ESE's works engine tuner

[peewee]

One big advantage of case reed engines is the better piston support on the inlet side

and theres a actual C passage. cylinder reed really has no defined C passage. its mostly just a doorway from the reed cavity to the cylinder bore

[jonny quest]

TZ, how are you controling the powervalve? The NSR cylinder only offers PV leakage for blowdown which isn't a good thing. If you can set PV to 50% closed, then fully open... I think that would be a worthwhile test on your mod cylinder.

[lodgernz]

The outflow may become sonic during a small part of each revolution but that should not create what you are describing. A 14,75 mm end cone restriction should be good for over 22 crankshaft-HP, so no problem there. Other noise-contributing factors can be a high exhaust timing, a late ignition timing and a low compression ratio.
And of course an absorbing-type silencer that is not absorbing because its stuffing is either too tightly packed, saturated with oil, or absent.

Thank you Frits. The exhaust opens 84* ATDC so not that. The ignition starts at 30* and drops to 14* by 11,000, so probably not that. I've tried several mufflers, all brand new and the same type that make my 90 very quiet.

Compression IS low at 12.5, so maybe that's it?
I must say that possible cause was a surprise to me. Can you please elaborate a little?

[teriks]

Compression IS low at 12.5, so maybe that's it?
I must say that possible cause was a surprise to me. Can you please elaborate a little?

Not Frits but..

Less compression also means less expansion before ex port opening, resulting in more energy in the exhaust pulse.
Given equal combustion pressures etc..

[Frits Overmars]

You said it, Teriks. And that stronger exhaust pulse is the main reason that I am fond of low compression ratios.
We are using even lower ratios in some successful engines. These do sound healthy, but I can't say they produce much more noise than the competition....

[JanBros]

We are using even lower ratios in some successful engines.....

now I'm curious as what is considered as "low" ? 12:1? 10:1 ?

[Juho_]

14,75 mm end cone restriction should be good for over 22 crankshaft-HP

Is it possible the end cone restriction could be too small and cause the lack of over rev?
When: running on alcohol fuel (E85) and pipe is designed for example 13,000rpm peak hp and the engine now produces the peak hp @ 14,500rpm.

In my case.. it probably is not the problem, or will never be the problem. (last ignition timing change @ 13,000rpm, ducati am6/derbi cdi unit, max. rpm only 15,500 now and peak hp as said above; at 14,500rpm currently on new pipe)
Just interested if 'too small' end cone restriction could cause lack of over rev.

Erm, no the case looks neater to flow. And if done right less section change with large reed.

@F5 Dave - e.g rotax 453 cylinder (used in sleds, like ski-doo mxz 440) has typical 'rotax -like' boyesen ports. Same thing at 122/123 cylinders (found in aprilia rs/sx/mx 125).
They are aimed straight (to A/B duct divider), instead of to crankcase like most (if not all) japanese 2-stroke cylinders have (like YZ 250).

I've had an opinion, the boyesen ports should be aimed to crankcase, because then the B ducts can be then made better shaped.
But I have no much experience of these cylinder reed engines , and don't really like them much and atleast on my knowledge and skills it is not even close as powerful as case reed engine (or have the potential).

[breezy]

Has anyone found a reasonable priced supplier of blank cylinder sleeves since Akunar ...? only ive just buggerd up my £125.00 bespoke liner which took 5 weeks to be produced and then of course in my excitement 10mins to knacker , even though i spent all day making a jig for holding it on my lathe, marking it up and buying a slot drill to cut the ports with. still never mind aye...practise makes perfect.

[tdc211]

Attachment 332543

Well I got to try my new nicely ported NSR cylinder. The workmanship of the last porting effort was a bit disappointing and I was not convinced by the results. Disappointingly my first effort only made 31hp. 31 is that as good as it was going to get or was it being held back by poor workmanship???? I was hoping for more than 31 on the new cylinder.

Attachment 332545 Attachment 332544

The good news is that today's tests confirmed that for off pipe slow speed fueling, under piston injection gives much better results and was noticeably better than crankcase injection.




On my second attempt. I was very happy with my workmanship opening the ears up on this new ported cylinder to make it look more like a RS cylinder. But after hours of work on the dyno getting the PV right and ignition and fueling spot on it also did not make more than 31hp, Red line.

Inlet is 240 duration and both cylinders ported and std are 200 Ex duration and 132 Transfer duration.

The Blue line is a standard NSR cylinder with its droopy down exhaust port and the modified one, Red line had the top of the exhaust port leveled off for more blowdown time area. At this point I think the standard cylinder would give better on track results.

Attachment 332546



I will take your advice about "bowling" out the exhaust port. Also what you say about the short circuiting from the "A"s now that the cylinders have been ported makes sense. Engmod tells me that the transfers have enough transfer time area.

A Honda RS125 makes 40-43 hp. Because both my ported cylinders topped out at 31hp I suspect a common link and think that it might be that the exhaust nozzle I am using is going sonic and choking. I will look here first because that is easiest.

Jonny if you have been working with NSR cylinders I would love to know more about what you have tried and the results.

I have some experience with engines of this size
52 x 48.95 stroke. 117/118/119 tranfers. 82 ex 85 subs.
32mm carb 790 pipe. 1.34 case comp . Case reed
104cc. Or it's called a KTM 105. 34.8 hp. Cyinderis terrible from ktm
Tookabout 4 years on and off trying things. Pipe big help
29.5 carb goes 34.2hp on same numbers. But different cyinder.
So I not sure if it's the carb. Or just maybe my cyinder litte better on that particular one. Balanced sta in sim 40hp worth. With low tranfers.


