Author Topic: popping on decelleration (Read 4528 times)

MMICAFE · « **on:** June 24, 2009, 08:45:50 PM »

ok i just got some new spark plugs the ngk d8ea or what ever is the recomended midrange plug per honda specs i set the gap to .06 on all the plugs and im still getting popping on decelleration im confused by this i cant remeber what it is that im supposed to do mess with the idle mixture screw or the jets some one help me out im in newb mode right now

CBGhia · « **Reply #1 on:** June 24, 2009, 08:52:37 PM »

The D8ea plugs are hotter plugs and it sounds like you may be a little lean, Try the d7ea plugs and see if that richens things up enough to help.

MMICAFE · « **Reply #2 on:** June 24, 2009, 10:10:05 PM »

i think i will try that but it seems like the popping is coming from the left side of the bike

OakBehringer · « **Reply #3 on:** June 24, 2009, 11:45:33 PM »

Classic lean condition symptom. Can you read your plugs? Helps to know if they're all lean...

Hush · « **Reply #4 on:** June 25, 2009, 12:27:38 AM »

Lean

WHALEMAN · « **Reply #5 on:** June 25, 2009, 04:15:50 AM »

I thought popping on deceleration was also a sign of an exhaust header leak. Dan

CBGhia · « **Reply #6 on:** June 25, 2009, 05:03:05 AM »

It can be as an exhaust leak would cause a lean condition as well.

Since it is popping only on the left side, you may want to look for any exhaust leaks on that side. Look under your pipes as well. You could have a hole there that is causing it.

fishhead · « **Reply #7 on:** June 25, 2009, 05:05:15 AM »

On the 1979 650, on the left side of each carb under a cover with 2 screws there is what is called a "cut off valve". It is a diaphram type thing that should keep the popping on decelleration from happening.
It could be stuck or the diamphram could have holes in it. The most common "problem" I have seen with the cut off valves are the PO has sprayed carb cleaner through the passages and NOT removed the CO Valves, there by destroying the rubber of the diaphrams and making them useless.
You will need to seperate the rack to replace all 4 of the cut off valves (1 per carb).

Johnny5 · « **Reply #8 on:** June 25, 2009, 05:48:37 AM »

Quote from: CBGhia on June 24, 2009, 08:52:37 PM

The D8ea plugs are hotter plugs and it sounds like you may be a little lean, Try the d7ea plugs and see if that richens things up enough to help.

I believe the D7ea are hotter than the D8's. The lower the number, the hotter the plug.

tsflstb · « **Reply #9 on:** June 25, 2009, 06:39:06 AM »

Don't mean to come in with my own problems, but this might help the original poster also. Which part of the carb circuit affects this? Popping seems to occur more when I'm rolling off from higher RPMs on my 400F with mechanical slide carbs.

I just replaced my exhaust gaskets to eliminate any leaks. I also raised my carb needles by one clip to see if it was a lean condition even though my plugs looked like the mixuture was fine. Synchronized the carbs afterwards and it still sounds like the 4th of July when I roll off the throttle. Should I play with the air screws?

MCRider · « **Reply #10 on:** June 25, 2009, 06:42:32 AM »

Quote from: Johnny5 on June 25, 2009, 05:48:37 AM

Quote from: CBGhia on June 24, 2009, 08:52:37 PM
The D8ea plugs are hotter plugs and it sounds like you may be a little lean, Try the d7ea plugs and see if that richens things up enough to help.

I believe the D7ea are hotter than the D8's. The lower the number, the hotter the plug.

Yes 7 hotter than 8. 8s are standard on CB750, don't know about 650s.

cxtecs · « **Reply #11 on:** June 25, 2009, 07:13:24 PM »

Are you guys also getting any popping or burbling while its just idling?

MMICAFE · « **Reply #12 on:** June 25, 2009, 07:33:12 PM »

nope just on decell

Clyde · « **Reply #13 on:** June 25, 2009, 10:08:58 PM »

Try closing the mixture screw by 1/4-1/2T on the side/cylinder that is popping. This will richen it slightly and could stop the popping

CBGhia · « **Reply #14 on:** June 26, 2009, 03:37:59 PM »

Quote from: MCRider on June 25, 2009, 06:42:32 AM

Quote from: Johnny5 on June 25, 2009, 05:48:37 AM
Quote from: CBGhia on June 24, 2009, 08:52:37 PM
The D8ea plugs are hotter plugs and it sounds like you may be a little lean, Try the d7ea plugs and see if that richens things up enough to help.

I believe the D7ea are hotter than the D8's. The lower the number, the hotter the plug.
Yes 7 hotter than 8. 8s are standard on CB750, don't know about 650s.

Well damn, I had it backwards. I need to swap my plugs then.

fmctm1sw · « **Reply #15 on:** June 26, 2009, 05:11:39 PM »

I also vote lean mixture. Try richening up tour idle circuit...

Pirateonjerseyshore · « **Reply #16 on:** June 28, 2009, 07:36:55 AM »

My cb550 pops alittle on deceleration but i think it's because i put a new muffler on and there isn't that much back pressure now. I'm pretty sure i need to get the carbs adjusted so it will be in sync with the new muffler.

Clyde · « **Reply #17 on:** June 29, 2009, 06:35:58 PM »

Quote from: Clyde on June 25, 2009, 10:08:58 PM

Try closing the mixture screw by 1/4-1/2T on the side/cylinder that is popping. This will richen it slightly and could stop the popping

Did you try this?

Pirateonjerseyshore · « **Reply #18 on:** July 03, 2009, 11:21:37 AM »

I have not tried that yet but will now! Thanks.

WFO · « **Reply #19 on:** July 03, 2009, 12:21:02 PM »

Try turning the pilot screws out a little and see if that helps also a fresh set of plugs well help tell you if you are running lean try a plug chop first and see where you at at then go from there.

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Author Topic: popping on decelleration (Read 4528 times)

WHALEMAN