ESE's works engine tuner

[wobbly]

The BSL had late model TZ250 reed blocks, that were not symmetrical pyramids - but angled upward under the cylinder.
From memory they had nearly 40% more port area than the CR/RS125.
I tried VeeForce as they were keen to sponsor us, but the petals fretted in no time.

[husaberg]

The BSL had late model TZ250 reed blocks, that were not symmetrical pyramids - but angled upward under the cylinder.
From memory they had nearly 40% more port area than the CR/RS125.
I tried VeeForce as they were keen to sponsor us, but the petals fretted in no time.

Cheers by symmetrical I was meaning the reed cavity were all the same shape and position and layout. only reversed for the lower cylinder of course.
pics to follow.
bugger I cant find the decent pic of the engine in the frame I seen the other day.
V angle 110-120?
BSL500

NSr500
YZR500
Added the Roberts three just cause I could, looking at it. it looks like it has the reds spun 90 degrees like a NSR250
this version below of the Roberts three has the pump around carbs and pretty low tech fabricated rubbers plus either they swapped the two up one down or this ones carbs are upside down
my moneys on it being upside down
https://www.kiwibiker.co.nz/forums/a...7&d=1463388722

[Muhr]

Haufen, no TM dont have a CFD setup, they should as they use NX as a CAD platform.I have their full solid model of the C cylinder so I could use it in the SolidWorks
CFD package, but hell I find it hard to keep up with work as it is , without trying to learn a new platform as well.
But for sure I will try a blanking gasket and see the changes in the dyno data , and go from there.

I would have loved to put my hands on that file and see what one can find out

[lohring]

Below is an article I edited to help explain two stroke scavenging. It includes a series of CFD pictures of Aprilia 125 cylinder scavenging flow.

Lohring Miller

[guyhockley]

Added the Roberts three just cause I could, looking at it. it looks like it has the reds spun 90 degrees like a NSR250
this version below of the Roberts three has the pump around carbs and pretty low tech fabricated rubbers plus either they swapped the two up one down or this ones carbs are upside down
my moneys on it being upside down
https://www.kiwibiker.co.nz/forums/a...7&d=1463388722

In the Mike Sinclair book he talks about the early KR triples being a flying web v-twin with the third pot added on, then he left when they redesigned it as a Honda style v3. Can't remember if they changed the 2 up or 2 down configuration but I think, maybe, the picture you linked to is the "mark 1" and the picture you posted is a "mark 2"?

[wobbly]

The BSL reeds were 68mm wide ( this is the size that VeeForce make for most 250cc cylinders ).
But as it turned out the TZ250 reeds were just right.
The engine was designed around having these reeds across in line , and the cylinder centers were based on keeping symmetry.
As it turned out I should have made the whole thing 15mm wider , and not used an integral crank pin , as this proved impossible to build reliably without forging or NASA steels.
The reason being that for the best compromise between rotating mass , and balance force reduction , the firing order was No1 LH at 0* then the middle down and
RH upper together 120* later ( 120 Vee angle ).
This produced a torque harmonic across the driving crank pins , and even with big rads and bead peining , they cracked.
Using all press fits fixed it immediately.
With a balance shaft driven of a gear between the common firing pair ( also went out to the clutch ) there was no resultant primary imbalance , only a constant radial force on the mains.
It had no vibes at all, and as the always forthright King Kenny said to his team whilst hanging onto a footrest - you cunts aint got no clue , these guys can do balancing , you dont.

[husaberg]

In the Mike Sinclair book he talks about the early KR triples being a flying web v-twin with the third pot added on, then he left when they redesigned it as a Honda style v3. Can't remember if they changed the 2 up or 2 down configuration but I think, maybe, the picture you linked to is the "mark 1" and the picture you posted is a "mark 2"?

I typed a reply but it wouldn't save
Lozza posted something about the two models or both were designed by a Japanese one was okay the other wasn't
i came across these pics from Kenny ranch either they are mock up or he had some plastic cases i guess its a mock up engine.
they look to be CNCed rather than cast resin

The BSL reeds were 68mm wide ( this is the size that VeeForce make for most 250cc cylinders ).
But as it turned out the TZ250 reeds were just right.
The engine was designed around having these reeds across in line , and the cylinder centers were based on keeping symmetry.
As it turned out I should have made the whole thing 15mm wider , and not used an integral crank pin , as this proved impossible to build reliably without forging or NASA steels.
The reason being that for the best compromise between rotating mass , and balance force reduction , the firing order was No1 LH at 0* then the middle down and
RH upper together 120* later ( 120 Vee angle ).
This produced a torque harmonic across the driving crank pins , and even with big rads and bead peining , they cracked.
Using all press fits fixed it immediately.
With a balance shaft driven of a gear between the common firing pair ( also went out to the clutch ) there was no resultant primary imbalance , only a constant radial force on the mains.
It had no vibes at all, and as the always forthright King Kenny said to his team whilst hanging onto a footrest - you cunts aint got no clue , these guys can do balancing , you dont.

Cheers Wob

[wobbly]

The first engine was designed by the Honda engineer that did the Freddie tripple.
It was a disaster , too long ( gearbox shafts on the horizontal split line ) and Bud Askland had to grind huge amounts out of the case ( right down to the main bearings )
to get close to the correct volume.
It vibrated like hell , I simply could not hold the throttle with a bare hand it hurt so much.
The later engines were done at the Roberts facility in England using much better technology.

[lohring]

I like this version of the piston port with boost port better.

