BOTM

* Sponsors


Author Topic: Bad Reed Valve symptoms?  (Read 13428 times)

0 Members and 1 Guest are viewing this topic.

Offline hayduke

  • Zamfir: Master of the Pan Flute
  • Posts: 118
  • Karma: 0
Bad Reed Valve symptoms?
« on: April 26, 2009, 10:42:45 AM »
I'm getting sick of chasing this pop-pop-pop on at idle and very slight throttle openings (ie pilot circuit), it's only on the left side, if I just squeeze the throttle open it'll smooth out and pull to 8K+. Since I built this motor ~3 years ago it's always had this pop-pop-pop and it's always on the left. Even when I switched from RD350 carbs to RD400 carbs it still did it.

I've got daves carbs, drilled 5/64" air jet, all manner of jetting and synchronizing and tuning makes no difference. It pulls clean and strong but idles like a pig rrrrPOPrrrrrrPOPrrPOPrrrrrPOPrrPOPrrrPOPrPOPrrrrrrrPOP and at slow speed puttering around thru the neighborhood its the same, but if I give it just a little more throttle it clears up and hums along.

*It passed a pressure test with flying colors, holding pressure for hours.
*It's got a fresh top end with very similar cylinder pressure, ~120psi cold.
*Timing is 1.9 both sides
*Carbs are synched and checked 3 different ways (dimple on slide, and two different size dowels holding the slide up and different throttle openings- ie -fancy Popsicle stick method)
*each cylinder idle speed adjusted with the RZ crossover plugged
*Points new and gapped .016", condensors fresh, Mikesxs coils fresh, plug wires fresh

About the only thing I haven't looked at are the reed valves, they're ~32 tears old and I seem to recall one had a little more light showing thru the seal than the other, should I see any light? And what kind of symptoms would a slightly leaky reed valve cause. :umm:

Any other ideas, I'm about ready to sell this bitch and I don't think I want to  :(

Oh 77 RD400, 3rd over, ~500 miles on fresh top end,

Offline sweetriden76

  • Zamfir: Master of the Pan Flute
  • Posts: 116
  • Karma: 1
Re: Bad Reed Valve symptoms?
« Reply #1 on: April 26, 2009, 12:11:20 PM »
if they are still metal reeds get rid of them regardless, if one cracks/frags and decides to throw some metal through the engine it'll do some damage...I put TDR reeds in mine, I think boysen makes some also but TDR seems to be favored by many ppl here...when installing my reeds I noticed a small air gap(ie. light showing through) so I very carefully trimmed and sanded the rubber till it sat flat like the other side...mine give a slight pop every so often when idling too, but nothing that unusually loud or odd for a two stroke to do...

Offline JA-Moo

  • Dr. 2-Stroke, M.D.
  • Posts: 2003
  • Karma: 58
    • Location: Middle of New Mexico
Re: Bad Reed Valve symptoms?
« Reply #2 on: April 27, 2009, 12:02:33 PM »
Gaps are no cause of concern. Reed don't "seal" as most think. They basically "bounce" shut and open in milliseconds, even at idle.
Just because you almost won once at Operation, doesn't qualify you to do actual surgery..........

Offline sweetriden76

  • Zamfir: Master of the Pan Flute
  • Posts: 116
  • Karma: 1
Re: Bad Reed Valve symptoms?
« Reply #3 on: April 27, 2009, 07:12:13 PM »
right, should have clarified, mine had a pretty decent gap which is why I fixed it...what jets are you running and are there any other mods to the engine...

Offline hayduke

  • Zamfir: Master of the Pan Flute
  • Posts: 118
  • Karma: 0
Re: Bad Reed Valve symptoms?
« Reply #4 on: April 28, 2009, 05:14:21 AM »
Thanks for the replies, I was suspecting the reeds because I've tried just about everything else. But in 5 - 6 years on the forums I've never seen any threads about bad reeds (other than broken).

My most recent 'decent' tuning was...

