Bonneville America Forums Forums Technical Forums Accessories Exhaust question

I have the thunderbike exhaust on my 05 america. I just love them. but..... When I travel down a long hill with the throttle closed I get alot of popping. Lots... Also once in a while while starting up a warm engine I will get one extremely loud pop & then the engine will start. It can be a little embarrasing. Some people think it was a gun that went off, it's that loud. Any ideas or remedy's for this? I allready know that I am lacking a little on the main jet. I didn't change anything with the thunderbike mufflers. Airbox is stock, I only opened up the pilots to around 4 turns open. It runs good but as I said top end may need a little more on the main jets. I have just under a thousand miles on it so far.

Jerry

Jerry,
Mine likes to do the loud startup pop ocassionally too. It always happens if I even touch the throttle when starting it. It scares the crap out of people, makes them jump really high and girls squeal. Hee hee. Sometimes I do it on purpose for poops and grins. I also am one of those people that rarely turns off my petcock.
What condition is your airbox/snorkles?
Definetly up your mains a bit too and get a lot more giddy up for a few $$.
If you are running 4 turns out already, you may want to try 45 pilots and turn the secrews all the way back in and start from there.
You will never get rid of all the popping, but you can decrease it a lot.
Mine pops on decel slightly still, but it doesn't bother me as long and it's not like a machine gun.

Jerry,

Back when I first got my Speedy, I bought Bub Megaphones. At first there was this horrible popping on deceleration (just as you describe). The biggest change came when I removed the A.I. system (air injection). Then, when I installed "the Freak," and put in the supplied 160 main jets, that also helped. Now it purrs.

My setup now is as follows,

Pipes = Staintune-Slashcuts
Filters = K&N's
Airbox = Removed (The Freak)
AI system = Removed
Mainjets = 160's
Pilot Jets = Stock
Air screws = 3 turns out
Needle shims = 1 - .020 shim on each needle

With that, it runs close to perfect (my elevation is about 200 ft. above sea-level).

-BT

I have the D&D's and I love them, I wouldn't call it popping on decel, it sounds more like backpressure, I kind of like it

Guys, thanks for getting back to me on this. As I said, my airbox is stil stock but I forgot to mention that my air injection is plugged.

jerry

Jerry,
Try pulling your snorkel. (That should elicit some further replies!) Seriously, if it's popping, it's igniting unburnt fuel. Add some more air and the fuel should burn where it's supposed to. This experiment is entirely reversable as well.
The snorkel is an interference fit in the rubber housing over the filter..

BTW, the weather liars say it's supposed to be relatively dry Sunday. I've never been to Perryopolis, so I plan on cruising down your way. If you see a black TA with a denim clad fool on it, that would be me...

Grump, The other fool on a green TA in the blue coat was me. Me and the Mrs. did a 75 mile circle Sunday (today). We went up thru Fredricktown & Millsboro then back thru Belle Vernon via rte 201. If you keep going thru Fredricktown on 88 then tie up with 21 & come home on rte 21 thru Uniontown makes a decent ride also. Wifes knee was acting up the last 2 weeks. Today was the first time she was able to try out the corbin pillion that I got for her. She really likes it. All I can say is AMEN. Was really getting tired of having to stop every 25 miles. Do you know the gentleman who lives up on 857 outside of Uniontown who has all the BSA's. Can't remember his name but he said that he is down Steve's place all the time looking for parts & stuff for his bikes. Nice guy. Sometimes I go for a ride to Morgantown & then hit rte 7 that goes to Kingwood. At Kingwood you can come home on rte 26 thru Brueston Mills thru the country back to Uniontown. My son lives down that way.

Jerry

My Specialty Spares act the same way. I had the a/f screws out 3.5 turns and had no popping. My plugs looked a little rich (although they say you really can't read plugs anymore with unleaded fuel) so I moved them into 3.25 and have a little popping. I kind of like it, me and Dinqua think alike!
I also get the loud backfire on start up if I touch the throttle. Mine is so loud it startles everyone and I'm thinking that can't exactly be good for the bike. This seems to occur whether or not the petcock was off. My mileage is also poorer than most, I never get more than 41 mpg (18 tooth sprocket). The bike runs like a champ except for that occasional backfire and low gas mileage.

Quote:

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low gas mileage.

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Check your float levels Al, that'll help your gas mileage considerably. Mine were way off too and I went up about 4mpg after adjusting one of them.

Al, I don't know if it is the way I ride. (like an old fart) but my gas milage is always around 50gpm. I have got as high as 52. AI removed, 4 turns out on stock airbox & thunderbike mufflers.

Jerry