Bonneville America Forums Forums Technical Forums Exhaust Bub exhaust jetting recommendations

I have been trying to decide between Specialty Spares and Bub exhaust for awhile now. I sold the exhaust off of my my bike today and sent the mounting brackets with the mufflers which helped me decide on Bubs since the SS pipes require reusing the stock brackets. So, to get to the point, Specialty Spares was going to include jets with their kit, but I have to do the jetting myself with the bubs. I have done the airbox removal and battery relocation on my bike using K&N Pod filters. What jetting would be recommended for Bub exhaust with this setup at 4500 ft elevation?

Thanks for the help,

Mat

jet calculator

This jet calculator is as close as we come to holy gospil here. So by simply punching in the numbers, depending on your pilot jet size, looks like it calls for a 157ish size. That seems a little rich to me. I run 45/155 on open pipes. Hope that helps.

The caculator helps, but it leaves some options:
Pipes: Bub
Filtration: K&N Pods
Average Elevation: 3,000-4,000 (I live at 5,000, but I would rather be a little rich and able to drop down in elevation safely)
So, what is recommended for
1. Needle: Stock, TBS, or Thruxton
2. Pilot Jet: 42, 45, or 48
3. Needle Shim: None, 1, or 2
4. Main Jet

Thanks again for any help

I have Bubs, K&N Pods, 42 pilot, 160 main, Truxton Needle, Adj.air fuel.
I live a approx 1500' ele. have ridden @6000' w/no adjusting
The 160 is probably a little rich I only get 120(main tank) miles per fill up, but my plugs look good, exhaust outlets get a little blacker than i think they should, not sooty or oily
Hope this helps

It wasn't long ago I Suggested to the author of the jetting calclator (Dinqua - Pat) it might be an idea to update the J calculator and he agreed but having done so much earlier on in the game, he just rightly believes someone else should be stepping up to the plate. Fair enough I reckon.

You see, the calculator was collated from a number of members at the time (like 6 years or More ago) when we were still learning heaps about these bikes and there was still just a little bit of subjective opinion in the mix.

So now whilst some may disagree which is par for the course, I and Pat did agree the calculator was and does suggest jets should be just slightly on the rich side than the opposite. Better that than lean though.

Anyway you asked the question so IMHO and after having SS pipes myself which are pretty much identicle to Bubs In there breathing capacity being straight through pipes, and with K&N's etc, my suggestion as a start would be:

1. 45 pilots (definitely)
2. Stock needle with 1, perhaps 2 shims ( 2 cos of elevation) and,
3. 150 mains.

My reason for these suggestions is, I had my bike dynoed with these settings and the numbers and a/f ratio was sweet.

The reason for the 45 pilots is, I couldn't even get my bike to run properly with the 42's.

The stock needle with one shim helps in not trying to do too much too soon, otherwise you can end up chasing your tail.

Finally the 150 mains gets back to the calculator being a tad rich. I realise you don't want to run lean at your altitude cos I was at 2000' but if in doubt another shim on each needle should prevent any doubts there.

Then when you feel the response from nil to wot on your bum dyno is good, work out your fuel consumption and check your plugs as a basic indicator to previous readings to see if you're on the right track and if so, I'd see how thruxton needles go with no shims and debateably 42 pilots. I've found the mid range using the thruxtons are brilliant but I have staintunes now without restrictors which change things a bit.

It also wouldn't be a bad idea to have a look at the dyno table (sticky at the top) to compare the various results and settings to get a good picture on what and why. After all, that's the idea of the thing in the first place.

Of course you still can't beat an experienced operator on an up to date dyno to confirm you're on the right track once your bum dyno is satisfied and other readings correlate.

Yeah, it's a bit of a puzzle to start with and sometimes different bikes just have their own mind but once you feel you're close to nailing the sucker, there's no better feeling (except the obvious of course LOL)

Good luck

staffo

The jetting calculator works better on the 790 engines than the 865 engines. I've found that while a 790 engine with free flowing pipes and pod filters can take a 150 main jet or maybe even larger, the 865 engines probably can't go much bigger than 140. That's just my personal experience. Maybe others have found a way to go bigger, but the 865 cam seems to be the limiting factor. I'm running relatively open pipes and pod filters on my 865, but really need to replace the cam to get any more horses on the top end. That's going to be my next project.

Maybe I spoke too soon, after re-reading this thread it looks like Brett is running 155 jets on an 08 America. Must be some very free flowng pipes on that bike. I put together a home-made exhaust over the winter which has a small internal baffle and am running a 45 pilot and 138 main jet with one shim on the stock needle and the mixture screw turned out about 1.5x right now. Tried more open pipes, but they were just too loud.

My bike is a 2006 America 790. I noticed that I did not include the year and motor in my first post. Thanks for all of the suggestions. I now feel like I at least have a starting point. I sent an email to Bub, who replied that they would not make jetting recommendations. They are obviously scared of the liability involved, but it is frustrating.
British Customs recommended:

In CA at sea level most have been running a 13 or 140 main with 42 pilots with about 2 1/2 out on idle mix screw. With your elevation you may just need to tweak the idle screw a tad more to compensate for elevation. We do not use shims which is why we go bigger on the mains but have heard of my dealers in elevation areas such as CO that do for elevation.

Since you've got a 790, I'd start with Staffo's recommendation and go from there. Trial and error will get you to the right combination eventually and you might get lucky and hit the correct setup on the first try.

I am going to use Staffo's jetting as a starting point. What is the stock jetting for my bike>

The stock jets were 120/42.

No way. That's brilliant news. The MAN himself is back. Way to go brother, you've made my day.

Staffo

Yeah Staffo, I think we all owe Pat a huge thank you for putting up his website. I probably would have never started messing with the carbs if it wasn't for Pat's site and first hand advice from other BA members (Big Poppy and Uncle Charlie in particular) who showed me the ropes.

just tell em he brews the bestest beer and had the fastest motorsickle. that'll stroke him proper like.

Seriously, THANKS PAT!

Hi Pat. I'm a Mac guy since 1984 and would love to be able to run your calculator on my computer. BUT, I don't have the skills to make it possible. Hopefully, there's someone who does.

I'm hearing you Patrick. Without going overboard and him getting to big an ego, I too used his website to venture into the world of jet changes etc. He just made it that less daunting for a newbie, and from then I was on my way so yeah, a big thanks from Staffo is well and truely appropriate also.

Staffo

I bought mgpauls's TORS. I just added a Hyde bellmouth and K&N high flow filter to my '07 865 America. I'm just looking to perk up throttle response and overall performance a bit - particularly in the low to mid range. I have a Thunderbird which is currently in the shop having the Big Bore kit installed, so there is no point in dumping a bunch of time or money in the BA chasing performance that I already have in the bird.

I'm no mechanic so I will have the dealer do the rejetting. The Hyde bellmouth comes with instructions that recommend 124 mains at a minimum without saying anything about exhaust changes, and the calculator shows 126 for TORS with K&N single and snorkel removed. It doesn't appear to have an option for the bellmouth, but I would guess it would require at least a couple of sizes bigger.

My dealer is pretty good, so they may be able to measure the A/F mix.

Anyone know what the stock jetting is on the '07 America 865?

I'd go with a 125 main jet and maybe a shim under the stock needle or a TBS (Thunderbird sport) needle. I ran that setup with TORs and it worked well.