Hi guys,
Right over xmas I will be taking the top end off my 3xv to do a few tweaks. While the top end is off I was thinking about modifying the rear legs of the cylinder in an attempt to open the path to the transfers up a bit. So I have a few questions:
1. Do people copy the TZ layout?
2. Will piston life be significantly shortened?
3. Does anyone have any dyno evidence to prove this modification actually makes a difference?
Here is a stolen pic of a 4dp cylinder. The legs are minimal and not very chunky:
(https://pure2strokespirit.net/forums/proxy.php?request=http%3A%2F%2Fi189.photobucket.com%2Falbums%2Fz125%2Fmaccas125%2Fdsc03418.jpg&hash=12b2986dd5fc21aad9ecd782ae192066b43805f4)
And here is one of my SP cylinders sat on the crankcase:
(https://pure2strokespirit.net/forums/proxy.php?request=http%3A%2F%2Fi189.photobucket.com%2Falbums%2Fz125%2Fmaccas125%2FIMAG0664.jpg&hash=0c731f9664e91a05f5ed117085875545ad00dee9)
I see that on Paul's 3xv cylinders the inlet legs have been shortened and rounded off: (sorry for the stolen pic Paul):
(https://pure2strokespirit.net/forums/proxy.php?request=http%3A%2F%2Fi189.photobucket.com%2Falbums%2Fz125%2Fmaccas125%2FCRPTZR2503XVCYL2.jpg&hash=94b797ee465628e7c7591c2206047809545addd4)
I also found these SP cylinders on yahoo Japan that came with kit pistons, the rear legs have been modified on those too:
(https://pure2strokespirit.net/forums/proxy.php?request=http%3A%2F%2Fi189.photobucket.com%2Falbums%2Fz125%2Fmaccas125%2Fmaredc888-img600x450-1228638201ax69h082281__22294_zoom.jpg&hash=4b2b001e8b590c87aa29718a005b2df2c3a525d4)
Looks like it might be the way to go???? Yamaha must have designed the legs on a TZ like that for a reason.
Also using paul's photo again, has anyone tried adding material to improve the radius into the transfer tunnels where I have shown the red arrow:
(https://pure2strokespirit.net/forums/proxy.php?request=http%3A%2F%2Fi189.photobucket.com%2Falbums%2Fz125%2Fmaccas125%2Fradius3xv.jpg&hash=a986dfa722d1d5bf55c588eb3da3418a802c8811)
Yamaha must have done this for a reason too. There is a step between the transfer tunnel and the radius on the base of the cylinder. The TZ cylinders have a lovely smooth transition from base of cylinder wall into the transfer tunnel. Looking at it I would fill that step with JB weld to get a nice smooth transition into the transfer tunnel. Would people agree that I should do that?
Also the blue arrow shows that Mr Coker has put a nice radius on both sides of the lower part of the cylinder wall, I will copy this I think. I have read elsewhere that this is the way to go now. People may argue that it is not worth doing as that part of the cylinder wall is meant to match up with cut-out in the side of the piston, but transfer flow begins well before the piston is at BDC :)
All thoughts, theories, opinions welcome.
Dan
If you want to separate theory, specualtion , old fashioned 'what looks right' and people who visualise things from what just makes shitloads of HP , follow what Jan Thiel has done with the Aprilia RSA/RSW engines. These are probably the most powerful 2 stroke engines ever made. Was the result of 100 people working full time , 2 dynos and 3-4 cylinders tested per day. If it didn't make more HP it went into the recycle bin. No other criteria.
First throw away what ever you thought you knew about a 2 stroke cylinder. Then forget that Yamaha had a complete grasp of what they were doing(Bartol stories will come later)
All of transfer flow WILL BE AT BDC. That is the best time to cool the piston and form a rising column(we'll talk about the rising column later). Next is the INNER wall does all the work, the intake just follows the outer wall shape. A short transfer passages begine to flow sooner and finish sooner than long ones. Having the transfer flow peter out not long after BDC is what you wantas that helps form the rising column with little turbulence(more on that later).
