WillBrown Internet -
Q: What fuel/oil ratio should I use in my 2T Trials machine?
This is a question that is asked time and time again on the trials chat forums, and while some of the answers provided are quite helpful to anyone who has a newer machine, responses suggesting older machine with "steel" liners need to run ratios of 50:1 or sometimes even 40:1 are misleading, and will only result in badly clogged exhaust systems, which will lead directly to poor running and reduced performance.
In all trials applications heat generated by the motor is going to be far, far less than road race or MX motors, which in some conditions do indeed require the type of fuel/oil ratios often recommended on the chat forums for the older trials machines. The primary reason for running additional oil has more to do with the level of heat generated by the higher output motors, which is dissipated more easily by additional oil in the fuel. Indeed in some instances road race bikes will use more oil on tracks where full throttle openings are more prolonged, and heat levels are increased.
However considerations relevant to road race and MX are not of any great concern to trials riders, and are irrelevant, as heat being generated is a great deal less. All 2T engines will commonly lose around 30% of their fresh intake charge through the exhaust port on each and every revolution of the crank, which in the case of bikes using more oil than is required, will quickly result in exhaust systems being clogged with carbon and unburnt oil residues.
All air cooled 2T trials engines will run very well on 80:1 fuel/oil mix using a GOOD QUALITY FULLY SYNTHETIC OIL, and whether the cylinder wall material is cast iron or Nikasil is totally irrelevant, as no trials engine generates the levels of heat which requires fuel/oil ratios similar to those used for road race and MX applications. The modern fully synthetic oils will work just properly whether the engine is air or water cooled, and anyone who is sceptical about this, might like to have a close look at the very stringent tests that need to be passed by any modern synthetic 2T oil, in order to gain JASO approval.
Finally for anyone who might take issue with the above, there is no reason not to continue using what ever fuel:oil ratio they are happy with, and reducing fuel:oil ratios to a more appropriate level, will not improve the running of bikes with badly clogged exhausts, which for the best possible running must be properly cleaned out or renewed entirely.
300 Fantic front pipe, cleaned out and ready for repacking, after many years of running too much oil.
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Q: I want to take up twinshock trials, which bikes should I consider?
A question which is pretty difficult to answer as individual rider requirements and financial issues have to be very carefully considered before making any recommendations. But saying that its not a problem to provide some general info covering the more commonly available machines, which might help a newcomer to older bikes, to better decide what might or might not suit their own particular needs.
Spanish bikes: All but the very early and some of the rarer late model Spanish bikes are available at prices that are somewhat less than the more popular Japanese and Italian machines. In general a properly rebuilt Spanish bike will be reasonably reliable, but perhaps not quite so trouble free as later Japanese and Italian machines, and all will benefit from having regular careful maintenance work carried out.
Spares availability for Bultaco is relatively good, but some parts for Ossa and Montesa can be very difficult. Spanish bikes can be a very good choice for anyone wanting to try twinshock trials, but maybe not wanting to spend the sort of money being asked for the more popular Japanese and Italian bikes.
Italian bikes: Currently Fantic is one of the more popular choices of twinshock riders. Fantics' are available in 156, 212, and 249cc formats, and all the bikes are reliable and perform well. Spares availability is quite good, but parts prices can be quite high, and this is something that needs to be carefully considered by anyone looking at "project" bikes.
Swm machines can sometimes be found for very reasonable money, but in common with some Spanish bikes, contact breaker ignition systems can present problems as can worn kickstart mechanism parts. Spares for SWM can be found relatively easily, but the cost of some engine parts is pretty high, as are parts associated with the kickstart. A good choice for someone reasonably handy with the spanners, and bikes are very robust and well made.
Italjet and some even less common Italian bikes sometimes turn up, but non existent parts supply, means this type of machine is perhaps of more interest to a collector than anyone wanting to compete on a regular basis.
Japanese bikes: Arguably just about the best bike for a newcomer to trials who wants to ride twinshock rather than modern, has to be the TY175. These bikes are still available for reasonable money, but some caution is required as some TY175s are being fitted with Majesty tanks, and described as such by sellers eager for a quick profit!
The TY250 in standard form is not quite so good as the 175, but parts availability is very good so that it is quite possible to build a Majesty Yamaha replica, with nearly all new parts, and several differing options of engine spec mean the bikes can be built to suit a wide range of rider ability's.
All of the Majesty type Yamahas' are very popular at the moment, and are reliable and ride reasonably well, the only problems being the likely asking price of a good example, and the apparent need to fit TY mono forks to the 250cc based bikes.
The Honda TLR has got to be the best choice for those favouring 4 stroke power, and also wanting bulletproof reliability. TLR250's are currently commanding very high prices in tatty condition, and some parts such as pistons can be very difficult to find. Many people find that a properly modified TLR200 works almost as well as the bigger cc bikes, and a very competitive bike can be built for around the same sort of money as a TLR250 in reasonably good order is likely to cost.
Older TL125 machines are worth looking at for anyone on a strict budget, but these machines can be updated and improved with chassis kits that provide more modern handling and lighter weight, with motors being modified to give extra power. RS Honda derivatives are sometimes available but these bikes are very rare, and the prices being asked means they are perhaps better seen as collectors items, and a properly modified TLR is possibly a better option for anyone wanting to compete regularly.
The Beamish Suzuki is perhaps just about the most reliable twinshock bike around, and spares supply is not bad, with some parts being remade through the Beamish Suzuki owners group. These bikes can be found for very reasonable money, but this is a bike that merits a good test ride if at all possible, as some people simply cannot get on with the handling.
Classictrial modified TLR200
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Regarding choice of bike, if possible its always a very good idea to try and arrange a test ride on the bike that's being considered, as even though something like a Majesty, Fantic, or Honda may appeal to many riders, they simply might not suit someone else, and its very easy to make an expensive mistake in choosing a bike that's not ideal.
* Finally please remember that all of the above information is provided on the strict proviso that any modifications or changes not carried out specifically by Classictrial, are not guaranteed or warranteed in any way, and are entirely the responsibility of the individual carrying them out, and that Classictrial are not responsible in any circumstances for damage or injury that may occur as a result of poor workmanship *