ESE's works engine tuner

[husaberg]

The +3mm CR85 pistons I have here are just over 51mm skirt ( so fine for a 50.6 stroke ) with a 24mm pin bore to timing edge.
Gives plenty of room for the long rod.

So that leaves 27 mm center of wrist pin to end of skirt. within 1 mm of the std NSR125If you allow for the stoke as wob said.(But Vanessa will indeed have a fairly short skirt)

In hindsight maybe the 50mm Cr80 piston has a lower pin than the nsr125 as well so maybe a couple of mm there too, to be gained.
Unfortunately my budget won't stretch to an infinitely long rod either.

But i did find the odd extra long one but with a 24mm pin as Wob said lots of 20mm pin ones go to 110mm But not sure how to accommodate without screwing up the rest of the engine clearances i would have thought around 106-108 would be easily doable though as well as allowing for the decrease in stroke. But wob will know how to fit them in and still make it work i guess.
I assume the decrease in stroke will make the port timing more racy and the Longer rod will increase the port time area as well?

In hindsight maybe the 50mm Wiseco CR80 piston has a higher placed gudgeon pin? so maybe a couple of mill there as well?

Were any of my assumptions correct? Broadly speaking.

Turns out nearly 6mm diff in between Cr80 plus 3mm piston and NSR125 piston or so in pin location to top of piston outside edge.

So if a std nsr rod is 104mm center to center.

I intend to loose 4mm stroke so that's 2mm up.(and 2mm down or so)

So a center to center rod length of arround 112mm rod would be close to the ideal number required.
Which would also give a rod ratio of 2.21:1. Similar to the Aprilia RSA125.(Pos not available so 110mm will likely have to do)

Although all of these changes will reduce the primary comp ratio i guess.

Therefor Vanessa will likely have some big lungs on her then

Some stuffing may be in order? (Implants to enhance her curves?)

Does that mean it would be better to start with a smaller id Crank and stuff the whole case?

[wobbly]

Its of no importance really where the cylinder sits once its all mocked up, a spacer plate a couple of gaskets and we can move it around to get whatever we want.
Then cut the case/cylinder and fill with Devcon as needed to get good flow from the reedbox as well as the correct vol.
So broadly we need a small big end pin at around 20, 110 centres with 14mm small end - get looking.
I have just done a Pavesi 144 rotary valve that ended up with a 6mm lasered spacer,with its new long rod and oversize KX125 piston the case vol ended up at 1.26, getting close to the RSA.

[husaberg]

Its of no importance really where the cylinder sits once its all mocked up, a spacer plate a couple of gaskets and we can move it around to get whatever we want.
Then cut the case/cylinder and fill with Devcon as needed to get good flow from the reedbox as well as the correct vol.
So broadly we need a small big end pin at around 20, 110 centres with 14mm small end - get looking.
I have just done a Pavesi 144 rotary valve that ended up with a 6mm lasered spacer,with its new long rod and oversize KX125 piston the case vol ended up at 1.26, getting close to the RSA.

Found 3 of them?

There were others but i consider a 18mm od on the small end to be a better bet as there is more small ends bearings available with superior cage designs.

What next

[wobbly]

What width - the same as the existing rod would be perfect, what are they from??.
Get one and I can start modding the crank.
We can skim the crank OD if needed for vol, as the short stroke will move the pin hole away from the outside.

[husaberg]

What width - the same as the existing rod would be perfect, what are they from??.
We can skim the crank OD if needed for vol, as the short stroke will move the pin hole away from the outside.

will pm you as they are unique and rods are always top secret.

But they may Spanish or Italian i can never tell the difference.
It could even be Asian as well.

[Frits Overmars]

.....there is some thought that 34 crank hp may be more than the thermal limit of the air cooled GP engine.Attachment 260589

To me it is shocking surprising to see the words air cooled and GP engine in the same sentence .
Do I see a single exhaust port there? I can hardly imagine the blowdown time.area will allow for more than 9000 rpm. That means: any more revs and the hot exhaust gases will blow down into the transfer ducts, heating up the cylinder quite effectively. If that is the case, not even water cooling would give you reliability.

[bucketracer]

To me it is shocking surprising to see the words air cooled and GP engine in the same sentence .

"1978 Air Cooled Suzuki GP125" calling it a GP, I guess is another example of the advertising copy writers enthusiasm for the company's product, in their defense the GP is loosely based on the single cylinder air cooled rotary valved Suzuki GP racing bikes of the 60's. Although TeeZee is getting more hP out of his than Suzuki did from their air cooled rotary valved racers of the time and they probably had a bigger R&D staff and more than one dyno.

