Bonneville America Forums Forums Technical Forums Performance Mods Jetting verification and opinions

Not a newbie, but haven't dealt much with this stuff in a while. Here's my set up:

• Specialty Spares short slashcuts (new(to me)!)
  
• TBS needles, no shims
  
• stock pilots (42s)
  
• Dual K&Ns (like the Freak)
  
• Bellacorse thumbscrews (which has no option in the jetting calculator)
  
• Carb slide holes drilled to 7/64"
  
• 3-4000 elevation
  

Jetting calculator says 144 mains, I have 145s. Pulls really strong (sounds incredible). I think I have the air mixture screws turned out 1.5 turns, but I have a lot of popping on deceleration. Sounds cool but it's getting annoying.

Refresh my memory, I turn those out to deal with the popping, right?

Any other opinions on my configuration? Thinking about swapping out the TBS needles for stockers with a couple shims. Just for the heck of it.

I know there has been some talk about the Bellacorse thumbscrews in the past, but am I correct in recalling that they don't really effect the jetting?

Yep, turn the idle jets out a bit to reduce popping. You could disconnect your TPS also. I'd be curious to see how your bike responded if you did.

I'm running TBS also. Can't remember if they were better than my stock needles with 2 shims or not.

Loosing it....

I think you are lean down low, should bump up those pilot jets a size then adjust the rest.

Put a shim on the stock needle

John,
For reference....
I run K&N PODS, SS longs.
Karens bike runs OEM airbox and SS shorts. She started with a UNI and I installed a DNA yesterday.

NOW....to maybe help you heres what I did on our bikes:
Mine runs 45s/150 and you've seen/heard it run. No issues. I have switched to Thrux needles and that seemed to help a bit of midrange drop I was feeling.

Karens started w/ 40s/120, TORs and a UNI. This was fine and ran very good.
I installed the SS shorties, upper her to 42s/130. It felt better BUT still felt like it had more to give. Almost like something was holding it back. It had a hard time starting as well....really hard.
I upped her to 45s, Thrux needles and still running the 130s at just under 2 turns out. Starts with only a minor backfire on startup and a nice mellow popping on decel. Bike pulls strong and feels GREAT!
I installed a DNA filter in the airbox yesterday and took a spin around the block. Got rid of the minor popping but feels like it lost some pull. Ill try another half turn out and see where I wind up. I think I might need to up a jet size again with the DNA.

Hope that info gives you some insight. I claim no level of expertise other than you and I tun similar set ups.

I guess I'll start by cranking up the mixture screws to get rid of the popping. Then I'll try disconnecting the TPS. From there I try either the larger pilots or the stock needles with shims. I think I'm close, I just need to tweak it a bit here and there.

I disconnected the TPS... no popping. Gone. A distant part of my memory. Maybe try pulling the plug first... if you are happy, great. If not, onto other things.

Did you remove the AI? I might have missed that. Doing that killed all my popping and I disconnected the TPS for fun.

Yeah, it's long gone.

UPDATE: I'm going to run my bike as is for a while. I put fresh squirrel condoms on and it runs like a raped ape. No sign of backfiring at all. I might pull the TPS plug for craps'n'giggles.

QUESTION: When I fired my bike up yesterday, I heard the loudest backfire I've ever heard. Ran completely normal after that. Ran very strong on the highway.

Ideas? I've heard backfires on starting before but this made my ears ring a little.

On my bike, if I pull the choke all the way out I can get some mean backfires, but someone here (can't remember who) suggested pulling it all the way out and then push it in slightly, then hit the starter button. I found that if you follow this procedure, it will reduce the backfiring at startup.

I'll try that. I've gotten in the habit of pushing the choke in halfway or so after a couple minutes of warmup time. Of course, it's only happened once so far (this severe anyway).

I'll get a backfire here and there when starting up as well. I also use the choke trick. Plus, its rare I actually need the choke all the way out. I'm running K&N's, no AI, no TPS and spectres. I know I'm running pretty rich. I need to drop down a main jet. Not that any of that helps you but I have a backfire here and there too!

As a general rule, decel popping is lean & the "big bang" backfire is rich.

I've read a few things about the TPS... what does it do and is it safe to just remove? I'm suffering from major popping/backfire on decel and am going to do the AI removal.. but was wondering what the TPS removal was.

I'm guessing as well that all my jets etc are standard to the bike (america 2005)... but in all honesty I have no idea about jets, pilots etc...

You might first try turning the mixture screw out a bit and if that doesn't help things you can remove the TPS. I still have my TPS on and don't have too much popping, but others report good results from removing it.

Just adjusting the mixture screws may not do it you also have to re-jet if you haven't yet.

I think adjusting the idle screws in the first instance would be a better idea and then if it still happens now and again, and even after the choke trick, then the tps. Personally I only did my tps cos I wanted less wiring and perhaps less things to go wrong. I wasn't disappointed cos she's been run brilliantly ever since. I did do the tps at a time of other jetting so because I've got my jetting just about right, it's hard to say what actual better effect removing the tps has had. Certainly hasn't caused any issues.

Btw, thanks for the tip on the choke start up procedure guys. The last time I had a major back fire it was colder than normal and I know I'm slightly on the rich side from my dyno so I'll give that one a go from now on myself.