Removing the Backfire on a VTX1300 Motor Trike...

skuuter · Mar 18, 2012

Mitzie's Honda VTX1300R Motor Trike with the stock/as provided twin mufflers, has always had a very annoying "backfire issue" going down mountain grades and any remotely abrupt roll off the throttle. The sound is fairly loud also. I cured this 100% with a set of Fiberglass Packed Baffles (Part # 1524) from Parts Unlimited. These are actually manufactured/marketed by Cycle Shack, Inc. They are 1-3/4" size, and fit correctly in the Motor Trike provided mufflers. I've had several PMs about this annoying problem, so decided to post this thread after extensive testing. 
 
These provided a deep, mellower exhaust note, and the Trike has NEVER backfired since under any conditions. We rode the Mountains and a lot of "Country Twisties" yesterday afternoon...CURED...!!! 
 
Installation is very simple, requiring only a couple of 7/16" wrenches and a Drill with a 1/4" bit. Wrap "ALL" of the provided packing around the Baffles. Slide Them into the Mufflers with the open side of the perforations toward the engine and the closed side facing out. HINT: If You're having a hard time getting Them to slide in, wet the Fiberglass Packing and press it down.

The Hot Exhaust will dry and fluff it back out in a minute of idling. Next drill a 1/4" hole through the muffler and baffle. Keep this hole close to the tip of the muffler, as in maybe a 1/2" from the opening to simlify bolt installation. Next push the Included Bolts through the hole from the inside of the Muffler to the outside, and tightening the Provided Locknuts (yes, they are locknuts...they look like standards, but notice the tiny rectangular crimps/they won't vibrate off)......Your Neighbors and Their Dogs will Thank You, and No More Cannon-Sounding Backfiring...I purchased These at Our Local Honda Dealer, and depending on Your "Friendship With Your Dealer Status", should be purchased in the $30 to $40 Range for a Pair (They are sold seperately). When I get a chance, I'll take and post a Pic...I hope this Helped some of You.....<img src="images/smilies/thumbup.gif" border="0" alt="" title="ThumbUp" class="inlineimg" />

skuuter · Mar 19, 2012

VERY Successful Fix Folks.....over 1000 miles since doing this, and not a single backfire...much quieter, but still with a lot of "character" left in the exhaust note.....ThumbUp :10:

skuuter · Mar 30, 2012

If Anyone gets around to trying this, post up Your results.....Mitzie's still hasn't backfired yet.....ThumbUp

Ol' Grey · Mar 30, 2012

Good on ya, "skuuter"! Sounds like a solid and straightforward fix ThumbUp

When you say "backfire", was it like a true backfire (sounding like a gun shot) or a series of loud "popping" ?

Reason I ask is that it's common for there to be popping on decel or off throttle, the popping being caused by traces of unburnt fuel igniting inside the hot exhaust pipes. The popping can be more noticeable with open pipes or mufflers that aren't adequately designed. In reality, on a bone stock machine without any exhaust/muffler mods, the post-exhaust stroke trace ignitions inside the exhaust pipes are happening, but good quality mufflers "muffle" the popping sounds and the rider won't hear them.

Am wondering if by adding the fiberglass packing, you essentially succeeded in muffling the sound. Again, trace ignitions could still be happening, which is normal, but you may have dampened/removed the audible noise annoyance....

Either way, glad you got it managed and Ride Safe..........

Veritas44 · Mar 31, 2012

Ditto to Ol' Grey... 
That is the A.I.S. (Air Injection System) that is inherent on newer Honda Cruisers (Shadows & VTX). It is part of the emissions junk the manufacturers are required to install. It is typically located behind the carb(s) under the seat area and looks like a valve assembly with 3-4 hoses approx 3/4" O.D. It senses the abrupt decel/throttle-down and injects hot air into the header to burn the excess unfired fuel that has already entered the combustion chamber and is expelled when throttle down ends/retards the plugs firing. This ignites that unfired fuel in the exhaust pipes. As Ol' Grey said it sounds like a high-pitched "rice-burner/fast-n-furious" car exhaust popping and may do it only once or several times depending on how abrupt you have rolled off throttle. If that is it, you can disable it easily which will eliminate that and also provide a more pleasing "throaty" overall sound to your exhaust. Just plug the inlet side of the valve and bypassed. Then remove all the packing you put in the baffles. Easier than complete removal and easily reversed if you ever want or need to. 
 
Gotta be careful when tweaking, adding, and deleting from the air-fuel-exhaust system.

