Henk Jager.   Thijs Hessels.

Developments underway concerning the He-Ja Honda RS125 Kit.





Klik en ik word groter.

Click and I will be big.

Klik en ik word groter.

Click and I will be big.


Here you will find a pair of tests carried out on our own test facilities on the new barrel that we at He-Ja Motor Techniques last year have developed for use on the RS125- He-Ja kit.

Through an improved flushing a modified cylinder head and a new type of piston, we have achieved this result.

This type is now available in limited quantities





*125cc Class He-Ja riders*


Picture on the right is Austrian Stefan Lichtenberger. 2010 Champion in Austria in the 125 cc roadraces using a He-Ja kit type “B”.

Picture on the left is Mr Jerry Dennis (He-Ja Technics Importer) with Peter Galvin’s machine. Dennis is a Top Class 2 stroke specialist with 20 years international experience. Jerry has worked with many champions in both 125 and 250 cc class.

Second picture from the left is Peter Galvin in race leathers. Australian 125cc  National champion. Participated in 125 GP’s in 1991/92. Has 6 National Titles to his name. Currently using a He-Ja Kit type “A”.


Second picture from the right shows Peter Galvin racing the He-Ja Honda 125 to the national title in the Australian 125cc championship.

Apart from these riders: John Schneider Jr managed 3rd spot in the Australian 125cc Championship using a He-Ja kit type “A”. This machine is also prepared and maintained by Jerry Dennis.

Click the following images to enlarge / reduce.

Jerry Dennis.

Peter Galvin en Jerry Dennis

Peter Galvin.

Stefan Lichtenberger




*AVGAS B kit.*


After many requests we decided to make a kit fitting Honda RS125 carters especially for countries where racing with AVGAS is allowed.


This was possible as a result of the experience and numerous tests done in New Zealand and Australia.


The results are impressive (see the AVGAS “B” kit graph). It shows a step test from 9K to 13K rpm in 5th gear.



With higher compression ratios possible with AVGAS, this results in increased power. A kit type”B” does not have an exhaust valve, so is relatively economical and simple. The existing JHA or the standard ignition can still be used.


Two different heads were made (volume). The difference shows in the graph “Head Test AVGAS”. The new kit can also be used with standard or race petrol. The supplied head will be one for the correct (lower) compression ratio.

To illustrate and give you some insight in our work methods the following pictures:
(Click to Enlarge/Reduce).


Milling the plastic Reed block.

Calculating the intake.

Reed block for A and B type kits.





Exhaust Flange.

Modified housings.

Complete engine.


Note: These kits supplied on indent only, email for prices.



THOR THOR Elektronica for the RS 125 He-Ja kit.


The objective in developing this racing racing-kit was to obtain a better and useful power and tongue with respect to the standard engine and what is more important a longer lifetime of the piston and cylinder.

A cooperation of Jasper Blom of THOR ignitions and Thijs Hessels of Hessels Racing Technics and Henk Jager of He-Ja Motortechnics was made to come to the desired results.

By now we are already one year further in this project and the result are very satisfying. (Look at the power graphic).



The crew has chosen for the best material which we can make or buy. The crankshaft is a VHM product type AK20017T, middle weight '' of 2582 gram. The piston also VHM, is been made of a very resistant alloy, with a piston ring of 0.7 mm and a weight of 117 gram.

Including a short piston pen + clips and the piston ring the total weight is 148 gram. (Stand time average 6 hours after which the where upon measured is 0.04 mm).

The cylinder is a type with three exhaust and five transfer ports, with a electrically managed valve in the exhaust served by means of a servo-motor. This flap is been carried out in two parts by means to come to an optimal control of the embarrass opening.

For the details of the Aprillia-cilinder click here.


The cylinder has a Nikasil lining which is as we know very durable to wear and gives after a lot of testing (±1500 Km) no measurable wear to see. The exhaust port has no support in the middle, because this gives always somewhat problems, and the lifetime of the piston is negative influenced by this.

Furthermore the cylinder has been made in a way that the piston in the bottom section still has a total conductance to the cylinder part, this gives almost no overturn, meaning that in all the test Km the spring never has being fixed and locked in the piston groove.

This cylinder is a counterfeiter from the original Aprilia cylinder of Thijs Hessels (which already has proved itself many years in the roadracing scenery) and has been adapted to fit on the HONDA RS 125.

This has demand a lot of drawing and designing work, but the result of all of this is that with a small adaptation of the casing this cylinder fits perfectly on the RS125 from 1998 until now. 


Binnenkop He-Ja.RS125.

The cylinder head is of course of the divisible type with a loose insert, manufactured from a very hard aluminium alloy as a result of which is not possible that the insert is affected by detonation.

The exhaust and the silencer device is also a Dutch product, made by Sam Balder of the well-known SAMBA-Exhaust Systems.

Of course is this exhausts tem designed on our cylinder and timing spec's.

For the ignition, we have chosen the products of Thor Netherlands, made by Jasper Blom who over the years with his products in Racing has proved itself to the best one can belong.


Buitenkop He-Ja. RS125.


Were it concerns the adjustments of the MCU/CDI Unit we have gratefully taking advantage of his great experience.

