Author Topic: 77 Reed Block  (Read 4627 times)

0 Members and 1 Guest are viewing this topic.

Offline Maico-Mac

  • C-Grade
  • **
  • Posts: 54
    • View Profile
Re: 77 Reed Block
« Reply #15 on: January 03, 2017, 06:40:13 AM »
An I've also made a model 76 reed cylinder.
But this time I used a selfmade case with Yamaha reed.
It goes like hell and need also the big exhaust pipe of the 400ccm!!


















Offline shelpi

  • Legend
  • *****
  • Posts: 2039
    • View Profile
Re: 77 Reed Block
« Reply #16 on: January 03, 2017, 11:05:06 AM »
no like button So LIKE!

Offline tony27

  • Legend
  • *****
  • Posts: 1790
    • View Profile
Re: 77 Reed Block
« Reply #17 on: January 03, 2017, 01:40:40 PM »
Did you make a sub plate for mounting the GEM reed block to the earlier cylinder rather than build up with weld? Looks like a very elegant way of doing it that would be able to be reversed
Your homemade reed block looks good, do you remember what the yamaha reed you used was out of?
Very impressive work

Offline Lozza

  • Legend
  • *****
  • Posts: 4190
    • View Profile
Re: 77 Reed Block
« Reply #18 on: January 03, 2017, 04:42:05 PM »








I still don't know why people think reeds are open at BDC  there is no intake charge ready to flow through the piston port when they are exposed .   :o
Jesus only loves two strokes

Offline Tomas

  • B-Grade
  • ***
  • Posts: 265
    • View Profile
Re: 77 Reed Block
« Reply #19 on: January 03, 2017, 07:47:07 PM »
That makes sense. Windowed  piston allows more flow, more continuous flow therefore 250 pipe is restrictive and 400 pipe allow for more/fresher charge in cylinder. Also larger pipe should allow expanding gasses to escape faster when exshaust port is open which on the other side creates  vacum in crankcase and sucks new charge above the piston and windowed piston helps to extend this. Bit like when atomic bomb creates mushroom cloud but much much faster  :) Like your creation and how you apply physics in two stroke modifications. Good work

Offline Tomas

  • B-Grade
  • ***
  • Posts: 265
    • View Profile
Re: 77 Reed Block
« Reply #20 on: January 03, 2017, 07:55:30 PM »
Also. If you dont mind me to ask. Does your cylinder have any kind of boost port added/drilled? Thank you ;)

HeavenVMX

  • Guest
Re: 77 Reed Block
« Reply #21 on: January 03, 2017, 11:30:31 PM »

 You can draw more air through a drinking straw than a 100mm conduit.

This is one of the most ridiculous statement I have ever seen posted on this site. It is not only plainly wrong on so many levels it requires us to ignore every principle relating air flow that it is not even funny. The real clincher in this statement is the reference to 'draw more' air through a straw which is far far harder to do than to push and the 'more' indicates a higher quantity. Just think about the proposition that more air can flow through a 5mm tube compared to a 100mm tube. The flow rate is directly related to pressure difference, cross sectional area and air density.

Try putting a straw in your mouth and only breath through it and then start running. See how long before you either open your mouth or pass out FFS. Then after you have recovered try the same thing with a 100mm tube.

I think or hope you are confusing flow velocity with flow rate ::) At a given flow rate the air velocity through a straw would be many many times higher than a 100mm tube.

Offline Maico-Mac

  • C-Grade
  • **
  • Posts: 54
    • View Profile
Re: 77 Reed Block
« Reply #22 on: January 04, 2017, 03:08:19 AM »
Did you make a sub plate for mounting the GEM reed block to the earlier cylinder rather than build up with weld? Looks like a very elegant way of doing it that would be able to be reversed
Your homemade reed block looks good, do you remember what the yamaha reed you used was out of?
Very impressive work

Yes, there is a sub plate between cylinder and case in both cases.
For the square barrel the GEM Kit includes this plate and you just have to customize it for the round intake hole.

The yamaha reed is out of a RD350YPVS or Banshee 350 Engine.
« Last Edit: January 04, 2017, 03:10:21 AM by Maico-Mac »

Offline Maico-Mac

  • C-Grade
  • **
  • Posts: 54
    • View Profile
Re: 77 Reed Block
« Reply #23 on: January 04, 2017, 03:31:31 AM »
I still don't know why people think reeds are open at BDC........

I don't think so too!
But after BDC when the Piston wents up the flow goes trough the holes until the piston skirt takes the lead, therefore they are so high  ;)
In the picture of the radial barrel the piston is not on BDC, it has ~30mm to go.

I think it's not good to open the 3.overflow to the intake, as shown in PCMAX cylinder,
because this spoils the flow.

Offline Maico-Mac

  • C-Grade
  • **
  • Posts: 54
    • View Profile
Re: 77 Reed Block
« Reply #24 on: January 04, 2017, 03:37:59 AM »
Also. If you dont mind me to ask. Does your cylinder have any kind of boost port added/drilled? Thank you ;)

There are no extra ports added..

