ESE's works engine tuner

[peewee]

wax ive put numerous cylinders in engmod and in every instance the intake and reeds seem to be undersized. i would dare guess your intake and reed block wont be to big

[bjorn.clauw.1]

Yep, the whole deal with cylinder reeds to is get as much unobstructed flow area directly into the case as you can.
Thus floor ports and Boyesens should be as big as possible.
Then the piston skirt should be as short as possible, and any holes as low and as wide as you can get them on the skirt.
One idea that works well is to turn normal Boyesens into partial floor ports by hogging them out downwards, and then cut away the rear vertical wall of the B transfer
entry in the case at an angle.
Going higher with the Boyesens upsets the flow regime in the B duct too much, and the flow ends up running across and crashing into the transfer divider wall.

Hi Wobbly, so above pictures would be the way to go for those of us with cilinder reeds. Maybe putting an extra ramp on the top of the boyesen ports to angle the flow even more downward into the case (guiding it as much away as possible from the b port entry).

[husaberg]

The downside is loosing velocity thru the reed ports.
As an example if you take a CPI Cheetah 400 cylinder for a Banshee and use the VF3-CR250 reedblock that its made for
then fit the smaller VF3 - CR125 block with a spacer ( as the reed block is 6mm narrower ),the power increase is 6 RWHp in the mid
and 2 RWHp at peak.
What tends to happen with the smaller reed is that as you push toward its flow limit by making more power, the petals will stay open longer, due to the increased velocity and column inertia.
In most cases a VeeForce in the hole will be able to flow more than is needed, and keeps the velocity up by utilizing low tip lift thru the large port area available.

Wob I can never find the pic.
But the NSR500 with its reeds, only seemed to breath through a small area of them with the intake boot only utilising and being directed 2/3 petals area.
best pics I can find at the moment but I have seen the same I am pretty sure with the YZR500 or RGV500 as well.

[philou]

Hello

I am looking for advice on scavenge for a cylinder 3 transfers port

[Frits Overmars]

I am looking for advice on scavenge for a cylinder 3 transfers port.

I wonder why, Philou. Is it a matter of regulations? Anyway, here is a crude suggestion.

[Frits Overmars]

Hi Wobbly, so above pictures would be the way to go for those of us with cilinder reeds. Maybe putting an extra ramp on the top of the boyesen ports to angle the flow even more downward into the case (guiding it as much away as possible from the b port entry).

You don't want to guide the inlet flow away from the B-ports, Bjorn. You want it to go into the B-ports; you just do not want it to go only into the B-ports; the A-ports should get their share of the flow as well. I think those Boyesen ports look pretty good as they are right now; I would not add any ramps.

[jfn2]

Here are some new boyesen ports. Please comment and any suggestions will be greatly appreciated. Thank you jfn2
http://www.kiwibiker.co.nz/forums/al...p?albumid=5034
I know that the tabs hanging down into the reed area need to be trimmed. One pic shows a before view. These go into the B-ports first.

[husaberg]

Come on TZ I know you want one of these
http://www.trademe.co.nz/motors/moto...1117556154.htm

[TZ350]

Come on TZ I know you want one of these http://www.trademe.co.nz/motors/moto...1117556154.htm

Probably work better than what I have now.

[philou]

I wonder why, Philou. Is it a matter of regulations? Anyway, here is a crude suggestion.

Thanks for your reply.

The cylinder from a French moped, Peugeot 103

not expensive category requires only removing material for the engine.

Expansion Pipe and carburetor 15 mm authorized

for the corners of A-port I thought he had a hook on the rear side is Good idea ?

[Frits Overmars]

for the corners of A-port I thought he had a hook on the rear side is Good idea ?

Only if the leading flanks of the A-ports point sharply rearward like the red lines in my drawing.

[1948rod]

hi frits would the mods on a 3 port engine work on a reed or rotary kart 100cc engine. if not would a much wider a port work better with a divider for direction. thanks frits.

[Frits Overmars]

You're not exactly overwhelming me with information, Rod. I would need a little more than the number of ports and the cylinder capacity.
But in general all available real estate in the cylinder circumference should be used for ports. So if there is room to widen the ports, use it.

[wobbly]

3 port engines as used in direct drive karts are very sensitive to even tiny changes to the scavenging regime.
Mess up this and all the bottom end needed will disappear.
They usually have plenty of transfer area with just the 3 ports as drawn, due to the restricted Blowdown capability.
And again, if you go cranking in a heap of transfer STA, and get it mismatched with the Blowdown, you will immediately loose stream velocity
and thus directional control at low rpm.
How many zillion dyno tests do you think the top engine guys have done to get the things to where they are now, and it appears that 3 port
transfers are plenty for a wide power band starting at 8000 and going past 22,000.

[peewee]

guys I had some scrap bits sitting around that I been trying different boyesen ideas. their pointed down but with this style of cylinder I see no other way to do it without grinding them higher which lifts the rear wall of B. which effectively shortens the B tunell as well I suspect ? maybe I could make a small radius on the roof corner of the rear B wall/ boyesen without lifting the wall to high but small radius may not be as effective as bjorns cylinder