel taps, lines and a vacuum pump, the only other thing to do is start wheeling!

Dr Ross answers: Linton, I can't think of any single part that could be making that type of noise under load. The only answer would be to strip down the motor and inspect all the spinning gears, surfaces and bearings. It could be hard to track down any other way if the noise isn’t getting any worse and there is no metal showing up in the oil or filter. And congratulations, Linton, your letter has earned you a Shell Oils prize pack valued at $150 from the boys at Moto National.

Dr Ross answers: Dave, the YZ-F muffler is going to liven up the WR-F quite a bit. The newest YZ-F muffler seems to be very effective at controlling the noise without power loss. If you can talk the dealer into fitting it for free go for it. As for fitting, I haven’t seen both bikes in the same place at the same time so I don’t know for sure if they’re interchangeable, but all of the earlier ones have been.

Dr Ross answers: Funky, generally the cranks on 125s should be replaced every 50 hours or once a year. Lots of people get a couple of years out of them, but running them until they fail is the wrong way to go about it. If you’re racing the bike, it's cheap insurance to rebuild it each season. As for doing the job yourself, the Honda owners manual is perfect and will guide you though the job. But you’ll need a few special tools – such as heat and rattle gun – to get it done properly. If you’re going to tackle the job you’ll need to replace the crank, main bearing, main seals and gaskets.

Dr Ross answers: Steven, most of the guys have been running a 175 mainjet, 42 pilot jet and 55 leak jet with the fuel screw set at two turns out with an open pipe fitted. This should get you close. The White Brothers pipe will liven things up and the cam will get the CRF-X up to a reasonable speed.

Dr Ross answers: Nathan, I'm sure your Mum's a smart lady. I learnt a lot about bikes from my Mum, growing up in a single parent family. Silkolene Pro Gear is one of the best two-stroke gear oils on the market. Be sure to change it often. As for the fork oil, seven hours sounds a bit too frequent for a casual rider and most owners simply service the forks every six months.

Dr Ross answers: Billy, the clutch noise is a known thing on the older LC4 motors. The baskets are a hardened alloy and they ring like a bell at idle with the clutch plates rocking back and forth. When you spread the plates by pulling in the lever they don't all move together and make less noise. The jetting could still be a bit lean on the pilot jet, or your idle could be set too low. It's pretty common to see the idle too low on these motors as they will happily bump away at 500rpm when the idle is supposed to be at 800-1000rpm. If you hear the auto decomp clicking occasionally, your idle is too low. As for the steering damper, either the Öhlins, Scott or MSC damper from Shock Treatment (02 4773 9115) are the best. You can’t beat them.

Dr Ross answers: Ian, there's a good chance that the auto decomp activator is worn and not depressing the valve far enough or for long enough. David Woodard, the technical guru for the Husaberg empire, suggests that you should test for wear in the decomp by closing up the exhaust valve clearance to the minimum setting to see if that improves starting. If it does you’d be safe to go ahead and order a new decomp assembly. If not, you’d better have the wiring, battery and starter system tested for voltage
drop while starting.

Dr Ross answers: Matt, both the WR250F and TE250 are great off-road racing bikes, but they're not really built for hours of highway riding. With off-road gearing, the life of the engine will be used up very quickly. If highway use is going to be minimal, the Yamaha motor is a proven thing and that's where my money would go.

Dr Ross answers: Anthony, many early WR-F owners have updated to the '03 exhaust camshaft to get the easy starting of the later model. I have fitted these many times. Just order the cam from the '03 model, which comes with the cam wheel already on it and is ready to fit. Then just follow the steps in the owners manual and you'll be fine.

Dr Ross answers: Nathan, basically the KX125 isn’t meant to idle. It is a motocross bike after all and, as such, it has been designed to be started, revved up and raced away from the startline. Sitting there and idling away while you open and close a gate was never in the design brief for the little KX. Given that the KX is now 11 years old, I can imagine that the carby would have some wear in the needle and slide, making holding an even idle less likely. If, after adjusting the idle screw, the bike seems to hold the right revs for about 10-15 seconds before stalling, that would be pretty normal. Getting it to purr like a four-stroke just isn't going to happen.

