GT 200 testing

I was asked a couple of years ago to test the prototype barrels for the new GT200 kit,
The GT186 kit had been available for many years and had proven its self to be reliable and powerful for a small block kit. As I’m an avid advocate of cast iron barrels I was more than happy to take part in Richard Taylors new venture.

The GT200 has boyeson feeds from the inlet that meet the transfers, pictured below:

They come with either a single exhaust port or with a bridged exhaust port,

The bridged port is wider and lower in the barrel than the unbridged port, the bridge port is also not as high as the unbridged meaning that the lower edge of the port is higher than the piston crown at BDC. On all the bridge port barrels I have built or sold I have lowered the bottom of the port so that it sits slightly lower than the piston crown at BDC.
Having said that though, I do know of other bridged GT kits that have not had this done and run fine!The exhaust timing on the standard kits running with a standard crank (58/107) are:
bridged 178 degrees
Unbridged 181 degreesOn the current batch of the barrels (May 2015) the port heights have been slightly changed to:
bridged 176 degrees
Unbridged 179 degrees
There were concerns over the bridge port version that the bridge may not be strong enough so the first prototype bridged barrel was ran for nearly a year. The fears about the bridge proved to be unfounded when the bridge in this prototype barrel survived a catasrophic rod failure.
The piston was destroyed leaving just the crown intact and a very bent broken rod, when this happened the bridge in the barrel would have suffered many impacts but it stayed intact.
The damage resulting from the rod failure,

The barrel pictured above was later used for my own GT250 conversion, info about the GT250 later!

The head on the GT200 is the GT Porcupine.

The head has its fins radiating from the center of the head which helps to transfer heat from the combustion chamber more efficiently than the conventional Lambretta head design.
The head also has two options for spark plug placement, centre or side. Which ever option you choose there is a plug for the other hole.

Porcupine head, pictured below:

The reed block is pictured below showing the replacable reed petals:

The Inlet manifolds pictured below:

The GT200 Piston is the same piston used in the Yamaha 350 LC Power valve engines. There are 9 piston over-sizes for complete kit longevity!

The first prototype kit was fitted to Mik’s GP200, it was an unbridged barrel and was first tried with an AF big bore box exhaust and a 25mm Delorto Carb.
Mik was instructed not to “run it in” to see how it would be if poorly looked after from new. It was also decided not to blueprint any of the ports and to just bolt it on.
It pulled from low down really well due to the reed and revved on nicely even though it was running a big bore exhaust. The exhaust was a few years old and the extra power soon finished it off. After trying an old JL4 for a while his new Franspeed race exhaust arrived. The “Fran Race” transformed the performance as you would expect, it still pulled extremely well at low revs but now revved out and had a nice kick as it hit the power band. It clocked 82.7mph on gps and still didn’t have more than 200 miles on the barrel. his gearing was 4.8 final drive.

This GT200 is shown in the video below, from time stamp 2:08
Im shooting the video following Mik on my 30 bhp motor