Gran Turismo Performance

09/05/2026

Model C and Lc stainless exhaust going out for testing

26/04/2026

Final bit of work on the J50 with GT110 kit. New headset bearings and seats. Gear cables fixed and inlet derestricted so the stock look carb induction and hose can be retained. To do this, the filter and housing are removed. Then the steel plug in the end of the inlet tube is drifted out. I’ll back to back test this configuration against an open carb to see how much power is lost.

20/04/2026

Model C stainless exhausts coming together. These exhausts will have internal lagging and a machined brass nut. The first fit and function prototype will be running in a week or so. The brass nut has the same external dimensions as the model D exhaust so it uses the same spanner. This shouldn't be a problem on open frame engines but I might have to address some clearance problems if the cylinder has a cowling. Hopefully the prototype should be able to identify any issues.

18/04/2026

I've been meaning to get my J50 (kitted with a GT110) running for ages finding a good exhaust was always the obstacle. Saw a post from Adam Bower (Sole Power Tuning) in the USA about the expansion pipe he makes for J range and thought I'd give it a try. The pipe arrived, I got on the bench today to fit it up and see how it performs. The fit was excellent, anyone with a J knows that routing an exhaust inside the frame an panels is pretty tight, this went together very easily. The only minor thing is cable tie the control cables down to the engine bar to keep them from melting on the header pipe. The performance is very spritely, need to iron out a few build errors next week (head stock bearings and gear cables) then take it for a proper spin. The engine is built on a budge, running the original gearbox and clutch but pulling a 16T primary and 46T crown wheel on 3.00x10 wheels (converted from the original 9" rims). The ignition is V**E, carb is PHBG19 (I ran it open in the end), standard clutch with stronger springs. Gearbox calculators suggest a cruising speed of 50mph to 55mph which is perfect for ride outs.

20/03/2026

20/03/2026

Today’s little bit of fun, my model D is starting to progress at Disco Dez Scooters. Sporting an anti dive front brake, GT150 kit with booster exhaust and a supercharger, just placed in position for now. Still a bit of work to complete the top end but definitely have something to put the spanner’s on now

23/01/2026

First castings for the GT125Lc have arrived. Some minor clearance tweaks to do to the tool as the production process changed. Won’t be long before we see the first ever serious performance kit for these early shafters.

29/12/2025

Lots of exhaust work has been happening behind the scenes and we're very close to firing up the first engine for test. This is the first "get up and running" exhaust. Rotax did make all the SkiDoo and SeaDoo engines work with 2 into 1 but they had big budges and less space constraints. For now, I just want to get it in a frame, shake down the electrics, plumbing, fuel system, put some miles on it and have some fun. After that things should come together quite quickly. Lots of crazy stuff is pencilled in for 2026 keep an eye on the page to see what's happening or drop me a message if you need anything special.

22/11/2025

Our friend and Rotax fan Joerg has built his Gran Turismo 580 Rotax engine. The weather is very cold in Germany so it will be a few months before it’s warm enough to get this weapon gets out on the autobahn.

21/11/2025

Another day on the crank building but this time a bit different. I've been building Gran Turismo cranks for a very long time and I know the parts extremely well but todays building as a little bit different.

The customer asked me to re-rod 7x 60 stroke 110 Mec cranks with Gran Turismo rods and bearings. Pretty straight forward but there's a catch and the devil in the detail. Stripping the webs for rebuild was easy enough, they came apart at 3.5 tons (one was missing a shim but I had some spares). The customer wanted a tighter fit on assembly so I used one of my over-sized step pins that I had made a few years back. These pins add an extra 0.02mm interference and need to be assembled with Loctite 640 to lubricate the initial fit and then set.

Everything worked out well will a 5.5 - 6 ton press fit. However, I noticed that those tricky fellows at Mec have a slightly longer pin than standard (41 not 40.5). This meant that assembling the new tighter pin had to be stopped short of the ground face by 0.25mm.

To achieve this I took a leaf out of the Vietnam restoration guide and made a small shim out of a coke can lid. This was placed between the press bed and the pin and had the desired effect.

The rod was then re-assembled with the rod being wiggled until the top web just started to nip, back off the hydraulics and the rod frees up nicely. I got the builds nicely systemised but a heads up for anyone building cranks to double check the pin length, rod and web widths before piling in with the press.