3xv rear cylinder leg modification. SP 3xv-10 cylinders??

[EEKNOWS]

Interesting.
Eeknows, I´m not 100% sure, but don´t both RSA and RSW have a rotary intake system?
The RSW being a "rear loader", and the RSA a side loader?
They also have longer rods (115-120mm?), and the cylinder is quite short/engine block high, all this making for more place for an uninterrupted flow of incomming charge?
If so, these are different designs in comparisson with the reed valve TZR engine, as incomming charge from the reeds meets these cylinder protrusions instantly after the reed petals, and maybe that is not the case?

I recall reading a page or 2 about the negative effect that the rod had on the charge flowing into the crankcase on the sideloader engine.
Maybe that had something to do with the rod being an obstacle, very close to the point where the charge comes into the crankcase?

RSW 115 rod side intake
RSA 120 rod rear intake


Intake charge will meet a rod coming toward it in a reed engine. The notion that "reed engines make better mid range" is a old wives tale correctly set up rotary valve engines make way more mid range than reed engines. What is different with the Aprilia's is they must be ridden ON or OFF the throttle. No feather the throttle mid corner like you can with a reed engine Easier said than done on a 100+ HP 250 sub 100kgs. When you get your head around that race wins quickly follow

[Paul]

nice work MBsteve
may i ask, i see you did a load to transfer ports and piston skirt legs, What did your client ask for regards the porting?
i am interested to know it you changed the inlet port timing, i.e. the top of the inlets and if when calculated out if there is any reason to change the height.

[maccas]

...........all this making for more place for an uninterrupted flow of incomming charge?
If so, these are different designs in comparisson with the reed valve TZR engine, as incomming charge from the reeds meets these cylinder protrusions instantly after the reed petals...........

Rui,

You have summed it up there in your statement. The aprilia engines were designed from the start with a clear unobstructed shot into the transfer tunnels. The TZR with a little work can be vastly improved in this respect. The TZR crankcases are a very nice design, probably the best 250 road bike crankcases excluding the KR1/S (which are very good indeed especially regarding the angle the reed block makes with regard to the cylinder  ).

Over xmas I am going to:

1. Make the rear lugs smaller and more rounded focussing on being holistic with the crankcase and reed valve in mind.
2. Add JB weld or similar to the step on the inner wall of the transfer tunnel in order to make a smooth un-interrupted radius from lower port wall to transfer port.
3. Add a radius on the inside of the lower cylinder wall (like on Paul's worked cylinders  ).

I will add progress to my project thread.

Thanks to all who have contributed to this thread.

Dan

[Warwick]

Yup. Not sure if you managed to dig out my pics, but that is pretty much the way I went when further modding Martin's original base work. Seems to work well. I cut back the legs quite significantly (not quite to TZ spec, but close). It opens up the intake path quite significantly. It's quite a bit of work if you have to do it all with only hand files, mind...

[maccas]

I did have a good look through about half of the posts Warwick but didn't find them. Was it definitely on the old old forum? There is a wealth of information on there isn't there! I will have another look at lunch time 

Dan

[EEKNOWS]

http://www.youtube.com/watch?v=ju2X9OVEvQw&feature=youtu.be

50cc with over 20HP at the wheel with a reed valve grafted onto the side of the engine. Disc  valve makes 1HP more . Look at the path that the intake has to negotiate.

[Warwick]

I did have a good look through about half of the posts Warwick but didn't find them. Was it definitely on the old old forum? There is a wealth of information on there isn't there! I will have another look at lunch time 

Dan

I thought so, Dan. Might have been Ash's though? Shame we don't have a back-up of that  . I'll have a root round at home when I get chance and see if I can find any pics there - not very good at keeping organised records... I'll be splitting the motor over winter in any case so could take some then. TBH though, as you know, when you sit the cyl on the case you can  see where flow improvements can be made.   

[Paul]

http://www.youtube.com/watch?v=ju2X9OVEvQw&feature=youtu.be

that is incredible!!

i've been thinking about a fast 50 and joining these guys or a similar bunch http://www.youtube.com/watch?v=EQzMKvmEkxE&feature=g-hist

[Neal]

Ahh the good old days ! I had a MR 50 and traded up to a Gamma 50 . Used to make sparks as you touched the footpegs down around the corners , at night it was cool !

[Crank]

Man I miss my RZ50!

[uminom]

This are some photos from a cylinder of German racer. Hope they are clear enough !
Enjoy

[Wullie3XV9]

Here's my tuppence worth. Some before & after photo's of modifying the -00 cylinders from my own bike myself.
As you can there's less of an obstruction to the incoming mixture flow so make up your own mind if it's worth doing or not.   
( I also gas flowed the cases to round off the corners by the base of the transfer ports ).

Before. ( On lower / R.H cyl. ) :-


After.


Here's the upper / L/H piston at Bottom Dead Center to show reduced piston support there.
My top-end has done 9000 + kms like this with no problems experianced at all.   

[Neal]

As I know nothing about bikes I have a thought I would like to get out . If you mod those legs etc , you make a bigger area , the incoming charge will slow down as the area is larger ?
That is if that is the only mod done , sound correct or rubbish ?

[peterbike]

If 3xv's were not so scarce here I would be churning them out. There is no proof the legs are a "restriction" and the spinning rod and crank have by far the biggest influence on what happens in a crankcase.There would be no way of separating if there was a "restriction" or simply the engine wanted more case volume once you added better pipes/cylinders. JB welded pistons no problems.
Something like this will further your cause.

First question.    churning what out ?   
Second.    Something like this will further your cause. ?      What am I supposed to be looking at ?   

[peterbike]

Sorry the above post did not come out very clear.
The first bit is a quote from Loz on the second page , but done wrongly.  (how do you do it so it comes out blue)
Lozza this was aimed at you, can you clarify a bit for me  ?
Also were you saying that dan's exh. sub ports could be extended further around the bore towards the east/west, if exh is north ?