ESE's works engine tuner

[Frits Overmars]

WOS , with a Rotary valve on a race engine it is all but impossible to mechanically make the intake too short.
Cut off that huge duct and make a pad on the cover to fit an off the shelf Mikuni oval carb rubber manifold.
This will get you real close , real quick.

I put the rubber manifold inside the clutch cover, looking out. Got us real close, real quick
PS: the carb on the picture is not the one I used. I fitted an ultra-shortened 38 mm Mikuni in 1979. This picture of my engine turned up 39 years and umpteen owners later.

[Wos]

What odd things come out of the woodwork. Sadly you will need filtration and that horrible compromise will be an eye closed venture.

I remember riding a GP100 roadbike with knobblies downhill. There was a small log. A quick blip was called for. Quick flick of throttle .
Bleeer.
Thud over log. . . Braap.

Thought about it. RV had loaded up downhill and taken a while to clear.

Are you stuck with this engine?

Tanks Dave, wob and frits,

The frigerio was the choice of my friend and driver. He fellt in love with the bike

But i was aware this will be hard to tune. As backup, if we fail, we have strongest reed bike in the competition, a TGM.

In reglementation we can change engine, but have to keep year and aircooled

Tracks vary from race to race. From more cross to more hillclimbing or trail sections.

But we could change bike from race to race and the puchs seathight is bit lower, better for some races

Rotax advertised 28 hp and to tell you an range that we dream for ... lets say real 32 hp

Found many things we can do better

Head has no squish area!!!

Exwindow has widest area after blowdown... never seen!! Oh ... about bit over 40mm!!! Transfers aimings ar nearly horizontal

Bosch HKZ with heavy rotor...not programmable

Rod, piston and pin are heavy

Exducts ending 39mm

Pipe to shallow

Roundslide carb

Frits!! You better tell us engines that are NOT touched by you!!!! ???

Please tell us more secret specs from your rotax 124 and if you would...the storys behind it

Tanks a lot !!

Grüße Wolfgang

[Frank S.]

Hi Wolfgang,
if you mount the carb on the side, just make a cage of some steel pipes to protect it. Inside the cage might be room for an airbox with the carb inside it.
This cage can also protect the driver's leg when hitting a tree.
Grüsse Frank

[Wos]

Rotax horror pics

Folks!

If you are to weak for...immediatly close your eyes!!!

This ist stock GS ( in german GELÄNDE SPORT) offroad sports zylinder with iron cast sleeve

Try to get a rare alu nikasil aircooled next

[Wos]

Hi Wolfgang,
if you mount the carb on the side, just make a cage of some steel pipes to protect it. Inside the cage might be room for an airbox with the carb inside it.
This cage can also protect the driver's leg when hitting a tree.
Grüsse Frank

Tanks neighboor frank,

Every idea welcome!

Let us discuss from face to face after liedolsheim race, having some beers in front of the object of love you are invited

This will be a long term project for autum and winter



Have a nice holiday in france! ✌😎

Wolfgang

[Frank S.]

Tanks neighboor frank,

Every idea welcome!

Let us discuss from face to face after liedolsheim race, having some beers in front of the object of love you are invited

This will be a long term project for autum and winter



Have a nice holiday in france! ✌😎

Wolfgang

🍻maybe we will drink from the winner cup😎

[Peter1962]

Tanks Dave, wob and frits,

The frigerio was the choice of my friend and driver. He fellt in love with the bike

But i was aware this will be hard to tune. As backup, if we fail, we have strongest reed bike in the competition, a TGM.

In reglementation we can change engine, but have to keep year and aircooled

Tracks vary from race to race. From more cross to more hillclimbing or trail sections.

But we could change bike from race to race and the puchs seathight is bit lower, better for some races

Rotax advertised 28 hp and to tell you an range that we dream for ... lets say real 32 hp

Found many things we can do better

Head has no squish area!!!

Exwindow has widest area after blowdown... never seen!! Oh ... about bit over 40mm!!! Transfers aimings ar nearly horizontal

Bosch HKZ with heavy rotor...not programmable

Rod, piston and pin are heavy

Exducts ending 39mm

Pipe to shallow

Roundslide carb

Frits!! You better tell us engines that are NOT touched by you!!!! ???

Please tell us more secret specs from your rotax 124 and if you would...the storys behind it

Tanks a lot !!

Grüße Wolfgang

Talk to Fletner, he has extensive knowledge on how to change an old rotary valve aircooled engine (kawasaki big horn 350) by dumping the carburator and mounting fuel injection. The long intake duct can still be used for air intake, but the injection can be mounted very close to the rotary valve.

[Wos]

Talk to Fletner, he has extensive knowledge on how to change an old rotary valve aircooled engine (kawasaki big horn 350) by dumping the carburator and mounting fuel injection. The long intake duct can still be used for air intake, but the injection can be mounted very close to the rotary valve.

Peter ...thanks

My knowledge is to small for injection...as the pocktets of us��

Made first measure of space between crank and crankcase...distance is small...so my guess is that we have relatively small free volume

Maybe its one additional way to gain some power to enlarge case free volume? Frits...? �� Good idea?

