ESE's works engine tuner

[DoldGuy]

KTM made a completely new engine in 2017, the first with a balancer. This engine is (in its enduro version) now totally dominating the enduro championships.
Look for instance at the latest entrylist of the famous Erzberg Enduro : more than 90% are two stroke engines. And a large part of those are KTM or husqvarna (same bike, different colours)

This prompted TM to rework their 250 engine, now they have also an internal balancer, plus a very compact electric starter. They also have an electronic powervalve.

But on the japanese front : nada... The yamaha 250yz is a 2006 engine. Suzuki, kawasaki and honda have nothing.

As much as I love the 2 strokes, I have to disagree they are at an advantage over the current 250 foulstrokes as they (MX Motors) are almost making the same peak power as the 2 strokes but with WAY MORE range. If you also compare the lap times (again MX) the 250?s are very close to the 450?s which will currently kill a 250 two stroke in range and peak power. If they are allowed it should be MUCH more cost effective and hopefully bring in new/more participants.

The extreme enduros are totally dominated by 2 strokes, and as of late, many more manufacturers with competitive bikes, Gas-Gas/Sherco/Beta...

[Flettner]

As much as I love the 2 strokes, I have to disagree they are at an advantage over the current 250 foulstrokes as they (MX Motors) are almost making the same peak power as the 2 strokes but with WAY MORE range. If you also compare the lap times (again MX) the 250?s are very close to the 450?s which will currently kill a 250 two stroke in range and peak power. If they are allowed it should be MUCH more cost effective and hopefully bring in new/more participants.

The extreme enduros are totally dominated by 2 strokes, and as of late, many more manufacturers with competitive bikes, Gas-Gas/Sherco/Beta...

Agree, trouble is there has been no real development of the twostroke ( short of TPI ) in the last 10 years. Jolly fourstrokes have the advantage of as you say wide power spread AND superior hook up. A modern twostroke using sliding gib rotary valve plus the advantage of TPI manipulation will have way more peak power, way wide torque curve and hook up that can out perform a fourstroke. Whats stopping the manufacturers? No one wants twostrokes anymore. Stick with 4T until electric makes its way to the top of the heap. This preasant situation is ripe for a good old fourstroke ass kicking by a twostroke of most modern design, but it will have to be funded private. Even TM are not forward thinking enough.
I've designed my 360 mk2 TPI so it can be dropped to 250, same stroke, brings the bore and stroke more or less square. I'm not suggesting I could build an MX winning bike but I think we could do a lot better than whats available at the moment.

[koenich]

2017 EMX250 rules also allowed 250 4strokes vs 250 2 strokes - but as already mentioned with the currently available 2strokes I absolutely agree that a 4stroke is a major advantage. Range, throttle response/controllability and much easier to ride (read less tiring). If I remember well there weren't even many starters on a 2stroke.

I own a YZ250 and recently had a chance to try a YZ-F250 on the same day and track, it's scary how much easier a 4stroke is to ride

Enduro is another animal but I'm sure in terms of rideability a 4stroke would be at advantage - but spilling coolant in the first slow section...

[Flettner]

2017 EMX250 rules also allowed 250 4strokes vs 250 2 strokes - but as already mentioned with the currently available 2strokes I absolutely agree that a 4stroke is a major advantage. Range, throttle response/controllability and much easier to ride (read less tiring). If I remember well there weren't even many starters on a 2stroke.

I own a YZ250 and recently had a chance to try a YZ-F250 on the same day and track, it's scary how much easier a 4stroke is to ride

Enduro is another animal but I'm sure in terms of rideability a 4stroke would be at advantage - but spilling coolant in the first slow section...

I know what you are talking about, I had a 250F and rode it a while. Gutless but fast, and easy to ride compared to my 2T YZ. (but not as much fun).
Sold the engine out of it, that fixed it. Its the frame the 360 MK2 TPI is in now. I would like this 360 to be just as 'rideable' as the 250F was only a shit load more power. With the use of electronic control.

[ken seeber]

250 2 strokes against the 250 4 strokes.....fantastic.
We're the underdogs.....
Now, all we have to do is to beat the bastards...

[Carel H]

Finished crankcase, finished as of 35 years ago.

Casting was necessary for the flanged chamber of the gearbox. I kept the casting as simple (or industrial) as possible. Better mill a bit than having nothing at all. Most of the retainers for the bearings are separate parts, the crankcase bearings with rings in grooves.

This is how I wanted it, ball and roller bearing for the crankshaft in a horizontally split case. There were a lot of crankshaft bearing religions where I was not a follower off.

Visible is the tilted split for the crankshaft, with 2 nuts above the cilinder base and 2 in pockets on the underside.

[Tim Ey]

250 2 strokes against the 250 4 strokes.....fantastic.
We're the underdogs.....
Now, all we have to do is to beat the bastards...

That might actually be more of a challenge than you might think.

[husaberg]

That might actually be more of a challenge than you might think.

I have heard of friendly dynos but i suspect that one would be humping as well as pulling your leg.
that is where i have seen most 450's sit.
here is a dynojet on a CRF450
Dynojets are are know to be friendly

to put this into perspective how little they have evolved my 19 year old Husaberg puts out 50HP at the rear wheel from 50cc more.

[Flettner]

This is my F9 Kawasaki rear wheel HP. Not ideal bore and stroke, 80 x 70, shitty hacked up FMF pipe, untouched 1973 transfers, just barrel raised, air cooled (and ethanol) with some exhaust port widening it would have to be close to 45 RW HP now. No power valve. This engine has never been optimized in any way just seat of the pants tuning (and a bit of a stint on Robs dyno early on)

It would make sense that a water cooled 250cc version with a much more modern cylinder with proper ports, chamber made by someone that knows what they are doing, exhaust power valve and the same sliding Gib valve housing should rev harder, produce similar bottom end and have way more mid range power. In a decent frame?