Stock motor
3rd over bore w/~500 miles
~120psi each cylinder
SpecII pipes
10mm reed spacer (between barrel and reed cage)
RZ boots and crossover
Dave F carbs, 5/32" drilled air jet, 27.5 Pilots, 200 mains, needle clip on #3 with a shim (half way between 3 & 4)
K&N Y-boot
NGK Iridium spark plugs (stock heat range)

Basically it ran very good, I could putter at a walking speed and it would pull clean and strong to 8K+rpm, but at a stop light or almost closed throttle I'd get the rrrPOPrrPOPrrrrrPOP, etc....(maybe I'm expecting too much from a 30 year old machine)

I guess I'll try swapping ignition parts left to right and see if it's not weak electrics at low speed, at 2K rpm I get ~14V at the battery and it never goes flat when it sits a few weeks.

Then I'll try just swapping the reed blocks left to right to see if the POP POP POP moves also.

I'm stumped, and getting frustrated, maybe all RD do the PO POP POP thing, this is the only one I have any experience with.

Thanks





Offline D C

  • 2-Stroke Tuner
  • Posts: 542
  • Karma: -15
Re: Bad Reed Valve symptoms?
« Reply #5 on: April 28, 2009, 09:37:15 AM »
 10mm ! ? reed spacers?? umm why.. do you have rz reed blocks shoehorned in ?

Offline hayduke

  • Zamfir: Master of the Pan Flute
  • Posts: 118
  • Karma: 0
Re: Bad Reed Valve symptoms?
« Reply #6 on: April 28, 2009, 06:00:12 PM »
They're supposed to move the powerband lower in the rev range, suits my riding style.

Dang 79 thread views and no definitive answer to the question of the symptoms bad reed valves may cause, I guess they only go bad when they break... :sigh:


Offline sweetriden76

  • Zamfir: Master of the Pan Flute
  • Posts: 116
  • Karma: 1
Re: Bad Reed Valve symptoms?
« Reply #7 on: April 28, 2009, 06:10:04 PM »
like I said, I'd get the metal ones out anyway...also arn't spacers only for ported motors, I think you'd benefit more from a set of banshee manifolds with the crossover tube...

Offline hayduke

  • Zamfir: Master of the Pan Flute
  • Posts: 118
  • Karma: 0
Re: Bad Reed Valve symptoms?
« Reply #8 on: April 28, 2009, 06:42:48 PM »
I'm digging in there this weekend, I'm psyching myself up for another saturday in the garage, checking and changing parts.

I appreciate your help.

Offline mkane63t

  • Retired
  • Addict
  • Posts: 1628
  • Karma: 10
    • Location: 100 miles N. Of SF
Re: Bad Reed Valve symptoms?
« Reply #9 on: April 28, 2009, 06:57:29 PM »
Bad reeds will make the bike hard to start, the edges will be frayed if they are bad. Your timing, at 1.9 is not the best for a 400, unless you are running gas from Mexico. 2.1 will give you a wider powerband, and it may clear up this ppppoopp thing you have going on. I've been running mine @ 2.3 using mixed gas, approx 95 oct., and it will idle forever. Would hardly run at 1.8
Racing is life. Anything else is just waiting.

Offline motorcycleman1975

  • I'm a regular here
  • Posts: 77
  • Karma: 1
Re: Bad Reed Valve symptoms?
« Reply #10 on: April 29, 2009, 01:05:38 PM »
Mine is doing the same thing but not at idle, rather right when I take off.  I think its your reeds.  I just got some new ones and will install this weekend. 

Offline GSXRDman

  • Banned Members
  • Dr. 2-Stroke, M.D.
  • ***
  • Posts: 2568
  • Karma: -146
  • As I see it through clear bullet proof glasses
Re: Bad Reed Valve symptoms?
« Reply #11 on: April 29, 2009, 01:24:26 PM »
Thanks for the replies, I was suspecting the reeds because I've tried just about everything else. But in 5 - 6 years on the forums I've never seen any threads about bad reeds (other than broken).

My most recent 'decent' tuning was...

