ESE's works engine tuner

[Condyn]

You mean from or through intake port? If through you can connect crankcase with pipe which will pass through the middle of the inlet or with two pipes which will pass through corners of the inlet port. It depends of the configuration of the cylinder, studs and crankcase base but usually single center pipe is better option cause of bigger pipe cross section and inlet side walls are formed to follow cross section of the inlet port with transfer pipe in center.
CZ bikes used to have this kind of arrangement.

From the intake

[Condyn]

So first question, can you use the matching pistons to the new rods? I found out the hard way when my new piston was a few mm wider. The std piston was tapered at the top to retain the bearing and I never spotted it being too obsessed with moving ring peg, etc. OK i was a Klutz.
I used some hardened thrust washers which worked well but needed replacing every year racing.


2nd, and most obvious, can you fit a reed cage? Then you can fashion a straight std boost port in conventional style above reed cavity.

I used to cut the back 20mm off a scrap barrel and tack each corner so its strong without warping things, dig out the cavity and devcon the gaps. That gives you matching reed and manifold to use.

Or if your case, and desire to make things difficult for yourself, add the reed to the crankcases. Done that twice.

This particular engine has to remain a piston port. I have quite a bit of devcon in this engine already. Any more would make me cringe.

I may have found thick washers but not certain they will work yet. Is it not advised to stack thrust washers on the big end bearings to make up for a more narrow rod?

[Condyn]

what size length and widths are you wanting?

Ideally:
C-C=120mm
Width both ends= 20mm
Big end bore= 31mm
Small end bore= 22 or 23mm both bearings avail

There is a rod that’s 17 wide on both ends that is readily available but would need to find oddball thrust washers. The bottom rod/bearing is offset on the pin to one side

[husaberg]

Ideally:
C-C=120mm
Width both ends= 20mm
Big end bore= 31mm
Small end bore= 22 or 23mm both bearings avail

There is a rod that’s 17 wide on both ends that is readily available but
need to find oddball thrust washers. The bottom rod/bearing is offset on the pin to one side

TS-250ER
B.E.BEARING DIA (mm)：Ａ 31.0
S.E.BEARING DIA (mm)：Ｂ 23.0
B.E.& S.E. PITCH (mm)：Ｃ 120.0
B.E.THICKNESS (mm)：Ｄ 19.8
S.E.THICKNESS （mm)：Ｅ 23.8
CRANK PIN DIA (mm)：Ｆ 25.0
CRANK PIN LENGTH (mm)：Ｇ 58.0
Ts250ER a little wider in the small end.


Dt250 5mm to long
MODEL
DT-250/YZ-250
B.E.BEARING DIA (mm)：Ａ 31.0
S.E.BEARING DIA (mm)：Ｂ 22.0
B.E.& S.E. PITCH (mm)：Ｃ 125.0
B.E.THICKNESS (mm)：Ｄ 20.0
S.E.THICKNESS （mm)：Ｅ 20.0
CRANK PIN DIA (mm)：Ｆ 25.0
CRANK PIN LENGTH (mm)：Ｇ 60.0

i will have a proper look tomorrow

[Condyn]

TS-250ER
B.E.BEARING DIA (mm)：Ａ 31.0
S.E.BEARING DIA (mm)：Ｂ 23.0
B.E.& S.E. PITCH (mm)：Ｃ 120.0
B.E.THICKNESS (mm)：Ｄ 19.8
S.E.THICKNESS （mm)：Ｅ 23.8
CRANK PIN DIA (mm)：Ｆ 25.0
CRANK PIN LENGTH (mm)：Ｇ 58.0
Ts250ER a little wider in the small end.


Dt250 5mm to long
MODEL
DT-250/YZ-250
B.E.BEARING DIA (mm)：Ａ 31.0
S.E.BEARING DIA (mm)：Ｂ 22.0
B.E.& S.E. PITCH (mm)：Ｃ 125.0
B.E.THICKNESS (mm)：Ｄ 20.0
S.E.THICKNESS （mm)：Ｅ 20.0
CRANK PIN DIA (mm)：Ｆ 25.0
CRANK PIN LENGTH (mm)：Ｇ 60.0

i will have a proper look tomorrow

I appreciate it. I don’t know if machining the rods width down is advised, but if that’s a possibility I would be willing to go that route.

[jonny quest]

I appreciate it. I don’t know if machining the rods width down is advised, but if that’s a possibility I would be willing to go that route.

You can narrow rods on a belt sander. Just do one side at a time and keep checking how square it is to original side. After you have half your intended width removed on the one side and it's still square to within .001", do the other side and keep that square.

Just be honest with yourself, this new rod from a performance engine, or heavier piston than what you have.... it's usually ok to take off some width.

