Back firing and popping and farting on decelaration manly in 1,2,3 gear

[WIDELANE]

Good afternoon all, I am a new member and new to Valkyrie riding. I have a 1998 F6 from the eastern states and has 34,500 miles on it. When I am decelerating and going down a hill manly in 1,2,3, gear the bike pops, farts and sometimes backfires out the exduast. I have changed the plugs oil and filter but to none the better. I run top grade gas with 104 octane booster, 1 oz per tank full. Any one got any thoughts?

[Bighead]

Stock exhaust?

[nogrey]

Thoughts? Oh, you'll get lots of thought here! Welcome aboard!
Typically, popping, and backfiring are caused by a few things.
Farting, well, that sounds like a personal problem and we won't go into it here!  
Back to the popping and backfiring. In my experience, this is due to too lean of a fuel mixture during decal. The question above asking if you have a stock exhaust is VERY pertinent, because aftermarket exhausts typically reduce back pressure, and cause lean fuel mixture issues during decal.
Basically, what we're talking about here is pilot screw adjustment, or possibly slow jets.
Also, let me advise you, that 87 octane for these girls is just fine. No need to plunk down all that extra money for higher octane. If you can get non-ethanol fuel, all the better.
Also, there are six "air cutoff" valves, one per carb, that control air mixture on decel. If the hoses on those are cracked and leaking, this can also cause this issue.
Please answer the question regarding exhaust. And check the hoses to the cutoff valves.

[Chrisj CMA]

simple things first, sounds like cracked vacuum lines.  The two lines that go from the center intakes to  a "T" connector typically are the ones that need changing.  Id check the screws holding the clamps for the intake runners (18 in all) and also the header nuts, careful on these they don't need to be real tight or they break, just snug.

You check all that, and I think you will solve it

[Mtn Valk]

I know this won't solve your problem with the popping but you will hear this more than once, with 97 octane it seems as if mine runs a bit smoother. I ran Chevron premium for the first year, then I learned from the board that regular was the absolute best, just as Nogrey stated in a previous post.

[Jess from VA]

I know this won't solve your problem with the popping but you will hear this more than once, with 97 octane it seems as if mine runs a bit smoother. I ran Chevron premium for the first year, then I learned from the board that regular was the absolute best, just as Nogrey stated in a previous post.

Unless you have a modified ignition or trigger wheel.

[nogrey]

simple things first, sounds like cracked vacuum lines.  The two lines that go from the center intakes to  a "T" connector typically are the ones that need changing.  Id check the screws holding the clamps for the intake runners (18 in all) and also the header nuts, careful on these they don't need to be real tight or they break, just snug.

You check all that, and I think you will solve it

not to be contrary, while it is true that a vacuum leak can cause popping on decel, the most noticeable issue is poor idle and poor low speed performance, neither of which were mentioned. If low speed performance and poor idle ARE also an issue, then yes, there may very well be a vacuum leak.

[WIDELANE]

thanks for all the response folks. ok I just went and checked the exhaust system out, it appears to be a stock Honda system as I found "HONDA SANI<EI 2345" on the stainless steel muffler and attached to the end of that is a 4" by 18" chrome hollow pipe. I can see the baffles in the muffler and it all looks good.

[Bighead]

The pipes have at least been modified. So the sounds you are describing could be a result of the mods. How long have you had the bike and has it done it the whole time you have owned it?
The 4"x18"pipe is not stock but a tRuck stack added so previous owner may have also modified the muffler itself.

[WIDELANE]

I have only had the bike since Aug16/14 and yes it has done it the hole time, we have oly put on about 1200 miles. do you think a set of stock tips may help and can I ask on this forum to see if there are any for sale. Now that I think about it that 4" 18" long hollow pipi would just act like a mega phone.

