ESE's works engine tuner

[Flettner]

Yep....... certainly would in F4.

Good, wouldn't want to go to all that effort for nothing, thankyou.

[koba]

Good, wouldn't want to go to all that effort for nothing, thankyou.

My advice is to check the rules and read through them all.

This one might not be compatible with a completely freshly designed engine:

1.a Engines must be derived from non-competition motorcycles. Motocross, Road Racing, Enduro and Kart motors and
transmission parts are not permitted. There shall be no restriction on the make, type or design of carburettor, ignition,
exhaust, piston, cam, valve springs or cooling system except for class eligibility.

The rules can be found here:

https://mnz.co.nz

Appendix W is the current Miniture Road Race (Bucket) rules, but others are also relevant.
Also, speak to organisers; it's a lot easier to work it out before the project and build accordingly than to show up on race day with a bunch of conflict and disappointment.

[wobbly]

The component parts can be anything not manufactured for a race machine, ie those scooter/ small bike cylinders /cranks etc.
OR - completely home made, designed, built parts, even if they are commercially manufactured using sintered laser technology from the CAD files.

[F5 Dave]

Well you could throw a CX500 crankcase in the melt pot which does two things. Make it derived from a roax engine. And gets another maggot off the road so it doesn't become a sad cafe racer.

[Flettner]

If I go to this effort I fully expect to be able to enter it.
Used to be, if it was home made, it was acceptable.
This will be completely home made, and or, none competitive parts.
Actually I (we) will start with a single cylinder, because I have a version of that under construction now, but 125, for Hustler class.
E10 is acceptable also I see. Designed so we can have both a 100 and a 125cc version.

[F5 Dave]

I seem to recall a certain ConcoursdeDungHeap prize 🤔

[Flettner]

I seem to recall a certain ConcoursdeDungHeap prize ��

You have a good memory.
Are you suggesting my new build will be worthy of the same accolade?
Ill only be responsible for the engine design and build, others will be in charge of the real work, frame, tuning and fettling. So a good chance it might actually be competitive, perhaps.

[F5 Dave]

Perhaps get you daughter or long suffering wife to sign off the aesthetics

[husaberg]

Let me get this straight, if a home made tandem twin twostroke, 100cc, was presented to race, it would allowed to race? Not based on anything farm bike or road bike, and not a factory race engine.
That is how the rules once we're, is this this still case?

You have a good memory.
Are you suggesting my new build will be worthy of the same accolade?
Ill only be responsible for the engine design and build, others will be in charge of the real work, frame, tuning and fettling. So a good chance it might actually be competitive, perhaps.

Perhaps get you daughter or long suffering wife to sign off the aesthetics

I like a wider angle tandem, you could reverse the cylinders for the off road version

but it you do the tandem I like how Kawasaki supported the primary

never seen any other pics of the uniflow 100?

[andreas]

Months ago, I read somewhere on a forum, perhaps here or on Facebook, that an exhaust only starts working properly at timings of 190°. I have no idea why.
With this in mind, I tried first 185°. It produces a better power curve than the single exhaust port. So I thought, yes, 185° will be fine.
With your explanation Neels, I now understand what I read about 190°. A pipe will probably only starts resonating at 190°.

I'll definitely try that in Engmod.

Just a question for information. I learned in Mechanics that when designing machines, engines, bridges, etc., you have to pay attention to the natural frequencies of the structure.
When the load or operating conditions generate a frequency close to or at the natural frequency of the structure, this leads to total failure.
For example, as everyone knows, a platoon of soldiers shouldn't walk across a bridge in rhythm, or the bridge could resonate and bend further and further until it breaks.
This applies to solid matter, but apparently a gas can also resonate? A resonating exhaust.
Apparently, those resonating gases don't cause fracture.

I once read from Frits that the waves in a 2-stroke exhaust are not the same as the sound waves in a trumpet, for example.
Difficult material for me to dig deeper into.

In any case, I'm going to try a 190° version in Engmod and then come back here.

Hi JVH,
Saw your project with the RD 125, interesting. Seems like you're primarily doing simulations (I'm not), and possibly making a new cylinder. However if your goal is 31 hp you can achieve that with fairly crude means, 199*ex and 130*tr as you mentioned will do it, or just copy any mid 80's mx cylinder, yz 125 carb&reeds and tuned pipe. Don't think you'll have any luck with Ex under 195*, which probably means a little over 10,000 rpm. As for your quest for ex sta, it is possible to make the original cylinder into a triple port -attached pic of an unrefined job, but you'll get the idea.

[Jan Van Hamme]

Hi JVH,
Saw your project with the RD 125, interesting. Seems like you're primarily doing simulations (I'm not), and possibly making a new cylinder. However if your goal is 31 hp you can achieve that with fairly crude means, 199*ex and 130*tr as you mentioned will do it, or just copy any mid 80's mx cylinder, yz 125 carb&reeds and tuned pipe. Don't think you'll have any luck with Ex under 195*, which probably means a little over 10,000 rpm. As for your quest for ex sta, it is possible to make the original cylinder into a triple port

Hi Andreas, thanks for the suggestion. After a long time, I’ve found that what works best for me is a main exhaust port height of 50% of the stroke, a 3-port exhaust, with a radial distance of 5° between the bridges of all ports.
Stagger between A, B and C (no-powervalve).
A step between the header and the cylinder outlet. Cylinder outlet exhaust duct oval, header inlet cylindrical.
Generate an FOS exhaust in Engmod and then split the diffuser into 3 parts and the rear cone into 3 parts as well.
Squish ratio approximately 50%.
Adjust the stinger and compression so that there is no detonation.
Run the simulation. Check the combustion efficiency and then enter that combustion efficiency into Engmod. Run the simulation again and retune the tuned length of the exhaust to the engine speed.

With very high exhaust timing, front-end power is lost. At 195°, that’s still manageable.
I also read somewhere that above 10K rpm the OEM crankshaft off an RD125LC can start to twist if you don’t weld/secure the pin. I’d rather not weld on a crankshaft.
With a no-powervalve engine, there’s always a big dip in Tubmax (begin powerband) regardless of the bore/stroke ratios.
Those are more or less my findings with an RD125LC.
Just to be clear. I’m just an amateur. These are my findings after years of asking questions here and there and trying to learn from people who are much smarter than me.
Designing a cylinder in SolidWorks has also presented its fair share of challenges in getting everything right, but I’m almost there.

Cheers,
Jan

[F5 Dave]

I like a wider angle tandem, you could reverse the cylinders for the off road version

but it you do the tandem I like how Kawasaki supported the primary

never seen any other pics of the uniflow 100?

Picture doesn't show the tank which was from memory dirty white perhaps with vivid marker scrawled uniflow.
It was serious cool, just not pretty.

[andreas]

It's a nice project, best of luck.