GT 200 testing

I decided to see what scope there was for tuning the GT200 barrel, so with the other prototype barrel I created a 240 conversion.
For this I used 62mm webs with a 115 rod which had an 18mm wrist pin so used a KXD 70mm piston.
This conversion didnt last long due to the crank twisting so I then used 60mm webs with a 107 rod with 16mm wrist pin and decided to see if a TS225 piston (70mm) would work with the kit.
I lifted the exhaust port to make the blowdown longer and gave all the other ports good chamfers

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The 230 was dyno’d early in 2014 along with the standard bridge port GT kit as part of a Scootering magazine article on the GT kits

The blue line is the GT230, Red line is the standard GT200 and the Green line is a tuned GT186

Over the next few months my GT230 did various rally’s including Coast to Coast, Cobblesoul, Tenby and Whitby, both Tenby and Whitby were done as day trips both over 350 miles each day.

Then after doing many miles with out problems I filled up with standard unleaded fuel saver from Shell on the way back from a day trip to Catcliffe and 35 miles later holed the piston.

Very clean hole and damage to the head.

The holed piston gave me the opertunity to try something else, something I had been considering for a while. I had purchased a 70.25 Wossner piston from AF which has no reed windows
The plan was to try the GT with out reed windows to see if there was any difference in performance, the GT’s Boyesen feeds are above the piston face so if the engine wants to pull charge into the barrel it would be able to with out reed windows when the inlet is closed by the piston skirt
The only problem I had was that it was Sunday night and I was due to leave on Thursday to take part in the LCGB Lands End to John O Groats trip, so i had to get the rebore done very quickly for me to have time to also rebuild the engine and get some miles under its belt to iron out any issues.

A friend of a friend said he would be able to do it and get it back to me the next night (Monday) so I decided to risk it and give it to him to do.
Monday night I went to the pub to meet the guy only for him to arrive and say he had left it at work, I insisted he go and fetch it as I was running out of time so he did. when he came back I tried the piston in the bore and thought it felt tight.
I had asked for 4 thou clearance and the guy asured me that was what he had done it to. I had no other option but to get it built and see how it ran.

I had to cut an arc in the piston to improve inlet timing

I managed to get the motor built and running by Wednesday night and took it out for a test ride. The bore was tight as it nipped up at only 40mph
I decided I would still do the LeJoG event but would have to run it in on route taking it very easy. To say it was a pain is an understatement,

During the first day riding from Lands end to Warwick any speed over 40 mph resulted in a seize, I must have seized it that day more than 20 times but it made it and loosened up a little as the day went on, by the end of the day I could just about sit at 50 mph.

Day 2 was Warwick to jedburgh in horrendous weather, the rain helped the motor in that it kept it cool as it was still very tight. That day I only seized it 5 or 6 times and was traveling a bit faster than the day before so it was improving.

Day 3 was jedburgh to Fort William, great roads through the Highlands and that day I only seized it once.

Day 4 was Fort William to John O Groats, Again the motor ran better and better all day, with about 50 miles left I decided that as it now had 900 miles under its belt that I would ride it normaly. on the last streach of road which leads to the Finger post at John O Groats I finaly opened it wide open and let it rev out in 4th only for it to seize yet again just before the end of the road.

Everytime it seized that weekend I never once pulled over with it still seized, i rolled and let the clutch back out to get it running again, I’m sure if I hadn’t done this I would not have made the trip due to gummed in rings.


With the Euro in Davos coming up I needed to get the bore sorted so i decided to take the barrel and piston to Ralph Saxelby for him to bore it while i was there.
When he measured the barrel the bore was very tight at the bottom and oval, the most clearance was near the exhaust port and even then it was just under 3 thou.
My only conclusion regarding the quick bore it had had was that as the piston was only 0.25 bigger than the piston that was in it that the bloke hadn’t measured the bore at all but had tried the piston in the bore and just given it a hone.

Ralph bored it and gave it 4 thou clearance, the clearance I had asked the first guy to bore to.This meant I had to run it in again before the euro.

I rebuilt the engine and got it back on the road to do some miles and before no time I was on my way to Davos for the Euro.

We had planned to ride to Davos going through as many countries as possible and this is how the trip went:

Day 1, Birmingham to Charleroi, 3 countries.
Day 2, Charleroi to Saarbucken 3 countries


Day 3, Saarbrucken to Basel 3 countries

Day 4, Basel to Davos 3 countries ( we popped into Austria and Liechtenstein )


The GT230 had no problems at all, in fact the only problems I had were with my helmet cam, it eventually stopped working so I had to buy a new one while in Davos .

After a fantastic three days in Davos on the Euro Jamboree we headed of for the next part of the trip, the part all of us had been looking forward to.
We rode over the Alps taking in as many passes as possible including the ledgendary Stelvio Pass. We passed into Italy before Stelvio and after it we headed to Milan.
The weather on that Sunday was terrible, it rained most of the time in the Alps, we even saw snow falling while getting warm in the cafe at the top of Stelvio Pass, but the weather really turned bad as we got closer to Milan. Thunder and lightning and the heaviest rain I have ever seen, it rained so much that as we got close to Milan the motorway was closed due to flooding and we had to take a detour which resulted in us having to ride through water that came up higher than the floor runners on the Lambrettas. We were sure that one of our engines would suffer water penetration and stop running, but the gods were on our side that day and we made it to a Hotel in Milan with out any mechanical problems.

The next day we rode into the centre of Milan and then out to the Innocenti factory ruins, from there we made our way to Casa Lambretta and recieved a warm welcome from Vitorio who proudly showed us round his Lambretta museum.

Later in the afternoon we rode to the Monza race track before heading back up into the Alps for the return trip.

We made it to a hotel in Lucerne at around midnight after riding through some of the longest tunnels in the world and up over the Alps in the dark. Again we had no mechanical problems between our four Lambrettas.

Those two days are among the best two days ive had riding my Lambretta!

Big thanks to Russel Baker, Chris Butler, Chris Canavan and John Jack!

and my wife for letting me go 🙂

We rode the rest of the way and arrived in Cleathorpes the following Friday for the national rally.


The video below is the 1st cut version showing some of this adventure



The trip proved that the GT big block kit was viable. I am still riding GT powered Lambrettas to this day. One is still this 240 and the other is a 250 conversion.