[xStevex]

Hello Friends,
Spring is more or less in the air up here in central CT, so the RE is back on the road, reborn now as a 'quasi-clubman' Bullet.

In pursuit  of this end, I purchased the velocity stack that CMW offers (http://store.royalenfieldusa.com/bullet-500-bell-mouth-velocity-stack), and before I put it on my machine, I'd like to get input from the folks out there who know about these kinds of things.

I was wondering if this was an item I could take on and off, swapping it with the Ace cannister which is presently on the Bullet. I know enough to know that the stack wouldn't filter anywhere nearly as well as the cannister, but outside of that is there anything else I should know?
Would using it occasionally for bike shows or runs be harmful- in my mind it looks cool, but I wouldn't run it if it could cause harm to the bike.
Would I need to rejet to run it?
What's the best way to set it up?
Would it offer anymore performance than the cannister (which is a great piece of kit, for sure. My reason for getting the stack was almost purely aesthetic- to capture the look of the great clubman singles of the day: venoms, goldies, conti gt's, etc.)

My present motor set-up is:
Goldstar exhaust
Ace Air Cannister
Stock carb (rejetted for the exhaust & cannister)
PAV removed



thanks in advance for your help and input!
xStevex
Onionville, CT

[Rick O'Shea]

I like the way they look too; and have the same questions, wonder if there is a way to inprove filtration ?

[ace.cafe]

The velocity stack has basically no filtration. It has a screen to keep out rocks and bugs, but that's about all it keeps out.

A short velocity stack doesn't do much of anything on these bikes, but it can help a little with unrestricted intake flow. To do anything more than that would require them to be longer length than anybody offers. