deceleration backfire solved

[muaymendez1]

So again, this bike is new to me. 99 venture. It had an annoying afterburn pop in the mufflers. Like an old harley.

 

After the valve adjustment , some basic, carb clean( lazyman) and k&n filter clean and recharge. No more afterburn.

Don't know which did it, but it's done.

[kevin-vic-b.c.]

Good on you... do keep us in the loop as to if it stays away.

 

I have done the seafoam cleaning... a few cans, carb sync, valve adjust, AIS disconnect, and removed K&N for stock style replacement filters and the back fire as bad as ever if not worse. It goes to mechanic next week for the carb adjusting and re-sync.

 

Hopin

[cowpuc]

Hey Muay,, if it turns out that the popping comes back another thing to check for is idling to low and exhaust leak.. Even the smallest gasket leak in the exhaust system can cause symptoms like you are describing....

Puc

[muaymendez1]

When I took things apart lots of stuff wasn't snug. I took the time to put a thin film of rtv on every connection except carb to intake.

Rechecked the floats, cleaned and used dielectric on plug boots ,Ais ,is plugged, andasjusted valves toloose side of the allowance.

The K&Ns were also black. I don't think the P.O ever serviced them. As I said before, he wasn't much for preventive maintenance.

I used the clean and recharge kit, it is red or pink in color and breathes better.

Will ride her soon to see if any more kinks develop. Small problem is that I destroyed a coolant hose and need to replace before any rides. She's is just put together temporarily.

[steamer]

look for pin hole leaks in the rear Y pipes, these pipes seem to rust out faster then the front pipes. I believe they are made out of a different material.

[Squidley]

I have had many time doing a carb sync on other members bikes has taken the popping away. It's not a fool proof thing, and leaks in the exhaust as others have mentioned will cause this popping. A good carb sync is a good and easy place to start....

[KIC]

Why does a pin hole in the exhaust cause popping ? I would think that even on deceleration there is positive pressure in the pipes and not a back pressure that could affect the combustion in the cylinder.

 

The 2nd Gen I am bike sitting has a very bad case of back firing when decelerating. I am going to sync the carbs for him, but will also look for the other causes.

[muaymendez1]

Why does a pin hole in the exhaust cause popping ? I would think that even on deceleration there is positive pressure in the pipes and not a back pressure that could affect the combustion in the cylinder.

 

The 2nd Gen I am bike sitting has a very bad case of back firing when decelerating. I am going to sync the carbs for him, but will also look for the other causes.

 

Kic. Unburned fuel or even flamable gasses escape the combustion chamber on the exhaust stroke. Allowing cool oxygen to the hot pipe will cause the carbonmonoxide and flammable gas to BREATH causing an Afterburn explosion. It is not a backfire.

The two are different

[Bones158]

On my 05 Venture when I had the popping on decell and could not figure what was causing it, I turned the PMS (Pilot mixture screws) out 1/4 turn on each carb. They come set from the factory on the lean side to meet emission tests. Stopped it in it's tracks.

[cowpuc]

Riding next to my cousin one time,, he was on his old Virago 1100, I pointed across his shoulders, he looked away for a second and I reached over and hit his kill switch.. We were doing about 70,, slowed way way down - down shifting trying to get his bike started,, I laughed and pointed at his kill switch, he bumped it on and KAAAAAAA - BOOM, blew off a muff :rotf::rotf::rotf:

Tried to catch me but aint no way no how no chance no Virago is gonna catch a 1st Gen,, even with no second gear

[muaymendez1]

On my 05 Venture when I had the popping on decell and could not figure what was causing it, I turned the PMS (Pilot mixture screws) out 1/4 turn on each carb. They come set from the factory on the lean side to meet emission tests. Stopped it in it's tracks.

so the popping cameback with avengeance. Someone riding behind me said they smell raw fuel. I am getting 42 mpg and the bike runs fine. So I decided to mess with the poilot mixture screws. the left side was 1/2 turn from being seated. I know cause I turned 1/2 turn and they were seated. The right side I turned 2 full turns before noticing a drop in rpm Like it was gonna vut off.