Stock motor
3rd over bore w/~500 miles
~120psi each cylinder
SpecII pipes
10mm reed spacer (between barrel and reed cage)
RZ boots and crossover
Dave F carbs, 5/32" drilled air jet, 27.5 Pilots, 200 mains, needle clip on #3 with a shim (half way between 3 & 4)
K&N Y-boot
NGK Iridium spark plugs (stock heat range)

Basically it ran very good, I could putter at a walking speed and it would pull clean and strong to 8K+rpm, but at a stop light or almost closed throttle I'd get the rrrPOPrrPOPrrrrrPOP, etc....(maybe I'm expecting too much from a 30 year old machine)

I guess I'll try swapping ignition parts left to right and see if it's not weak electrics at low speed, at 2K rpm I get ~14V at the battery and it never goes flat when it sits a few weeks.

Then I'll try just swapping the reed blocks left to right to see if the POP POP POP moves also.

I'm stumped, and getting frustrated, maybe all RD do the PO POP POP thing, this is the only one I have any experience with.

Thanks






what i was running ON PREMIX @ 32:1 or 4 oz. a gallon on my old 76 RD400 (dave freist):

230 main jet (probably 210/220 on injector)
169-P4 needle jet (4th clip)
35 to 40 pilots (not sure which one & Probably @ least a 30 pilot on injector)
Airscrews @ 1-1/4
Timing at 1.8mm BTDC

what i am currently running on my daytona w/ R5 carbs, 2.5 slides PREMIX 32:1, dave freist mod w/ 2.0 airjets FPP pipes:

240 main jet
169-P5 needle jet (middle clip)
#50 pilot
Timing @ 1.75~1.8mm BTDC

I would hazard a guess and this is what i would try in your bike IF IT IS INJECTOR  (premix? Main jet to 230-240, pilot most likely a 40 pilot):

210-220 main jet
169-P4 needle jet (middle clip on 5DP7 needles or shim it between 3rd & 4th clip or directly to 4th clip if it turns out lean in the mids, it will also help down low too)
#35-40 pilot
Timing @ 1.8 mm BTDC


backfiring or popping through the exhaust while crusiing indicates a lean symtom and that 27.5 pilot looks a bit too lean.  I also found on a recent ride when i was in the mountains and cold that a larger main jet helped me get home with no more popping throught the exhuast.  Although i still suspect a slightly lean pilot (when the problem started just putting in the higher elevations...didn't have a larger pilot at the time). be aware that the stock R5350 carbs ran a huge #40 pilot stock, so that is factored in the equation, even though i installed the 2.0 airjet to fill the gaping airjetless hole the carbs came w/.  Lyn G. runs as  large as a 55 pilot in his street bike...most likely the ethanol content affecting it in the gas is my guess.  I do find that the P-5 needle jet in  my daytona is just about right, probably would be smaller if the gas wasn't so alcoholic.  P-4 should be enough for the standard RD400 though.

keep in mind that a COLD RD properly jetted will be rich until the oil in the bottom end is blown out and it warms up to full operating temp.  You don't want to jet for the run to the local Albertson's.  You want to jet for the GP runs in the backroads a full hour away.  When you have it jetted for those conditions, it's right.  It will run a slightly rich in town, but will kick ass on the backroads.

The extra fuel might make your plugs darker, but it will also help keep your motor cool and really helps in the midrange.  Both plusses in my book.  I can deal with changing REGULAR spark plugs every month or so.  You don't need the fancy plugs.  Might as well save a few bucks.  The only plugs i would spen money on are the gold palladium style where the electrode melts before the piston does...I don'tknow if you can find those anymore, but B8ES to B9ES is fine.  if you are just the average rider, then B8ES should be all you need, might foul a B9ES.



« Last Edit: April 29, 2009, 01:43:07 PM by GSXRDman »
RD400F modded to RD400 specs, 29.3mm R5 carbs, 240 mains, 2mm shroud 169-P2 needle jet, 5DP7-5 (full rich), stock R5 slides (2.0), #30 pilot @ 7/8ths airscrews.  2010 Spec II "classics", Y-boot UNI, TDR yellow one piece reeds, B9ES plugs / stock gap, 1.9mm BTDC.  Amsoil Interceptor 24:1, pingel tap!