They are highly linked and symbiotic in relation in that one small change (adding stuffing to a baffle) can disrupt the entire system robbing horsepower, torque, inefficiencies in fuel economy and damage to the overall powertrain. Baffles are commonly misunderstood and generally overlooked in their importance to performance. Too little (removal of baffle) can retard the scavenging and negatively effect HP/TQ and too much can do the inverse and also damage the engine. No offense but believe you are treating the symptoms and effects not the root cause and in doing so may be creating another issue(s) with increased undesirable ramifications. Try disabng the AIS, remove the packing and add a tuned baffle such as the BCT-Big City Thunder. 
 
If it is a True Backfire, then you need to tune or re-jet your carb(s) and I would also suggest modifying the Air intake and filter system prior to doing that. If you have the time and means it is actually more desirable to tweak the whole system at once by changing the exhaust and/or baffles, the Air induction system (K&N & Hyper or Tornado intake) then re-jetting and tuning. You will love the effects and that will definitely solve the cause of your backfire plus increase the efficiency of your engine giving you more HP & TQ to the ground without cracking the jugs. Now that it is a trike, the more the merrier. Well, Trike or Not... More power is always better especially when the cost is low comparably.

Ol' Grey · Mar 31, 2012

Excellent post, Veritas44, very thorough and well written ThumbUp

I know you understand the theory, but wanted to share a little add-on......The exhaust gases aren't running in a constant "stream" thru the exhaust pipes, but in a series of "pulses" as the exhaust valves open and close. One can get a sense of this by placing the palm of their hand near the end of the exhaust pipe and feel the rythmic puffing against their hand. Imagine someone blowing smoke rings. Each exhaust puff would be like a smoke ring with a certain amount of unspent fuel that can ignite.

Many remember the homemade flame throwers for giggles 'n grins (something that looks impressive, but I wouldn't recommend). Folks would install a spark plug near the end of the exhaust and could direct current to fire the spark plug by flipping a toggle switch. Some might add a little more raw fuel in the mix to enhance the flame effect, hit the toggle switch, and the spark plug would ignite each puff as it was exiting the exhaust pipe, producing the spectacular flame throwing visual..........

skuuter · Apr 2, 2012

Great Posts from both of You (Ol' Grey and Veritas44)...THANKS, Really Good Contributions to this Thread....ThumbUp...having owned 2 VTX1300Cs in the past, and adding aftermarket exhaust to both, I've already been up the "carb-tune, air filter" etc. routes. I had already made carb adjustments, one hose removal, etc., etc. on Mitzie's Trike. Yes, it is/was a definite full-blown backfire. My other mods relieved it to the point of removal/almost removal except when the throttle was abruptly chopped shut, or winding down long mountain grades. The baffles cured it 100%...I put everything back completely stock and tried it with the Baffles to see if this worked solely on it's own merit before posting this Thread.....It did, so I posted this as a "quick fix" that is both simple and cost effective. She/We is/are still riding it this way.....ThumbUp

Ol' Grey · Apr 2, 2012

Thanx for the up-date, skuuter.........My concern was with the backfire vs. normal popping. Typically, a true backfire speaks of poor timing or serious air leaks, but neither of these appear to be the case as it's unlikely that the fiberglass packing alone would have eliminated those causes and it sounds like you and Mitzie are very happy with the results.

Guess it's possible that with a larger engine of 1300cc's and if the exhaust pipes are larger diameter such as 2", then what might be a "pop" on a smaller machine might be amplified to a backfire on Mitzie's.

Veritas44 is obviously more knowledgeable on the VTX's and if he concurs with what is only theory on my part, then Y'all might be good to go........ThumbUp

Ride Safe..........

skuuter · Apr 2, 2012

Ol' Grey said:
Thanx for the up-date, skuuter.........My concern was with the backfire vs. normal popping. Typically, a true backfire speaks of poor timing or serious air leaks, but neither of these appear to be the case as it's unlikely that the fiberglass packing alone would have eliminated those causes and it sounds like you and Mitzie are very happy with the results.

Guess it's possible that with a larger engine of 1300cc's and if the exhaust pipes are larger diameter such as 2", then what might be a "pop" on a smaller machine might be amplified to a backfire on Mitzie's.

Veritas44 is obviously more knowledgeable on the VTX's and if he concurs with what is only theory on my part, then Y'all might be good to go........ThumbUp

Ride Safe..........