Where is a good place to start on these screws.

I thought leaner was better. too rich causes popping?

[Peder_y2k]

Too lean causes popping.......lean causes unburned fuel mix to enter exhaust....then when it is exposed to open flame from another cylinder....KA BAAAM!!

-Pete, in Tacoma WA USA

[kevin-vic-b.c.]

I know little to nothing about "setting up" carbs. I have been battling this for about a year since I bought my 02. valve adjust, carb sync, exhaust gaskets, AIS disconnect and then had local mechanical shop "adjust" carbs and re sync carbs.

I am told the screws are "normally" 2.5 turns out, mine are now about 4.5 turns out and there is no longer any backfire from the bike.

Don't know or really care what it does to my fuel mileage, no more backfire.

 

Take it for what it is worth.

[VentureFar]

Riding next to my cousin one time,, he was on his old Virago 1100, I pointed across his shoulders, he looked away for a second and I reached over and hit his kill switch.. We were doing about 70,, slowed way way down - down shifting trying to get his bike started,, I laughed and pointed at his kill switch, he bumped it on and KAAAAAAA - BOOM, blew off a muff :rotf::rotf::rotf:

Tried to catch me but aint no way no how no chance no Virago is gonna catch a 1st Gen,, even with no second gear

I am not sure when I will stop laughing, I hope soon because my ribs are hurting something awful ! Now here come the tears. I don't know what it is but you crack me up.

See you soon my friend.

VentureFar...

[muaymendez1]

I know little to nothing about "setting up" carbs. I have been battling this for about a year since I bought my 02. valve adjust, carb sync, exhaust gaskets, AIS disconnect and then had local mechanical shop "adjust" carbs and re sync carbs.

I am told the screws are "normally" 2.5 turns out, mine are now about 4.5 turns out and there is no longer any backfire from the bike.

Don't know or really care what it does to my fuel mileage, no more backfire.

 

Take it for what it is worth.

 

I'm up to 4 turns. Ill try another half. How soon before they fall out?

Still popping

[Neil86]

Before going to extreme on the pilot screws do an inspection of the caps or

hoses connected to the synch ports....if you tried using cheap caps

theres a good chance they are cracked and leaking vacuum, causing the exhaust

popping.

Most 'jobber" caps can't tolerate the heat and deteriorate quickly.

[muaymendez1]

I just replaced them but ill check

[The Tooch]

Riding next to my cousin one time,, he was on his old Virago 1100, I pointed across his shoulders, he looked away for a second and I reached over and hit his kill switch.. We were doing about 70,, slowed way way down - down shifting trying to get his bike started,, I laughed and pointed at his kill switch, he bumped it on and KAAAAAAA - BOOM, blew off a muff :rotf::rotf::rotf:

Tried to catch me but aint no way no how no chance no Virago is gonna catch a 1st Gen,, even with no second gear

 

Now Puc you reminded me of something I hadn't thought of in years.

Back during the recession of the 80's the powers that be decided to try and save some money on gas by switching our fleet of cars at work over to propane. Well don't know who the 1st guy was to discover this but it wasn't very long before it spread like wild-fire. If you got the cars up to speed, say 55 mph, then bumped her up into neutral, shut the ignition off, let her coast, pumped the gas pedal like crazy and then reach down and turned the ignition back on to re-fire her.........BOOM! It would blow the bottom right out of the cadilitic converter. Well the fleet were new cars and of course they tried to get GM to fix them under warranty but GM blamed the company that did the conversions from gasoline to propane. The propane conversion company couldn't figure it out.......We went back to gasoline cars!

[muaymendez1]

I just replaced them but ill check

So I cracked and pulled the carbs. Didn't see anything way off except right front carb float was high by a small amount.

7.5 mm. I moved it to 8.

All pilots set to 2.5 from seated. I'm gonna put them back in and see.

