ESE's works engine tuner

[peewee]

Great work Peewee on your pistons. When I raced RD's we cut the bottom part of that central rib away. It inevitably broke off in the inlet port otherwise.

Attachment 343053 TZ750 and a Attachment 343054 Vertex piston.

these cyl have a center inlet bridge but i wasnt sure if i need to leave (for stability) or remove the middle finger of the piston skirt. pistons are wossner forged but i have no experience with them so i dont know how strong they are

[katinas]

She should be happy about what happened to her number.

[TZ350]

these cyl have a center inlet bridge but i wasnt sure if i need to leave (for stability) or remove the middle finger of the piston skirt. pistons are wossner forged but i have no experience with them so i dont know how strong they are

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


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

[TZ350]

.
Following on from Katinas last post.



Eva Nugis of Latvia racing what looks like a 350cc IZH-54
great motorcycle blog here

https://thevintagent.com/2017/07/02/...-racing-women/

[oldjohnno]

these cyl have a center inlet bridge but i wasnt sure if i need to leave (for stability) or remove the middle finger of the piston skirt. pistons are wossner forged but i have no experience with them so i dont know how strong they are

I use Wossners because they are so light, significantly lighter than anything else I've tried. On the downside though the skirts are very thin and tend to collapse pretty quickly. I've never had one crack or break but they'll shrink quite a lot (0.2mm or so) after a couple of hours of high rpms/load.

[Pursang]

If you (or anyone else in this thread) ends up at Pikes Peak again, the beer (or other beverage of choice) is on me! I found exactly what I was looking for to fix my confusion re: carbs' circuits referred to mainly/only by throttle position and not engine speed.

Remember a carburetors air/fuel ratio at WOT becomes increasingly rich as the air flow through it increases with increasing rpm unless there is some sort of fuel correction. Anyway for what its worth, that is my take on it..........

So, is this the reason that carbs that are considerably larger than required, for fuel delivery purposes, can provide a top end performance gain?
At WOT, (or WFO, if you read Dirt Bike in the 70's) air velocity and vacuum actually falls and a degree of leaning off occurs.

Time to replace the old Amal 32 with a 36mm?

Cheers, Daryl.

[husaberg]

So, is this the reason that carbs that are considerably larger than required, for fuel delivery purposes, can provide a top end performance gain?
At WOT, (or WFO, if you read Dirt Bike in the 70's) air velocity and vacuum actually falls and a degree of leaning off occurs.

Time to replace the old Amal 32 with a 36mm?

Cheers, Daryl.

My understanding is this high speed over enrichment is only a factor with a correct or smaller than optimum carb.
AFAIK If its to big it will actually not auto enrichen.

[mantonakakis]

Got a chance to try out this idea of needle/needle jet controlling WOT mixture at low RPM. Surprise surprise, Wobbly and Frits seem to be onto something

On my 50cc single-speed, I am using a 19mm PHBG, 32 pilot, about 2.5 turns out on the mixture screw, 260AU atomizer, 60 slide. Yesterday I used a W9 needle (2.5mm at the top, 1.4mm at the bottom, I think 20mm taper length, next-to-leanest clip setting). With a 69 main jet, I was a little too lean at WOT, especially once RPM got into the pipe's range. Never saw more than 450C EGT, ever.

Today I changed to a W11 needle, similar length and top diameter, but 1.8mm end diameter. One notch richer on the clip, and now 80 main jet. Low RPM WOT performance improved significantly, and EGT rose closer to a 500C minimum, with a solid 600C-650C while climbing a steady grade for a couple km at about 11k-12k (on the pipe - too rich at high RPM and couldn't rev much higher). Closing the throttle a little from WOT brought the EGT up a little bit and seemed to give more power - maybe a little leaner due to the needle. This was especially the case as RPM decreased, I think.

Anyway, vast improvement in low RPM performance thanks to this concept! Can't wait to keep tuning!

[peewee]

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


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

it probly wouldnt be a bad idea to do something with the center tang. what do you think of the red line on the photo ? im sure the thrust force will be less on the side tangs but maybe i could do something with them as well. most of the side tangs are protruding into the cyl window and not giving any support anyways. anything to make the engine hold together longer

i wonder if your broken tang had anything to do with a smaller inside corner radius ? what length conrod were you using ?

also included is a paper of stress concentration which someone might find useful for making piston windows and cutouts

[peewee]

ok im a idiot. i think maybe most of the thrust force would happen around bdc when the piston is starting upward. in which case, the side tangs would be in full contact with the cyl wall below the windows. so i should probly leave the side tangs mostly intact

[F5 Dave]

So, is this the reason that carbs that are considerably larger than required, for fuel delivery purposes, can provide a top end performance gain?
At WOT, (or WFO, if you read Dirt Bike in the 70's) air velocity and vacuum actually falls and a degree of leaning off occurs.

Time to replace the old Amal 32 with a 36mm?

Cheers, Daryl.

Time to replace the old Amal with just about anything else carburetor or otherwise.

[peewee]

getting this shit box sorted. .44mm gaskets on both sides of the spacer looks to be just right. transfer bottoms are flush with piston top edge and theres a bit of material above the ports to play with as exh open 86atdc and trans 120. hopefully get some material this week and make the small bearing washers

[Pursang]

Time to replace the old Amal with just about anything else carburetor or otherwise.

Harsh!

[F5 Dave]

Do your period rules allow you to slip in a Keihin from a CR or something?

[Pursang]

Do your period rules allow you to slip in a Keihin from a CR or something?

Any period(ish) Roundslide is ok!

I wont even use a Keihin on my Honda...


SL100 with 28mm Amal Mk2

Cheers, Daryl.