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turbohead

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About turbohead

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  • Bike
    SWM TL 320

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    Sweden
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    Male

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  1. turbohead

    His fork kits

    HFS is an excellent update for all old bikes, no matter if it is a SWM, Fantic or something else. If you can afford the PRO version, you enter a new era for 35 mm forks....
  2. turbohead

    1982 SWM 320TL NEW

    I must admit my enduro background make me a pretty lousy trials rider, still. Back then, when things got real tricky, speed could save your day if you were good enough and that is very hard to forget or get entirely out of your mind, so nowadays I still ride though sections too quick with too many dabs. Perhaps I should put the blame on my TXR engine and its primary gearing, not myself....? Seriously, you have a point. I'll begin with a 56-60t sprocket and see what that mean to me. Before summer I could even consider taking the engine apart, if things turn out your way. Maybe! (BTW no Telford this year, working a couple of weeks in Africa!)
  3. turbohead

    1982 SWM 320TL NEW

    I am using a swingarm from a later Aprilia TXR bike, as they were more common, at least in northern Europe. No problems to make them fit any '80s SWM bike, just make some spacers between frame and engine, then weld on a pair of shock mounts and a fitting for the rear brake. However, regarding primary gearing, that must be a matter of personal taste from b40rt, as the higher gearing works perfect for me. If not, why go to all the trouble changing clutch basket and so on when you could go for a 56-60t rear sprocket (if you really need to go that slow....)?? 🙂
  4. I only have a rather low res pdf of this, but hope this may be what you are looking for. SWM 125.pdf
  5. turbohead

    SWM Modifications

    As I wrote above, sound level is (almost) comparable to stock. If you are in sensitive surroundings, don't go for a larger single outlet pipe or mx silencer. Regarding welding, I always use TIG for high stress or vibration exposed welds. You can get decent results using MIG, but the heat affected zone is bigger, the bead process is harder to control in detail, so I play it safe (or use my MIG to fix the parts and then do the actual welding with my TIG). Brazing with a gas torch (or TIG) is an alternative (but take some practice), specially on high alloyed steels.
  6. RIP mr Pickering. Very sad news, indeed. I have been collecting parts and advice for a planned Bantam build over the last year or so and Jim was a goldmine of tips and tricks. As an expert always willing to share his thoughts, he was one of the very few real authorities.
  7. turbohead

    SWM Modifications

    I agree with b40rt on most issues, specially regarding the footrests. Use CrMo plate of the same thickness as the side plates and TIG the bits in place, pre-warm the plates and keep them warm, making the plates and welds cool down slowly (check for any sign of cracks after every ride during the first couple of weeks). However, regarding the midbox and rear silencer, a bit more work than b40rt suggest is well worth the effort. Cut them both up longitudinally with a thin disc and start removing whats inside. Repack the midbox with good hi temp insulation and reweld. Then, cut out everything inside the rear silencer and cut off the rear part as shown. Get a bit of perforated pipe or make one up, to fit between the inlet and a new wall in the rear part. Weld the front part longitudinally and do the same with the rear part. Then, weld the new wall in place in the rear part, as shown. Finally, fit the perforated tube into the front part and fill up with insulation before riveting the two parts together, then paint. I have kept the original twin outlet pipes on this one, but you can also try a bigger single pipe if you like (louder and less back pressure). The silencer shown here is almost as quiet as the original, but is a much better starting point when tuning for better power delivery all through the rev range (porting, ignition timing, carb set up and so on). Of course, you could use any modern mx type silencer instead, but a little visual cheating can be nice, or....?
  8. I asked myself the same question as you the other year, but decided to thrash de whole decompressor kit, took the head off and welded up the hole from both ends. Strange, but I have never missed the decompressor after that, as the Rotax engine is such an easy starter (when set up right).
  9. turbohead

    Electronic Ignition

    Of course, anyone considering to finally get rid of the old crap should go for the Pro version! You simply never know when you need that extra power. Seriously, the sooner you go electronic the better, Pro or not!
  10. turbohead

    airbox

    As we are talking Fantic here, not disc-valve engines, the bigger-is-better rule applies. Regarding Aprilia, SWM and others with Rotax disc-vale engines, you are right, they are less sensitive to airbox volume because of the dampening effect of that long inlet tract and the precise timing of the disc.
  11. turbohead

    Electronic Ignition

    At last, Martin! A little late, but definitely worth waiting for! Of course, there are other systems like these available and there are other ways to go electronic for everyone willing to do a little homework, too. However, as bolt-on and go systems, these look very interesting and good value for money, the PRO version in particular (of course). Regarding lights and such things, a total loss system with a small NiMH battery somewhere on your bike, usually keep police and MOT-people happy.
  12. turbohead

    airbox

    Have a look at any modern mx bike and you see the answer. As big a box as possible for the frame and with be biggest filter and cage you can fit inside. The old twin-shock frames are much easier than any modern trials bike in this respect, so it's just a couple of hours of relaxing thin sheet metal work, for example 0.75 mm aluminium (or as thin as your welding skills allow). Try finding a cage and filter from any mx dealer and you are almost there. The cost for all this is......very relevant for what you get, in terms of looks and (often) performance. Perhaps the difference to your wallet can be justified, after all...?
  13. Rotax in the older days did things their own ways, sometimes a bit too much their own. Like their disc valve controlled intakes for mx, enduro and trials engines. And the use of magnesium for transmission and magneto covers. Also, their clutch operating designs, as shown here. Everything a bit more self-willed than outstanding. Of course, this clutch operating system can be made to work OK, but ..... . The answer from Rotax came a few years later, with a conventional solution, like on most other dirt bikes. Much more rugged, simple and reliable, lighter to operate (see below). On the other hand, complicated solutions, exotic materials and so on are always nice to find when examining an old engine design......
  14. And what Bantam you have there! Please, give us all details of frame, wheels, suspension, engine spec and so on! (just thinking of starting a first D1 build myself, while I am getting used to trial for the second time in my life, now retired and riding an '81 SWM 320 .....)
  15. Or just leave the spring as it is and buy one of these, to be used an hour or so, daily. Then use your other hand, too. No problems whatsoever riding any bike a couple of weeks after that .....
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