ESE's works engine tuner

[husaberg]

2 strokes on overrev with closed throttle as well as the engine being driven by a wheel and rider or a drum on a Dyno do not get any significant lubricating oil. 4t's survive this better a most have positive lubrication systems not reliant on a petrol mist.
Honda for the 2ts at least (but pretty sure XR and the like also) used to colour code roller cages the big end even own the commuter bikes like H100's offer many different specs std for selective fit ,after market not so much.....

Wobs way is obviously the preferred method
but different Honda ones used to be on one of the first few pages in the parts fiche.



Bell devotes a lot of space into how to build decent big ends and cranks in his book

[Wos]

2 strokes on overrev with closed throttle as well as the engine being driven by a wheel and rider or a drum on a Dyno do not get any significant lubricating oil. 4t's survive this better a most have positive lubrication systems not reliant on a petrol mist.
Honda for the 2ts at least (but pretty sure XR and the like also) used to colour code roller cages the big end even own the commuter bikes like H100's offer many different specs std for selective fit ,after market not so much.....

Wobs way is obviously the preferred method
but different Honda ones used to be on one of the first few pages in the parts fiche.



Bell devotes a lot of space into how to build decent big ends and cranks in his book

Cloed Throttle...

The more important is to have a well tuned idle jet/ airscrew to be not too lean there...

[koenich]

Re winning with Motul 800 - if thats the case then they are not pushing the mechanical/thermodynamic limits, but in every case they are leaving power on the table.

We are talking 8h endurance racing - depending on the year we had differences of ~15 °C ambient temperature from start of the race 11:00 am to noon. Even if the weather is supposed to be stable, I wouldn't jet on the edge as a part of risk mitigation to make it the full race disctance.

[Peter1962]

50cc big end pins are Ø15 or Ø16 mm; that is roughly equivalent to 22 mm for a 125cc engine. The RSA had a 24 mm big-end pin, which posed no problems; an RSA crankshaft survived a full season on the test bench. Wob, what is the big end pin diameter in the KZ engines?

What does fail on the 50cc engines, are poor-quality big end and small end cages and poor-quality axial thrust washers.

Frits, could forced lubrication of the big end, like Neil Hintz is doing on his 360 engine make a difference on the freetech 50cc engines concerning reliabilty ?

My mate emot.nl is concentrating on developing more reliable stuff for the Freetech racers. But I don't think they are going to rev to 20.000 rpm any time soon. Some things, like boundary layers, are not scalable which means the smaller the engine, the harder it becomes to create sufficient angle.area.

Most certainly not with the actual trend of using more reed valve engines, compared to some years ago, when a lot of the freetech engines were rotary valved. Strange evolution...

[Larry Wiechman]

While we are on the subject of cranks and "reliability" ....





They are mold-forged from "forty pound steel" (40cr?) a rather common chinese grade of steel; they come out of the forge mold red hot and are near immediately dropped into a water quench

Final hard machining occurs after this.

There is ALSO a custom crankshaft manufacturer who produces essentially this exact crank starting with 4140 prehard material, machining them in the hard state.

A generous, ground & polished radius may help.

[Frits Overmars]

Frits, could forced lubrication of the big end, like Neil Hintz is doing on his 360 engine make a difference on the freetech 50cc engines concerning reliabilty ?

Absolutely. It will easily double the lifespan of the big end.

[wobbly]

If you do any research on 4130/4140, the answer regarding its suitability as a crank or shaft material is obvious - At 45Rc you are asking 4130 for everything it's got. It has the lowest carbon content of any directly hardenable
alloy steel which is why it's used for welded structures.
Thus getting the required case hardness of Rc 58/62 to a minimum depth of 0.5mm is in reality, impossible.
This material is routinely carburized, but that is only microns deep.
To get the ground surface in a condition suitable for reliable direct needle roller use, with a suitably malleable core strength, something like EN35 or equivalent is a minimum requirement.

In the situation of a press in big end pin, these are easily case hardened to Rc 60 - 64 from 0.5mm to 1mm deep, using the right material.
Anything less creates rapid Brinelling where the needle point load eventually pulls the case hard surface off the substrate - as you see in many one piece forged crankshafts.

And yes, having the " correct " pilot/air screw setting is vitally important to the overun on closed throttle.
We use a very rich pilot in KZ, with alot of air screw to get some semblance of transition onto the needle/tube, and this setup is reliable and the fastest - but still creates the first deto signs above the boost port
indicating a leaner condition in transition off the bottom.

[Wos]

If you do any research on 4130/4140, the answer regarding its suitability as a crank or shaft material is obvious - At 45Rc you are asking 4130 for everything it's got. It has the lowest carbon content of any directly hardenable
alloy steel which is why it's used for welded structures.
Thus getting the required case hardness of Rc 58/62 to a minimum depth of 0.5mm is in reality, impossible.
This material is routinely carburized, but that is only microns deep.
To get the ground surface in a condition suitable for reliable direct needle roller use, with a suitably malleable core strength, something like EN35 or equivalent is a minimum requirement.