Dr Ross answers: Arm pump is a serious issue for a lot of riders, Nathan, but unfortunately you haven't mentioned much about yourself, your age, abilities, how often you go riding, or about your off-bike training schedule. Many Pro riders suffer from this and often the cause isn't bike-related. At 65kg you are a little lighter than the average rider, and depending on your ability you could benefit from slightly softer springs. The non-bike related theories are vast and varied. Mostly, the problem is that the rider hangs on too tightly to the bars and overworks the forearm muscles, causing them to "pump" up and block blood flow to the hands. Riding more often and becoming more relaxed when racing are the most effective solutions.

Dr Ross answers: David, SFB racing has covers listed for your YZ400F. Give Steve at Cisco's in Melbourne a call on (03) 9801 9022. The SFB Part number is 2400420201

Dr Ross answers: Andrew, it's a very brave man who needs more from a WR500! The gearing you have is good for up to and over 140km/h. You either need a KTM 950 Super Enduro or to start looking for more challenging terrain!

Dr Ross answers: The swingarm will fit, Chris, but you will need to heat up the airbox to make more room for the shock reservoir as the swingarm mount is further back and will pull the shock into the plastic. Also the shock needs to be shortened 6mm, revalved and a softer spring fitted to match the more aggressive rising rate. Other than that, it goes straight on. And congratulations, Chris, your letter has earnt you a full set of SBS brake pads and a hat and tee worth $150 from our mates at Monza Imports

Dr Ross answers: Michael, I tested all the pipes for the '03 CR125 while helping out supermoto star Nick Brain, back when he was a struggling privateer motocrosser. The best combo was the FMF Fatty and Power-Core muffler. If you have the budget, get yourself a VHM head and V-Force reed-block. Those three items will really wake up the CR!

Dr Ross answers: Ian, yes the KLX is fitted with possibly the spongiest front brake on the market. Luckily all it needs is a new braided front brakeline. I fitted a Goodridge line from www.johnstamnas.com on a project bike a couple of years ago and it did the trick. They're Aussie-made and one of the only ADR-approved aftermarket brakelines on the market.

Dr Ross answers: Justin, it could be that the head gasket isn't sealing and the compression gasses are forcing out the water. 300ml is way too much to be losing and you need to get to the source of the problem before the engine winds up damaged.

Dr Ross answers: Ryan, Honda doesn't offer complete replacement engines for your CRF.
Although, with plenty of people in the same boat as you with three- or four-year-old bikes with blown motors, you'd think they would! The way it's done is: simply make a huge list of the damaged items and weigh up the cost against the replacement cost of the bike... sorry!

Dr Ross answers: Tony, unfortunately the 426's rattle is unlikely to be due to valve adjustment. Riding in the dunes is very hard on any bike and it could be he has overheated the top-end and had the piston nip up. I would recommend you put a new piston kit in and check the big-end and main bearings while the top-end is off. His 426 is a few years old now and it's probably overdue.

Dr Ross answers: Ryan, the plates in your clutch are simply sticking together. It could be because the oil is too thick and they don't separate until the oil is heated up and thinned out. Try changing the oil to auto transmission fluid (Dextron III) or a quality two-stroke gear oil and see if the problem goes away. You should change the oil in your two-stroke gearbox after every 300-500km of off-road riding.

Dr Ross answers: Will, fitting a electric start to you XR is way too expensive to even consider. You'd need to replace both cases, the crank, as well as buy the starter, switches, wiring and a battery. There are great e-start alternatives like the 250EXC-F and WR250F out there to get you back on the trails!

Dr Ross answers: With most of the newer 250Fs, there is little or no running in to be done. If everything is assembled right, things will be fine. Taking it easy for a few laps to check for oil or water leaks is all that passes for running in nowadays!