Modern engines also tend to get more "valve overlap" than used to be the norm in the "Old School" engines also.....exhaust system changes can be very sensitive to them.....ThumbUp

Veritas44 · Apr 3, 2012

Interesting... Well, adding backpressure to the pipes by stuffing is retarding the exhaust side of the combustion process without a doubt. So, if it is really solving the backfire and not just masking/mostly eliminating the resultant effect (the noise) then it's definitely a timing issue and may be resolved by adjustment of the valves. That can be a tedious and trying exercise to say the least depending on your experience and how "virtuous<img src="images/smilies/grin.gif" border="0" alt="" title="big grin" class="inlineimg" />" your character. Combine that with the possibility that although probable it may not be the actual solution to the root cause, your efforts could be all for naught. However depending on mileage and time that valve adjustment may be a prudent PM service that is due anyway. If you haven't done that already, it's worth a try. It could also be a simple air-fuel issue solely or in part but since you have tuned and jetted the carbs along with an improvment in the air induction that is less of a probability although may remain a contributing factor. Have you actually Jetted? If not, I'd perform that as well as the valves.

There are several sources for research that list bike, elevation, exhaust system, air induction givens that will guide you to the best jet combo to maximize your particular bike, config, and relation to sea level. Search the VTX forums and you will find a plethera of trial & error successes to refer to without having to repeat the failures yourself. All this would explain why it is a relatively new issue which also seems to have coincided with triking. Triking adds a lot of weight (about a 35% increase?) so when all that begins to transfer toward the front on a down-grade or throttle-down situation it has an engine braking effect on the powerplant. Then factor in the mass effect growing as that weight wants to continue in motion so transfers harder toward the front then that @200 lbs acts more like @350 lbs. This further retards the valve train which may explain why it manifests in the down hill and abrupt roll-off situations. You could probably check that by applying rear brake (dampen the weight transfer stifling the engine) and the clutch (completely seperate the ground form the engine) during those occurances and see if it still backfires (none or less). I'd bet it lessens but is still present. My money is on more than one piece of the process being out of whack. Multiple perps so to speak.

 
All this may not matter to you at all and that's cool. However, if you want your bike and trike to be all they can be (GO ARMY!) then getting all that tweaked, modded and adjusted to its best and most symbiotic can be done and the true cause terminated. 
All the best and many safe and enjoyable miles to you both <img src="images/smilies/thumbup.gif" border="0" alt="" title="ThumbUp" class="inlineimg" />

skuuter · Apr 3, 2012

At least the 1300 has valve adjusters....much simpler than doing the "shim-n-bucket" procedure. Yeah, I re-jetted the carb, but removed it just to see if this would eliminate the problem by itself and simply, so most Anyone could use a "simple fix". Even taking exhaust temps with a Temp Gun, doesn't really seem to vary. This works simply and easily done by most Members at a very reasonable cost. So far, I've seen no ill results from anything caused by the baffles.....Spring/Summer is here...High Mileage and Long Term Testing has started.....ThumbUp

Ol' Grey · Apr 3, 2012

Another very informative post, Veritas44, delivered professionally and diplomatically. ThumbUp

I've ridden modifieds with aftermarket carbs/air cleaners/open pipes, dialed in and nary a pop.......Have also ridden less modified bikes with minor pops on off-throttle downgrades without any worries as the pops would be normal if the mufflers had been stock.

Backfires do concern me tho' and sometimes require more wrenching than I'd prefer, but that's all part of the trip.

You've chosen to roll the dice, Skuuter. Here's hoping that all goes well and I mean that sincerely. I'm of the school of "whatever works" now and then, too, and with varying results, so it's a wait 'n see........rollin' dem bones with Lady Luck at your side

Ride Safe...........

skuuter · Apr 3, 2012

Ol' Grey said:
Another very informative post, Veritas44, delivered professionally and diplomatically. ThumbUp

I've ridden modifieds with aftermarket carbs/air cleaners/open pipes, dialed in and nary a pop.......Have also ridden less modified bikes with minor pops on off-throttle downgrades without any worries as the pops would be normal if the mufflers had been stock.

Backfires do concern me tho' and sometimes require more wrenching than I'd prefer, but that's all part of the trip.

You've chosen to roll the dice, Skuuter. Here's hoping that all goes well and I mean that sincerely. I'm of the school of "whatever works" now and then, too, and with varying results, so it's a wait 'n see........rollin' dem bones with Lady Luck at your side

Ride Safe...........