Leaving aside for the moment the preparation of the cylinder and the piston that are "work in progress", this is the first part of the upgrade that includes : a new profiled intake manifold, special works to the carburetor and reed valve, new air filter, a wing placed into the "Venturi" of the carburetor, adjustable ignition advance.
I've set up a second engine block, restored to new in all its parts, then I've started to test it across dyno runs an the at the end, on the track (altough my bike is the full power Belgarda version, as a modded engine, it can only be ridden on closed circuits). So I can place back my stock engine on my bike when I want to come back to everyday use on roads.
I engineered, designed and prototyped a special inlet manifold basing on my former project: this is shorter (this makes also carburetor manteinance easier
) and wider than the original. Made to optimize the volume of the flow to the reed valve at any engine speed. This gave an amazing fast response to any throttle openings and the engine has gained a few hundred RPM in the high-end, versus my already nice performing intake manifold.I've tried different thicknesses aluminium block spacers between reed block and cylinder to increase crank-chamber volume. I decided to abandon this solution because it only gives a gain at low RPM, which could be a good thing if you are using your bike offroad.
Then I've tried a Dell'Orto VHSA 32 from a Belgarda TZR/R : the bike was very lazy under 8000 RPM, then the power "exploded" until 11500RPM, but when you come out from turns you have to use the clutch, to have a quicker sprint. So I decided to have a special processing of my standard Dell'orto PHBH 28, reboring to the maximum allowed by the body and smoothing the "Venturi". Obviously I had to have a new setup for the jetting. Great job : together with the new inlet manifold, the bike is so much more "aggressive" in the response, without loosing performance at low RPM. The sound of the engine is now deeper and even more since I've built a new air filter with very permeable sponge.
To have better response coming out from circuit curves, I studied a wing that placed into the "Venturi" gives the effect to have a smaller carburetor until middle throttle openings ( but you can configure the position of the wing), and so more torque in the low RPM. Works fine, but carburetion setup is a little bit trickier.
I reworked also the reed valve, that has lost the original stoppers and uses double petal reeds. The bike runs smoothier in the midrange. The same in the high end.
Then, to "finish the job", I've made ignition advance adjustable. Only by a maximum of 4 degrees, since I have the same variable advance CDI as the TZR/R, and it's already "sporty". Tried at 4 degrees, and have a lot of gain in performance, but also some dangerous detonations, so I decided to lower the advance by 2 degrees. Enriched the jetting at any level, the bike is very quick in gaining RPMs along all the power curve.
That's "all" for the moment, as soon I'll have a final dyno run to see which is the level of performance. From what I can feel, maybe 2-3 HP were gained, but the real difference sits on the driveability. You can run the bike at any RPM: so not an extreme tuning, just made it sportier, and having fun designing and prototyping all this stuff.
Only a few last words : 1) Do not do this tuning on bikes that you use on roads : in addition to not be allowed, if you really want to enjoy your bikes, have a turn or two on track. Enjoy yourself without taking risks.
2) The tuning I've given my bike, is the result of study, tests and very accurate setup : this means that these modifications, if executed improperly, could seriously damage your bike and yourself, at your own risk. I decline any possible responsibility.
...........hopefully one of the other members may be able to reply to your question. 
This forum is full of solutions, tips and amazingly competent people, and it is a pleasure to share with you all my passion for two strokes and TDR in particular. 