Looking at the cylinders there a 3 things that stand out.
1.Altering the little legs will do SFA to promote transfer flow
2. The inner wall is far too long
3. The radius where the inner wall meets the transfer duct is to small.
Shortening the inner wall down to close to the base of the cylinder will allow you to put a decent radius an shorten the inner wall. Win win in junior manager speak.
Aprilia RSA cylinder
(https://pure2strokespirit.net/forums/proxy.php?request=http%3A%2F%2Fi155.photobucket.com%2Falbums%2Fs297%2FLozza85_2007%2Fedgeradius.jpg&hash=162936f5e46900096efd78aa4c6c4d91cca0a49f)
(https://pure2strokespirit.net/forums/proxy.php?request=http%3A%2F%2Fi155.photobucket.com%2Falbums%2Fs297%2FLozza85_2007%2Fcylinderamppistonskirt.jpg&hash=7db9ba6ce5673892e466db606cf6c22dc7602096)
Hi lozza,
Thank you for that information, I will do some more reading :)
Dan
Quote from: maccas on November 23, 2012, 01:32:49 PM
(sorry for the stolen pic Paul):
quite alright dan, only i cant remember if those are my spares or the ones on the bike.
interesting observations
the entire inlet tract; rubber to piston-edge/crank was also machined out
eeknows is right (i gather from his wisdom) that there is more to it, and i believe a lot of the machining Coker did from carb inwards was an inlet volume thing.
TBH, he did very little work to the ports, just the exhaust ports were opened and raised and PV's altered to suit, most the work is in
"blueprinting" original then improving cases, bottom-of-barrel, heads and pipes.
(https://pure2strokespirit.net/forums/proxy.php?request=http%3A%2F%2Fi172.photobucket.com%2Falbums%2Fw26%2Fndwedwe%2F81D2EDB7-699D-4576-BE1B-46487E95AEB1-1543-00000294FD080759.jpg&hash=9543260797753729d8a3804a890457293e2e11f3)
(https://pure2strokespirit.net/forums/proxy.php?request=http%3A%2F%2Fi172.photobucket.com%2Falbums%2Fw26%2Fndwedwe%2FCD0303D7-7202-4BF9-895A-4B5E9BA5F666-1543-000002950678885D.jpg&hash=1e1d2bccc118a00db1aca564a8b1c35c0300b700)
(https://pure2strokespirit.net/forums/proxy.php?request=http%3A%2F%2Fi172.photobucket.com%2Falbums%2Fw26%2Fndwedwe%2F4027D6DD-3B9E-4149-88AF-809487B5690D-1543-000002950E1BC821.jpg&hash=58a0eadcb624d5c84f77f23adf4abbecbe9e79ac)
(https://pure2strokespirit.net/forums/proxy.php?request=http%3A%2F%2Fi172.photobucket.com%2Falbums%2Fw26%2Fndwedwe%2FA8ABE29D-EF17-4E34-B08F-8C7C1A937C96-1543-00000295163538A4.jpg&hash=e0b787bedd701d02634d09726eaf2e25b7d5992b)
keep in mind his instructions were to de-restrict, improve reliability and give me a nice mid range. it is not a track bike, but would love to try it on a track one day.
i just came back from a ride on the 3XV, it is hot as hell here today, and that was back to back after the TZ. the 3XV is a very pleasant and easy bike to ride, it has a mid range like you cant believe (well i think you can, your dyno graph is very similar to mine, linear) and a nice top end which i dont ride it in much (thanks to good mid range and my engine wrecking mental control, developed recently$$$$$).
are you going completely track? i would "clean it up" but not get radical, even for track, unless you got a recent sponsor!
those RSA cylinders look the bollocks
Thanks for the close up pics Paul that's really helpful!
It is very interesting that Graham Coker didn't raise the transfers at all. Are you running the standard thickness base gaskets?
Dan
pleasure
im using 0.7 base gaskets
Hey Dan ,
email me - nealgreyplumba@hotmail.com . I have a 50 barrel that i can send pics of . I just can't load them yet as i am a computer numpty .
cheers , Neal
Emailed!
