ESE's works engine tuner

[jbiplane]

Hello guys

Could you recommend 70...125cc very light cylinders capable produce 13...17 hp for a long time permanently.
Says for 30 minutes+
I want to make 2-cylinder 25hp + engine which should weight no more than 7,5 kg complete with radiator end exhaust

[koenich]

Did you check the Airsal range for Derbi Euro 2 or 3 engines? Plenty of options reg bore/stroke and everything above 70cc should be able to produce the power you are looking for...plus they are cheap and readily available.

[41juergen]

Can someone help me with that problem: I'm preparing RZ cylinders to get aux ex ports in to increase the blow down. The currently mounted Woessner piston has cutouts to reduce the weight. So how far shall I go with the aux ex port? Going to approx. the middle of the bore I would gain more blow down than going only until were the cutout starts… So will the higher blow down eaten up by the short circuting with the Transfers?

[Frits Overmars]

Can someone help me with that problem: I'm preparing RZ cylinders to get aux ex ports in to increase the blow down. The currently mounted Woessner piston has cutouts to reduce the weight. So how far shall I go with the aux ex port? Going to approx. the middle of the bore I would gain more blow down than going only until were the cutout starts… So will the higher blow down eaten up by the short circuting with the Transfers?

The blowdown will be fine Jürgen. But before the exhaust ports even start to open, there will be a massive short-circuit between the transfers and the auxiliary exhaust ports. So forget about using those pistons in combination with aux ex ports.

[F5 Dave]

Interested to know how you were going to get around the cotton reel powervalve? Also the aux port looks as high as the main which for much of the time will be lowered by the pv. On a steel bore you will need a thicker bridge than you would get away with with plated.

[wobbly]

What they said before me - except to add that having the Aux at the same height as the main is never a good plan.

[41juergen]

The cylinder in the left picture with the wide aux port was a trail on an damaged one to see how to do the porting. The cylinder in the middle pic is the one I work on currently. I'm aware to have the aux ports lower, I have them approx. 2mm lower than the main.
So Frits would you think the samller aux ports (which do not go into the cutout) would be a problem? Of course depending on the budget of my finacial minister I will get some new pistons somewhen…
@Dave: I have attached some pics how the porting looks like currently incl. the modified / (rough) cutted bushing of the inner side. This is not the final version, I will modify the bushing (with the "nose" as the mounting point) to get the "channel" done. The bridge between the aux and the main port is approx. 5mm thick.

[jbiplane]

Did you check the Airsal range for Derbi Euro 2 or 3 engines? Plenty of options reg bore/stroke and everything above 70cc should be able to produce the power you are looking for...plus they are cheap and readily available.

Thanks. Still estimating. One friend suggest me
to use a 50cc cylinder "bigbored" to 95cc or 100cc (52mm) with 44mm stroke

Are there are racing scooter engine called Malossi C-One / RC-One, it use "flange" style cylinders like racing motorbikes.
the 95cc cylinders are 24-26hp peak power, the lightest seems the Stage6:

it seems very small cylinder to be a 95cc
https://www.motoscoot.net/cilindro-m...ulon-14mm.html

I want as well try Vespa 125 cylinders cutting of some metal to make it light

Are there another brands like 2fast
https://www.scootfast.net/2fast-cyli...crankcase.html

[Frits Overmars]

Frits would you think the samller aux ports (which do not go into the cutout) would be a problem?

I can't see a problem with that, except that you will be very limited in the width of those ports. Maybe you can enlarge them afterwards, when your financial minister approves the purchase of decent pistons.

[41juergen]

I can't see a problem with that, except that you will be very limited in the width of those ports. Maybe you can enlarge them afterwards, when your financial minister approves the purchase of decent pistons.

That's the plan...
Would you go up to approx. the middle of the bore even with that "large" 66 mm bore? Of Course that will increase the blow down dramatically on the engine, I need also to check and balance the transfer TA's as also a bit limited in the width… Neels software will help.

[peewee]

if your just wanting a common 64mm yami banshee style piston then you could use wossner 8075da. theres no pin cutouts at all. but its a bit heavy so you might want to machine off some material from the underside.

[F5 Dave]

I'm surprised there was room there. Might be a little soggy in the middle but so what. Be interesting what effect it has. I've added auxiliary to my MB100 race bikes on a few cylinders.

[Frits Overmars]

That's the plan...
Would you go up to approx. the middle of the bore even with that "large" 66 mm bore? Of Course that will increase the blow down dramatically on the engine, I need also to check and balance the transfer TA's as also a bit limited in the width… Neels software will help.

Is a 66 mm bore large? Wärtsilä mechanics will disagree, and I would say large is a rather undefined term. If you have sufficient material in the right places, and good quality piston rings, extending the auxiliary exhaust ports to the middle of the bore shouldn't be a problem.

if your just wanting a common 64mm yami banshee style piston then you could use wossner 8075da. theres no pin cutouts at all. but its a bit heavy so you might want to machine off some material from the underside.

Most of a piston's mass is concentrated between crown and piston pin holes, so if you want light pistons, try to find pistons with their pin holes close to the crown.
Maybe Yamaha TZ750-pistons could be an option. They have a 66,4 mm bore, so if you have a big enough hammer, they should fit

[41juergen]

Jeep, you are right that are really big engines, our company will supply the catalysts in future, that will be a nice business. Maybe we will sell only for 2 or 3 ships per year, but the volume….
I will talk with Woesser what they have, I need the piston for the 115 mm rod either, so let's see. And material for the wide aux ports is there, so let's see.

[tdc211]

Been a while since I been on here.
I still fiddle around with 2 strokes time to time.
This last time I really wanted up my power on the newer ktm 85. No small feet. I was already at 29ish hp. Up from 23. So I flowed the cylinder on my flowbench and redid the exhaust tunnel with clay to find the optimum shape.then welded it and it is pretty much right on size to eng mods rules in sim and I found the cfm as well on the bench. But yet no more power with close to my usual port timings. Of course I tried many things. Had adj ign box as well . Of course next time I will probably do the tunnel 1st. Before grinding to my usual timings. And I am guessing results will be different. What do u think wob?