In stock form the TLR200 suffers from a lack of power/torque, when being used in
serious competition. This is compounded by the stock wide ratio gear-box, which has
a quite large jump from 1st to 2nd and 3rd gear ratios. However while the TLR250
is obviously more powerful the front end of the bigger capacity bikes is very light,
and grip is often much harder to find than with the smaller machine, which means
a properly modified 200 is well worth looking at.
During 2008/2009 Classictrial have done quite a bit of basic development work with
the 200 motors, and have found that with simple changes to carburetion and exhaust
the bikes can be improved very noticeably. However while the changes made are very
straightforward, they involve the use of special custom made exhaust and air box,
which are realistically not commercially viable to make in the type of numbers required
to reduce the cost of these parts.
Something else we have tried is using engine parts from the ATC200X trike on the
TLR 200. These trike motors are easily recognised as the kick-start operates in the
forward direction, and cooling fins on head and barrel are slightly larger than the
trials motors. Parts for ATC200X are scarce in some parts of the world, but can still
be found relatively easily on the USA Ebay site.
*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 warranted 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*
The complete ATC200X top end can be fitted to the TLR, and it is possible to use the far superior early type head mounted ignition pick up and mechanical advance/retard unit, as long as the ATC200X cam is also retained. Porting on the trike head differs to that used on the trials motor, and the compression ratio is higher, another less obvious advantage is the fact the motors run a little cooler due to increased fin area.
Higher compression ratios always result in more torque, but while its very easy to fit a Wiseco forged piston with higher compression to an otherwise stock TLR200, there are very likely to be problems with detonation, as full ignition advance is reached at a relatively low engine speeds. If the stock ATC200X type ignition system is retained, this can be carefully modified to exactly suit each particular engine set up, and problems with detonation can then be avoided.
Carburetion and exhaust are still very important on a bike using ATC200X parts, but with increased compression and a proper linear advance curve tuned to suit a particular motor, the deficiencies of stock or less efficient aftermarket intake and induction systems are not quite as noticeable. The improved porting provides more top end power, but lower speed running is compromised to some extent as gas speed is reduced a little, especially so if a 24mm carb is being used.
A TLR200 motor using parts modified by Classictrial, has been built for for use in the 2010 British twin-shock championship. This employs the ATC200X head casting, which is fitted with a special bronze inlet valve seat to improve gas speed at low rpm. The shape of the inlet port itself has also been altered, which helps provide improved pick up, and completely eliminates any of the problems related to hesitation and flat spots, common on some 4T trials motors.
It is worth bearing in mind that while fitting an ATC200X top end and ignition system, will certainly improve performance noticeably, that its definitely not simply a matter of bolting on alternative parts, and the fine tuning and final set up work required is at least as important a factor in the final result, as use of the parts outlined above. We are pleased to assist with advice on using parts from the ATC200X to improve the TLR200, and have a source in the US where parts can sometimes be obtained.
