ESE's works engine tuner

[F5 Dave]

Forgive me. Indeed that fine steed deserves the best racing Amal (was wondering if spell check would improve on that) available.

[RAW]

Making the auxiliary ducts wider than 12mm made less power was my experience

The 12mm wide
Are you indicating that the maximum width of a sub exhaust duct in the RSA is 12mm at its widest point within the duct ?
I have an aprilia APE cylinder with sub exhaust ducts measuring almost 14mm in width & 13.4mm in the vertical axis at its largest point within the duct

[RAW]

Making the auxiliary ducts wider than 12mm made less power was my experience

The 12mm wide
Are you indicating that the maximum width of a sub exhaust duct in the RSA is 12mm at its widest point within the duct ?
I have an aprilia APE cylinder with sub exhaust ducts measuring almost 14mm in width & 13.4mm in the vertical axis at its largest point within the duct

[jamathi]

The 12mm wide
Are you indicating that the maximum width of a sub exhaust duct in the RSA is 12mm at its widest point within the duct ?
I have an aprilia APE cylinder with sub exhaust ducts measuring almost 14mm in width & 13.4mm in the vertical axis at its largest point within the duct

More than 12mm gave less power....

[JanBros]

back from the 10hour race in Laon, France. it was a

undetectable step for manking
giant leap for us


Attachment 343100

1st in our category in only our second attempt

Attachment 343116Attachment 343117Attachment 343118

it's all about teamwork, even in the pits :

Attachment 343120

and perhaps the most important picture of the WE :

Attachment 343119

my new suspension survived the race, the soft side worked flawless but it seemed as if the hard part didn't and we just bottomed out the soft part. But this picture says it all : the hard part was not way near hard enough .

Thx to everyone sharing their info on this great site, you're all a part of our victory


edit : first effort at hosting pictures on kiwi biker, but seems I'm doing something wrong ? why are they only links and no pictures visible ?

[sispeed]

These are cast RD400 pistons, one has lost its tongue. The RD and TZ Yamaha's have wide inlets.

Attachment 343059
Will you be Ok with forged pistons and the bridged inlet port? I don't know, sorry........

If this type of piston is used in a RD 400 there is no wonder that one lost its tongue. They are YPVS Water-cooled Style and there is a bridged Inlet. RD 400 don't have a bridge, so chances are good the tongue snaps at the lower port of the inlet.
If I use such pistons in Air-cooled Motors, without a bridge I remove the tongue before installing and using the pistons
Regards Siggi

[mantonakakis]

Still trying to understand why/how the needle/tube annular area sets the fueling at low RPM WOT, and main jet takes over once engine speed increases enough. I tried the trick of removing the main jet completely, with the biggest needle tip diameter available, and I just made a lot of smoke and stalled the engine. But with a main jet in place, changing the needle tip diameter and/or clip position does indeed seem to make a big impact at low RPM WOT.

Maybe in my case this is due to a relatively small main jet which ends up restricting the flow even at low RPM. I am using a 0.80mm main, 1.80mm needle tip, and 2.60mm atomizer tube. This gives a needle/atomizer tube annular area ~5.5x greater than main jet area at WOT (I would need ~1.87mm main to make them equal). With no main jet, I suppose this annular area is simply far too large for my 50cc engine?

In trying to get a better understanding of this, I went through the Dellorto manual again. For my PHBG, the bushing/nozzle/shroud has an air feed hole from the idle circuit air inlet. It seems this allows air to flow through the idle circuit inlet and around the OUTSIDE of the atomizer tube before entering the venturi. And I guess when air flow is low in the venturi and there is little vacuum (low speed WOT), the shroud should cause a pressure drop around the atomizer tube outlet that pulls air through the idle circuit inlet and fuel through the main jet and out the needle/tube annular area?

In the case of my 50cc engine, should I trim down the shroud as Wobbly mentioned here?

[wobbly]

The drilling from the very front of the bellmouth thru into the emulsion shroud well is referred to as the Main Air Corrector circuit.
In most carbs this is adjustable with a replaceable jet , but that Dellorto doesn't have this facility.
A bigger air corrector drilling reverses the tendency for the fuelling to become richer as air flow increases.
A similar effect is seen with the shroud height , as is detailed in the Dellorto manual - a lower shroud richens the mixture at lower rpm
and then leans off the fuel curve at higher rpm WOT.
Having an annulus area at WOT that is 5 times the main jet area indicates a real weird jet combination that can never be tuned
to have any effect on low rpm WOT jetting - exactly as you discovered.

