Two-Stroke Exhaust Design

Improve the performance of your two-stroke engine with a TorqSoft designed exhaust system. We shall send you a pdf document with the templates for manufacturing your exhaust. So whether you have a 50cc road bike, a 500cc motocrosser or a classic racer, we will design the perfect exhaust system for you.

Your new performance exhaust shall be designed and your pdf document emailed to you within 48hrs after filling in the form below with your engine details and the payment of 55 euro via either paypal or credit card.

No. Ports
Exhaust Port
Port Opened Duration


For our design example we are going to design an exhaust system for a 50cc Minarelli AM6 engine. This water cooled, reed induction engine is used in a variety of 50cc production road bikes such as the Aprilia RS50, Yamaha TZR 50 and the Rieju. Our example has an after market 50cc performance cylinder with a bridged exhaust port.

In the design form first select the water cooled and reed induction options from the dropdown menu's. This cylinder has two exhaust ports and five transfer ports so enter 2 in the No. Exhaust Ports input box and enter 5 in the No. Transfer Ports input box.

Next enter the dimension for the exhaust port. This is the length from the piston face to the end of the exhaust flange. The diameter is the internal diameter of the exhaust flange. In this example the dimensions are 45mm and 27mm respectively.

Next enter the cylinder bore and stroke which are 40.3mm for the bore and 39.0mm for the stroke.

Finally, enter the exhaust duration of 184deg and the peak power speed of 12500 revs/min and click the Design Now button.

TorqSoft - Two-Stroke Exhaust System Design

Check your input data and click the paypal button. Note that you do not require a paypal account as you can use your credit card.

TorqSoft - Two-Stroke Exhaust System Design Validation

On receipt of your engine details, we will design an exhaust system and create a pdf document with all the templates required to fabricate your pipe - as shown below. This pdf document will then be emailed to yourself. Click on the image below to open a sample exhaust design pdf file.

TorqSoft - AM6 Pipe Design pdf


Success Stories

1st - 2015 BSA Bantam Championship

Over the years we have had a number of riders win the BSA Bantam Championship using Torqsoft designed pipes.

2016 - 1st Mike Powell

First long stroke 125 cc engine to win championship in 39 years

2015 - 1st Mike Powell

2013 - 1st Mike Powell

2012 - 1st Nick Bramley

2010 - 1st Pete Tibbitts

50cc Cobra Motocrosser

First time out with his new Torqsoft designed exhaust system fitted to his 2006 cobra and 8 yrs old Simon scores a hat-trick of wins - his first ever. Indeed with only one race to go in the 2011 championship series, Simon has an 100% win rate.

TorqSoft - 50cc Cobra
50cc Cobra

BSA Bantam Road Racer

After a very competitive 2010 British BSA Bantam Championship, it went to the wire with three riders in contention at the last race - Cadwell Park. Pete Tibbitts emerged victorious with his TorqSoft designed exhaust system. BSA Bantams only have three gears and thus the exhaust design had to give a wide power band. The result was 25hp at the rear wheel with the engine coming on the pipe at 7000 revs/min and producing usefull power to 11000 revs/min - using the original cast iron 125cc cylinder.

TorqSoft - 125cc BSA Bantam
2010 Championship winning 125cc BSA Bantam

50cc Minarelli AM6 Engine - 17.76 hp

Aprilia AM6 engine (40.3 mm bore, 39.0 mm stroke) converted to disc valve induction by Torqsoft. Dyno curve below shows an excellent peak power of 17.76 hp @ 14,750 revs/min with useful overrev to 16,000 revs/min. The engine pulls strongly from 11,000 revs - 8.33 bhp - which is actually greater that the production engines peak power, thus giving the engine a very useful 5,000 revs/min power-band.

The cylinder used for this test is homologated and fully road legal. Carburation is via a 20 mm diameter diaphragm carb.

TorqSoft - 50cc AM6 Dyno
Dyno curve for 50cc AM6 Engine

TorqSoft - 50cc AM6 Engine Dyno Testing
TorqSoft - 50cc AM6 Engine Dyno Testing

Bridgestone 350cc (1968)

Pipe design for a 350 Bridgestone Racer. This project required a specially designed pipe due to the lack of ground clearance.

Checking fitup of new pipe

TorqSoft - Bridgestone 350
Notice pipe is only tacked at this stage

TorqSoft - Bridgestone 350
Welding of front pipe

74cc Cobra Drag Bike

Bike is the Cobra cx50 motocross bike with large bore cylinder and an extended swinging arm. Pipe has been designed to peak engine at 13,200 revs/min.

TorqSoft - 50cc Cobra Drag Bike
Cobra Drag Bike with rider Eric Edwards jnr

2013 TM85 Motocross Bike

Bike is the TM85 motocrosser. Pipe has been designed to peak engine at 12,000 revs/min with excellent over rev to 13,000 revs/min.Engine pulls extremely strong from 8,000 rev/min resulting in a very flexible power band.

TorqSoft - TM85 - ktm destroyer
2013 TM85 with torqsoft designed pipe