ESE's works engine tuner

[SS90]

As does my yamaha, RGV and KTMs (to a point, depended on design), I would think that it is mostly to do with the power values and making some attempt to reduce thermal expansion on the barrel casings and the potential for binding the power values up...?

2 cents worth

They primarily cool the bridge to stop it expanding (particularly when warming the engine up from cold), If the bridge heats up too fast, it expands into the cylinder, and can actually seize an engine (termed a "cold seize") as the heat cannot travel from a thin piece of aluminium (or in the case of a RG150, steel liner, which is actually more prone to cold seizures than an all aluminium cylinder) to the rest of the cylinder fast enough, and it simply expands.

There are other methods of achieving a similar result, the most common is to drill two 2mm holes on the exhaust side of the piston skirt that line up with the bridge.... the air/oil/fuel mix under the piston will travel through these small holes, and assist in keeping the bridge cooler, you can also relieve the bridge back slightly (particularly if it is a cast iron liner), as, afterall, the bridge is only there to stop the ring protruding into the exhaust port (if the exhaust port width is wider than 72% of the bore that is), and it is quite acceptable for it to be a few thou away from the piston skirt to allow for expansion....the practice of thinning the bride out to increase port area is normally the biggest cause of this type of problem.

In a water cooled performance two stroke, cooling the bridge is not a silly idea. Particularly if you widen the exhaust port alot,(or even if th efactory has them quite wide) which increases localised heating of the exhaust side of the piston crown (as well as the bridge).

[Bert]

That makes sence, hadn't though of that at time of typing...

anyway though that some might find these pages useful, when it comes to sizes/product numbers of conrods and bearings etc.

http://www.kevinbreedonracing.co.uk/...ts_conrods.asp

[F5 Dave]

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. . .
Carburation is a single 38/24mm venture carb made from an RS125 carb feeding into a split manifold.

Eh? so you are running a 38mm carb that sleeves down to 24 & then feeds both cylinders?


& Mike, Pete's twin was a T90 so could run 2 carbs of any size (before 125 rule anyway). Steel cylinders limited development as did 5 speed gbox. Pretty sure he still had it last time I was past his shop (but that was a few years back now & he was clearing out stuff).

[TZ350]

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I think Chambers is going with a conventional 24 first, then when the bugs in the rest of the new bike are ironed out he might try the 38/24.

But yes, 38/24 feeding both cylinders. We have been successful with a 28/24 combo on the GP125 and now have a 38/24 that shows real promise on the flow rig.

One of the problems I can see, is low signal strength at the main jet. Our 28/24 run conventualy uses a 130 main. Keihin 38’s on 125 MX’s run 180-190 mains std.

So I expect that on a 38/24, the main will need to be even bigger. Because of the reduced signal from lower airflow passing through the 38mm metering section at full throttle due to the more restrictive 24mm venturi section of the carb down stream.

My guess is 200+ for the main on our 125's using a 38/24 venturi carb...................

Also we figure, if you can't drop a 24mm ball brg through a carb with a circular throat then the cross sectional throat area is equivalent to or less than a carb of 24mm and so satisfies the 125 2-Stroke carb rule.

The beauty of the 38/24 combo seems to be that the airflow in the 38 section gets straightened up before entering the 24mm venturi allowing a higher flow rate in the venturi area.

The details and pictures are in earlier posts. From memory, if the venturi is 60-70% of the pipe (carb) diameter then there is a 94-98% pressure recovery (air flow) down stream for Reynolds (gas velocity) numbers less than 0.5.

So you can see that its possible to make a 38/24mm combo carb that flows like a conventional 34mm. But wether it works on the track we wont know untill we get one of the new bikes going.

Remember you heard about this idea of 38/24 and 28/24 carbs from Team ESE first..............

[TZ350]

Its 4-Stroke but useful for getting an idea of how things behave in an inlet tract..

“Relationship of Intake Port to Torque Peak

For a given intake port design, the cross-sectional area of the runner affects the location of an engine's torque peak in the RPM band. The runner length and shape is also very important, but the cross-sectional area will be the strongest determining factor.

Also, keep in mind that peak torque and peak horsepower do not occur at the same rpm and that when you shift it is always better to fall back to a region of maximum torque instead of trying to "climb the mountain" to get back to your next redline shift point.

We cannot emphasise enough that you must view the engine as a complete system and not concentrate on only one aspect of it.”