Add state of the art TPI (the new version, much better homogenization ) the sliding open and close Gib, perhaps even dual rotary valves, I'd be surprised if it didn't give the 450's a hurry up.

Or am I just stuck on planet twostroke? (deluded)

[ken seeber]

PART 2. Sorry, but PART 1 is under Foundry...my stuff up.


?So, it?s now off to see Henri Tiben (another national champion). Bit out of the way, just only 800 met from the German border.? Henri is a Freetech 50 man, his current bike running a Bidalot cylinder with a side mounted rotary disc valve.

Attachment 342338Attachment 342339Attachment 342340

In the best interests of a positive relationship between northern and southern hemisphere 2 stroke types, the southerners offered some simple 2 stroke tuning tips, which I?m sure will give a 2 hp increase over the 22 hp of a 50 cc bike. Obviously I?d love to tell you more, but we?ll have to wait until the patents are fully cleared.

Overall it was really great, so many thanks to Frits, Martijn and Henri for the day. And the giggle of the day was:

Attachment 342341

[Peter1962]

This is my F9 Kawasaki rear wheel HP. Not ideal bore and stroke, 80 x 70, shitty hacked up FMF pipe, untouched 1973 transfers, just barrel raised, air cooled (and ethanol) with some exhaust port widening it would have to be close to 45 RW HP now. No power valve. This engine has never been optimized in any way just seat of the pants tuning (and a bit of a stint on Robs dyno early on)

It would make sense that a water cooled 250cc version with a much more modern cylinder with proper ports, chamber made by someone that knows what they are doing, exhaust power valve and the same sliding Gib valve housing should rev harder, produce similar bottom end and have way more mid range power. In a decent frame?

Add state of the art TPI (the new version, much better homogenization ) the sliding open and close Gib, perhaps even dual rotary valves, I'd be surprised if it didn't give the 450's a hurry up.

Or am I just stuck on planet twostroke? (deluded)

A nice cocktail would be a KTM or TM 250 model 2019 (so with balancer) and then the fun can start : I would take my Mastercard and order :
-a rear mounted, detacheble rotary valve, toothet belt driven and made out of the best aluminium, and a layer of bronze to protect the valve from excessive wear. The intake flange should be able to be used with the carburator (SX) or for the enduro version the injection body. (interchangeable)
-the sliding double gib system made by Fletner is an absolute must.
-surface treatment of the gearbox, crank and rod as described here on Ese's thread, but can not recal the name of the kiwi company...
-forced lubrication of the big end, suzuki GT750 style, or a more modern oilpump from a rotax E-Tec engine.
-Fabio's PowerCDI module for ignition, and since his system can take care of 2 additional features, it would command the sliding gib system
-The TM already has an electronic powervalve, to be coupled to the PowerCDI
-For KTM : ditch the actual mechanical system, and mount the new 2019TM electronic powervalve system without cables, to be coupled to the Power CDI
-SX : a 38 Smartcarb model 2 with TPS, as an alternative for a Keihin 38 with TPS and electronic powerjet. Of course the standard mikuni goes to the clicker
-Enduro : the TPI system that comes standard with KTM, or the new TM system, but coupled to Power CDI
-the exhaust : full analysis in Engmod by Master Jedi Wobly, to be ordered in double because of the rather clumsy riding habbits of me-myself, coupled to the infamous Law of Murphy that prescribes that the beautiful exhaust will be ruined after just one ride. And ordering a new exhaust in New Zealand, to Belgium, should probably take more than 24 hours.
-on the Enduro model (so, with TPI) : order a sticker : 'thank you Fletner' and apply to both sides of the bike in the most visuable place just to annoy KTM
-AS3 Performance : oversized water pump impeller

Next fase : explain to the missus where all the money has been spent...

BUT : destroy the lads who come to the local trac with their honda crf 450 farming equipment.

[Flettner]

All we have to do is just make it happen.

I'm quite keen on this 175 engine I've got lined up next. Same tech but a new piston design so I can have exhaust ports right around to half way. Bridged exhaust but both ports leading to two separate outlets (back to the future, CZ) get as much blow down time area as possible and best exit flow for the exhaust gasses. Easy to run the water right up to the bridge as well. Still side RV, convenience, probably put a balance shaft in it, use that to turn the crank backwards, like my 360. Reverse pipes like the 360 for pipe safety and heat retention with river crossings etc.

It seems harder to get stuff done these days, easy to talk. In saying that I should get the last shafts off to get hardened for the 360's kick start system today. After this its just the wiring.

[Flettner]

I have spent a lot of time getting a reliable / repeatable home foundry up and running for such projects. As I've said on the foundry forum, I don't mind pouring other peoples bucket projects if they arrive on my foundry floor. I will advise on pattern making but won't be doing any for other people myself. Sand mold making can be done here also but material cost will have to be covered.

I'm expecting a flood of twostroke cylinder casting

[TZ350]

Ok..... so its boats and dirty four stroke V8's but you have to be dead if your not impressed by the effort and results, over 200 MPH.

[DoldGuy]

I have spent a lot of time getting a reliable / repeatable home foundry up and running for such projects. As I've said on the foundry forum, I don't mind pouring other peoples bucket projects if they arrive on my foundry floor. I will advise on pattern making but won't be doing any for other people myself. Sand mold making can be done here also but material cost will have to be covered.

I'm expecting a flood of twostroke cylinder casting

And this has drawn my admiration of your “Get it done Attitude”. Your willingness to pursue, what many of us only dream of, keeps me excited to see what you have next!