ESE's works engine tuner

[lodgernz]

I often receive pistons with these circlips, and I never use them, as I've heard that the tags can break off in an engine.

Is this just an old wives' tale, or has anyone actually had this problem?

This type would be much easier to fit than the preferred pain-in-the-arse un-tagged type.

[husaberg]

I often receive pistons with these circlips, and I never use them, as I've heard that the tags can break off in an engine.

Is this just an old wives' tale, or has anyone actually had this problem?

This type would be much easier to fit than the preferred pain-in-the-arse un-tagged type.

This might be more of a widows tale.
I have never seen a modern MX or GP bike with tailed circlips so i think there might be something in it.
this was bell.

Another problem with standard replacement pistons is that many do not have any
circlip extractor slots. This means that only tail-type wire circlips can be used and
unfortunately this type of circlip wrecks engines. The constant rubbing of the gudgeon
pin against the circlip wears through the tail, allowing it to drop into the cylinder,
scoring the bore and possibly seizing the motor. If tail-type circlips are replaced
regularly, say after every second race meeting, this kind of damage can be avoided

A better solution is to machine extractor slots into the piston so that tailless
circlips (or tail-type circlips with the tail cut off) can be fitted (FIGURE 7.7). The slot
need only be '/sin. wide to allow a small electrical screwdriver or the point of a scriber
to fit under the circlip so that it can be flicked out. It should be cut in the position
shown, using a small round key file or a '/sin. dia. mounted grinding tip. Do not use a
hacksaw blade or three cornered file to make the extractor slot, as the abrupt corner
will form a stress point and eventually cause the piston to crack.

[wobbly]

P12 re the 500 sim , some pointers.
The Exhaust duct is 90 long , but where is the slip joint - its not in the pipe numbers before the header where it should be.
The reeds are miles too thick with a 1st Mode @ 12193 rpm.
12.5:1 A/F on Premium is impossible and also gives way too high gas temp - and that leads to unrealistically low pipe wall temps needed.
The pipe itself is a complete abortion , not even remotely suitable for anything that works even 1/2 way properly.
Having the Blowdown capability @ 83 Hp and the Transfers @ 95 Hp is always going to create big anomalies in the sim/dyno results , even more so as the
reed ports are down @ 65 Hp
You should , if everything is close to ideal have 15* timing @ peak power , this has it at 8200 , so alot more than necessary at peak.
But you can probably get away with this due to the big STA anomalies , the shit pipe design and no compression to speak of.

[lodgernz]

Yeah, thanks Husa, pretty much what I've been told.

[p12palof]

P12paplof,

The stock cr 500 has a ridiculous head Design...squish gap nearly 3 mm...area 60 percent...

Thats what honda did to keep a 500 2 stroke rideable

In your dyno chart there is a powerdip short after 4000 where retard drops... in my opinion it drops to early...
Ignition timing at peak power is little to high...bad for max power and overev...better do 15 degree at peak and drop steeper after peak...



Change head to more modern values as you did...keep compression low and do your own ignition curve

Grüße Wolfgang

Thanks for the reply Wolfgang. You are correct, the stock CR500 head is a disaster from the point of view of theorical design... When I tuned this engine in 2008 the first head that I put in the bike was the '86 version with less squish area and higher compression. The bike run hard in mid with a noticeable better response in comparison with the stock '94 head... But the majority of Honda CR comes with sheet metal head gasket and I experienced gas leakage problems. This is what I changed to Cool Head. This head has larger volume (60cc) and lower squish area with tighter clearance. I built another toroidal custom head with 1.2mm squish gap, 55cc volume

The result is always the same, with higher compression, you can feel the extra torque and better response in partial throttle openings, but in the dyno, the curves are always the same. You can´t feel noticeable differences at WOT

P12 re the 500 sim , some pointers.
The Exhaust duct is 90 long , but where is the slip joint - its not in the pipe numbers before the header where it should be.
The reeds are miles too thick with a 1st Mode @ 12193 rpm.
12.5:1 A/F on Premium is impossible and also gives way too high gas temp - and that leads to unrealistically low pipe wall temps needed.
The pipe itself is a complete abortion , not even remotely suitable for anything that works even 1/2 way properly.
Having the Blowdown capability @ 83 Hp and the Transfers @ 95 Hp is always going to create big anomalies in the sim/dyno results , even more so as the
reed ports are down @ 65 Hp
You should , if everything is close to ideal have 15* timing @ peak power , this has it at 8200 , so alot more than necessary at peak.
But you can probably get away with this due to the big STA anomalies , the shit pipe design and no compression to speak of.

Thanks for your time to respond, Wobbly, I appreciate so much your expert opinion. Talking about the exhaust duct, I "included" in the exhaust port menu from Dat2T the spigot, It has a CNC blend round to oval shape. I´ll correct it in the next simulation data. At the time of dyno test, I´ll test this bike with a 47mm diameter equivalent area restrictor but then I tested in the road this same spigot grinded to 51mm diameter and I felt a slight improvement in top end and overrev power... I´ll need to test this mod in dyno. I attached the pics for the new CNC spigot with o rings. I will work on the rest of the simulation points that you indicate.





