turbohead

The Rotax engines were a bit late to get modern ignition systems, compared to other European engines of the '80s. However, they can still be made to work today like they were all those years ago if you perform the daily routines as described above, over and over again. Points and condenser often cause problems, just like they did in the old days. However, if you are prepared to spend the money, an electronic ignition is better, give more consistent performance and is a fit and forget solution when done right. There are a few suppliers around and the price is €300-€450 for a complete kit, less if you need ignition only (no lights). But how are you going to spend all that time in your workshop if you don't need to adjust points and change other parts on a regular basis anymore....?

I am a bit reluctant buying air tickets, train tickets (or rent a car), hotel and two days entry tickets plus a few pints, going all the way from Sweden to Telford. Perhaps it is a well spent couple of hundred pounds, but I don't know, having never visited this show before. What do you veterans of the show have to say, go or save, staying at home in the dark and snow....?? Please, give me your honest opinion!

Keep up the good work, of course you deserve a modified side plate. Simply because it can be done (and make your bike look even more works)!

A simple little question there. Unfortunately, the answer is .....not so simple. Please, have a look at the link below as it shows just about the same approach as I prefer, except for the welding, where I prefer my (modern) AC/DC TIG. No very special tools or other equipment, just practice and more practice and a little patience.

There is another way to do this, if you have basic metalworking skills and like the sound of your AC/DC TIG's HF arc. Once you get the hang of it, you can do one for yourself and then another for ...... and so on. Perhaps a bit of a long way to an affordable alloy tank, but very rewarding even before you have finished your first one. Great therapy after a hectic day at work.

I ordered the simple kit with ignition only, when I need lights I use a separate battery and LED-units both front and rear. Performance is very consistent and starting is much improved, no matter the ambient or engine temperature. When I run into trouble and stall it, a single kick is all that's needed to get going again. Regarding pick-up, the engine response is very crisp and the plug always show the dry(ish) brown electrodes you want to see. In fact, it run like a proper set-up ignition of any kind should do, with the big difference of a consistent system, always giving the same kind of power delivery without the demand for any service or new parts. Of course, it is not cheap, but great value for money anyway.

Great! My only problem is lack of time and too much office work...... Seriously, the Powerdynamo kit does exactly what it should, i.e. a nice fit and forget kit once you have adjusted the timing to suit your riding style. I started out with the original timing, tried both a bit more advance and also a bit less, just locking the crank with the screw up front and turning the flywheel (as it has no key) and then checking with an indicator. As it is right now, I am running 0.12 mm less advance than standard, but I use a Keihin PWK carb, a slightly modified exhaust and airbox, so the package is not exactly standard. However, the kit is very easy to fit and work on, so everyone with basic knowledge and equipment should have no problems to get a modern ignition system on their Rotax (or any of the other engines listed by the guys in Berlin).

Yes, b40rt know what he is talking about. Give it a (careful) try. Just a short note on the old woodruff key issue. The key is not needed at all, really. It is just for helping with a rough timing at assembly, nothing else. Use a small chisel and perhaps your hot air gun to remove what is left of it. Then grind the flywheel and the the crankshaft carefully with old-fashioned valve-grinding paste until both surfaces has a smooth grey color (can take a little while). Use a timing disc or an indicator through the spark-plug hole to get the timing right and carefully tighten the flywheel nut. Check the timing again and fully tighten the nut, check timing again... The key is just for positioning, not for holding the flywheel. I have not used keys for a couple of decades, just carefully positioned the flywheel until the timing is according to basic spec, before starting to slightly try altering the timing to suit track and rider. Works on all 2strokes in mx, road racing and on the odd old Rotax, too.

1988 was his last year as an international. Eric Geboers won the title at Namur, but Carla stole the show by winning the races and having that classic beer on the last lap. In a way, a little sad to be remembered for such a show...... but it was another world 30 years ago.

It was a sad day when he passed away a couple of weeks ago. Perhaps one of the hardest racers of all time, certainly among mx champions. Pain was never an issue, even when he should have stayed away from going for another win. That's the way heroes are made, but often there is a price to pay later in life. He left Sweden long ago, for the comfortable climate in France for a used body, but also out of reach for everyone. Death by natural causes is almost like a joke for such an ironman, but that's the way it is. We never know when and where it's time to leave and perhaps that's the real mystery of life for us all.

Sorry, but you can not compare different forms of motorsport just like that. I agree, Bou, Raga, Dabill and others are the true trial heroes of today. But at the same time, Rossi, MM, Lorenzo and others are the true road racing heroes. The ability to control and balance a trial bike is certainly an art in itself, but so is the ability to ride a 250+ hp bike at silly speeds and controlled two wheel drifts. When mentioning Valentino Rossi, he is an extreme example of commitment to his sport, riding at the top since the 90s, a position hard to find in any form of racing. So please, enjoy them all and admire their very special skills while doing so. But do not try to compare incomparable riders and disciplines.

Yes, Sir! But welding is nice therapy. You feel better and the bike look better afterwards, too. Then, the next re-packing is easy using the old welds as a template when cutting the box open. TIG re-welding, a little grinding and it's almost invisible....

Better do some proper welding, very easy work with MIG or TIG equipment. If you try to open and pack the WES box, of course you need a TIG. The rivet and silicon solution could work on any box, but is a more provisional repair (if I may say so...).

Lots of clever advice here. And an ultrasonic cleaning bath is a lovely thing to use for anything regarding carbs, injection and so on. In the old days we didn't know about them, but still got our engines running, so you don't need it if you do your homework well. However, there could be another possible source and that is your magnificent Ducati electrics. The CDI units in particular has always been prime suspects when mysterious things happen. When I raced Husqvarnas and Cagivas, we had to deal with these often unreliable parts and always kept plenty of spares available. When my son bought himself a GasGas 125 to play with in 2009, the old Ducati story was repeated. Before he sold that one, he used 3 CDIs in less than 20 months. Terrible! So, if you are absolutely sure your carb is OK .....please, check everything on the ignition side of life.