[wobbly]

Rotary Valve engines can use bigger case volumes - under 1.3 , the Aprilia was 1.24 and was helped by using a long rod.
This may be easy to do in your engine and fit a plate under the cylinder.

[Wos]

Rotary Valve engines can use bigger case volumes - under 1.3 , the Aprilia was 1.24 and was helped by using a long rod.
This may be easy to do in your engine and fit a plate under the cylinder.

Yes wob merci!

Thats next option besides milling crankcase 😀

Original piston pin is 18 mm ...conrod 110

From rotax 122 there is a rod for piston pin 15mm in 110 and 115mm length

Then we can use light suzuki motocross piston, everywhere available

Grüße Wolfgang

[Frits Overmars]

Frits!! Please tell us more secret specs from your rotax 124

If memory serves, I once posted the specs in a forum, probably in Pit-Lane, but I'm not sure.
Later.....
I've been searching through Pit-Lane for half an hour now, without finding what I was looking for, so I will leave the searching to you.
One thing I do remember: Rotax used an inlet disc with an ultra-late closing timing because of the ultra-long inlet tract in the original Rotax 250 engine, on which the Rotax 124 was based. I encountered that same disc timing in the '124' and about the first thing I did, was to mount the disc one tooth (16°) earlier without altering the disc itself.
Then I shortened the disc cover stub and I enlarged the hole in the clutch cover, so I could fit a Mikuni inlet rubber between the disc cover and the inside of the clutch cover, and I enlarged the inlet tract diameter from 34 mm Ø to 38 mm Ø.
How and why I modified the cylinder, is posted 'somewhere' in the internet. If you manage to find it, please let me know where.

[Wos]

If memory serves, I once posted the specs in a forum, probably in Pit-Lane, but I'm not sure.
Later.....
I've been searching through Pit-Lane for half an hour now, without finding what I was looking for, so I will leave the searching to you.
One thing I do remember: Rotax used an inlet disc with an ultra-late closing timing because of the ultra-long inlet tract in the original Rotax 250 engine, on which the Rotax 124 was based. I encountered that same disc timing in the '124' and about the first thing I did, was to mount the disc one tooth (16°) earlier without altering the disc itself.
Then I shortened the disc cover stub and I enlarged the hole in the clutch cover, so I could fit a Mikuni inlet rubber between the disc cover and the inside of the clutch cover, and I enlarged the inlet tract diameter from 34 mm Ø to 38 mm Ø.
How and why I modified the cylinder, is posted 'somewhere' in the internet. If you manage to find it, please let me know where.

Hope i could do you a favour frits...but you did bigger for me within spend your time for me!

Wow...frits is wasting time only for me!! ?...for us!? Applause from me in the name of all gasheads here...������

Frits OvermarsJeu 13 Juin 2013 - 17:12
par Frits Overmars
By '2 mm clearance' I assume you mean 1 mm either side between crank and case, and 1 mm between outer crank radius and inner case radius. Viscous drag increases strongly below 1 mm clearance; enlarging the clearance beyond 1 mm has only a limited effect on viscous drag. So if increasing the clearances beyond 1 mm improves power, I would assume that this improvement was caused by the increased crankcase volume. It could also have been caused by improved inlet flow, but I cannot comment on that without knowing your engine so I will leave this aside for now.

The most striking example of crankshaft clearance I saw in the old Rotax-124 kart engine that I worked on from 1978 onward. It was really a 250 cc motocross engine with a 125 cc crank in it. If I remember correctly the case diameter was about 12 mm larger than the crank diameter! But it was easily the fastest engine of that era, and the most susceptible to tuning modifications. It was also the grandfather of the Aprilia RSW125 Grand Prix engine

And

http://www.pit-lane.biz/t4072p250-gp...ighlight=frits

Pleasure for me if you were searching this

Your writing 2013 went round and round in my head...

12 mm space...wow...have further questions as we have much less space/volume free

Merci danke thanks ��✋


Wolfgang

[Wos]

The night is young here in europe frits! Isnt it

So I have a question to you

Is increasing small free volume of crankcase with this uggly long intake duct ..effctiv too?

Did you tested this ? Or only with carb direct on rotary case?

Rotax long intake duct Function is clear to me...only giving carb protected Position, that we need in enduro use...

And..we should not worry about things that are not available in the moment...new circumstance...and we have to find new fitting answers? Your great findings will never fit perfekt for my expectations...for example enduro engine!?... so how could Iexpect clear numbers frits?

Make us understand physiks of 2 stroke...as you did/ tryed... ...if impossible...still continue tryings ...please





Tank you frits so so much!

Grüße Wolfgang

[Wos]

For last 3 days.... late later closing disc timing was my conclusion for Stock long duct

Cause of long duct with big slow moving mass inside?
To use a kind of charching effect of its energy in action!?

Do you agree?

Danke!

Wolfgang

[190mech]

Wos,
We ran the CanAm motorcycles (Enduro and Motocross) back in the 70's that had that engine. In that time it was a great engine! It had a wide powerband, good transmission ratios and was reliable. We liked the 175 as it would keep up with the 250's on the long dirt roads between trail sections, the weak points were the CDI which was very expensive to replace and the rotary side crank seal leaking causing bad smoking..We ran them basically stock except for some pipe work and lots of frame modifications to increase suspension travel.