collapse

www.dimecitycycles.com


www.restocycle.com

www.CITYLIMITMOTO.com

www.jadusmotorcycleparts.com

www.bisonmotorsports.com

www.speedmotoco.com

www.cognitomoto.com

www.townmoto.com

www.sparckmoto.com

www.Moto-Madness.com

www.pistonsociety.com

www.steeltowngarage.com


Author Topic: CB350 Popping on deacceleration  (Read 1022 times)

Offline plyzo

  • Posts: 230
  • 1970 Honda CL 350
    • Plyzo Studios
CB350 Popping on deacceleration
« on: Jun 17, 2017, 02:59:48 »
I just finished an engine rebuild and got the bike running through idle to full rev with no problems. One thing I am having an issue with is on deaccerlation I get tons of popping. The plugs don't look lean or rich but will post a pic to show the group.

I am running Mikuni vm30 with filters and custom exhaust 2 into 1.

Slides: 2.5
Needle: 6F4
Needle Jet: 159-p4
Pilot Jet: 22.5
Main Jet: 170
Jet Needle clip: 2nd position from top


I am wondering if it is still running rich where should I start in making the system rich. The pilot jet first?




Sent from my iPhone using DO THE TON

Offline plyzo

  • Posts: 230
  • 1970 Honda CL 350
    • Plyzo Studios
Re: CB350 Popping on deacceleration
« Reply #1 on: Jun 17, 2017, 03:00:37 »



Sent from my iPhone using DO THE TON

Offline plyzo

  • Posts: 230
  • 1970 Honda CL 350
    • Plyzo Studios
Re: CB350 Popping on deacceleration
« Reply #2 on: Jun 17, 2017, 03:02:37 »



Sent from my iPhone using DO THE TON

Offline trek97

  • DTT SUPPORTER
  • *
  • DTT BOTM WINNER
  • *
  • Posts: 5178
Re: CB350 Popping on deacceleration
« Reply #3 on: Jun 17, 2017, 06:11:22 »
Popping on decel is completely normal for any carbureted engine. "Engine braking".  It is a lean condition caused by rolling off the throttle (closing butterflies) and cutting off the air, using the engine vacuum to slow down.  Its simply more noticeable w some exhaust systems than others.

If you pull in the clutch while decelerating the popping will stop, because the engine rpms will quickly drop to normal idle.

If you try to overcome the popping through jetting or A/F adjustment you will probably find it runs too rich at idle and carbon fouls plugs.

The exhaust on your bike is pretty neat looking.  May need to add some heat shielding.  :o 

If you find you have rich issues w the right carb.  You may find its boiling fuel in the bowl.
« Last Edit: Jun 17, 2017, 15:01:16 by trek97 »

Offline plyzo

  • Posts: 230
  • 1970 Honda CL 350
    • Plyzo Studios
Re: CB350 Popping on deacceleration
« Reply #4 on: Jun 17, 2017, 14:23:26 »
Thanks Trek for the info. It doesn't pop as much when I pull in the clutch.


Sent from my iPhone using DO THE TON

Offline trek97

  • DTT SUPPORTER
  • *
  • DTT BOTM WINNER
  • *
  • Posts: 5178
Re: CB350 Popping on deacceleration
« Reply #5 on: Jun 17, 2017, 15:01:47 »
 ;)

Offline teazer

  • DTT SUPPORTER
  • *
  • DTT BOTM WINNER
  • *
  • Posts: 8200
Re: CB350 Popping on deacceleration
« Reply #6 on: Jun 17, 2017, 15:44:40 »
Popping is usually the result of an air leak in the exhaust allowing unburned furl to ignite.

Try sealing the joints in that beautiful exhaust and see if that helps

Offline plyzo

  • Posts: 230
  • 1970 Honda CL 350
    • Plyzo Studios
Re: CB350 Popping on deacceleration
« Reply #7 on: Jun 17, 2017, 15:54:40 »
Teazer: I put the clamps on there to help with that on the jointing areas.


Sent from my iPhone using DO THE TON

Offline CrabsAndCylinders

  • DTT SUPPORTER
  • *
  • Posts: 1561
  • Careful With That Axe Eugene
Re: CB350 Popping on deacceleration
« Reply #8 on: Jun 17, 2017, 16:16:52 »
I have to add, that is one beautiful exhaust.
Lighter, Quicker, Faster.
ZX-14, 900F x 2, 1100F, R100, CBR600, SR500, GT500, RZ350, KZ1000 x 2, Moto Guzzi Lemans lll, CBX550, RD 350, 750 SOHC police special, RG250, TL1000R, GT750, KTM Super Duke 1290 R, Harris/Z-1, Norton 750 Commando, Green 77 KZ650

Offline CrabsAndCylinders

  • DTT SUPPORTER
  • *
  • Posts: 1561
  • Careful With That Axe Eugene
Re: CB350 Popping on deacceleration
« Reply #9 on: Jun 17, 2017, 16:29:00 »
It may just be that with that exhaust (which looks to be a loud one) popping that you could not hear before is now loud enough to annoy you.  You still should make sure that the exhaust is tight, from the exhaust seals to the last joint.
Lighter, Quicker, Faster.
ZX-14, 900F x 2, 1100F, R100, CBR600, SR500, GT500, RZ350, KZ1000 x 2, Moto Guzzi Lemans lll, CBX550, RD 350, 750 SOHC police special, RG250, TL1000R, GT750, KTM Super Duke 1290 R, Harris/Z-1, Norton 750 Commando, Green 77 KZ650