About the ignition curve, I post the best curve that I could obtain in the dyno. In low end more advance does not give me more hp, but in top end, this bike wants higher advances than the ideals.



And 2 pics from the reed cage. After years here are the Vforce 2 surface... A mix from lack of blowdown, a little higher transfers and carburetor size restriction causing hot gases return to crankcase?

[Haufen]

Thanks. Btw, the first link says


What is the reason behind the dual angle kinked negative squish area? Did KTM have pistons with a corresponding shape, or a bowl, too?

Attachment 354188

Comments on the KTM head, anyone?

[p12palof]

Comments on the KTM head, anyone?

I´m not an expert in GP engines but I know that there is "semi flat" pistons for TM KZ karts, consisting in flat top, with a large bevel 4º angle in the piston crown / edge. It seems that this KTM GP head copies this semi-flat piston shape....

Below the VHM piston for KZ engines

[wobbly]

Speaking of Bartol copying everything - I showed him my semi flat top design for the BSL500 when he was still running the Yamaha 125GP team.
Funny how that made it into the KTM GP engine.

And when you can wind in alot of advance , this immediately indicates that the dynamic compression ( dictated by the engines efficiency ) is low to begin with
As I said a crap pipe and no compression.

[husaberg]

pretty sure the A kit stuff for the NX4 was a flat top design
as well the works 98 and 250 twin crank and the 2001 single crank version


that said thaose pics of the KTM a couple appear to be tordial.


these TZ125 appear flat top
https://www.kiwibiker.co.nz/forums/a...1&d=1411727294

That said Greeves had flat top pistons in the 60's pretty sure Herman Meiier had them in the 50's

[Haufen]

For me, that (particular) head in the picture is not a semi flat but looks something like this:


I drew a half section and used three colors in the squish area to highlight what I mean

[Gradella23]

Speaking of Bartol copying everything - I showed him my semi flat top design for the BSL500 when he was still running the Yamaha 125GP team.
Funny how that made it into the KTM GP engine.

And when you can wind in alot of advance , this immediately indicates that the dynamic compression ( dictated by the engines efficiency ) is low to begin with
As I said a crap pipe and no compression.

multiple people in Italy say that KTM had even more power than an Rsa (56hp) but with less range so they were still slower. If the engine was an Honda copy, how could they match Aprilia's power? wasn't the Honda engine around 50hp?
I'm a little dubious tbh but this is what i've heard...

and another little question, if you can speak publicly about it: when you tried the reduced exit area on Kz engines, how much did you gain? how much was the final port height, something like 28mm? i remember your welded cylinder pics here. the new tm R2 black has the aux ducts "ears" on the exhaust flange but this in fact increases the exit cross section, so i don't know if they're going after your theory

[aljaxon]

mickey mouse alert.
in my latest pipe design ive got zero over rev. 32 68 header diffuser. pipe pulls great below peak power. miles better than previous design. but ive overdone the lack of over rev. will a shorter belly longer rear cone help?

ive gone a bit mad 2 stage header 3 stage diffuser and 3 stage rear cone, each getting sharper. belly might be a bit long. 90mm in a 992mm pipe. and ive built in a restrictor end of rear cone with a short 10 degree diverging cone to my stinger.

with 32 68 am i fighting a losing battle trying to get back over rev unless i lengthen the rear cone belly which then reduces the peak rpm. or like i said earlier shorten belly and lengthen rear cone.

im prepared to pay for this lunch.

[aljaxon]

[wobbly]

Al , I sent a DM so you can pay for lunch , just for starters you have a THREE cone header and why do you want a diffuser after the rear cone - absolutely wrong.

Gradella , there is alot I cannot say about the R2 on here , but alot of work inside the duct was tested at the factory that I did not do.
Yes , the duct exit area is a bit too big , and the ears transition in the spigot is not elegant CNC programming at all - it could be done way better.
Here is my hand prototype.

And regarding Mr Bartol - yes he did copy and take credit for others work , but he also had access to a Czech flow analyzer that as I said other top class tuners regarded
as a seriously good tool.
Jan didnt like it , others did , so maybe Harold understood enough from its results to achieve serious power.
But then again , he simply copied an A Kit Honda exhaust , and even Witteveens attempt that Jan was forced to engineer around , was a far better pipe.

[jamathi]

Al , I sent a DM so you can pay for lunch , just for starters you have a THREE cone header and why do you want a diffuser after the rear cone - absolutely wrong.

Gradella , there is alot I cannot say about the R2 on here , but alot of work inside the duct was tested at the factory that I did not do.
Yes , the duct exit area is a bit too big , and the ears transition in the spigot is not elegant CNC programming at all - it could be done way better.
Here is my hand prototype.

And regarding Mr Bartol - yes he did copy and take credit for others work , but he also had access to a Czech flow analyzer that as I said other top class tuners regarded
as a seriously good tool.
Jan didnt like it , others did , so maybe Harold understood enough from its results to achieve serious power.
But then again , he simply copied an A Kit Honda exhaust , and even Witteveens attempt that Jan was forced to engineer around , was a far better pipe.

At Jamathi we made such a Jante flow machine ourselves.
After some time we concluded that it was useless!!!
Jante was an East-German who invented this system. We still used it at Bultaco