The 50

[husaberg]

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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


]

Any more detail on the carb I must say it looks pretty epic.
So it has no overlap on the fuelling circuits other than the PJ which is electronically pulse controlled.
I didn't see a tps, is it inline an RGV250?

[bartarie]

The lectron needle could be used standalone, works pretty good.

The pwm works great, at mid-range it seems you cannot choke the engine in fuel. It gives you a lot of confidence, t feels great. During the whole season i believe i just once adjusted the needle. (During a demo on a big airfield). Just to be sure and because it was a demo.

A TPS is not nescesarry, just place the exit of the PJ on 75% of the height of the throttle slide.
Just like yamaha does on the tz125 and honda on the 96/97 cr250.

Dont make things un-nescesarry complicated you know.

OMT

i am very negative About using a "on off" style PJ it is way Too rough, for sure on a 50cc.

[bartarie]

Oh plate,

Plate is to hold my det counter sensor snug in place while using 10mm Plugs instead of 14mm

[chrisc]

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.

Okay, I'll bite. I'm curious to know more about what you'd consider a proper freetech50 Frits.

Can you use MX engines in the freetech50 class?

[sonic_v]

Okay, I'll bite. I'm curious to know more about what you'd consider a proper freetech50 Frits.

Can you use MX engines in the freetech50 class?

Yes to MX engines.

http://www.freetech50.com/?t=en&p=page&s=reglement

[cotswold]

Okay, I'll bite. I'm curious to know more about what you'd consider a proper freetech50 Frits.

Can you use MX engines in the freetech50 class?

The KTM 65 with the 50 cylinder seems to be popular with some in the uk
I am plumbing in a 2nd radiator for tamuranui not sure if I've got the flow correct

Frikkin picture is upside down again, this is pissing me off as it's fine everywhere else

[husaberg]

Frikkin picture is upside down again, this is pissing me off as it's fine everywhere else

Turn up computer the other way.

[TZ350]

I am plumbing in a 2nd radiator for Taumarunui not sure if I've got the flow correct.

Should be in at the head and out at the bottom of the cylinder for max head cooling.

[F5 Dave]

Disagree. You have it going through the engine the right way as every engine I've seen, but through the rads in reverse. If the pump was strong enough it wouldn't matter but why fight thermosyphoning action? Hot in at the top.

coolest enters the low part of the engine to keep charge cool as possible and ideally exits the head at ideal temp if you have enough cooling.

[cotswold]

thanks guys......................

[kel]

Why two radiators? I have none, bike seems to go alright most of the time.
Taumarunui must be one of the hottest bucket meetings temp wise, bloody bike has failed their twice from thermal melt down. Maybe a radiator under the seat isn't such a silly idea

[richban]

Why two radiators? I have none, bike seems to go alright most of the time.
Taumarunui must be one of the hottest bucket meetings temp wise, bloody bike has failed their twice from thermal melt down. Maybe a radiator under the seat isn't such a silly idea

Do you run an egt kel?

[kel]

Do you run an egt kel?

Not yet. Have bought a couple of these http://www.ebay.com/itm/252006895656...%3AMEBIDX%3AIT will have it set up for the GP.

[cotswold]

Why two radiators? I have none, bike seems to go alright most of the time.
Taumarunui must be one of the hottest bucket meetings temp wise, bloody bike has failed their twice from thermal melt down. Maybe a radiator under the seat isn't such a silly idea

Mainly because the man that owns NZ's winningest 50 told me I should and because it makes sense as mine was made for a bike with 4bhp and it now has more than triple that and revs its tits off must be making more heat than it used to.

[richban]

Not yet. Have bought a couple of these http://www.ebay.com/itm/252006895656...%3AMEBIDX%3AIT will have it set up for the GP.

I will never race a 2 stroke without one. Saves engines and body parts.