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Bad reed symptoms? Empty Bad reed symptoms?

Post  Michpatriot Fri Feb 10, 2023 9:55 pm

What symptoms would bad a reed produce on bladder? I have my stamp running now, filed and polished the blunt needle Sharp and shiny it will seat and shut off flow and got it to stop flooding and actually run, not really getting the rpms but it runs just OK on 35% with a low comp head..tried the high comp head with several differing glow gasket stacks up to 5 but then ended up trying 15% nitro then the low comp head with just 1 shim and generally got it to needle and hold rpm with 35% and the low comp head in the end..went all the way around the block and not really seeing a screamer..it does have the old style copper reed and wondering if maybe I should just change it out for a new white oval reed? Can the new style reed go in its place?
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Post  Ken Cook Fri Feb 10, 2023 10:22 pm

The production backplate can be opened up a bit more if you desire which can offer a few more rpm's. If you press out the spraybar, you can open the venturi opening up. I was using 11/64" when running suction. One thing I like to do is to check the reed to insure it's sealing properly. This means obtaining a piece of tubing that fits over the venturi. Use a large syringe and place the tubing over the venturi. Withdraw the syringe plunger. You shouldn't be able to pull it out AT ALL. If it's even mildly leaking allowing you to withdraw it, it's not functioning correctly. Just be certain if it does withdraw, it's not your tubing leaking around the venturi.

I use a tool that I bleed my brakes with which is a Mighty Vac vacuum pump. I can pull a vacuum and I can watch the gauge to insure it's not leaking. You can try and flip the reed over and try again. Placing a drop of oil on it and insuring the oil gets under the reed can also assist. Just insure that the reed is not leaking down. You should be able to push the syringe down, just not pulling it out. What I will say is that I have had more success using the clear reeds which are rectangular. They seem to seal with regularity but the lifespan is shorter than the copper star. They tend to deform where it lays on the venturi opening. I flip them over when this happens which offers a bit more life. I had what I believe was a white Teflon reed which was offered by Davis Diesel. I know high claims were made for this style but I never found it to work well due to it's thickness. I had issues with it fitting properly under the reed clip. Always insure that the clip is seated and that the reed moves freely under the clip. Take a X-acto and carefully spin the reed under the clip after installed by pushing on one of the corners. I've seen the copper star where the very edges tend to roll up onto the walls of the sides which pinches them down when the clip is installed. If the edges of your reeds even show deformation where the clip is, I would discard it. I've successfully removed dents and slight folds by using two ground and hardened machinists blocks and clapping them together with the reed sandwiched.
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Post  Michpatriot Fri Feb 10, 2023 11:00 pm

Thank you Ken, I'm going to try a new reed and save the copper one in my stash..also will check the seal and remove the screen..I'm a little scared of pressing out the spray bar since its the only one I have.  I am going wait to open up the venturi..but may try it in the future..might remove the screen though. I'm amazed with the difference after changing the shape of the needle with a file, drill spinning the needle held in the on position and finishing it spinning with 2000 grit paper..gives me hope with this fine thread backplate..its ALIVE!
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Post  Ken Cook Sat Feb 11, 2023 8:54 am

There's nothing difficult about pressing out the spraybar. It won't break the backplate. In addition, regardless of what others might say on the net, orientate the hole directly in the center of the spraybar for best results if it's not already doing so. Take note if when your pressing it out. I use a drill press with my backplate on blocks. I turn a drill bit upside down and press. It pops right out. Reverse procedure to re install. Having additional piston and cylinders can also yield different results. I wouldn't assume because a combo has good compression that it's a good runner. I've had piston cylinders that felt like they had very little compression which would run like no other. As long as it starts and hot starts, it's fine.
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Post  Michpatriot Sat Feb 11, 2023 11:18 am

Ok ill try it Ken..spray bar holes centered in venturi vertical spray pattern up and down?.I take it there are two holes or just one? I have gaskets and parts coming this week so ill take it all apart and fiddle with it..I ran it again this morning and was only able to get a wavering 14-15 thousand rpm using 5-4 grey cox prop...not clean and crisp as the TeeDee..I'm making progress though and having fun..the kitten is getting closer!

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Post  Ken Cook Sat Feb 11, 2023 11:48 am

I personally even wouldn't consider using a 4 pitch prop. Running bladder pressure doesn't like a load as it makes it more difficult to needle to keep it consistent throughout the run. Is this engine a dual port cylinder? Your down on rpm's about 5k. One prop I like to use is the APC 4.5 x 3.5.



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Post  Michpatriot Sat Feb 11, 2023 12:18 pm

#1 cylinder that came on the stamp..sorry misspoke its a 5-3 prop the only APC I have is 4.75-4.
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Post  Michpatriot Fri Feb 24, 2023 9:50 am

Still not sure on the spray bar positioning, with two holes, 180° apart on the bar..do I face one toward the fire wall and that would leave the other one facing the reed?? Seems like it would wash the firewall? Ken Cook to the rescue!
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