Author Topic: Strange sound from exhaust  (Read 345 times)

Offline bigmike76

  • Moving Up
  • **
  • Join Date: Aug 2012
  • Posts: 13
  • Karma: 0
Strange sound from exhaust
« on: 06.06. 2019 15:08 »
Hi, I don't know if anyone has come across this before? I have an A10 with electronic ignition fitted, on tick over when I advance the timing you start to hear a black sound like the exhaust valve shutting, if I retard it the sound disappears. Could this be something to do with the waisted spark system on electronic ignition? The bike seems sluggish in the retarded position, and a lot better in the advanced but with a funny clacking sound. Any idea what's going on?

Online muskrat

  • Global Moderator
  • Wise & Enlightened
  • **
  • Join Date: Jul 2009
  • Posts: 8233
  • Karma: 106
  • Lake Conjola NSW Oz
    • Shoalhaven Classic Motorcycle Club Inc
Re: Strange sound from exhaust
« Reply #1 on: 06.06. 2019 21:15 »
G'day Mike.
Both mine have Boyer ignition but I can't say I hear anything disturbing. But then I just set it with a strobe light and don't fiddle with it.
Can you do a video for us to listen?
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Online Triton Thrasher

  • Scotland
  • Wise & Enlightened
  • *
  • Join Date: Feb 2009
  • Posts: 1497
  • Karma: 20
Re: Strange sound from exhaust
« Reply #2 on: 06.06. 2019 21:33 »
Normal riding is done at full advance.

Retarding slightly may help the idle and very slow riding in traffic jams.

Online terryg

  • Valued Contributor
  • ****
  • Join Date: Nov 2012
  • Posts: 459
  • Karma: 6
    • thecarshipenterprise
Re: Strange sound from exhaust
« Reply #3 on: 06.06. 2019 22:28 »
I would be checking the timing, just in case it's been set a little too far advanced and what you're hearing is pinking when you advance it further.
Terry
'57 'SR', '59 SR, '63 RGS

Offline Swarfcut

  • Wise & Enlightened
  • *
  • Join Date: Oct 2018
  • Posts: 1022
  • Karma: 12
Re: Strange sound from exhaust
« Reply #4 on: 07.06. 2019 08:55 »
    I understand some electronic systems incorporate the advance curve within the  control box. Any chance this is happening here, and that despite setting the timing correctly at full manual advance, once running the control box is  advancing the ignition as normal and the noise is simply a big dose of pre-ignition pinking (pinging) when you add more with the manual control.
  Just a guess, not knowing which ignition system you have, and for how long it has been fitted, and if these symptoms are something new.  I would check whether or not it needs a manual control.
 Symptoms would indicate either the timing is incorrect, as the noise is exacerbated by advancing the ignition, or a mechanical fault made worse by adding advance.  Checking the timing is as it should be is the main priority.
 The wasted spark is of no consequence, firing as it does at the end of an exhaust stroke.

 Swarfy.

 

 ,

Online muskrat

  • Global Moderator
  • Wise & Enlightened
  • **
  • Join Date: Jul 2009
  • Posts: 8233
  • Karma: 106
  • Lake Conjola NSW Oz
    • Shoalhaven Classic Motorcycle Club Inc
Re: Strange sound from exhaust
« Reply #5 on: 07.06. 2019 09:50 »
G'day Mike.
Trying to set the timing the old fashioned way on electronic ignition only gets you close but no cigar. measuring piston height with a pencil down the plug hole then spotting the center of the screw through a hole in the timing plate is fraught with inaccuracies.
I have a degree disc behind the cush nut marked in 5 degree increments (about 1/8" apart on a 3" disc) and a pointer. Find TDC and mark disc, at 30 and 35 degrees anti clockwise from TDC mark is where your timing should be (depending on tune and fuel) with a strobe light at full advance. Set and forget. Mine get checked once a year or anytime the primary cover comes off. Ha, no need on my cafe.
Cheers 
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Online Angus

  • Suffolk, UK
  • Resident Legend
  • *****
  • Join Date: Nov 2012
  • Posts: 501
  • Karma: 10
  • The A7
Re: Strange sound from exhaust
« Reply #6 on: 07.06. 2019 10:31 »
Sorry off topic Musky how did you get that Rclip in there. I have to beat a thin split pin in and it bends to hell on the A10. Usually takes two or three failed attempts and knackered split pins before I get one in. Nut done up to 65ftp + a little.
1961 A7 since 1976
1960 A10 Gold Flash Super Profile Bike
1958 Matchless G80 Project
1952 Norton Model 7 Plunger
1950 T100

Online muskrat

  • Global Moderator
  • Wise & Enlightened
  • **
  • Join Date: Jul 2009
  • Posts: 8233
  • Karma: 106
  • Lake Conjola NSW Oz
    • Shoalhaven Classic Motorcycle Club Inc
Re: Strange sound from exhaust
« Reply #7 on: 07.06. 2019 20:58 »
G'day Angus.
It's a real wiggle. It all depends how close to the nut the hole is. A lot I've seen the hole is outwards of the nut needing a washer behind the split pin. You could turn a few thou off the back of the nut if the hole is too close.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7