Lohring Miller

[ken seeber]

Lohring,
The one thing to be considered here is that if the piston skirt length is set to suit the inlet timing, then this skirt length would be wrapped around to the side of the piston, into the area normally left open as the cutaway to feed the transfers. From what I can seem the B port and some of the A would have the piston skirt interfering with the crankcase to transfer passage entry flow. Of course, this might be dependent on the overall engine design though in terms of the designed piston length.

[husaberg]

The first engine was designed by the Honda engineer that did the Freddie tripple.
It was a disaster , too long ( gearbox shafts on the horizontal split line ) and Bud Askland had to grind huge amounts out of the case ( right down to the main bearings )
to get close to the correct volume.
It vibrated like hell , I simply could not hold the throttle with a bare hand it hurt so much.
The later engines were done at the Roberts facility in England using much better technology.

I found Lozzas post which covers the second version.
I must admit i am struggling to get my head arround your description of the BSL crank layout but i might have to draw it.
Honda had formula they used on the narrow angle offset crankpin twins like the bros Hawk and VT500.
If i recall corectly it went along the lines of 1/2 the v angle -90 dregrees equals the crank pin offset to make it think its a 90 degree v twin.
I am not sue but i think for over 90 degrees it might work out to be 180 - the v angle?
I could never figure out how Two bros used to get those cranks which are effectively flying web, to last a big revs, well it turns out they couldn't no mater what they tried they just threw a new one in every race. Pretty sure Hondadid the same with the RS750 that used to run flat track.


Okay maybe not here is the formula they used in the sales ads

he XRV 650 engine is a V twin-cylinder, with the pistons at the angle of 52o (see the picture bellow). According to the formula “V= 180-(2 x 52) = 76”, invented and applied by Honda, the corresponded angle between the piston-rods is of 76o. That means a crankpins offset of 76o, resulting in a better mechanical balance and subsequently reducing vibration and other stresses. Thus compensates the mechanical design compared to a V-twin engine with an angle of 90°, which inherently gives a very good mechanical balance. Due to specific crankpins offset, applied on the engine of Africa Twin, no balance shaft is required. The elastic collars of the engine mounting are adequate for the amortization of the inherent to motor’s design

Roberts fell flat on his arse when he had a go of making his own engine. Wasn't until he hired (ironicaly) Oguma-san and ex Yamaha GP engineer Yoda-san(I forgot his firstname) they redesigned the engine to be shorter, narrower and increased the V angle and incorporated a balance shaft did that Modenas start to go like a GP bike. The shorter and narrower engine allowed a longer swing arm which gave better traction made it handle like a GP bike. That all came to naught when the 4T rules were announced a short while later . In which the cycle began again, best results were with the HRC V5 and some pointers on frame flex.
HRC always seem to perform best when there is a stern hand on the rudder, though with a smart cookie like Nakamoto they should be winning for some time to come.

.

[lohring]

Lohring,
The one thing to be considered here is that if the piston skirt length is set to suit the inlet timing, then this skirt length would be wrapped around to the side of the piston, into the area normally left open as the cutaway to feed the transfers. From what I can seem the B port and some of the A would have the piston skirt interfering with the crankcase to transfer passage entry flow. Of course, this might be dependent on the overall engine design though in terms of the designed piston length.

You're right, but I haven't got that far along into my layout. We do cut away the piston skirt around the wrist pin area with the normal 4 transfer design, but the inlet port is much smaller. The power level I'm looking for, over 10 hp at 18,000 rpm or so, needs a big inlet port. It probably means I'll need a custom piston and a rethinking of the transfer entries in the crankcase. I'm also wondering what is a good way to model the profiled intake port in EngMod. At present I'm using two trapezoid shaped ports with the same area and similar top and bottom lengths. However, this gives a smooth transition from beginning to full opening.

Lohring Miller

[wobbly]

Husa , put simply the LH cylinder fires first, then the other two fire together 120 later.

[wobbly]

Tried a trick on the 30mm Dellorto carb off the KZ2 engine.
We used to do this on Rotax kart engines before it was banned and a measuring tech tool introduced.
Lowering the height of the emulsion tube shroud , works great in classes where the jetting is limited or fixed.

This is supposed to reduce the low pressure vortex created behind the shroud , thus leaning out the mixture as air flow increases.
The dyno showed it did exactly that , but in this case when the jetting is changed to replicate the egt at peak Hp there is no advantage to be had.
Bugger.

[flyincat]

Hi all, first post here! Greetings from the far side of the pond. Number one, amazing thread and unreal info sharing. Thank you!!

These parts of the world are snowmobile country, so I hope you can forgive me for bringing non-bike material. I've been interested in resurrecting some 70's, 80's, and 90's vintage twin cylinder 2T snowmobile engines, which somehow lead me to the endless 2T info here.

Lohring - having searched and searched for piston port info, I was excited to see you post something recently about a piston port project. Here are some pictures you might find interesting, or not. This is from a Arctic Cat (Suzuki) 500cc twin, case reed, single exhaust port, non power valve motor, ~85-90hp @ ~7800-8000rpm. Not much for performance, but I've seen references that it is intentionally limited in design, and power, to race in a 85hp class. Anyway, the lack of boost port, aside from being case reed, looked quite similar to one concept you proposed. Maybe the port layout is helpful? Just an FYI, but performance shops are porting these engines, along with supporting tuning adjustments, and making 105+hp @8200-8500rpm. I wish I could see a picture of a ported cylinder. There may be a hint in the rear of the cylinder, where it is boxed off. This is the same as the big brother motors (600cc & 800cc), except this boxed in area on the bigger engines houses a boost port along with coolant passages to the crankcase. In this 500 cylinder, there are two coolant passages and a lot of space between them, and space between B ports. Perfect place for a boost port?