 

 

I'm also gonna plug the ais abd run some marvel. In the tank.

The carbs are really clean, no need for seafoam.

[Neil86]

You might want to check your mystery hose thread........

[muaymendez1]

connected the hose as it looks in manual pictures.

Here is my findings after re instralling the carb. front right carbs had little to no idle surge when turning the Pilot mixture screw. Plug is fine, FLoat level to 8mm. Carbs just cleaned , valves just done.

If I remove the vacuum caps on any cyl the idle drops and sounds like it will shut the engine off,

All except front right cyl. I pull the cap and no change in idle. There is vacuum pressure there.

STill a pop on decal although not as pronounced and not as many.

I also plugged the rear AIS as the front AIS has been removed.

[cowpuc]

I am not sure when I will stop laughing, I hope soon because my ribs are hurting something awful ! Now here come the tears. I don't know what it is but you crack me up.

See you soon my friend.

VentureFar...

 

Count on it VentureFar,, count on it!!!!

 

Now Puc you reminded me of something I hadn't thought of in years.

Back during the recession of the 80's the powers that be decided to try and save some money on gas by switching our fleet of cars at work over to propane. Well don't know who the 1st guy was to discover this but it wasn't very long before it spread like wild-fire. If you got the cars up to speed, say 55 mph, then bumped her up into neutral, shut the ignition off, let her coast, pumped the gas pedal like crazy and then reach down and turned the ignition back on to re-fire her.........BOOM! It would blow the bottom right out of the cadilitic converter. Well the fleet were new cars and of course they tried to get GM to fix them under warranty but GM blamed the company that did the conversions from gasoline to propane. The propane conversion company couldn't figure it out.......We went back to gasoline cars!

 

:rotf::rotf::rotf::rotf::rotf::rotf:

 

Tooch,,, now you reminded me of one I hadnt thought of in years... Back in the early 70's I worked for a company who manufactured pneumatic tools in their maintenance dept.. One of my buds there almost knocked one of my Oxy/Acetylene tanks over and I yelped at him,, he's like - whaaaatt, its just oxygen,, whats the big deal.. I said Oxy under a LOT of pressure,, besides combine oxy with acetylene and this stuff will blow like you cant imagine.. Lunch time came around, he wondered back in the shop and I said, come here,, I wanna show you something.. Took a condom out of my wallet (he stared at me really funny), put it over a torch, hit a good mix on the torch, blew that baby up till it was about 5 feet long (stop laughing VentureFar), tied it off, took it outside (working third shift so this was like 3 a.m.), took a few feet of masking tape, taped the condom to the wall under the lunch room area, left a few feet of masking tape hanging down, lit the masking tape "fuse" and ran back inside......

Stood by the lunch room door as the people were leaving thinking they were under attack,, walked in the lunch room - finished off eating a few vacated burgers,, looked at my unbelieving buddy and said - "now ya know".....

[muaymendez1]

Ok. Complete. After rewelding pipe on my exhaust system I found that the rear header pipe was slipping in and out of the system. I tightened that and no more pop.

 

[ATTACH]84630[/ATTACH]

[kevin-vic-b.c.]

Ok. Complete. After rewelding pipe on my exhaust system I found that the rear header pipe was slipping in and out of the system. I tightened that and no more pop.

 

How do you mean that it was slipping in and out of the system?

I have not had any backfiring other than a minor poof a couple times.

[muaymendez1]

Ok sorry for the lakee explanation. I went for weeks changing the mixture screw and in the midst of trying to solve the popping my left muffler rusted. Actually the muffler was fine the pipe rotted. I had the system completely off to repair and while ready to install the rear header rell out. Luckily the gasket was not damaged . I skipped it back in. And crashed the bolt another full turn which kept it tight.

It made me think if it was loose on one side it may be loose on the other side. I called it 1 1/2 turns abd violla. No more popping and my exhaust is repaired.

Whos so happy? This guy, that's who.