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Discussion Starter · #1 · (Edited)
I am trying to help a friend with his 2006 Bonneville America. The bike is nearly new with only 1500 miles and is completely stock. The previous owner messed with the carbs and it runs like crap below 1/4 throttle.

I have disassembled and cleaned the carbs twice now. 17mm float height, 120 mains, 42 pilot jet. mixture screws any where between 1.5 and 3 turns out. No cracks or leaks that I can detect anywhere in the airbox or boots. Shiming the needle seems to help with power but doesn't solve the problem.

No matter what I do it backfires into the airbox.. mostly on the left carb. and in general seems to lack power.

Anyone have any ideas?
 

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I'm not sure what the stock jet sizes are for the america - maybe someone can chime in. What you have are very large compared to the bonneville, which runs 110 mains, 40 pilots, mixture screws 2.5 turns out. If the rest of the bike is stock you should make sure the jetting is stock too.

But like davidc says - could be the coil. Especially if only one side is acting wierd.

EDIT: I went and looked at pat dinquas guide, looks like 120 mains and 42 pilots 2.5 turns out is the stock set up for the america, so like davidc says, I'd consider the coil.
 

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Discussion Starter · #4 ·
Thanks

I will switch the suspect coil over to the right side to see if the problem follows. Thanks for your help.
 

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EDIT: I went and looked at pat dinquas guide, looks like 120 mains and 42 pilots 2.5 turns out is the stock set up for the america, so like davidc says, I'd consider the coil.
According to Jenks, the 790 Americas had 42s, but the 865s have 40s. I know we're all thinking its way too rich at idle.
 

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Ah - yes that was my thought and that could be it. You are right - Pats setup was on a 2003 america, which would have been a 790 of course. Good catch!

Get 40s back in there and see what happens, though swapping the coil is an easy test too.
 

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Discussion Starter · #7 ·
I have the official Triumph workshop manual and it states 42 is the pilot for the 2006 America. I switched the coils and the problem followed the coil. I put a timing light on both sides to monitor the spark to confirm the issue. Where is the best place to order a new coil?
 

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Nology coils, at least for Bonnevilles, seem to be in short supply. Tried newbonn and BritCust and back ordered for over a month.
Try Baxter Cycle or Hermy's. I got a used one at Hermy's and hope to get it tomorrow so that I CAN RIDE MY MOTORCYCLE! :(
 

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Well done! That's that sorted.

New coil from your dealer, or failing that call hermys - I believe that's where davidc got his.

Ah! davidc was replying as I was! :thumbsup:
 

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Discussion Starter · #11 ·
Thanks for the help guys! I will call Hermys in the morning and order one. It's hard to believe on could go bad in 1500 miles.
 

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Damn, I'm glad I live close to Hermy's, heck that's where I got my bike....they seem to always have what I need in stock!! I just have to deal with the BMW guys whenever I get in there...:p
 
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