Hi
Here comes my GT200 Big block experience.
The engine was built during last winter/spring. It was back in to the bike by May-June. Since then I have done approx. 1000km during the summer. So here are my experience with the kit.
This was the first time I run an engine with reed fuel induction, I've been used to piston controlled fuel inlett.
I ordered the GT 200 kit from Rich. Top service.
The engine.
This was a SIL200 engine I've used for over 10 000km. Bought new back in 2007 and never touched a thing within the engine. Guess I was one of the lucky ones to get one that lasted for so long.
The last year it started to act up and upon inspection I found that the sil crank was misaligned. This left me with a 200 engine to try the GT 200 on! Perfect!
First, the ignition was upgraded to BMG stator with full wassel battery DC. Paired with a BGM CDI (died in august, Mitsubi one in now). SIL lightened flywheel on 17°.
I also did instal Rich T's prototype GT Cranks. The ones with SIL webs, Japan 110 rod and plastic stuffers with 58 stroke.
Indian GP gearing with final ratio at 5,22.
The carburetor is a PHBH 28 Dellorto with jetting according to the GT manual. After reading through this thread and the Scootering article I upped the main jet to 135. The PHBH breathes through a standard GP rubber below and a Ram air foam filter with some filter oil on. This way I recon I could run the carb with no filter if I wanted to with only a main jet upping to 140.
AV268 atomizer, X13 2nd clip needle, 40 slide, 55 idle jet, 70 choke jet.
For exhaust I choose the MBGM big bore V2. Sounds awfully loud but it does it's job and performs like an expansion.
I did polish up the exhaust port and matched the transfers to the casing.
The experience.
The kit with the phbh setup and the MBGM exhaust gives a clear power band. It starts to kick in at 4600RPM and revs on to 7000. keeping it within this range I can easily go through the gears and maintain speed and acceleration.
Anything bellow this revs and the scoot feels kinda, tired and hesitant to pick up. As soon as it reaches 4500 inch RPM it flies off like it's been kicked away! Turbo powers

Makes me happy with a smile. slow riding in traffic to work and it just feels a little bit hard on the low revs plus it drinks a lot of fuel. It needs revs and speed. I have calculated an average consumption of 0,76 l per 10 km.
I could go down on jetting on the range 1/4 to 3/4 range, to sort out the low revs running but the jetting is perfect when the engine is in the correct rev range so I'll keep it for now. Maybe either drop the needle one clip or change to X7 and do plug chops to see what happens.
One other thing I've noticed, when the revs reach the rate at which power kicks in it always makes a short hesitations before it kicks of. Something like the engine goes, yes, no, yes, on, yeeeeeeeeeees and off. This regardless of throttle position. It connected to the revs. I guess it's down to the boysen ports start to kick in.
a month ago I did a 400km trip 2 up. The bike worked prefect, never any trouble to overtake cars or climb hills. It pulled really well and acceleration was just a twist away.
Overall I'm very happy with the kit, would gladly recommend it to others. Also working with Iron means this kit probably gona survive a long time.