Cheers Neal!
Dan
Dan what are the port heights from the top of the cyl? The cyl looks blowdown limited, there is free HP there demanding to be released.
I see the sub exhaust doesn't extend around to the 9/3 o'clock (or as far as it can go with a piston cut out) line on the cyl. Check the angle on the bottom of the A and B ports should be 15 deg.
Jan Thiel said he found no extra HP in the cases and the few if any people know what happens once the crank is spinning
My. Man Dr Neels does nothing to the cases too .
When he does porting for me . To my untrained eye it looks like not much has been done but the dyno tells the truth afterwards !
http://www.sylmasta.com/acatalog/Creative_Kneadatite_Putties.html This is what Jan Thiel used aparently survives replating :o
Quote from: Neal on November 24, 2012, 05:47:17 AM
My. Man Dr Neels does nothing to the cases too .
When he does porting for me . To my untrained eye it looks like not much has been done but the dyno tells the truth afterwards !
Say hello to the good Prof next time you see him Neal.
Quote from: EEKNOWS on November 23, 2012, 10:37:11 PM
The cyl looks blowdown limited, there is free HP there demanding to be released.
Eeknows, about blowdown limited.
Some years ago, when I spent a fair amount of time analysing TAs and the formulas (or formula) for calculations that people were using... to me it looked wrong, the old formula from the scrip "aspirin takers
something " developed by 2 gentlemen when working about cylinder design for an yamaha racer.
I don´t remember the formula by heart, but it was something like it was analysing crankshaft rotation degrees generally, and not taking into account the actual speed that the piston has when traveling at at given point of the crankshaft position. (hope youguys understand what I mean).
Since then, I found a picture by Frits Overmars, of TAs analysis (wich I can´t find anymore, off course), and a writing (can´t find that either) explaining theyr point of view how TAs analysis should be conducted. And it was not just as simple as the early formulas.
Do you have fresh info on that Eeknows?
The old way talked about time/area which is wrong because we never worry about time, a better term is angle/area so exhaust open 196 deg is a angle, but we are not concerned with the engine just sitting there so we add the equation of dividing them by cc's of the cylinder and by rpm of peak torque and we get specific time/area.
You can never have enough blowdown STA.
So the next crazy idea is - How much would it cost me to have 2 cylinders cast by an enthusiast with all these Aprillia improvments ?
Here is your guy !!!!
Gabriele Gnani / check his videos on youtube.
http://www.youtube.com/results?search_query=gabriele+gnani&oq=gabriele+gnani&gs_l=youtube.3...179430.180773.0.181062.4.4.0.0.0.0.144.431.3j1.4.0...0.0...1ac.1.j8PTe7JQTL4 (http://www.youtube.com/results?search_query=gabriele+gnani&oq=gabriele+gnani&gs_l=youtube.3...179430.180773.0.181062.4.4.0.0.0.0.144.431.3j1.4.0...0.0...1ac.1.j8PTe7JQTL4)
Quote from: Neal on November 25, 2012, 08:36:21 PM
So the next crazy idea is - How much would it cost me to have 2 cylinders cast by an enthusiast with all these Aprillia improvments ?
I think there is significant scope to incorporate many improvements within the 3xv cylinder already, no worth it trying to re-engineer the engine completely. Just get a 3MA frame and stick a Rotax 256 with FPE/RCS/PVP cylinders on it and go directly to 85HP with 38/39mm Delorto's or 90 odd HP with the 42mm carbs. There is no way you see those sorts of numbers from TZ's even.
PS carbs on their way over neal
Hi guys,
Thank you for all the replys :D
Paul,
Thanks again for the pictures of your cylinders, on closer inspection Graham has kept the length of the legs the same and just rounded off the backs of them by quite alot. This is probably to try and keep the engine more reliable than anything else by giving the rear of the piston more support at BDC.
Neal,
Thank you very much for the pictures of the 3xv-50 cylinder. Are you happy for me to post the pics up here?