[wobbly]

I to can confirm that there is an optimum duct size for the Aux ports.
There is a catch 22 involved,making them bigger may well increase Blowdown flow Cd but in doing so you are also
increasing the area change where the side duct intersects with the main Ex.
This then increases the duct volume - and as going smaller has been the route to big power increases , this isn't a good thing.
The only way to find out is to ruin a cylinder like I did , by gradually increasing the width until power drops.
The other variable is the bridge length - shorter is better.
Again I kept grinding them back toward the bore with a concave radius on the exit side.
I lost power ( and the bridge started to bulge inward against the piston ) when going smaller than ( again ) 12mm length.

[mantonakakis]

The drilling from the very front of the bellmouth thru into the emulsion shroud well is referred to as the Main Air Corrector circuit.
In most carbs this is adjustable with a replaceable jet , but that Dellorto doesn't have this facility.
A bigger air corrector drilling reverses the tendency for the fuelling to become richer as air flow increases.
A similar effect is seen with the shroud height , as is detailed in the Dellorto manual - a lower shroud richens the mixture at lower rpm
and then leans off the fuel curve at higher rpm WOT.
Having an annulus area at WOT that is 5 times the main jet area indicates a real weird jet combination that can never be tuned
to have any effect on low rpm WOT jetting - exactly as you discovered.

Thanks so much for the insight, Wobbly. I just checked the carb, and there are indeed two air passages at the mouth of it - one that feeds the idle and starter circuits, and one that solely feeds the shroud/bushing around the outside of the emulsion tube (the one on the lower right in the picture). The emulsion tube/atomizer is about 0.8mm smaller in outer diameter than the inner diameter of the shroud piece, and sure enough, spraying carb cleaner into that inlet resulted in a nice flow around the outside of the emulsion tube and into the throat of the carb, and then on into my eyes

In my case, I guess the best option is to try making a fatter needle tip diameter? Or fill and drill the emulsion tube and decrease the diameter of the top of the needle.

[husaberg]

there are pages of stuff here the carbs have overlapping fuel circuits so there are many ways to skin the cat or at least massacring its hairsyle where the only option is shaving its head.
In Cameron's Street bike book there is the best description of tuning from zero i have seen.
Bell has lots of detail in regards to old Mikuni stuff esp VM and Rbinsons is worth reading

[oktrg500]

.
Welcome Octrg500

These are some earlier posts I found using the Google "site:" search option.

Thanks very much, TZ350. As always, you're very helpful. I appreciate it very much. The reason why I'd like to learn as much as possible about reading the smoke ring is this will also benefit my other projects: A 70cc aircooled engine. which started it's life as a 50cc Minarelli engine. A couple of Aprilia RS125 streetbikes, which are my rolling laboratories. And the RG500 streetbike, which is not so streetable anymore due to getting good help from a Swedish company tuning the engine

[TZ350]

Tim out peddling a Team ESE NSR110 around, number 77.



What we are trying to do now is make sense of the tire wear.

Any comments based on https://lifeatlean.com/motorcycle-tyre-wear-guide/ would be welcome.

[TZ350]

.
A bit more on air correction jets.

Just a small point TeeZee, the elongated oval formed around the main air corrector feed hole you will need to fit a thin wall sleeve in there, pointing directly out the bellmouth to a point where its not
affected by the venturi .
The idle air is going to be affcted as well but not as drastically.
If you dont, the air corrector orifice will be subject to increasing negative pressure as the velocity increases - exactly the opposite to what is needed to lean out the fuel curve
that naturally gets richer in any carb like this.

Attachment 258280Attachment 258281Attachment 258282

OK, used a bit of 1/4" SS tube and linished it down to 6mm, spinning the job with a battery drill makes for a fairly round finish, cleared the end with a center drill, tapped a 13mm length into the carb, Job done. The hole next to it is plugged and I may smooth it off with glue sometime.

But now I guess I have to go back and check it on the dyno again.

I may be able to use a bigger mainjet now more air will be going through the air correction jet.

Bigger main jet should mean richer down low to mid for smoother drive at the lower end of the torqe curve and then drill the air correction jet out untill the top makes best power.

Attachment 258284

On other sessions while testing different carbs the area between 8 and 9 K on the graph, the curve was much smother and sounded better on the dyno when it was richer there.

Attachment 258285

The blue line was the IE carb I tried a while back, the jetting on one of the runs didn't make much power but it drove well in the 8-9K area.

I wonder if with a bit of playing with a bigger main jet and carefully drilling out the air correction jet I can get the red line to drive as smoothly.

[peewee]

I've had good results with steel washers as well. I machine them from some big socket head capscrews I have on hand, not super hard but very tough, grade 12.9 on the metric scale or around 170,000 psi in old speak. Once they're parted off I polish the sides on some fine wet and dry on a surface plate.

hey mate im going to try some 4130 alloy in .63mm thick. which will give me about .6mm axial play of the bearing and it should be fine i think. since the bearing cage is far wider that the rod width, the washers wont reduce any lube to the bearing so i dont think ill drill any lube holes in the rod like i first thought. and its a short run engine on methanol so i wont have to worry about extreme heat