[nogrey]

You can go to the classifieds and place a "wanted to buy" post there. Stock pipes are also available on flea-bay. If you don't like the way it sounds, that may be the way to go anyway. If you are pleased with the sound and the performance is nominal, then you might just re-jet it with #38 slow jets. It would cost you about $35 if you do it yourself (it's easy).
http://www.chaparral-racing.com/Product/keihin-slow-jet/SD-19005.aspx

[biguglyman]

Almost all my popping on decel disappeared after I desmogged.

[hubcapsc]

I think you have a real simple problem, a vacuum leak somewhere. There's only
a few hoses to check and perhaps the exhaust gaskets are leaking (they go tick tick tick,
some people kind of sound like that when they're farting  )...

The hoses or caps on the backs of each of those chrome intakes are big suspects.

Inside that hollow can, you want to see "piggies"...



Some people cut them off...



Cutting them changes the sound (I don't like it personally) but doesn't
make the burps and backfires you're hearing...

-Mike

[Chrisj CMA]

I think you have a real simple problem, a vacuum leak somewhere. There's only
a few hoses to check and perhaps the exhaust gaskets are leaking (they go tick tick tick,
some people kind of sound like that when they're farting  )...

The hoses or caps on the backs of each of those chrome intakes are big suspects.

Inside that hollow can, you want to see "piggies"...



Some people cut them off...



Cutting them changes the sound (I don't like it personally) but doesn't
make the burps and backfires you're hearing...

-Mike

exactly right mike.  thanks for adding in the caps on the unused nipples, many overlook those and they can cause the popping too.  To the OP, someone said you don't have a vacuum leak if there is no idle problem or performance issue.  This is false, most that eventually change out cracked vacuum lines live with the popping for a long time before they actually change stuff BECAUSE its still running so good they think its not a big deal.  Mine were cracked where there was a 3" split in one and the bike ran great (except for the popping)

[Bighead]

I will almost bet it is nothing more than the modification,the reason I state this is if I am going down a steep hill in 2-3 gears on either of my Valks the back pressure on exhaust can be heard as a popping sound not loud but can be heard so if the muffler had been messed with it would sound much louder and cause the same as he is describing. And would bet this is what he is hearing.
And yes go to classifieds or eBay you can find stock exhaust but they won't be cheap.

[WIDELANE]

Thanks guys for all the info,
 I Think  will ride it and put up with the noise for the rest of this season and look into it this winter. We only have about 1 month of riding left before it gets 2 cold here in Britannia beach BC.

[WIDELANE]

Hey guys,
Upon further investigation I have found that the 3 longer pcs of  pipe that stick out of the back of the muffler have been butchered out and the 3 short stubs that would be left after cutting off the pipes have been drilled out and the pipes have been removed from the Honda muffler. next time I get into it I will take and post some pics. Hope you all have a good week end.
lane   

[eight_pockets]

I have a similar problem, and from reading here it is either:
- pipes (I believe mine are fully stock)
- vacuum leak
- o2 adjustment
- fuel grade (I don't think so...but I'm no expert).

My question is: should I fix it?  Driving old cars most my life, I've learned sometimes it's best to not mess with things if they are still working fine.  What do you think? Will it lead to other problems?

[R J]

I know this won't solve your problem with the popping but you will hear this more than once, with 97 octane it seems as if mine runs a bit smoother. I ran Chevron premium for the first year, then I learned from the board that regular was the absolute best, just as Nogrey stated in a previous post.

Unless you have a modified ignition or trigger wheel.

I run a 6* trigger wheel in MGM and still run on 87 octane with no popping & farting as you say.

Check all vacuum hoses.     Sounds like they need to be replaced.     I replace mine about every 12 months.    That cured all that popping & farting on MGM several years and miles ago.    MGM currently has 243K+ miles on the clock.

[Yfx4]

I realize they are different bikes but the principles are the same.

On my VTX1800 the desmog cured the decel popping which was most noticable at low gears. The pooping returned when I had a slightly loose exhaust pipe so was getting air in the hot exhaust--pop.pop.pop.

Air getting into the hot exhaust lets the unburned fuel from the cylinders, esp during deceleration, burn in the pipes causing the popping. Not to say that this is the only reason.