From:- http://www.rbracing-rsr.com/runnertorquecalc.html

You need to know this to be able to use the calculator,

One Sqr In = 6.45 Sqr Cm and one Cub In = 16.39 CC.

Runner length calculator:- http://www.bgsoflex.com/cgi-bin/intakeln.cgi?length=7

Runner length/area comparitor:- http://www.speedwaybids.com/calcs/in...nerlength.html

Metric:- http://www.exx.se/techinfo/runners/runners.html

Plenums:- http://www.team-integra.net/sections...?ArticleID=471

Halve the calculated rpm or inlet runner length to relate it to a 2-Stroke, and double the 2-Strokes rpm when entering data.

The inlet runner length is measured from the port window to the top of the carb's bellmouth.

They are not the Bible, or tell you everything, but these can give you a feel for what sort of changes affect things and by how much.

[TZ350]

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Chambers has been able to successfully convert his spoked wheels to tubeless like these Talon ones are.

Using silicon glue for the spokes and wide tape for the center section of the rim. Tapes tried were fiber reinforced packing tape, rubber electrical tape, and wide rim tapes.

The problem area was the welded part where the rim is joined, this area needed to be carefully cleaned up on the inside to get an air tight seal with the tyre.

On some rims the welded area can be ground down to far by the factory leaving a flat spot, this could be built up with devcon and shaped to match the rest of the rim.

[koba]

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Chambers has been able to successfully convert his spoked wheels to tubeless like these Talon ones are.

Using silicon glue for the spokes and wide tape for the center section of the rim. Tapes tried were fiber reinforced packing tape, rubber electrical tape, and wide rim tapes.

The problem area was the welded part where the rim is joined, this area needed to be carefully cleaned up on the inside to get an air tight seal with the tyre.

On some rims the welded area can be ground down to far by the factory leaving a flat spot, this could be built up with devcon and shaped to match the rest of the rim.

Why?

[TZ350]

Why?

So he can run GP125 slicks tubeless.

All the slicks we have seen are ribbed inside and although talkum powder helps, these ribs eventually wear through a tube puncturing it.

We have suffered more DNF's through flat tyres than anything else.

[Henk]

At a guess, because spoked wheels have a habit of wearing holes in the tubes, especially over long races.

[bucketracer]

Its 4-Stroke but useful for getting an idea of how things behave in an inlet tract......

Some video clips of reversion for those who are interested in such things………..sick bastards…

http://video.google.com/videoplay?do...73019926133763

http://video.google.com/videoplay?do...&q=V10+Engine#

Pic-01 particles in the reversion cone
Pic-02 Air flow Velocity

[Brian d marge]

Pic-01 particles in the reversion cone
Pic-02 Air flow Velocity

I have been using that program , and have that pdf that those JPEGs come from
I can model a basic room and get the air flow in that room but those inlets ,,,I am trying ,,
there are three things I would like to do
1. solid shaped in differing airflows
2, Oil through orifices
3. Air flow at differing velocities in Differing containers ( read air-boxes and inlets)

The program is OpenFoam

if you know anyone using I would love to open a dialogue !

Stephen

ps those Engines sounded fantastic !!

[jasonu]

Sounds like a lot of effort to run dodgey wheels. Sooner or later they will fail. (sooner is my guess)

[F5 Dave]

Woe & betide if you need to replace any spokes. That said my Trials bike has been running like this for a decade & it avoids any silly oddball spokes in a lip rim like on my Beta.

The other advantage is the 400g a tube weighs (front from memory) at the largest circumference of the wheel.

However I would still be careful to inspect the rim shape at the lip interface. if the tyre was to creep, slip or deform that would be uncool if deflation occurred. We often run quite low pressures.

[Buckets4Me]

Woe & betide if you need to replace any spokes. That said my Trials bike has been running like this for a decade & it avoids any silly oddball spokes in a lip rim like on my Beta.

The other advantage is the 400g a tube weighs (front from memory) at the largest circumference of the wheel.

However I would still be careful to inspect the rim shape at the lip interface. if the tyre was to creep, slip or deform that would be uncool if deflation occurred. We often run quite low pressures.

agin all very well and good

but these guys have all gone bald pulling there hair out time and time again with flat tires because of the tubes

and they like to fix things there way ( they use to replace the tubes every year)

[Kickaha]

but these guys have all gone bald pulling there hair out time and time again with flat tires because of the tubes

I've run tubes in 125 slicks on two different bikes which did 4 seasons between them with not a single puncture