ESE's works engine tuner

[andreas]

its not a fascination or a fashion it has practical benefits, aside form the lessening of thrust on the piston It also increases the piston dwell both near Top Dead Center, Which can improve combustion efficiency.

Does it really increase dwell at bdc? I think the opposite. At least it stays a comparatively shorter time in the bottom half of the stroke.

[TZ350]

... photo with three different Honda RS pistons side cuts and similar on NSR500V two cylinder pistons. But the rotary valve and piston ported engines maybe wants opposite.

I had not thought about the side cuts at TDC and did not realize there were differences in the RS pistons. I use a second hand RS125 piston in an old road bike NSR250 barrel. Our racing class rules allow the RS piston but not the RS cylinder. The TZ piston in your third picture is interesting.

[andreas]

TZ I seriously like your engine.

[husaberg]

Does it really increase dwell at bdc? I think the opposite. At least it stays a comparatively shorter time in the bottom half of the stroke.

no, I said the opposite.

[andreas]

[QUOTE=husaberg;1131140261]no, I said the opposite.

[katinas]

Very interesting pictures Katinas. Especially the compressor engine made me wonder. Some coarse reverse-engineering of your drawings yielded very oversquare engine dimensions of 29 mm bore and 15 mm stroke (the second engine, with the bigendpin-driven rotary disk, yielded a more conventional 24,5 mm bore and 21 mm stroke). The compressor impeller has a 46 mm diameter.
Assuming a piston speed of 22 m/s, the compressor engine would rev to 44000 rpm. The various angle.areas would not allow decent breathing at those revs, but let's ignore this for now. But a 46 mm Ø compressor impeller would need to spin at least five times as fast to do any good....
Now this old Gilera-sketch comes to mind:
Attachment 342865

Frits, your accuracy is 99 %. Engine with the bigendpin-driven rotary disk is 1970 E.Gusev 9,95cc engine 24 mm bore 22 mm stroke, crank big end 7mm (crank and rod material 12crni3) with 1.5 mm rolers, main shaft 10mm, rotary valve steel 0.3 mm. The engine was modified through years until 1980 and maybe more and ended with reed valve..
Compressor engine is more experimental for 10cc class. From the text impeller just for 10 cc engine, 45 mm diameter, 27000-28000 rpm just little help and can work only with pipe. For effective small impeller work it require very high rpm.
Add other drawings from this book. When car model moving so fast on circle, side force help to reduce piston force to cylinder wall or increase if spins in wrong direction.

Latest worrying stories with rounded piston and hydro diodes. One father from 50 cc (add power graph) wanted to stop his son on the track at training when he started to jump like others with 85 cc. Other father from 65 cc put 2 teeth smaller rear sprocket, because boy cant hold on the bar when accelerating.

Really Thanks.

[TZ350]

Yes Rob , this photo.

The good old TZ. This one has an aftermarket clutch basket that completely encloses the plates, good idea. I remember being hit with bits of broken TZ friction plates during really savage standing starts. Full throttle and moderate the revs with the clutch. The friction plates would crackup and bits fly out between the outer clutch fingers. The bike would keep going but two or three friction plates would be missing bits.

[katinas]

With shorter rod, piston goes faster through TDC and slower through BDC. Without higher piston side foce and lower under piston volume this changes all other things - ex and trans timing, needed different ignition timing, compression rise if use the same Ex duration like with longer rod, gas dynamic through crankcase and transfers changes at intake and transfer phases. Shorter rod is more aggressive on reed petals, when piston goes through TDC, and maybe on rotary engine intake needed close earlier.
Honda on NSR500V used 123 mm rod with 68 mm bore and 68.8 mm stroke, very short ( like 97.4 mm rod with 54.5 mm stroke ), but maybe because no left space for 500 2V 100 degree engine. From one 250 cc cylinder power 69 hp at 10250 rpm.

[katinas]

The good old TZ. This one has an aftermarket clutch basket that completely encloses the plates, good idea.

Remember one mechanic, with absolutely destroyed this type of basket in his hands, from, if remembers correctly, Antony West V2 Honda NSR500V at 2001 Brno GP.