You can also press your crank together a little more if you need to take up rod to cheek space. .5mm is a good gap. A bigger gap between cases and cheeks are usually preferred over what stock was

[WilDun]

You can narrow rods on a belt sander. ...........

Doesn't the removal of the outer hardened shell affect the strength? I tend to think it might! - but of course, if it works ........!

[Ns1Montesa]

Hi Josh, herzlich willkommen. I wish my German was as good as your English. But as I keep saying, German is a much richer language than English: if offers far more opportunities to make mistakes

You can compare a two-stroke engine with a 10-digit combination lock. Even if you get nine out of those ten digits correct, you won't know because nothing happens. Only when you have all ten correct, you may sing and dance.
How do you determine the bottleneck? Work, lots of work. And experience, lots of experience.
Attachment 346584

Raising the axial angle of the A-ports to about 25° can give a nice improvement. Better leave the axial angles of the B- and C-ports alone for the time being.
If you can find the time, visit one of the German SimsonGP races; free admittance if you give them my regards (and also if you don't ).
Several riders there use your type of engine, and a good one produces about 22 hp, even with the cast-iron cylinder.

Hello Frits,

yes, the german language is difficult, sometimes even for native speaker

Already thought about visiting the SimsonGP. Maybe I find the time for it. There are two events left for this years season.
22 Hp, thats a good number. Would be happy if I reach 20.

You are right about the bottleneck. There are too many variables in a two stroke engine to give a good answer to my silly question.

Hi Josh, like Husa said, it would be interesting to see more photos of the cylinder with all ports and piston.

Looks like original cylinder designed to concentrate intake flow mass directly to crankcase, through main intake windows/piston skirt together with another port arranged downward to crankcase, so there is no high flow through this additional holes, from piston movement (just from on-pipe) and its even better for back flow to reed space.

Rising piston side cutouts as high as piston construction allows, helps to rise flow velocity through this boyesens, as A and B opens longer at TDC and send stronger pulse to reed space, directly through this holes. And together with some original intake flow restrictions (base gasket with smaller cuts for down side intake) or piston without holes, mix velocity through boyesens could rise even more.
We noticed, modifications that concentrated intake mass flow more to transfers, require leaner mix.
Add photo of kit version for NSR/NS/mbx, and pistons, that could sing in a duet with the big boyesens, but not with piston ported or rotary valve type engines.

Keeping the transfers open for a longer time via piston cutouts to get some more sucktion to the boyesens is a smart idea. I will keep that in mind. But for now I will leave the piston untouched.

Simple answer to the bottleneck question , is you need to use a port calculator to ascertain the relationship between the intake/transfer/blowdown STA numbers.
The engine will always hit a wall as soon as one of these is out of sync with the other two.
You now know its not the intake that prevented better ( if they actually were better ) pipes from working as intended.

A perfect example of this was an LC350 I analysed during lockdown.
It had been ported by a well known English "name " tuner , and he had actually done a very nice job of giving the staggered transfers the capability of 52 Hp/cylinder , but sadly the Blowdown STA was down at 34 Hp.
This was why several sets of pipes made no difference at all - and the worst/skinnyest most horribly made pipes worked OK.
Banshee VF4 didnt work, 34mm carbs didnt work , more com didnt work , long rods didnt work etc etc.

Bigger/more holes are not always better. Thats what I learned from my boysen drilling mistake.
I will take the cylinder off, measure the ports, calculate the STAs and check if the transfers and the exhaust are capable of giving more power.

Although your engine has the long cylinder studs, it seems someone has managed to have aux ex-ports in it. Might be worth looking into.

hi andreas,

your picture shows the port map of the Italkit cylinder. Katinas picture shows a similar one. I think the only difference is the exhaust port.
The standard honda cylinder has got a bridged exhaust port.
The italkit cylinders are no longer produced and used ones are rare.

Katinas, I added a picture of the cylinder I am using(Honda). Portmap(sloppy one) and picture from the underside. Left is stock cylinder. Right is slightly modifyed. Only removed the sharp edges of the intake ports and transition from bore to transfers. Exhaust is widened a bit.


Thanks everybody

cheers

josh

[husaberg]

Doesn't the removal of the outer hardened shell affect the strength? I tend to think it might! - but of course, if it works ........!

Hi Will, The widths of the rods are the last things machined on the rods there is no hard skin remaining on this part of the rod that i have noticed.
On a belt sander they thin down like butter.

[katinas]

Josh, with additional boyesens, try to close crankcase intake port ( fully or partially, red line) , this is very easy to do with the base gasket. It was like, close the door when another opened.
Port map looks like really capable for 20hp.

