Bonneville America Forums Forums Technical Forums General Tech Fuel ignition in Carb

Hi all,

I have a 2006 America, picked it up used (5,000 km on it) last June, Just completed 10,000 km service 2 weeks ago.

On the weekend I tried to start my bike and there was a loud bang from the carb. From reading on this forum, it looks like I may have overfilled the tank (filled just before parking the night before).

Additional info; In the last year I have had a couple of backfires (2 to 4 at most) but don't think related. I also have a fair bit of bluing on the headers. From reading on this site this seems a bit excessive and I am beginning to think the mixture might be set a bit rich (more a guess as I am not that knowledgeable in mechanics, however I am able to follow simple directions)

Questions/concerns:

1. How serious is the bang in the carb?

2. I have notice since the bang in the carb that the bike sounds "throatier" at high revs (ie above 80km/h in 3rd) and possibly diminished power at the same rpm (although this could be in my head). Imagination or problem?

3. I read on a thread on this site about disconnecting a hose on the carb corrected what sounded like the same problem for someone else. Unfortunately I can't find the thread again. If this is the case can some one post a pic of which hose. Comments?

Jim

It may be nothing serious. Some of us have found that we get a backfire at startup if the choke is pulled out all the way. Solution is to pull it out all the way, then push it back in a little and then hit the starter. Worth a try.

The bluing on the headers is from the pipes getting hot. It could be running lead or from running in congested traffic. Are you running non-stock mufflers?

If it sounds different, you may have busted your airbox, or at least blown a hose off it.

The most serious thing about this issue is that backfire on start up is what is breaking the cases where the starter gear mounts.

If you headers are bluing excessively you are probably running lean / hot. Also, don't twist the throttle when starting the bike, this can cause backfires. Thirdly, replace the vacuum caps on the carbs and intake manifolds.

Thanks guys,

A wealth of information as always.

I had exactly the same problem, back-fire on start up and a shatterd air-box resulting! Bust into about 8 bits arround the intake of the RH carb. Only the lid busted but recon it's the whole box that needs replacing.
You'd think Triumph would have put in a blow-back valve, of maybe they are using too much re-grind in their molding process! The remains of my air-box seemed very brittel!!
Kenny

Thanks for the suggested info on the airbox. I have an 06 America w/9990 miles. The exact same thing happened to me yesterday. Started it in the morn and it backfired (loudest one yet...only backfired a few times since I got it 1-1/2 years ago.) It now has the same deep throaty sound with some minor loss in acceleration. Bringing it to the dealer today.

Pull the seat off and see if the airbox is shattered.

If it is it will be much cheaper if you do it yourself. You can easily pick up an airbox on ebay for a lot less than the dealer will charge for a new one. It cost me almost $600 and I could have done it myself for about $50 and a couple of hours of work.

ask around on the forum if someone has a used air box. I bought mine 2 months ago from a member.

the dealer wanted 250-300 for a new air box. It's worth to DIY.

It took me just over an hour. You'll need a lift to drop the back wheel so the air box can be removed. Get one a Canadian tire for $120.

Yep, The top of the airbox is partially shattered. Dealer wants $240 for the kit and about $200 in labor. Sounds like a DIY project. Time to look for a used spare.

$440 is a deal. I was charged $280 for the airbox and another $300 for labor.

Here is one on ebay for $50.