Yes Sir, a Dremel (or a Chinese clone), some heat and a sharp chisel. No problems, just watch out for flying parts in your workshop as you give it a nice blow after almost cutting through the bearing.

Oh yes, I remember that. The same piece of tarmac was even used for stages on the Lombard RAC World Championship Rally in those days.

Big Rich! Sorry, but you don't know ****, boy. I am soon 65, working 45 hour weeks, have a house full of people to feed and enjoy, plus mortgage over my ears. Still, there is a workshop for resting and plenty of land to use for other things than farming, like mx and trial bike therapy. No death in sight for decades to come.

We must remember the difference between Japanese tech and anything else. Honda is perhaps the ultimate manufacturer of bikes from a quality perspective, no matter if we look at mx, enduro, trials or road bikes (or racers). From the late '90s, there has been an enormous development of 4-stroke Japanese dirt bikes, mainly because of emission regulations and marketing strategies. The 4RT is an excellent example of all that and they keep on winning. However, if Honda had decided to invest the same kind of money developing a 2-stroke trials bike, I am sure it would have been at least as competitive and certainly superior to anything else on today's 2-stroke trials scene, in terms of quality, reliability and so on. The smaller, specialized manufacturers can never compete with the technology and build quality of a major manufacturer as Honda, but of course they can always produce bikes capable of winning in the right hands. As a weekend rider, you have the choice of paying to ride as much as possible (on a 4RT), or saving some money, but investing lots of time and keeping a low-tech bike competitive. Both ways can be very rewarding in different ways, but what would real men be without a little workshop therapy every now and then...?

There is an easy first step. Just take off the cylinder and head, get the bore are piston measured. Then you know where to start before spending any serious money.

It could be the perfect dirt bike induction system, perhaps for trials, too. I first heard about Athena's efforts 5-6 years ago and it is still in the promising stage, but closer to reality than some of the other systems presented during the 2000's. Ossa is still the pioneer on the trials arena, but I haven'r seen any emission tests or fuel efficiency comparisons. Perhaps others have tried and there could be followers around the corner. Problem is, from a riding point of view, the old carb is still rather good, simple and reliable. The injection systems is better, specially when looking at emissions, but add a bit of new tech, a little unknown to most of us. Having said that, just look at the bikes winning most enduro races today, the more extreme races in particular. If that is a sign of the future, two stroke engines are back to stay longer than most of us thought a couple of years back.

So, you just wished the 125 had very low mileage or did the previous owner tell you a nice little lie.....? Anyway, have a nice Xmas rebuilding the 125 top end!

Sorry for that! But this is no rocket science of any kind, just the simple principles of the 2-stroke engine. Having said that, IF you have tested with an ordinary automotive compression tester and IF you have done it kickstarting a hot engine and still got a reading around 100 psi, you have a first indication that the compression side of your piston probably can be OK. IF you have done it careful enough, your test can show a reading somewhat below what should be recorded when the test was made the proper way, with a proper instrument. Remember, leakage on the underside of the piston, through seals, crankcase and so on, is NOT properly checked with a compression test like yours.

This is an old and sometimes much disputed issue, I'm afraid. Compression testing is standard procedure on any car engine, but on a small 2-stroke engine things get a bit more complicated. Your reading at 100 psi is what a chain saw or lawnmower normally give, but are you sure you have done a reliable test..? Most compression test gauges are built for large-displacement automotive use, instead of small displacement 2-stroke motorcycle use. For example, the internal hose volume of a standard gauge is over 10cc and the entire combustion chamber volume in a 125 cc 2-stroke is around 10cc. There are special gauges for motorbikes where the hose has a 2-3cc inner volume. The much smaller hose volume of such a gauge mean the engine will need to spin a lot fewer times to get a reliable and repeatable reading. A few tricks when compression testing a small 2-stroke engine: Engines that have sat for some time may have oil leaked in from somewhere. The added ring sealing offered by the oil can greatly increase the pressure reading. Cold Engine only. Hot engines will yield lower numbers, and varying temperature will yield varying readings. Throttle wide open. To allow the same air volume entering the engine at all test runs. Spark plug in cap and grounded to motor. To make sure there is no damage to the ignition system Push the bike in 2nd gear. Push the bike at walking speed for about 10-20 metres. This make sure the engine always spin at the same speed. Repeat the push test a couple of times. Your kickstarter will not give the same engine rotation speed from time to time causing variations in the reading. However, compression tests are not the ideal or most reliable way to test a 2-stroke for trouble. A two stroke engine need compression above and below the piston rings, a two stroke engine must have a sealed bottom end that will hold both compression and vacuum. To test this, you have to place the piston at BDC, plug the intake and exhaust, then pressurize the crankcase through a fitting in the spark plug hole, and check if pressure remain for five or six minutes. The vacuum test is done the same way, with a vacuum pump and the piston in the same position.

There are some really nice builds on that forum. Unfortunately, lots of ****, too. To be kind, this one is a good example of how to not design an airbox.

Your 280 sound and run like it should, just as you say. Regarding your 125, it is most probably a case of too much fuel down low in the register or even too much fuel all the way up. Try smaller main, drop the needle to get it running almost right and then start tuning step by step. If you are running a standard (Bosch) points ignition, check once again points, timing and so on (don't forget the condenser, change if suspect). A small selection of jets and needles and some therapy in the woods is all you need to get it perfect.