GT big block experiance : New GT crank info added

[eden]

tried the Avanti and had a good look at one of the barrels,

rode along with all three several times.

I wont slag any of them, I don't think its good practice to slate something just because you prefer something else. so no comment on the others you have mentioned.

The GT isn't like anything else out there that's for sure and being cast iron it has more pro's than cons going for it.
I'm sure Richard could explain much better why cast iron is a far better choice for todays conditions than me.

What I will say is that once more of these kits are out there and more people either get to have a go on one or get to ride against one i'm sure more and more people will decide to buy one.

They do everything a lambretta rider wants, what ever their style of ridding. Also we have found they are very economical on fuel, not as economical as a standard 200 but not far off, an example is on the way back from the four nations last year I used nearly half the fuel the TS1 riders used at each fill up. It's so economical I haven't even bothered putting a long range tank in the scooter.

Next week I should be able to get a good comparison video as a few of us are ridding down to the Modra rally from the midlands just for the day, the engines in the scooters are varied, ts225's ts230's RB's and a few others. unless its fking snowing then I aint going!



Rosscla, yes we are both running them on lawnmower oil

[eden]

I fitted another bridge port GT200 to another mates GP this afternoon.

After fitting the kit and cabling up the new carb I turned the fuel on, put the choke on then kicked it over just to pull some fuel through and to my amazement it started with just that 1 slow kick.

This one is running a 30mm with a an AF big bore while he runs it in then he intends to fit an expansion.

the bits!


it was a standard 200



its also just a straight bolt on, I don't like doing this with out knowing whats in the engine but that's what the guy wanted.
standard crank, I wonder how many revolutions thats done over the years lol



Bridge port port layout



inlet



Exhaust port




Sounded sweat as he rode away with a smile on his face even though it was p1551ing down with rain

[dansacred]

are the bridge ports for sale now, much difference over the mono port?

[fastfrog]

Nice kit indeed; a bit "brut de fonderie" but feeders look like a valuable addition to the bridged exhaust....

[lammy57]

Is there any differences between the two! No happy if there is as I just bought one a couple of weeks back!

[olliewtf]

I am by no means an expert but I would have thought that a bridged port allowed for greater tuning on the exhaust port without the risk of dropping a ring? can anyone confirm cause I want to feel clever! these look like great kits, if I were on the market for a kit its probs what I would go for, but probably mainly cause its from Birmingham!

[eden]

One has bridged exhaust port and one doesn't, the one im running doesn't have the bridged exhaust.
Bridged one as far as I know isn't on general release yet as its testing has only just begun.

The unbridged version has proved its self over the last 12 months.


Lammy57, have you fitted your kit yet?


Yes olliewtf, the bridged version would allow for tuning, it has a little lower exhaust duration than the non bridged version.

the non bridged barrel I have isn't now like any of the production kits, I always wanted to play with the kit in terms of tuning and mixing and matching other components with the kit. after all, there are more people like me out there that don't just want to buy a nice engine, its fun to tinker and the kits have loads of potential for further tuning.
I would like to get hold of a bridged version to tune but I think Richard doesn't like seeing his babies butchered i'm still hopeful though
The performance seen so far on the untuned kits is far above my expectations, they don't need further tuning tbh. I just like cutting metal.

[Rich_T]

The Bridge version is not proven yet, the single port is.

Bridges have been around on Iron Barrels since the 80's but as they were fabricated in there was always a question about reliability. The traditional problem being that the bridge would over heat after extended periods at full throttle (motorways, dual carriageways etc). There are things that I've done to mitigate this but it's just theory at the moment.

These bridges are cast in on the GT200 and this was a test development after I made a couple of bridged 186 barrels just before the Avanti came out. Incidentally, There was not a massive difference with the 186 bridged port over the single. A small number of bridged GT200's were cast to test but I must add it is early days and there is not one dyno chart for it yet, just empirical testing.

The single port configuration has 18 months of road testing and is targeted at touring, with the potential for higher states of tune. As yet, the bridged version is relatively un-tested and if anything goes wrong with a bridged version it is history, no recovery is possible (with a single port there are lots of options if catastrophe strikes). Consequently the bridged version is a gamble, I really wouldn't be jumping about until it has 18 months of running.

[Spanish Fly]

A couple of questions:
I see some fettling has been performed on the inlet and exhaust ports. Is that how they come from GT?
Also the head appears to have two spark plug holes and the centre hole is plugged. Is that done like that for testing purposes or is it a "production" head?

Thanks
SF

[eden]

I haven't touched the kit pictured above, its how it came.

As far as I know the heads are production heads, you have the option to run a centre plug or side.