Sometimes I fix Stroker Engines for guys..Aka more transfer and
110-112 cc and I am where you are at. 31-32hp or so.
20hp at 9000 is common on 30-35hp. 100cc engines.
I still need more r&d time on those. Really the bigger Engines should make more at 9000 with correctly timed pv. Correct pipes (my biggest issue. That and pv seems to be my biggest issue on the strokers

I have posted on here in the past. But I have a Eng Dyno.
It's turned down now in these charts, to match most rear wheel hp dynos. So it's legit.

[RomeuPT]

Hello. It's me again, last time it was because of 2000€ part's to trash in a running in , never stopped reading the forum, would worth to start another read all over again

Some questions I would like to have clearer ideas.

At which rpm should a rider change gears in a tuned Honda RS 125, say making peak at 12,7 to 13k rpm, isn't it a lost of time to let the bike overrev to 14k or more in low gears?

Been doing some exhaust's like this (attached pic), no exhaust flange, but the oval to round transition in 3mm sheet plate and 1mm roled sheet, then 0,8mm mild steel going along the header, I question myself if this would not loose power against a well made aluminium spignot due to heating more the end gases....

Is there any dyno somewhere comparing carb sizes in a strong 125? like comparing change from 38 to 41? is it really needed to achieve the holy grail of 50cv on a 54x54,5?

Sorry for my faulty english

cheers

[husaberg]

Has anyone found a reasonable priced supplier of blank cylinder sleeves since Akunar ...? only ive just buggerd up my £125.00 bespoke liner which took 5 weeks to be produced and then of course in my excitement 10mins to knacker , even though i spent all day making a jig for holding it on my lathe, marking it up and buying a slot drill to cut the ports with. still never mind aye...practise makes perfect.

Google John Tice
give me a minute
http://www.smallenginemachineworks.c...inder_services
http://forums.everything2stroke.com/...round-the-Shop
http://www.everything2stroke.com/con...u-need-to-know
if your project is intesrting enough he will do a deal on doing it all

he used to make his own sleves and shows the process of casting them,
http://forums.everything2stroke.com/...the-Shop/page9
from memory he gets most of them from LA sleeve but he mentioned somewhere elese he calls N.W?
Northwest Sleeve Co.
https://www.manta.com/c/mmsq7lz/northwest-sleeve-inc
http://forums.everything2stroke.com/...the-Shop/page3

Bert Munro used to old gas pipe that was spun cast.
but i believe he once used a cast iron down pipe from a motel near Bonneville (not sure if that was in the movie or the book)

[wobbly]

Romeau, what you are showing will never work.
The whole idea is to reduce the duct volume, so to have a round duct, that then reduces is backwards thinking.
The best RS125 cylinder I have tested had a 32 by 41mm oval shape at the cylinder duct exit.
This then transitioned from that oval to a 41mm header entry.
38mm is plenty for any RS125 cylinder,as I can get 48.8 Hp ( sprocket ) from a TM with a 30mm carb.
The very best RS125 dyno I have seen was 47 HP - rear wheel, this being a PV factory setup as used by Itoh.
That had a stock 38mm SPJ carb, and that translates to close to 50 Hp sprocket.
The reeds in a RS125 are nowhere near as clever as those we use in the TM kart engine,I suggest you start looking there.

[Flettner]

Has anyone found a reasonable priced supplier of blank cylinder sleeves since Akunar ...? only ive just buggerd up my £125.00 bespoke liner which took 5 weeks to be produced and then of course in my excitement 10mins to knacker , even though i spent all day making a jig for holding it on my lathe, marking it up and buying a slot drill to cut the ports with. still never mind aye...practise makes perfect.

If its any consolation Breezy I did the exact same thing the other day, making a sleeve for a six cylinder outboard engine, spent all day making it then put a hole in the wrong place!! Outboard engines are shit anyway so who cares, well I did because I had to pay for a new piece of cast iron and remake it, all on my bill. Said some bad words I did.

[RomeuPT]

Romeau, what you are showing will never work.
The whole idea is to reduce the duct volume, so to have a round duct, that then reduces is backwards thinking.
The best RS125 cylinder I have tested had a 32 by 41mm oval shape at the cylinder duct exit.
This then transitioned from that oval to a 41mm header entry.
38mm is plenty for any RS125 cylinder,as I can get 48.8 Hp ( sprocket ) from a TM with a 30mm carb.
The very best RS125 dyno I have seen was 47 HP - rear wheel, this being a PV factory setup as used by Itoh.
That had a stock 38mm SPJ carb, and that translates to close to 50 Hp sprocket.
The reeds in a RS125 are nowhere near as clever as those we use in the TM kart engine,I suggest you start looking there.

I am not sure if you or if I understud. the pipe has in it self a oval to round transition, in this case from this cylinder 40,5x34mm and includes the lenght of the spignot, so theres is no more volume there then with oval to round spignot. The ideia is to have virtually the same dimensions, I was thinking if cooling at the spignot has a role to play and I remember a little some post about that.

About the overrev and gear shift, any ideia?

[JanBros]

idealy, you shift each gear at different rpm's, as the ideal point to shift gears largely depends on the drop in rev's and those drop's change from gear to gear.

basicly you need a dyno to determine the ideal shift rpm's.