Do You Run Velocity Stacks?

I've recently added some to my 2006 Bonnie and it's really made a big difference.

I was wondering who else has tried these and what they discovered.

 

Thanks for your responses. Was wondering if what I experience was an anomaly or is it factual.

At lower RPM I don't notice any difference, but at higher RPM's the bike starts to scream. I've re-map rev limiter, but rarely go above 7,000. I did change main jet from 1.40mm to 1.60mm to help feed her and made minor changes to pilot and needle.

The sound is insane at the higher revs and she now sounds threatening.

She's my commuter bike and because of where I ride, it's a constant race off the line. I like it, it's fun.

 

I based the design on mopar velocity stacks used on muscle cars. The idea is to get more oxygen into the cylinder which occurs at higher rpm. This is typically associated with the wider carburetor position. I did put in a larger main jet to compensate for greater air flow.

Not sure what EFI would do but hoped it would remap based on oxygen sensor. I didn't have this problem because the bike has a carburetor.

I don't have access to a dyno so had to use a long hill by my house. Before the velocity stacks I struggled in 4th gear. Now, it's 5th gear and I'm holding her back.

 

I'm running diesel cross over pipes from monster exhausts. She pumps well.

I incremented main jet size checking the plug for blackness. Seems to be about right, but this is seat of pants tuning. I had a larger one in there and she seemed to be drowning and went down to the 1.60mm. There's no black soot forming in the exhaust pipes. It seems to start ok on cold mornings. I've tried many options.



I've been monitoring dirt accumulation and haven't found any effects. She's tarnishing up from gas like normal. I ride her on the street and won't take her down a dirt road. Surprised at how clean they stay. Now, this isn't for everyone and I pamper her.

 

Thanks for your input, it's rare to find someone with your knowledge and for me having this type of conversation, I'm enjoying it.

I have changed the needle settings to help midrange. I guess if you're increasing the flow rate, then adding a little more gas across the range is a good idea. Checking for brown plugs seems to be working, nothing white or black. All I'm trying to do is beat the guy next to me. Not that I'm racing.

She's got close to 60k miles on her and I was worried about the valve seats. But she's not losing compression and the valves aren't needing adjustment.

I'm wanting to pull the head off and rebuild it. At the same time I was going to mill the head and increase the compression ratio. The engine seems like it can handle it. Clutch is slipping in 2nd gear and need to add stiffer springs to help it engage. I hate letting off the gas so the clutch will engage. I find myself pushing the hand grip trying to relax the cable.

Anyway, she's my favorite bike right now and gets a lot of my attention. I do ride her a lot and like tinkering with motors.

If you're ever in southern california, look me up I'd like to meet you in person.

 

Great read, thank you.

I've read the CVK manual for Harleys but not the triumph variant. The triumph version is very informative. One thing I now realize is that I need a thruxton needle.

I made a mistake in main jet size. Stock was 1.40mm and I'm at 1.60mm now, the pilot is .45mm.

I can confirm that opening things up liberates a triumph carbureted bike.

I'm her 3rd owner, bought her with 18k miles on her. I would classify her as a basket case and got her cheap. Figured out the problem, and have never looked back. I love the styling of the motor and had to have one.

Your document made reference to an amal carburetor and read through that documentation as well, guess what......a velocity stack #37.



I designed the velocity stack that's on my bike and there is some science behind the design. It's not just a funnel. Ok, maybe it's a fancy funnel but there are some fluid dynamic considerations in the design.

I'll work up some of my ideas and post'm. It'd be good to have someone check my math.

 

cruiser my ass! that's a rocket.



Thanks for your photo

 

I really like the aluminum side covers on your bike. Not sure why the bonneville america has so much chrome. Does the world think we americans like chrome, bling & shiny stuff on our bikes?

 

I'd could totally ride her like a rocket and have a blast.

I think we could drink beer together.

Thank you, she's really nice