Dr Ross answers: Kirk, checking the valve clearance is very straightforward and most owners should be able to check the clearance. If an adjustment is required, I think a dealer should probably do the work as you need to remove the cams to get to the shims. After 40 hours, the little SX-F is overdue for a clearance check. If the bike is ridden hard, the piston rings are probably due for replacement, at the least. I would recommend a top-end rebuild every 30 hours if you're racing and revving the bike hard. And congratulations, Kirk, your letter has earnt you a full set of SBS brake pads, a hat, and a tee – a pack worth a total of $150 from the crew at Monza Imports.

Dr Ross answers: Shane, your boy has managed to re-fit the cylinder without the power-valve hooked up correctly. Have him remove the pipe and power-valve cover and check the arm is hooked up correctly. Chances are it isn't!

Dr Ross answers: Ryan, I haven't had much experience with the K&N product, but have used the excellent DNA filters in some dirt bikes. Both DNA and K&N use oiled cotton, rather than foam or paper. Believe it or not, the paper-type filters actually have more surface area than some foam filters. The paper elements also filter the air more efficiently than foam, trapping finer particles. They work well ... but for pure off-road, there are drawbacks: the maintenance, cleaning, and the overall life of the paper doesn't add up for me.

Dr Ross answers: Stuart, the Trail Tech product is the pick of the litter in aftermarket speedos. It's feature-packed and the units survive the off-road bumps and scrapes quite well. The PowerNow is great for improving the bottom-end throttle response on most bikes. If you've already fitted an aftermarket muffler and rejetted it, this would be another step forward.

Dr Ross answers: Koen, yes, a full synthetic oil will help protect your XR's motor better in a hot environment. I always recommend that everyone should use the best oil they can afford, and change it often. I've been using Motorex's new Power Synt 4T oil for a while with outstanding results. It's a 10W-50 oil that works well in the heat, and still offers good wear protection without causing the clutch to slip. As for your fork, use fork oil. Most of the better brands are synthetic, or at least synthetically modified.

Dr Ross answers: Greg, when you throw a motorcycle down a hill, things will break! Broken cases caused by the gear lever is a rare occurrence. The only real insurance is a good bashplate. Whipp's has an excellent bashplate that wraps around

Dr Ross answers: John, I think the process should be easy. The stator needs to be re-wound, and you'll need to replace the regulator, fuses and bulbs. Give the guys at Small Coil Rewinds in Geelong a call on (03) 5218 8454.

Dr Ross answers: Your XR should idle away for hours and run perfectly. My guess is that the choke could be stuck open and the overly rich mixture is the culprit. With the bike's 10th birthday just round the corner, it could be time to treat her to a proper service at a dealer. Have the carby stripped and cleaned, and the valves adjusted as well. The little XR will soon be purring away happily again.

Dr Ross answers: Mike, the fork seems to just be over-damped. Just about any good suspension tuner should be able to sort it out. I would give Terry Hay at Shock Treatment a call; that's where KTM factory off-roaders Brad Williscroft and Ben Kearney get their suspension sorted out. And congratulations Mike, you've scored yourself a pack of Shell Oils worth $150 from our mates at Moto National.

Dr Ross answers: Geoff, it sounds like you may have installed your slide incorrectly. When installed properly, you will see a small hole near the bottom when you look from the engine side. It might also pay to remove the pilot jet, hold it to the light and confirm that you can see a clear round sharp edged hole ... if the hole appears blurry or soft, it will not work, and it'll need replacing.
Good luck!

Dr Ross answers: Dave, from what I know of the CRFs, the heads will be interchangeable, as are a number of other parts around the bike.

Dr Ross answers: Glenn, you’ve pretty much covered the usual fixes for the leaking needle and seat causing fuel to overflow. At a guess, the occasional leak you are now experiencing could be from the float level being too high, or a worn carby could be causing things to stick a little. If it’s a big drama, you might have to install a new carburetor.

Dr Ross answers: Steve, the RMX jetting is famous for problems that are caused by the ageing PJ carby. The PJ-series carby can be tuned by adjusting the bleed on the choke knob. This seemed to work fine when the bikes were new, but after a few years, the jetting issues seem to be incurable. The standard problem-solver is to buy a PWK38 or 39 carburettor and fit this with 42 pilot, 172 main and a DEL needle on the middle clip. With these mods, the bike's jetting troubles will be behind you. A mate of mine picked up one for his RMX for $200 on eBay recently. You can probably do the same, or buy one from any major wreckers. Good luck.

