|
|
Post by paydem on Dec 26, 2017 11:12:04 GMT -5
I bought these reeds because old ones were worn out. On the old ones, I had starting problems, bad acceleration until ~25mph, fuel spitting out of the exhaust until I reached my top speed. The old reeds weren't sealing the case properly and the air was coming back to the carburetor when cranking the engine, after putting in new reeds, the air was still noticeable, but not as much. The reeds were bent when I got them  , so the gap between the reeds and reed valve housing was around 1mm. I flipped the reeds over and the light is still shining through the sides. The reed valve housing is new, originally it came with steel reeds, it had a very very small gap on the sides, the gap with carbon ones is 3x bigger. I need your opinions. I tried two carburetors and still had the same outcomes. Maybe you were in similar situations, maybe the reeds are sufficient enough and maybe the problem is somewhere else?   |
|
|
|
Post by tsimi on Dec 26, 2017 19:00:13 GMT -5
I also ordered once Voca carbon reed petals for my Prebug. I didn't had any issues with my stock reeds but I thought since I have to install a BBK and a new carb I might as well replace the reeds just in case and besides they were cheap, like $6.
Well, I got the Voca reed petals and I installed them in to my stock reed block and as you I had a tiny space at the bottom. I also tried to flip them around but that just moved the space to the side.
I didn't continue to install it that way and reinstalled the stock steel reed petals.
Those carbon reeds that come with the BBK or the ones you can buy separate for the stock reed block are not worth it if you ask me. You better get the whole reed block next time. It cost a bit more but it saves you a lot head aches.
|
|
|
|
Post by ThaiGyro on Dec 26, 2017 21:47:48 GMT -5
I have had bad reeds, from age. I have never seen new reeds that were anything but flat. Bad manufacturing unless the reed cage is curved for some reason.
Every reed cage we have here has flat reed seats.
|
|
|
|
Post by pete130 on Jan 6, 2018 22:06:05 GMT -5
I use polini carbon fiber and lay between anything flat for a week and never have a proble with fitment you can order reeds reeds to size ask boyson if you like there reeds i just orded power reeds to try
|
|
|
|
Post by ThaiGyro on Jan 7, 2018 3:57:38 GMT -5
This thread got my mind working...I build many things for my bikes, cars and scooters. I often buy fiberglass, locally, or carbon fiber from anywhere where the price and quality is good. The roll I have here now, came from the USA...Washington, I think.
It was a "remnant" piece of about 2 yards of super thin carbon fiber...maybe I can make some, or play with the vacuum tapers...ohhh, I wish I had a dyno!
|
|
|
|
Post by paydem on Jan 7, 2018 12:05:58 GMT -5
Contacted the seller, he'll replace the reeds. Hopefully those ones won't be bent aswell.
|
|
|
|
Post by Lucass2T on Jan 14, 2018 13:11:38 GMT -5
I have had bad reeds, from age. I have never seen new reeds that were anything but flat. Bad manufacturing unless the reed cage is curved for some reason. Every reed cage we have here has flat reed seats. Some years ago I did an internship at VHM, known for their golden 2t cylinderheads, high-end pistons and crankshafts... .jpg) As you can see they engineer their own reedcages, the petals come (from what i remember) Carbono Racing SL in Italy. But the petals for these reeds are definetly curved. One day i needed to help a guy assemble a batch or reeds and he specifically told me to make sure i mounted the petals the right way because of the curve they had. |
|
|
|
Post by paydem on Jan 14, 2018 15:08:55 GMT -5
I have had bad reeds, from age. I have never seen new reeds that were anything but flat. Bad manufacturing unless the reed cage is curved for some reason. Every reed cage we have here has flat reed seats. Some years ago I did an internship at VHM, known for their golden 2t cylinderheads, high-end pistons and crankshafts... As you can see they engineer their own reedcages, the petals come (from what i remember) Carbono Racing SL in Italy. But the petals for these reeds are definetly curved. One day i needed to help a guy assemble a batch or reeds and he specifically told me to make sure i mounted the petals the right way because of the curve they had. You say that they are bent in a specific way that when you bolt them down they seal all all the way around? Like in this photo shown here. Because that's how my stock reed petals came in when I got them.  |
|
|
|
Post by Lucass2T on Jan 14, 2018 15:25:34 GMT -5
Some years ago I did an internship at VHM, known for their golden 2t cylinderheads, high-end pistons and crankshafts... As you can see they engineer their own reedcages, the petals come (from what i remember) Carbono Racing SL in Italy. But the petals for these reeds are definetly curved. One day i needed to help a guy assemble a batch or reeds and he specifically told me to make sure i mounted the petals the right way because of the curve they had. You say that they are bent in a specific way that when you bolt them down they seal all all the way around? Like in this photo shown here. Because that's how my stock reed petals came in when I got them. Yes, just like your image. I made a drawing to make it more clear.  |
|
|
|
Post by oldgeek on Jan 14, 2018 17:32:42 GMT -5
Both the Polini and the Malossi CF sheets I purchased had the same slight bow pictured. I made sure to take the bow into consideration as I marked out the outline of the reeds for cutting.
|
|
|
|
Post by 90GTVert on Jan 14, 2018 21:35:33 GMT -5
MotoTassinari VFORCE3 reed replacement instructions also note to be certain of the orientation of the curve in petals with an illustration quite similar to what Lucass modded.
|
|
|
|
Post by ThaiGyro on Jan 15, 2018 3:55:13 GMT -5
Very interesting...may be two ways to the same means, but I would have questions on either:
For flat reeds, the idea is to have a reed taper that matches the maximum opening at WOT. Many manufacturers have reed limiters made from stainless in pre-curved shape, to allow proper flow regime at OEM tuning...really, a bit beyond, but that is why the reed taper is mechanically limited.
In other words, the reed will gain maximum opening slightly before maximum vacuum. (Most of you know that vacuum drops off at some point.) The vacuum at WOT/max rpm/best spark condition, should be enough to maintain WOR...Wide Open Reeds. That allows the best possible stoichiometric ratio at WOT. (Best mathematical fuel/air ratio) That said...I tune for the best to create the highest torque & hp on a street engine...Never for top end, unless someone wants a drag setup.
I have seen where race tuners have played with pre-curve physical limiters, like the OEM engines, but the success is mixed....a trade off of torque and max hp. So...Reed tuning is quite fun, but not for beginners. Most important is that you must first decide what you want in your own engines performance envelope.
The above is related to flat blade (plane) tuning.
The thread question went toward pre-curved reeds. From my experience the reason is a good one. For street applications in a given flow regime, (Air/Fuel) an engineered reed can induce a performance envelope directly related to the desired engines throughput. Why? The OEM pipe has a specific flow dynamics that affect low and high boundaries.
We all love mods. Reality is that you can change the throttle response...effectively, fine tuning the carb tuning, by altering the reed curve relations.
Bottom line?
*Flat- linear reeds are typical old school OEM. You get what they give, based on designed performance envelope.
*Flat- tapered reed allow for some tuning at a given point. You can alter the tapers. Start flat and sand to desired levels.
*Precurved- Aftermarket version that can also be altered, but the engineering math becomes more involved. Unless you work for NASA, and are wealthy...forget modifications.
You may see here...the "tuning" of a 2T encompasses everything! If you want a new pipe? EVERYTHING else changes.
|
|
, so the gap between the reeds and reed valve housing was around 1mm. I flipped the reeds over and the light is still shining through the sides. The reed valve housing is new, originally it came with steel reeds, it had a very very small gap on the sides, the gap with carbon ones is 3x bigger.