[husaberg]

He does have the tripple port in reserve did you end up running the wobbly pipe?

Out of interest and seeing as i don't like secrets as it not the idea of the thread.
the ubiquitous Suzuki Bloop (B120) not sure if they were imported into NZ can't recall ever seeing one here.
but Suzuki sold millions of them they were almost the same mold of bike as the H100 only uglier. (Basic no frills commuter)
It does however have rod dimensions that would seem perfect for Vanessa other than being a fraction wide +1mm in the big end but as the std Honda washers are rather thick it could actually be made to work.
Yes the std bearings wont be up to much, but are common sizes.
Yeah the pin is wrong length as well. Who thought it would be easy.
Another Suzuki Gt250A/M also looks like it could also work as seems to be the same dimensions.(Below) it's Actually same conrod part number. TKRJ.

But there must be heaps of rods from Zundaps,Sachs, DKW's and minerilis Rotax's etc (Non Comp) that are not listed anywhere i know of that could suit as well anyone?


Oh Frits
can you please confirm, assuming it 's not a trade secret who actually made the Aprilia race rods.What sort of quality is Samarin's rods and bearings as well?
the aprilia rods would seemingly fit as well. I believe they are 20mm pin and 19mm little end do you have any lying about
Were those Aprilias non competition engines

[Frits Overmars]

It's not a trade secret any more, but I always tried to keep as far away as possible from commercial affairs, so I simply don't know who made the RSA rods; I only know the material came from France.
Samarin rods and bearings seem to be OK; they are widely used in 50 cc racers and do not give any problems there.

The Aprilia RSW rods had a 20 mm big end pin, a 15 mm piston pin and a center to center length of 115 mm. The RSA rods had a 24 mm big end pin, a 15 mm piston pin and 120 mm c--c length. But all this may have changed; after Jan Thiel went into retirement, several Aprilia people seized the opportunity to try their own ideas (like fixing alloy disks to the inside of the crank webs to decrease the crankcase volume). It's no secret that the RSA's were not as fast in 2011 as they were in 2007....

Sure, those Aprilias were non-competition engines. They were only used for a sunday afternoon stroll around a nice stretch of road that happened to be closed to other traffic .

[bucketracer]

He does have the tripple port in reserve did you end up running the wobbly pipe?

The plan is, Wobbly pipe and tripple port and maybe even a re visit with the plenum on the dyno after Kaitoke at Easter. I think there is a complete new engine on the drawing board, mostly about improved cooling and a plated alloy tripple port liner for better ring life. TeeZee is keen to get on with developing power spread from the engine and is frustrated that it takes so long to get things done.

[wobbly]

Here is the STA output of the file that was used to sim the single Ex port GP125.
It shows that at the outer limits of width and timing, with perfect port geometry, a top notch pipe etc the system is capable of 40 CHp,on Avgas.
The bmep and the rpm are all achievable,and believable, for an air cooled 125 bucket engine.
With imperfect ports, a Honda pipe and a 24mm carb the thing made 31RWHp, say 34CHp,so as always the dyno and the sim dont lie.

[F5 Dave]

. . .
the ubiquitous Suzuki Bloop (B120) not sure if they were imported into NZ can't recall ever seeing one here.
but Suzuki sold millions of them they were almost the same mold of bike as the H100 only uglier. . .

Yeah, there were heaps, no brakes, no power. A mate had one for years. & was you're mouth out with Soap. the H100 would roast the B120.
I do know Jimmy was running one the the rods in his Discvalve Kawi. But who knows how much metal they put in a rod meant to jold back 6 hp?

[twotempi]

"Sure, those Aprilias were non-competition engines. They were only used for a sunday afternoon stroll around a nice stretch of road that happened to be closed to other traffic ."


Nice one Frits

And I bet they never carried a pillion passenger on Sundays either !!

[twotempi]

A question for the technical gurus !!

What would be regarded as the minimum clearance for the crank webs inside the crankcase cavity so there is a minimum of viscous drag between the two items ??

1mm, 2mm or what ?

[Frits Overmars]

"Sure, those Aprilias were non-competition engines. They were only used for a sunday afternoon stroll around a nice stretch of road that happened to be closed to other traffic ."
Nice one Frits
And I bet they never carried a pillion passenger on Sundays either !!

If I were to try hard enough, I might even find a picture of an Aprilia rider giving a fellow rider with a broken down Honda or KTM a lift back to the pits .