Dr Ross answers: Lights on the KX shouldn't be a big issue, as long as using LED-style lamps to satisfy the off-road/enduro tech inspection is all you're looking for. GNCC racer Josh Strang's father Vince has used a basic kit on Josh's KX250s for the past couple of years, and they're available from Bert at Small Coil Rewinds in Geelong, Vic (03) 5278 8454. Basically, this kit "steals" a bit of power from the ignition circuit to run the LEDs. The Small Coils kit is just wires, LEDs and some instructions. You simply fit the LED bulbs into any aftermarket headlight or tail-light. Vince silicones them into place where the normal bulb goes. Aftermarket tail-lights are available, too, and you can wire one of those up if you're going to buy a tail-light assembly.

Dr Ross answers: Jed, slippers will reduce supermoto lap times and are a proven thing in the sport. However, in motocross and supercross, they're still rare. Many Pro riders are rumoured to use them for SX where it’s better to have the bike's rear-end contacting the ground and the rear wheel turning as the throttle is snapped shut.

I have had some experience with the Hinson slipper clutch. They come with three springs that make the uptake of the slipper adjustable to suit all riding disciplines. On a big-bore like your 550, you'll easily notice a big difference. Whether or not they’re worth the money, only you will know once you have one.

Dr Ross answers: Alan, the XR250 has a bullet-proof motor but a four- or five-year-old one could have some issues. If you're unsure of its service history, you should have the bike checked out at a Honda dealer. The ticking noise could be a sign of valve trouble that will be cheaper to fix earlier rather than later. The cutting out at full revs at speed will be fuel-starvation or an electrical problem.

Dr Ross answers: Dave, from what I know of the CRF's, the heads will be interchangeable.

Dr Ross answers: Doug, water in the fuel will do it every time. The water is much thicker that the fuel and will not pass through the jets in the carby. As the water blocks the jet, the motor is starved for fuel and stops running. Once the motor has stopped, the water will sometimes fall back down and clear the jet, then when you start the bike, the process starts again. Drain the carby and clean it out totally, including the accelerator pump assembly. While you're at it, drain the fuel tank and discard the contaminated stuff and re-fill it with fresh fuel.

If there is no water in the carby or fuel, check out the fuel cap vent – if it won't allow air into the tank to replace the fuel that goes out into the carby, a vacuum builds up and stops the flow of fuel to the carby. Once the bike sits for a few minutes or the cap is removed, the pressure equalises and the fuel will flow again. Hopefully it’s one of these two things; both are easy and cheap to fix.

Dr Ross answers: Ben, there are only two ways to fix it. Collect the broken pieces and have a competent welder re-attach them, or buy a new frame. The mount would've probably been cracked for a while and you just didn't notice it until the whole lot came off. If the mount has been re-welded in the past, the mount could have been weakened, or, more likely, was damaged in an earlier crash. In future, always keep an eye on the condition of the footpegs, pins, springs and mounts. Check them each time you wash the bike for damage and wear.

Dr Ross answers: Jason, if there's a lot of deep water around your riding areas routing the hoses and the engine breather pipes to keep them high and dry is a good thing. It will keep the water out, but remember the carb overflow tubes are meant to allow the spilt fuel to spill onto the ground and be replaced with clean air. As for other waterproofing tips; carefully applied duct tape can keep the water out the airbox, and dielectric grease and silicon on the wire connectors for the CDI and kill switch can save the day.

Dr Ross answers: Kristy, the CR125 was never known for its bottom-end power. By 125cc MX standards at the time, the CR was weak. You should check the top-end. Make sure the piston, ring, and bore are in good shape. The rings on these old CRs do wear out quickly and a lack of bottom-end power is one of the first signs of a worn ring. Given that you have just bought the bike, you should have it pulled down and fit a new piston and ring. Also, many CR owners found that a 53-tooth rear sprocket worked well on that model.