New Big Block Gran Turismo Kit 200-245cc

[Mr G in NYC]

Any news , updates, release dates on this GT 200-245 kit ? Thanks. G.

[Rich_T]

Two prototype barrels are cast and machined, one goes on test this weekend after I have honed it (66mm bore 58 stroke). This will be going into a stock "bolt on" build for a few weeks. The other will be going on a tuned engine in the very near future, it is just getting bored to 70mm for a DT250 piston conversion and 62mm crank (240cc).

There are a few mods required to the tooling before production but everything else is finished and ready.

[Yanker]

The LC barrel is 272cc on a 60 stroke. This is done for a couple of reasons, firstly to keep the cylinder length down (for foot print and packaging reasons),

Rich, can you please help with a few words to help me understand this aspect of the concept. I can understand cylinder length and frame constraints but "for foot print and packaging reasons" has me truly baffled. What does that mean?

[Mr G in NYC]

Thanks for the update, looking forward to hearing the results
Hope all goes well with the tests.......... G.

[Rich_T]

Foot print and packing are to do with the geometric constraints of positioning reed valves, inlet manifold design, routing inlet manifolds and carb positions / clearances.

Things like crank stroke and potential power have a big impact on web diameter and web thickness. This also dictates what type of rod you should be using etc. This then has a direct impact on where a reed valve and be fitted and how a carb and manifold can be routed. You have to also consider market flexibility and how the kits could be broadened in application without weakening the offering. Combine these factors with costs and how you can limit the number of specially machined components and you'll understand what I mean. You have to methodically work through the variables till you're certain of every decision you make.

These considerations greatly improve the design potential and reliability. It is why these more complex parts take time to achieve, it is almost a continual 12 month process of VA/VE analysis until you press the button for tooling and parts at the end. Even then you find odd errors and have to revisit design and tooling mods which is frustrating.

[dutch]

so what make of crank are you using rich ?

[Rich_T]

The stock GT200 big block kit will run with 58 or 60mm stroke cranks with stock 107 rod. This was the original design intention and configuration, as previous with the small block kit. You would need a good quality crank, Mec, Maz, BGM (with 3mm packer) etc, do not use stock Indian cranks unless they have been rebuilt with a new rod kit.

The stock 350LC piston rus out of oversizes at 66.5mm. From then on there are a multiple options up to 71.25mm bore. These include DT175, DT175K, YSF200, RM250,YZ250 and DT250. To achieve some of these configurations different rods and packers are used. I have a table for this which will be released with the kit and included in the build manuals. At that time I should be much more involved with cranks so I should be in a position to machine, balance and build special cranks.

The LC cylinder uses a special crank, it uses a CR250 rod with full width crank pin. The stroke is 60mm but the webs are much thicker and larger in diametre. They can just about be incorporated into a machined Lambretta casing. This new crank has a taper suitable for direct connection of the RS125 flywheel. Lambretta flywheels are nothing short of poo, big, way too heavy and have crap electrics in every sense of the word.

[dutch]

all sounds very exciting and just what i`m looking for, i have the small block gt and love it.
keep us posted rich.

[Darrell Taylor]

Lambretta flywheels are nothing short of poo, big, way too heavy and have crap electrics in every sense of the word.

i do think the replacement electrex and new casa ignitions with there 1 piece flywheels/rotor are very good ,theres options on weight on the casa too and on the electrex ive tested 4 different weights and the lightest one showed to be the least favourable although there is a noticeable improvement in sound and rapid pick up at low rpm but the dyno results and road tests prove very different
quite a few of the high power motors ive done have run the electrex for up to 3 years now and had no problems so are proving themselves ,sticky has the casa/ parmakit on for a year now and think its proven reliable as its just a varitronic kit but with a new flywheel to replace the only part that used to fail before

[Rich_T]

I understand your comments Darrel and I don't take them as contra or negative opinion. The current stock of variable ignitions satisfy a portion of todays current market that require spark advance/retard. Ironically, the RS ignition could be built by a DIYer for only marginally more than a standard Indian ignition and considerably less than a Varitronic.

The thing that I see, or want to do, is address the developments that could be made in the future, this will be things such as EFi and engine mapping. It is not possible to achieve this with any of the current ignitions, you need a platform to work on and add to. This is, in essence, what is driving the development in his direction.

There is no doubt in my mind that 2kg flywheels are far too heavy and probably a very good reason for some cranks getting twisted. If I were going to put dead inertial mass anywhere in a bottom end it would be in the crank webs where the extra width could be used more positively to retain the crank pin and counter balance the moving parts without a huge torque load going through the mag side taper.