Lozza,
When you say the cylinder looks blowdown limited are you refering to the black staining in the crankcase on my engine? I would also agree that this would pin point to there not being enough blow down. However in this case it is not the cylinders fault. The engine came from Japan a couple of years ago and by the look of how standard it was when I had it in bits it looks like it had only ever been ran with the standard 3xv-10 cdi. This is known to be a very restricted cdi and I doubt that the powervalves even get anywhere close to being fully open, hence the limited blowdown signs.
The stock SP port map looks like this:
(https://pure2strokespirit.net/forums/proxy.php?request=http%3A%2F%2Fi189.photobucket.com%2Falbums%2Fz125%2Fmaccas125%2F3xvspportspec.jpg&hash=4afbb8cefccd1a25be888d39df0b0e90a4abca4e)
Pauls cylinders transfer heights are approx 2mm lower than those in the port map at approx 40.5mm from the top of the cylinder so he probably has more blowdown than my cylinders but then I don't know the exhaust port height on Paul's cylinders so it is difficult to comment.
On the 3xv-50 cylinders the sub ports are closed by separate powervalves. The sub ports on those cylinders look to be larger than the ones on my SP cylinders. Obviously the sub ports can be made wider without sacrificing bottom end power as the sub ports are kept closed for longer and then opening at the top end giving greater exhaust port area and blowdown TA.
Regarding my original question:
Should I add material to remove the step on the inside wall of the transfer tunnel? I think yes I should especially as Lozza has pointed out that the mixture hugs the inside wall of the transfer tunnel. A smooth continuous radius from lower cylinder wall to port window should help here I believe.
I think a little bit of work on the rear cylinder legs won't do any harm either. I won't go quite as far as TZ extremes but somewhere inbetween that and what I have now can't do any harm I don't think.
Dan
Quote from: maccas on November 26, 2012, 11:48:24 AM
I don't know the exhaust port height on Paul's cylinders so it is difficult to comment.
now you do, 25.4mm
Black in the cases :o That port map has 30 deg of blowdown angle and precious little area, Pauls' does better with 37deg of BD angle. Look at the size of the legs on the RSA cyl round or big square mofo's makes not one bit of difference. The shorter that inner wall the better (an old TZ/LC trick) long columns take forever to start flowing then don't want to stop, short columns flow early and are easy to stop. How much thought have you extended to what happens between BDC and the squish band starting to work (say approx 30deg BTDC)? If you were at all like me until 2010 I didn't think much at all. At this point you will see the brilliant simplicity of why the Aprilia GP bikes won all those races and championships.
At BDC intake charge begins to form a 'rising column' , the intake streams gently collide and rise in the cylinder , hit the head and come down to meet the rising piston. Intake streams out of the transfers must have as little turbulence as possible. Turbulence while the exhaust port is open means mixing of intake and spent gasses. That costs HP and piston cooling.
Now you start to see why blowdown is so important, if you have say 120psi cold cranking then you will have 1200psi after the mixture goes bang, all of that heat and pressure must go out the exhaust before anything comes out of the transfers
Go for it Dan , I can try and send better quality pics to you if needed . I will try and do a port map again . Would you like TZ pics too ?
Paul,
Again thank you for that information, that is very very interesting. Slightly higher exhaust port timing than a stock SP cylinder but with 'R' model transfers.
Neal,
Sweet, I'll photobucket them and put them up. If you have the time to take better pics that would be really appreciated. TZ pics would also be greatly appreciated ;D thank you very much. I would guess that the exhaust port on the -50 cylinder will be a couple of mm lower than that of the TZ.
Lozza,
Again thank you for that information. I've been scouring the net to try and find a picture looking through the intake port in the RSA crankcases with a cylinder fitted to see how much the legs "hang down" into the intake flow. Sadly I haven't been able to find such a picture :-[ But what I did find is that the intake legs on the RSA cylinder are 21mm in height from the gasket face. Looking at a picture of an RSA crankcase half it looks as though the thickness of the metal where the cylinder fastens too is roughly 15mm (a rough guess). Added on top of that is the base gasket thickness (probably very thin) so the legs look to hang down around 5-6mm into the intake flow. The backs of the legs are nice and round which will help in directing the flow into the transfer tunnels. So what I am trying to say is, on an RSA the legs are big and chunky yes, but they have been designed with the crankcase in mind to not hang down into the intake flow much.
