ESE's works engine tuner

[husaberg]

The rest of the OW69

[husaberg]

Last two
( the text is cut off on the edge as thats How the Cycle World have scanned their mags)

If you look at the OW60 i posted a month or two ago they are really just bigger 500 GP bikes
I always thought the overbored bikes they ran in those years were only about 580cc
but 64mmx54mm is about 700cc

[Grumph]

Cheers for that.
I remember there was a TZ that raced here in the 80's that had CR125 cylinders Grump will remember it I think it was Brent Jones?
Ifi t was Brent Jones that would be pretty Ironic as he used to Races a RG500 cylindered (race Bike RG Cylinder not road) on a Kawasaki 125 bottom end (Early KX i think) I think it was made at MClearly's
The forrunner to a lot of bucket racers.

Don't remember a TZ like that - doesn't mean it wasn't done though.
I remember looking at the Brent Jones 125 one friday night in Jacks Yamaha. His dad Craig told me they'd found it in Asia somewhere on one of his race trips, liked it and bought it. Don't remember what the bottom end was. It's vanished now. Probably thrown in a deal with one of the race bikes they've sold overseas.
Craig had a habit of buying bikes on the trips to Malaysia, Singapore and Indonesia. H1R, various early TD/TR Yamahas...All sold now.

[katinas]

Last two
( the text is cut off on the edge as thats How the Cycle World have scanned their mags)

If you look at the OW60 i posted a month or two ago they are really just bigger 500 GP bikes
I always thought the overbored bikes they ran in those years were only about 580cc
but 64mmx54mm is about 700cc

Remember one magic motorcycle magazine, from my old shool days, that cousins father gave him when return from USA. One article was about F 750 with all three - Yamaha four, Suzuki and Kawasaki triples. When I be on a visit at his home, I'am do nothing, just siting with this article all day, and this repeated every time when I visited him. Remember, can't understand why Yamaha stopped at 700cc. Nice motorcycle and swingarm.

Interesting how things was going, if Yamaha translated OW60 code for square 60x60mm bore/stroke configuration on OW69.

Add reference from Racers about Yamaha 250 rotary tandem

[husaberg]

Don't remember a TZ like that - doesn't mean it wasn't done though.
I remember looking at the Brent Jones 125 one friday night in Jacks Yamaha. His dad Craig told me they'd found it in Asia somewhere on one of his race trips, liked it and bought it. Don't remember what the bottom end was. It's vanished now. Probably thrown in a deal with one of the race bikes they've sold overseas.
Craig had a habit of buying bikes on the trips to Malaysia, Singapore and Indonesia. H1R, various early TD/TR Yamahas...All sold now.

I looked back through the results i had posted ages ago checked and my hunch was right it was Brent Jones and it was raced at the 84 NZGP and won the 350 GP (that was the year they raced the Street circuit at Syndenham)
the results show it as a TZ250 bitza but else where in the mag it was mentioned as having CR125 cylinders. so it was either short stroked or maybe a bit bigger than 250.
As the CR's didn't have 54mm strokes until the next year.
Any Idea who would know anything about it? Who would be alive out of Jacks Jungle? Is Brent arround?
Aaron slight who i guess would have been lucky to be 18 finished second on a RZ350 and set the fastest lap of the day all classes.
Considering the field that day also included Robert Holden and Rodger Freeth isn't bad.

Remember one magic motorcycle magazine, from my old shool days, that cousins father gave him when return from USA. One article was about F 750 with all three - Yamaha four, Suzuki and Kawasaki triples. When I be on a visit at his home, I'am do nothing, just siting with this article all day, and this repeated every time when I visited him. Remember, can't understand why Yamaha stopped at 700cc. Nice motorcycle and swingarm.

Interesting how things was going, if Yamaha translated OW60 code for square 60x60mm bore/stroke configuration on OW69.

Add reference from Racers about Yamaha 250 rotary tandem

I think i have posted that on another thread. it was i think Cycle and done by Kevin Cameron
Either that or it might still be on my hard drive. I will have look when i get back home.
I thought Yamaha went contra rotating cranks on the other bikes a bit later on than that on the Reed valve bikes at least anyway.

[shnaggs]

Quick question for the knowing.

Take a look at these STA values, its for a newer KTM125. It appears that the exhaust port is on the small side in comparison to the transfers, but the blow down seems good. So does that mean since the blow down is good for 40hp that the engine should make 40hp, or is the Exh port still the limiting factor? As of now on my dyno the bike only makes 36.5hp

Thanks,

[tdc211]

Quick question for the knowing.

Take a look at these STA values, its for a newer KTM125. It appears that the exhaust port is on the small side in comparison to the transfers, but the blow down seems good. So does that mean since the blow down is good for 40hp that the engine should make 40hp, or is the Exh port still the limiting factor? As of now on my dyno the bike only makes 36.5hp

Thanks,

On mine it makes 38 with a known good reed block. Rejetted on pump.
My sta values look a liitke different than yours on a stock cylinder

[shnaggs]

On mine it makes 38 with a known good reed block. Rejetted on pump.
My sta values look a liitke different than yours on a stock cylinder

Thanks for the reply.

Would you mind sharing your STA values?

[jonny quest]

Quick question for the knowing.