With these MCU Unit the whole set-up of engine can be regulated such as; the set-up of the ignition-curve, the adjustment of the opening and closing time of the power jet and the opening and closing time of the exhaust valve.

By means of a date programme one can easy change and regulate the date's. In this way it is possible to interrupted the sparking during changing gear, and the same goes for the power jet and the flap in the exhaust port.


Silvio Herrfurth

During the race, the rider can made up his choice between two adjustable ignition curve's useable in for instance a dry and a wet track. In other words lot's of possibilities were it concerns experimenting and a the set up of a sublimely adjusted engine.

During this summer we took the advantage of hiring a well expired test rider in the figure of Silvio Herrfurth.

This German based rider has already raced 15 years on a Honda RS125 and is able to tell us how the bike feels on the track, and give us a lot of feedback and information to optimise the engine set-up.

Therefore we have decided to race in the German IG Köningsklasse, where a lot of practice occasion are given and one for example on a Friday can go out six times a halve hour, whereas on the Saturday before the race one can go out four times. In that way we have tested on the track of Ochsersleben in a certain weekend 98 laps!!!

Out of this came back a lot of useable data and results. In particularly, one of our main goals came forward, being the racing time of the piston, which was as we expected. For instance, during that weekend of 98 laps, the cylinder nor the head has being lifted, meaning that the mechanics and others can concentrate on other things and there is a lot of time to do so.

Meanwhile we have done four races in total with the He-Ja Honda RS125 and the result have been going in a rising line. The cylinder is still perfect and gives after 1500 race km and much test work on the Super flow testbenche no noticeable wear.

By now we have fitted the third piston in the engine and that satisfies exactly to our objective, namely to develop a cylinder with a long lifetime of the piston etc. Also the crankshaft of VHM gives up till now no wearing, and we will continue this winter to test all this items to yours and our benefit.


A look true the undersite of the barrel
Looking down from upside


De cilinder is nog steeds puntgaaf en geeft geen merkbare slijtage na 1500 race km en veel testwerk op de Superflow vermogen testbank. De derde zuiger is nu in de motor en dat voldoet precies aan onze doelstelling, namelijk een cilinder ontwikkelen met een lange standtijd van de zuiger etc. Ook de krukas van VHM geeft nog geen slijtage op, en we gaan er dan ook van de winter maar mee door testen.


Klik hClick here for the test rapport of the
  HE-JA HONDA RS125 met A kit


The HONDA RS125 HE-JA A kit cost in the complete outfit € 9700.= exc. VAT.

For the line-up of the complete A-Kit click here.



The B Kit is exactly the same as the A Kit, except the electronic. This one is to obtain from BPS or an other branch to rebuild it yourself. One can also use the standard MCU unit. Price € 6588.= exc. VAT.

For the line-up of the complete B-Kit click here.


It is also possible to obtain only the complete cylinder + Exhaust flense and cilinderhead.

The cost of this C Kit is € 3840.= excl. VAT.

For the line-up of the complete C-Kit click here.

For the line-up of the complete C-Kit click here.




























As mentioned, with a simple adaptation to the casing the Kits can be become assembled. A clear guide how to do one and other is present at ours.



Modifying of the crankcase and all the mechanic work to fit the HE-JA cylinder kit.


Of course is it possible to have the rebuilding done by our Company


Modifying of the crankcase and all the mechanic work to fit the HE-JA cylinder kit.

€ 125.=.excl.Vat
Building of a complete engine for a HE-JA cylinder kit incl. Milling works. € 350.= Excl Vat
Building the engine in the frame + set-up. € 650.= Excl Vat



Building of a complete engine for a HE-JA cylinder kit incl. Milling works Building of a complete engine for a HE-JA cylinder kit incl. Milling works Part of the He-Ja Motortechnics Scuderia.


Questions concerning price and delivery times are only possible by means of E mail at; Info@he-ja.nl.


The name HRT stands for Hessels Racing Technique.


Owner Thijs Hessels has gained a lot of years of experience on all kind of racetracks the whole world around, and has being worked as engineer for some prominent teams.


For the Aprilia 125 and 250cc HRT has developed a cylinder + head which is provided as a loose Kit.

Thijs Hessels busy; preparing one of his cylinders.

Complete cylinder for the Aprilia 125 and 250 deliverable as loose kit.



In this set all experience of Thijs Hessels is coming to terms with, and many others have gained fine results with it.

Price of this kit € 3840.=.excl. VAT (cylinder+ head + Exhaust-Flange)

More info at ;Thijs Hessels Fijnmechanica

Oosterstreek 70. 8388 NE Oosterstreek.NL

Tel.0031-561.433150 Fax.0031-561.432613

E-Mail; hesselsfijnmchanica@versatel.nl.


The APRILIA 125/250 HRT RACING KIT Includes:

Cilnderbasegasket (modified)0,4mm
,, ,, 0,5mm
,, ,, 0,6mm
Powervalve cover
Cap nut 5
Washer Cu. 5
Valve drive shaft
Pulley Powervalve transm.
Powervalve driving fork
Upper valve
Lower valve
Exhaustflanges+sensor connector.