The 3xv as you can see in standard fettle has huge rear legs that really hang down in the flow. They must hang down ~ 25mm into the reed valve housing/upper crankcase roof. I think that shortening the legs to open up the space a bit could help. The result would be a more synergistic crankcase/cylinder base combo geared up to help direct the intake flow to the transfer tunnels.
The TZ cylinders look to be a good improvement on my stock 3xv-10 cylinders in this area and the yamaha engineers gave the TZ a layout like this for a reason. Obviously I'm not looking to make a 80 hp TZR but if this small change can unleash 0.5hp anywhere in the rev range with no losses then it is worth doing and I have learnt more about workings of the TZR's engine in the process. Sadly I don't have a spare pair of SP cylinders in order to do a back to back comparison on the dyno :-[ I will certainly try and employ some of the tricks from an RSA where I can.
Dan
Yada, yada... Have a scope through the old, old forum Dan. Think I posted pics of my own base mods up in there somewhere a few years ago? No real idea how effective or inneffective they were on their own, but overall I'd think you are probably better off taking your cues from TZ cyls on the whole really as they are a proven design on this kind of engine; the 3XV is not a 'priller GP motor afterall... I wonder to what extent the diff' bore & stroke of the 'priller motor is a factor in ideal port design criteria?
Later SP cyls (20, 40 and 50) were basically the same broad design as TZ cyls with slightly tamer porting (not by that much though) Interesting to see how similar the RSA port layout is to the early 3XV layout though...?
C port flow goes through a 20mm wide gap between the rear legs, the back of the legs fit in the crank case. Aprilia had a full time staff of 100, working 5 days a week, 2 dynos running continuously testing 3-4 different cylinders per day from 1995-2007 all under the watchful eye of probabaly the best 2T tuner ever.End results was the most powerful and reliable 2T engine ever. Safe to say if it works it's on a RSW/RSA cylinder if not you don't need to worry about it.The transfer flow is helped by duct geometry and the pipe sucking hard at BDC.
As I said before short, long,square or rounded legs will make SFA difference on the track or dyno in fact I would be inclinded to make them larger.
Lately the Aprilia ducts have be copied from 50cc to 300cc bores with the same result more power better and piston cooling.
Quote from: EEKNOWS on November 26, 2012, 11:05:14 PM
C port flow goes through a 20mm wide gap between the rear legs, the back of the legs fit in the crank case...
As I said before short, long, square or rounded legs will make SFA difference on the track or dyno in fact I would be inclinded to make them larger.
Well, there you go then. Weld those suckers up and file 'em nice and square. Who am I to argue with that... ;)
Warwick,
Thanks for that, I will more than likely copy the TZ layout to a certain extent.
Lozza,
The lugs can't be made bigger because the reed valve is in the way. The reed valve is in close proximity to the rear legs of the cylinder. Much like it is on a 3ma. Making the lugs bigger would mean spacing the reed valve out with a spacer plate. This would be OK on an open carb set up but would make fitting the airboxes back on tricky.
Cheers,
Dan
Weld?? Who said anything about welding ??. This will survive replating and can be made any shape you want.
Posted on prev page
http://www.sylmasta.com/acatalog/Creative_Kneadatite_Putties.html
Even the best have little idea what happens to the intake charge under the influence of the spinning crank and rod.
Fill with weld or putty... I'd trust weld more there myself...
Though I'm not sure you'd be suggesting bunging that area up at all if you'd actually had a good look at a 3XV motor I have to say? ???.
As mentioned, I've not had the opportunity to dyno test my own cyl base mods in isolation, but personally I wouldn't think it at all useful to create additional intake restriction in this area.
