ESE's works engine tuner

[casal-fan]

I've been trying to think of an intelligent question to ask of our learned contributors for a while.

There have been heaps of things that have sprung to mind but I've been able to find reasonable answers myself by looking around and reading widely, asking such questions here seems a waste of a good opportunity.

So my odd-ball questions:

What is the up with the radial exhaust port angle?

I'm not sure if I have the correct term so I have attached a [ATTACH=CONFIG]Picture[/ATTACH] to illustrate.

Some exhaust ports exit straight (pic on left) but I notice others, including the RS125 barrel I have sitting here, have a shape more like in the right picture.

I can guess at why this might be done but is there any general wisdom of perceived benefits/drawbacks?

I did notice one small reference to it in the large pile of books I've been working through, that was in Cesare Bossaglia's book 'Two Stroke High Performance Engine Design and Tuning' (Quite an old book but still interesting and informative, a greater scope than most) from my terrible memory he said it has been used to update old barrels to higher performance without a major redesign.

Late answer to this post, but I haven´t read somebody looking at this from this point of view.
I see the bulge as being there for exactly the same reason as there is a buldge on the trailing side of most secondary transfers ports.
It shapes the exit horizontal angle to give the max possible effective port area.
Wobbly mentions flow increase with the buldges, but lost if exagerating the buldge horizontal angles. This "flows" good with what I just wrote... maybe...

[Frits Overmars]

I thought I remembered reading it?? Are you able to elaborate/confirm?

You can confirm it yourself. Some time ago I made a lot of Aprilia-documentation available to the forum. Just click the links and study the pictures.

[bucketracer]

I thought I remembered reading it?? Are you able to elaborate/confirm?

You can confirm it yourself. Some time ago I made a lot of Aprilia-documentation available to the forum. Just click the links and study the pictures.

And there it is ......

Thanks, Mental; everything seems to be fine now. So here they are again:

http://www.kiwibiker.co.nz/manual/Aprilia-1.zip (6.8 MB)
http://www.kiwibiker.co.nz/manual/Aprilia-2.zip (8.3 MB)
http://www.kiwibiker.co.nz/manual/Aprilia-3.zip (9.2 MB)
http://www.kiwibiker.co.nz/manual/Aprilia-4.zip (7.2 MB)
http://www.kiwibiker.co.nz/manual/Aprilia-5.zip (5.6 MB)

Collections of interesting tec links are posted on each decade page 320-310-300-290 etc to help with finding the interesting stuff, also using the "thread tools" and sorting and searching the images is another way of finding good stuff.

[timg]

I recently read a little piece on pipe design that got me thinking. One bit in particular spoke of badly matched pipes to ports. It said that any anomaly at the port end was a bigger problem than if say you had a dent further down the pipe. Due to greater force and speed at the port pipe juncture. Resulting in, as he put it ghost waves created. reversion I suppose. How important is it to have the transition seamless. I would imagine its very important. I know on my 4 stroke single the exhaust port is D shaped and does not match the header very well. I am thinking I should fix this now. Is this something you guys pay a lot of attention to?

Think ya should just put in a 1/4" penny washer in there. That should make it look nice for you

[husaberg]

You can confirm it yourself. Some time ago I made a lot of Aprilia-documentation available to the forum. Just click the links and study the pictures.

I was wondering what he meant.
but there is a ac couple of pics (pic 2 and 3) that if you look it does reassemble a elliptical shape.
A trick of the light no doubt.

While trying to find the photo i came across this (pic 4 )
What is the cast alloy piece it kind of remembles a disk valve cover design by the shock below the swing arm?It looks like the linkage is attached to it?

There is also a close up of the pin for the ring peg.(pic 1)

I also seen something i had never noticed in the transfer passage in one of the 500 pics (5th pic) a round bumper shape this may also be a trick of the angle the pic was taken as it may not be the shape it looks to me.

Yows bit below i would hazard a guess and it would be a guess is what looks like a sleeve is the coating extending over the top of the bore to limit detonation damage as per my bit i posted about Apitec

[Yow Ling]

Looking at Husaberks pictures above , is the RSW sleeved? pic 2 and 3.
What sort of material ? Any reason, run out of oversizes?

Also pretty clever piston machining for lubrication , kind of like an applicator nozzle. Cant remember seeing a 125 seize at motogp , maybe I just dont look hard enough

[dmcca]

You can confirm it yourself. Some time ago I made a lot of Aprilia-documentation available to the forum. Just click the links and study the pictures.

... and that is a gold mine of great info thankyou, however the reason for my confusion about the RSA head shape is that i very recently heard a respected person definitively say that the RSA did not have a toriod design. There are several pics in the files you kindly posted which appear to be toroids to me, however all of these are labelled as RSW so there was still a question in my mind as to the actual design on the RSA based on the comments i had read

[F5 Dave]

Having some carburtion issues. Does this look too lean?

[Buckets4Me]

Having some carburtion issues. Does this look too lean?

no it looks fine but dose have a small crack in the piston skirt

[Henk]

Looks mint, don't worry about the small crack.

[speedpro]

I'd replace the piston as a precaution, hell you have it out so why not. If you're careful taking the circlip out you could probably use it again.

[quallman1234]

Putting a new piston in a 50cc at the moment (okay its a scooter)... Idea's on getting the 10mm (im guessing) piston circlips in, bloody tiny little things anything bigger is piss easy. They are the open type, can't really use circlip pliers. Any hints?

[husaberg]

Putting a new piston in a 50cc at the moment (okay its a scooter)... Idea's on getting the 10mm (im guessing) piston circlips in, bloody tiny little things anything bigger is piss easy. They are the open type, can't really use circlip pliers. Any hints?

put a rag over the crankcase mouth Well you did say any hints?

[quallman1234]

put a rag over the crankcase mouth Well you did say any hints?

I know that one cheers .

[Frits Overmars]

...the reason for my confusion about the RSA head shape is that i very recently heard a respected person definitively say that the RSA did not have a toriod design.

Who?

There are several pics in the files you kindly posted which appear to be toroids to me, however all of these are labelled as RSW so there was still a question in my mind as to the actual design on the RSA based on the comments i had read

Fair enough. I did not post the RSA's cylinder drawings either; I don't fancy being shot the next time I visit Italy....
But I can assure you the RSA's combustion chamber is identical to the RSW's, although the outsides of the heads are quite different.