[lodgernz]

Would be awesome if somebody knows how to solve this issue or can explaine why boyesens are not working for me. And If someone knows more about getting power out of these honda engines, please let me know
josh

Hi Josh. I believe that grinding away (i.e. raising) the separator between the A & B ports a few mm allows some of the charge coming through the Boyesen ports better access to the A port. Without this, only the B ports benefit from the Boyesen flow.
Also, there are a lot of sharp edges on the lower cylinder outer that can impede flow. If you look into the reed cavity you'll see that the incoming charge has a lot of disturbance from these sharp edges and corners. Easy to smooth these off.

Although you can't get any really nice after-market cylinders any more for these engines, you can get a 44mm stroke Italkit crank, and you can of course bore them up to 54mm. You might be able to find a Malossi 53mm cylinder, which are cast-iron but with quite nice transfers. The exhaust timing on these is mild, but as it is cast-iron, easy to improve.

And if you really want to spend some money, get a VHM head with insert. They work well.

After all that, it is really matching the pipe to the cylinder that will determine the power.

[Greg85]

Milling the spark plug puts the spark gap closer to the middle of the camber. It also promotes access of the mixture to the gap between the electrodes, helping it to replace the burned gases with stuff that still wants to burn. And it cools the plug.
Attachment 346431

Speaking of tech rules: the above rule seems so simple; what could possibly go wrong? Well, I would claim that the mass electrode is part of the plug body, so this simple rule simply renders all present-day spark plugs illegal .

Hello frits, wobbly,
then yes indeed with this type of spark plug the ignition and much better!! its even corrects the carburations a little more fat.
I tested a spark plug for ngk 105 for rotary engine rx7 a 21mm body, is indeed it works because you bring the spark plug close to the piston but is illegal in kz2.
However, I wondered at that time when Max Verstappen at the 2013 World Cup in France didn't have a short spark plug but a standard spark plug for the ngk br10 but apparently, I think it was beneficial for the carburettor set-up because this track on the Varennes allier is very complicated to find a good carburettor setting. jos Verstappen himself said in a kartmag interview that it was difficult for the carburettor set-up here.
franco drudi tm in any case does not use long spark plugs but short ones...
so he must have a good carburettor set-up for everyone because he never breaks an engine! I saw in a post at wobbly that franco runs with a bigger cylinder head volume of 13.6cc so I think it helps from a detonation point of view that this works at the 13.02cc limit.

[Condyn]

Question regarding pipe wall temp and EngMod2t inputs.. I can’t afford to dyno test regularly so improvising is a necessity right now. We run cvt drive snowmobiles over here and I have devised a plan to test once we have snow. Since the engine rpm is influenced by the cvt system that uses a primary drive clutch and a secondary driven clutch. In order to determine when the engine is starting to get on the pipe I have manufactured this spacer (which I intend to replace with a safer quality unit) to stop the primary drive from closing completely. It limits how much the spring can close and is set so there is just enough belt pressure to move the machine. If I slowly roll into the run and ramp the rpms up my thought is that by watching the tachometer I will be able to tell when the engine begins to get on and then off the pipe. Also included is a photo of CHT thermocouples that I intend to fasten to the pipe wall at various places during this test. By facing a go-pro video camera at the gauges I effectively have a usable datalogger. I understand inner wall temp is used in the program, but could this method be accurately used?

[wobbly]

I have done exactly as you are proposing to do , this info was needed by Neels when he was implementing the wall temp varying with rpm option.
But I data logged the temp after doing several all gear runs , then 3 pulls in top gear averaged.
In all of the race engines I have modelled , produced a pipe , built it and dyno tested it , much the same wall temps work in testing as in the sim.
With the final header egt reaching 620*C every time, the average pipe wall temp starts at 325 under the pipe ( 8,000 for a KZ engine ) and reaches 425 at peak power ( 13500 for the KZ again ).
The problem with measuring the wall outer temp is that the header is hottest , but has a very small area comparred to the mid section temp.
The end of the rear cone ( about 1/3 up from the stinger ) is 1/2 way between those two temps , and that too is of much smaller surface area than the cooler mid section.
Those average numbers I found were worked backwards from the dyno result of existing pipes, and gave identical powerband shape and peak power rpm in the sim.

[Condyn]

Re wall temps *edited*
So you are saying that every race engine you have tested with 620° C EGT in the header, your prescribed wall temps of 325° and 425° have been spot on? I am a bit confused as to if your findings while performing the test I am proposing worked or if you ended up plugging numbers in until things lined up in the sim and dyno test? I guess my main question would be; if I install 4 outside wall thermocouples on the pipe in the proper places, will I end up with 325° start of powerband and 425° peak?