Build a plugged-up 3XV motor. Prove me wrong? ;). It's all just good development as far as I'm concerned :D.
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.
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?
Casal-fan, Yes both Aprilias are rotary valves and they do make more power than a reed valve engine. It is like comparing apples to oranges in terms of power. Reed valves make better power down low compare to the rotary engines. Also inside the engine you want everything with large round edges and also very smooth where you do not want oil to stick to.
Chuck Sorensen's RSV made 82+ Hp at high altitude and the same bike was 75-76 at sea level - Something about rotary valves vs. reed valves at altitude? Rich Oliver's TZ250 made 74 to 76 Hp on the same dyno in 2003. Eventho the Aprilia made more power than Rich Oliver's bike but Rich won every AMA 250 race that year.
Here is a couple of pics of a port job that I just finished for a customer
(https://pure2strokespirit.net/forums/proxy.php?request=http%3A%2F%2Fi675.photobucket.com%2Falbums%2Fvv114%2Fyzr500steve%2Fphoto-12.jpg&hash=48cf0f6a2bb56e882b8638e477866d4019772d64)
(https://pure2strokespirit.net/forums/proxy.php?request=http%3A%2F%2Fi675.photobucket.com%2Falbums%2Fvv114%2Fyzr500steve%2Fphoto-13.jpg&hash=678cb695413816ba98120359da8dcf19c761bee4)
Polished TZ250 crank
(https://pure2strokespirit.net/forums/proxy.php?request=http%3A%2F%2Fwww.tz250.com%2FiB_html%2Fuploads%2Fpost-6-38156-P1020238.JPG&hash=b3cb7e66f20c6dea79afb037bfc5eb4ef37bd8f5)
Quote from: casal-fan on November 30, 2012, 12:57:10 AM
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
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.
Quote from: casal-fan on November 30, 2012, 12:57:10 AM
...........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 8) ).
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 :D ).
I will add progress to my project thread.
Thanks to all who have contributed to this thread.
Dan
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... ;)
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 ;D
Dan
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.
Quote from: maccas on November 30, 2012, 01:17:52 PM
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 ;D
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.
Quote from: EEKNOWS on November 30, 2012, 02:09:04 PM
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
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 !
Man I miss my RZ50!
This are some photos from a cylinder of German racer. Hope they are clear enough !
Enjoy ;D
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. :P
( I also gas flowed the cases to round off the corners by the base of the transfer ports ).
Before. ( On lower / R.H cyl. ) :-
(https://pure2strokespirit.net/forums/proxy.php?request=http%3A%2F%2Fi341.photobucket.com%2Falbums%2Fo393%2Fwulliemckie%2FSTA41348.jpg&hash=fe93050ed8f91a05dc6db613d003b5a640e94a7f)
After.
(https://pure2strokespirit.net/forums/proxy.php?request=http%3A%2F%2Fi341.photobucket.com%2Falbums%2Fo393%2Fwulliemckie%2FSTA41349.jpg&hash=e68b83844fdc329da7f3f19de6e467e34346fee5)
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. :D
(https://pure2strokespirit.net/forums/proxy.php?request=http%3A%2F%2Fi341.photobucket.com%2Falbums%2Fo393%2Fwulliemckie%2FSTA41370.jpg&hash=39a211ffdc82cb4206b9cc0ddc9b9b38004950bf)
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 ?
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 ? ???
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 ?
Quote from: peterbike on December 16, 2012, 03:21:55 PM
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 ?
Peter in the top right hand corner of anyones post there is a "quote" button hit that and the text in that post will form the start of your post. While your making your post you will see that all the previous posts now have a "insert quote" in the top RH corner so if you hit that during making your post we get this
Quote from: peterbike on December 16, 2012, 02:35:49 PM
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 ? ???
Churning means well...............churning :D Think it was posted here that there is less than 10 3XV's in Australia so it's a small pool compared to say 1000's of RGV's.
Sub ports can be extended to, but not past the 3 o'clock and 9 o'clock positions if the exhaust port is at the top. So yes you have that correct