Take a look at these STA values, its for a newer KTM125. It appears that the exhaust port is on the small side in comparison to the transfers, but the blow down seems good. So does that mean since the blow down is good for 40hp that the engine should make 40hp, or is the Exh port still the limiting factor? As of now on my dyno the bike only makes 36.5hp

Thanks,

28.3mm ex 43.5mm trans heights 16 SX125. Why are your heights so different?

[Grumph]

I looked back through the results i had posted ages ago checked and my hunch was right it was Brent Jones and it was raced at the 84 NZGP and won the 350 GP (that was the year they raced the Street circuit at Syndenham)
the results show it as a TZ250 bitza but else where in the mag it was mentioned as having CR125 cylinders. so it was either short stroked or maybe a bit bigger than 250.
As the CR's didn't have 54mm strokes until the next year.
Any Idea who would know anything about it? Who would be alive out of Jacks Jungle? Is Brent arround?
Aaron slight who i guess would have been lucky to be 18 finished second on a RZ350 and set the fastest lap of the day all classes.
Considering the field that day also included Robert Holden and Rodger Freeth isn't bad.

Jungle and Brent are both still around. Doubt you'd get much help from either...Brent manages what used to be Canterbury Glass and hasn't been seen near a bike for years. Successful businessman now. Jungle is still Jungle - but worse if anything.
Not surprised at Aaron's speed at Sydenham. Tight bumpy street circuit - a stock RZ well ridden would be better than a TZ around that. I've mentioned Kirby's F1 ride before - gear linkage fell off on the first corner and he finished 4th in the F1 GP using only 2nd gear on an 1100 Suzuki....

[shnaggs]

28.3mm ex 43.5mm trans heights 16 SX125. Why are your heights so different?

Good question! From the factory my 16 SX125 came with the .6mm base gasket. The piston protrudes above the deck by .006" or .16mm. I also used Frits' way of measuring the ports utilizing welding rod at an angle and subtracting the OD of the rod at the given angle.

[jbiplane]

Muscle muffler for 2-stroke boxers

We finally tested it and got 1,5 power increase compare straight pipe exhaust.
Seems 2-stroke motocycle boxers is rare if ever exist. But...


Modeling in Engmod2t

[wobbly]

The STA values in EngMod are at the crank , and are directly variable by the Combustion Efficiency value entered.
But in any case there will always be a drop in displayed Hp depending on where it is measured.
At the rear wheel on a Dynojet , with the tyre and chain friction involved, as well as the primary drive /cluster , as well as Dynojets well known fudge factor
the reduction is 12.5 to 15% - I have seen this hundreds of times between the calculated power in Engmod and the RWHp figure.
On an inertia dyno with a chain on the countershaft sprocket , as is mostly used on karts , its around 7 -10%.

Re the STA figures for the KTM150 , the value for the Ex port itself is near on irrelevant.
In fact if its small , as in this case , that is exactly what we have been shooting for in the last 10 years - getting the duct volume down , smaller and smaller , by lifting the floor
above BDC and filling in the corner rads below the TPO.
Having the Blowdown and the Transfer STA matching is what is needed where the effective efficiency are both similar.
But this is affected by the scavenging model used to correct the efficiency of say crap transfer ducts , and in this case the transfer STA needs to be lifted above the EX blowdown due
to the real Cd of the ports.

But I just noticed that the STA numbers are generated at 11750 - so this must be used with a kart or road race type pipe , as no way would it be of any use on a MX track , peaking that high.
Then if being used in a kart or road race end use , the power is way low for that rpm , as we get 45 Engmod Hp @ 11750 from a stock 2002 CR125 with just a pipe change.
And that translates to close to 40 Hp at the sprocket.

[F5 Dave]

Mmmm. Fudge Factor.

[dutchpower]

The STA values in EngMod are at the crank , and are directly variable by the Combustion Efficiency value entered.
But in any case there will always be a drop in displayed Hp depending on where it is measured.
At the rear wheel on a Dynojet , with the tyre and chain friction involved, as well as the primary drive /cluster , as well as Dynojets well known fudge factor
the reduction is 12.5 to 15% - I have seen this hundreds of times between the calculated power in Engmod and the RWHp figure.
On an inertia dyno with a chain on the countershaft sprocket , as is mostly used on karts , its around 7 -10%.

Re the STA figures for the KTM150 , the value for the Ex port itself is near on irrelevant.
In fact if its small , as in this case , that is exactly what we have been shooting for in the last 10 years - getting the duct volume down , smaller and smaller , by lifting the floor
above BDC and filling in the corner rads below the TPO.
Having the Blowdown and the Transfer STA matching is what is needed where the effective efficiency are both similar.
But this is affected by the scavenging model used to correct the efficiency of say crap transfer ducts , and in this case the transfer STA needs to be lifted above the EX blowdown due
to the real Cd of the ports.

But I just noticed that the STA numbers are generated at 11750 - so this must be used with a kart or road race type pipe , as no way would it be of any use on a MX track , peaking that high.
Then if being used in a kart or road race end use , the power is way low for that rpm , as we get 45 Engmod Hp @ 11750 from a stock 2002 CR125 with just a pipe change.
And that translates to close to 40 Hp at the sprocket.

Think that's oke wobb