In the situation of a press in big end pin, these are easily case hardened to Rc 60 - 64 from 0.5mm to 1mm deep, using the right material.
Anything less creates rapid Brinelling where the needle point load eventually pulls the case hard surface off the substrate - as you see in many one piece forged crankshafts.

And yes, having the " correct " pilot/air screw setting is vitally important to the overun on closed throttle.
We use a very rich pilot in KZ, with alot of air screw to get some semblance of transition onto the needle/tube, and this setup is reliable and the fastest - but still creates the first deto signs above the boost port
indicating a leaner condition in transition off the bottom.

Thanks wobb!

What is your experience to avoid Detos in transition area to Needle?

Lifting throttle slide by screw/ increasing idle RPM ?

50cc..which RPM fits.

Difficult to find prefered RPM for 3 diffrent Riders, there wishes, there individual downshifting point before corners..prefered braking forces of engine

Forbid them to brake anyway!?

Grüße Wolfgang

[Frits Overmars]

Difficult to find prefered RPM for 3 diffrent Riders, there wishes, there individual downshifting point before corners..prefered braking forces of engine.

Don't give them what they want; give them what they need.
A trip down memory lane: I witnessed how Luca Cadalora wanted to change everything after his first practice session on the Garelli 125cc twin.
Old hands Nieto and Lazzarini, who knew the bike inside out, said: ‘Right, we’ll do all that as soon as you’re within a second of the lap record.’
The bike remained unchanged and Cadalora went on to become world champion on it.

[Wos]

Don't give them what they want; give them what they need.
A trip down memory lane: I witnessed how Luca Cadalora wanted to change everything after his first practice session on the Garelli 125cc twin.
Old hands Nieto and Lazzarini, who knew the bike inside out, said: ‘Right, we’ll do all that as soon as you’re within a second of the lap record.’
The bike remained unchanged and Cadalora went on to become world champion on it.

Wonderful Frits! THANKS!

Grandma said something wise:

jedem Menschen Recht getan, ist eine Kunst die niemand kann

"Doing right by everyone is an art no one can master."...

Grüße Wolfgang

[wobbly]

Wolfgang, the question regarding deto first forming due to a lean transition jetting has been driving all the best tuners in the World up the wall, forever.
No matter what " normal " fixes have been tried, the throttle response always suffers, and both the driver and the stopwatch complain bitterly.
We have to run the mad rich pilot inner and outer jets to cool the piston , and the pipe, when in the overrun down into a second gear hairpin, and although reducing more airscrew or
going fatter on the emulsion tube, or higher fuel level is better against the brake on the stand, its worse on track.
The result is low speed WOT deto, but as you will see on every title winning KZ piston picture, its just the reality of doing what is fast, not technically " better ".

[husaberg]

bell clickk three times.

[husaberg]

One that never fixed

[Wos]

Wolfgang, the question regarding deto first forming due to a lean transition jetting has been driving all the best tuners in the World up the wall, forever.
No matter what " normal " fixes have been tried, the throttle response always suffers, and both the driver and the stopwatch complain bitterly.
We have to run the mad rich pilot inner and outer jets to cool the piston , and the pipe, when in the overrun down into a second gear hairpin, and although reducing more airscrew or
going fatter on the emulsion tube, or higher fuel level is better against the brake on the stand, its worse on track.
The result is low speed WOT deto, but as you will see on every title winning KZ piston picture, its just the reality of doing what is fast, not technically " better ".

Thanks for telling your experiences !

LOW throttle

A carb is relatively slow reacting, extra slow on low air flow, smal RPMs i think

Injektion seems to be a s solution away from "normal"

Myself i had not to deal with, but the seen result i saw on Motocross Bikes is fantastic

Throttle Response and Power everywhere.

Liedolsheim 8 H Injektion is vorbidden... dont know if its free in freetech50 ?

Grüße Wolfgang

[Frits Overmars]

Liedolsheim 8 H Injektion is vorbidden... dont know if its free in freetech50 ?

I wrote the original Freetech50 rulebook so yes, injection and a lot of other things are free in Freetech50 (what's in a name )

About part throttle deto: it was a major problem at Aprilia. The RSA and RSW bikes were just about bulletproof regarding WOT deto, but they would detonate terribly at part throttle + high revs conditions. For that reason celebratory burnouts were strictly forbidden.
I figured out that the cause was actually quite simple: part throttle means low crankcase pressure and although there was ample blowdown time.area at WOT, the cylinder pressure drop before transfer opening was not deep enough for this part-throttle crankcase pressure, so exhaust gases entered the transfer ducts, heating up the fresh mixture.