Offline tony27

  • Legend
  • *****
  • Posts: 1790
    • View Profile
Re: 77 Reed Block
« Reply #25 on: January 04, 2017, 09:52:14 PM »
That means a YZ85 reed block will also fit, from what I've read there is a v-force unit that fits into the RD350YPVS & Banshee cylinders
Always surprises me just how small old reed blocks are compared to newer bikes, often the smallest modern bikes have the same size as something older 3-4 times larger

Offline Maico-Mac

  • C-Grade
  • **
  • Posts: 54
    • View Profile
Re: 77 Reed Block
« Reply #26 on: January 05, 2017, 04:11:09 AM »
That means a YZ85 reed block will also fit, from what I've read there is a v-force unit that fits into the RD350YPVS & Banshee cylinders
Always surprises me just how small old reed blocks are compared to newer bikes, often the smallest modern bikes have the same size as something older 3-4 times larger

Yes you are right, v-force is possible. But I don't think it's necessary.
I'm always surprised how good the small reed blocks work on higher revs. My expectation was that they will restrict the revs on a lower level than without reeds. But this is not the case  :D

Offline shelpi

  • Legend
  • *****
  • Posts: 2039
    • View Profile
Re: 77 Reed Block
« Reply #27 on: January 08, 2017, 12:01:56 PM »

 You can draw more air through a drinking straw than a 100mm conduit.

This is one of the most ridiculous statement I have ever seen posted on this site. It is not only plainly wrong on so many levels it requires us to ignore every principle relating air flow that it is not even funny. The real clincher in this statement is the reference to 'draw more' air through a straw which is far far harder to do than to push and the 'more' indicates a higher quantity. Just think about the proposition that more air can flow through a 5mm tube compared to a 100mm tube. The flow rate is directly related to pressure difference, cross sectional area and air density.

Try putting a straw in your mouth and only breath through it and then start running. See how long before you either open your mouth or pass out FFS. Then after you have recovered try the same thing with a 100mm tube.

I think or hope you are confusing flow velocity with flow rate ::) At a given flow rate the air velocity through a straw would be many many times higher than a 100mm tube.
what Lozza is saying is correct when certain conditions arise ie, 1 of them being in carburation there is no way you will get the correct metering (flow of fuel) threw a large carby have you sucked fliud threw a straw and the a bigger piece of pipe it gets expedentsially  harder as the diameter increases and that is opposite in the way you have applied it ( you see its in the application that changes the the rules in play) cause and affect

HeavenVMX

  • Guest
Re: 77 Reed Block
« Reply #28 on: January 08, 2017, 02:28:01 PM »

 You can draw more air through a drinking straw than a 100mm conduit.

This is one of the most ridiculous statement I have ever seen posted on this site. It is not only plainly wrong on so many levels it requires us to ignore every principle relating air flow that it is not even funny. The real clincher in this statement is the reference to 'draw more' air through a straw which is far far harder to do than to push and the 'more' indicates a higher quantity. Just think about the proposition that more air can flow through a 5mm tube compared to a 100mm tube. The flow rate is directly related to pressure difference, cross sectional area and air density.

Try putting a straw in your mouth and only breath through it and then start running. See how long before you either open your mouth or pass out FFS. Then after you have recovered try the same thing with a 100mm tube.

I think or hope you are confusing flow velocity with flow rate ::) At a given flow rate the air velocity through a straw would be many many times higher than a 100mm tube.
what Lozza is saying is correct when certain conditions arise ie, 1 of them being in carburation there is no way you will get the correct metering (flow of fuel) threw a large carby have you sucked fliud threw a straw and the a bigger piece of pipe it gets expedentsially  harder as the diameter increases and that is opposite in the way you have applied it ( you see its in the application that changes the the rules in play) cause and affect

He was referring to air flow not metered fuel flow. You are referring to the venturi effect through a carburettor causing a negative pressure immediately after the slide which is related to air speed through the venturi not quantity. As I pointed out for a given air flow, air speed is higher in a smaller tube. The fuel area ratio (metering) in a carburettor is a correlation of the negative pressure created by air speed through a venturi and the jet sizes.

Fuel is a non-compressible medium unlike air. The idea you are referring to about sucking through a straw is related to the fact your lung capacity is unable to draw a vacuum on a large diameter pipe but is able to draw a vacuum on a straw and there is also the fact you are lifting the water (heavy stuff compared to air) up a pipe/straw. If you tilt the pipe/straw point where the weight of the medium is cancelled out and apply your 'suck' I think you will find the larger diameter will make you choke very quickly as it delivers a much larger volume of water.

If you apply your 'suck' principle to just air it is far easier (less effort) and faster (no flow restriction) to fill your lung through a 100mm pipe than a 5mm straw. Think about it.

Think about fuel injection, the fuel delivery and air delivery systems are separate and independent. Therefore if the air flow situation was as originally posted all formula 1 and Moto GP engines would have straws as air intake stacks to maximise air flow  ::) :o they would certainly be easy to package.

Anyway if you believe the initial proposition then I have got some lovely pig that you may be interested in, they come in several colours and all fly perfectly ;) ;D joking OK joking

Offline shelpi

  • Legend
  • *****
  • Posts: 2039
    • View Profile
Re: 77 Reed Block
« Reply #29 on: January 08, 2017, 02:54:24 PM »
Like I said depends on application
orifice size depics flow rate, all pretty simple really as long as it is not mixed up in its application and mediums
once confusion regns no amount of explanation will sevice
cheers
oh look a squirrel