[wobbly]

Honda stuck with short ( 104,105 ) rods for years , but the last champ winning 250 had a longer ( 109 ) rod.
It would have been changed for only 1 reason - power.
Theoretically the short rod has longer dwell at BDC , but in my opinion the long rod with more dwell at TDC and the reduced bore
friction from rod angularity has more advantages than downside.
Going back to the questions I missed a few days ago ( been racing in OZ ).
The Denso ignitions starting from around 2000 are all the same basic hardware - 60mm stator and 12V output , and 1-5 taper.
There was a change to a one piece fully machined rotor , and this also has NdFeB magnets.
A 4 coil stator with these magnets makes the same power as an 8 coil with the older Ferrite magnets.
And that 8 coil stator with the good magnets will produce over 4A , enough for a DCCDI P2 running both CDI .
Lastly the radius on the bore edge / transfer duct entry.
I have ground dozens of these with a simple carbide rotary tool for roughing , then polished up with bonded cotton mounted points.
Never had chrome chipping or any issues at all.

[andreas]

Last plated cylinder I ported was chrome, I did the exhaust and all possible ports where the ring passes, there was no flaking, after alot of runtime that is
. Is niqasil more fragile?

[katinas]

Wob , I have doubts about NdFeB magnets on a one peace fully machined 75 mm rotors with 60mm stators. From what I had in my hands, magnets are definitely weaker than on rotors used for the first CRF EFI engines .
I think Denso started to use neodymium with EFI engines, for Honda from 2009 and (sadly for us) rotors are bigger 90mm and from 2017 even bigger 102 mm.
I could not found small 75 mm rotor with magnets as strong as on latest bigger rotors for EFI. Honda RS 250 NF 5 rotor magnets are slightly stronger than CR but weaker than EFI and RS 250 stator diameter is 57 mm .

Stators for CR125/250 engines 2002-2007 goes with two types
8 poles 12v- CR 250 2002-2007 and 2004 CR 125 all with TPI sensors ( only two wires from stator directly to small regulator/rectifier and then it is possible to adapt what we want even DC-CDI-P4 for three or four cylinders) With two original CR 125 2004 CDI it works really good on V 90 2 cylinders engine

4 poles only on CR125 2002-2003 and 2005-2007 with TPI sensor ( stator with three wires and 2 different circuit, one for charging, other low voltage for timing chip and all wires connected directly to CDI not to regulator/rectifier ) With two original CDI on V 90 2 cylinders engine work only at idle rpm. Maybe it work with 180 degrees 2 cylinders, but I did not tested.

[_____]

Honda stuck with short ( 104,105 ) rods for years , but the last champ winning 250 had a longer ( 109 ) rod.
The Denso ignitions starting from around 2000 are all the same basic hardware - 60mm stator and 12V output , and 1-5 taper.
There was a change to a one piece fully machined rotor , and this also has NdFeB magnets.
A 4 coil stator with these magnets makes the same power as an 8 coil with the older Ferrite magnets.
And that 8 coil stator with the good magnets will produce over 4A , enough for a DCCDI P2 running both CDI .

So would this stator be the right one to choose?
https://www.ebay.de/itm/CRF450R-3110...1/173739551192
Judging from the bolt pattern it looks like a copy of the Denso type. And that particular one has only two wires coming out of the stator - think I will buy one and test it.

Thank you katinas, I bought myself a CRF 250R Rotor and will start playing with that :-)

Also the Hidira rotor/Stator of the KTM 65SX looks a lot alike the denso type (bolt pattern wise)

Cheers
Chris

[katinas]

Chris, on CRF 250/450 carb models engines, with 60 mm stator, they used another, say, third type
8 poles, with two wires connected directly to CDI unit, not to regulator/rectifier. Similar to CR 125 2000-2001 CR 250 1999-2001, but this stators generated high voltage to CDI. So there is some doubts. Maybe there is some type of regulator inside CRF CDI, but I dont know

CR 250 2002-2007 and CR 125 2004 12v stators with rectifier could be compatible with your CRF 250 rotor and DC-CDI, or aftermarket 8 pole stators with windings for lightning.

[41juergen]

Thank's a lot for the feedback Wob. Have done a set of RGV250 barrels and they go into the engine soon.

Just one other question: I'm looking for a 115mm conrod with the following dimensions:
small end: diameter 21 mm, width min 16 mm
big end: diameter 31mm, width min 16mm
At least prox don't have an appropirate one, even with a wider width of the small or big end...