The 50

[Frits Overmars]

https://www.youtube.com/watch?v=46zTXbTM8ZA the onboard is taken from a classic 50 meaning it runs very skinny wheels and tyres but check out what can be done with a KTM cylinder on Ron Ponti cases with disc valve, 22bhp rocket ship.
I pinched the clip from the Freetech boys

You could have pinched the bike's power curve as well then. Here it is:

The Freetechs and the Classics were racing together in that video. In the corners the Freetechs rule; on the straights they are handicapped by their wide tires and fairings and their far too high weight. After all, they're mostly Honda RS125 bikes with 50 cc engines. I'm still waiting for someone to build a proper Freetech50.
Weight is killing the current Freetechs' performance. Compared to the Classics, the best Freetechs are not down on power. Below is the power curve of a decent Freetech50.

[cotswold]

You could have pinched the bike's power curve as well then. Here it is:

The Freetechs and the Classics were racing together in that video. In the corners the Freetechs rule; on the straights they are handicapped by their wide tires and fairings and their far too high weight. After all, they're all Honda RS125 bikes with 50 cc engines. I'm still waiting for someone to build a proper Freetech50.
Weight is killing the current Freetechs' performance. Compared to the Classics, the best Freetechs are not down on power. Below is the power curve of a decent Freetech50.

That is impressive, the europeans have it nailed, the British free tech lads are 17bhp or there abouts so we have plenty to do to catch up with them. We are slightly hampered by being unable to use some of the parts available to them.

Frits that free tech power curve, do you know what the engine was and whether it was reed or disc valve ?

[Frits Overmars]

Frits that free tech power curve, do you know what the engine was and whether it was reed or disc valve ?

I happen to know a thing or two about it but I'm not going to spill the beans here; I'll leave that to builder-rider Barrie Raterink, if he ever discovers this thread (it took me a long time). But here are some pics.

[cotswold]

I happen to know a thing or two about it but I'm not going to spill the beans here; I'll leave that to builder-rider Barrie Raterink, if he ever discovers this thread (it took me a long time). But here are some pics.

I have seen Barry's bike on a different forum. Kawasaki disc valve engine, very nice

[richban]

Weight is killing the current Freetechs' performance. Compared to the Classics, the best Freetechs are not down on power. Below is the power curve of a decent Freetech50.

Weight a problem with my RS50. The frame looks light but I need to strip the bike to see if looks are deceiving. The swing arm is steel and heavy. I am thinking maybe something from a small MX bike could be modified. Time to buy a new AC / DC tig.

[kel]

Kawasaki disc valve engine, very nice

With the inlet moved to the opposite side to allow for large disk, larger carb and short inlet passage
What model Kawasaki is the bottom end from?

[jasonu]

I happen to know a thing or two about it but I'm not going to spill the beans here; I'll leave that to builder-rider Barrie Raterink, if he ever discovers this thread (it took me a long time). But here are some pics.

I sent him a heads up email. Hopefully he will have something interesting to contribute.

[cotswold]

With the inlet moved to the opposite side to allow for large disk, larger carb and short inlet passage
What model Kawasaki is the bottom end from?

Ar50 or 80 I think as they were popular in the UK and europe

[Frits Overmars]

Ar50 or 80 I think as they were popular in the UK and europe

Last time I checked England was an island in the North Sea, off the European mainland. Some people seem to pretend it is a continent of its own .

[cotswold]

Last time I checked England was an island in the North Sea, off the European mainland. Some people seem to pretend it is a continent of its own .

Sorry Frits, I will put my hand up as an escaped Englishman, in my defence we were brought up to believe Europe started after an unpleasant boat ride.

[bartarie]

Comming in

Hi Frits,

Strange thing to see you in NZ
You see Frits everywhere around the globe!

If you guys want to know a thing or two please feel free to ask

Greetings

B

[husaberg]

Comming in

Hi Frits,

Strange thing to see you in NZ
You see Frits everywhere around the globe!

If you guys want to know a thing or two please feel free to ask

Greetings

B

Welcome and Feel free tell us everything about the engine.

[bartarie]

Lol i could tell but i am fairly busy!

Well its actually a fairly simple mod,

I took a AR50/80 engine, converted into bore 40 stroke 39,7.
The studpattern modified to m7x56, so i can fit Derbi cylinder.
Because of 2 points i decided to rotate the barrel 180 degrees, first i like the strait exhaust concept of the Aprilia RSR (and RSW)
Second point was to keep the original base of the frame, wich has a downtube in the middle of the frame.
This is solved by the standard AR50 by making a duct wich is exiting to the right (DOF).
Because it would have a rotary disc valve inlet things doesnt really matter wether it was front or rear exhaust.
Because the original unitrak system was way too high i modified it, its a conventional dogbone conversion seen on much bikes these days.
Therefor i made my own rearfork, and added a vintage WP USD fork (35mm) and at the rear also WP.
It would be no coincidence, steering damper also WP. Seat is self-carrying Apia RSW.

The clutch is made of several modified parts from KX65 and AR50 standard 3 plate now 6 plate.
Cooling pump is bosch electronic, ignition is Zeeltronic.
Carby is 75 percent home built, made my own velocity stack, powerjet and slide.
Powerjet has PWM. Main jets are removed and i fitted a Lectron needle.

Barrel is an standard moped cylinder from Derbi slightly modified.
Tube is an "tubo 102" (Apia GP tube) Converted to 50cc dimensions.

This winter i might make an dry clutch for my bike.
If this is finished i'd like to make my new frame, its inspirated by JJ-cobas TB5 (alex criville 1989)
Shorter wheelbased, steeper steering angle. Shock fitted vertical instead of horizontal.
Also will have an RSW Carbon Seat to drop the weight

B

[TZ350]

I like it ...

[lodgernz]

What is the purpose of the plate over the cylinder head?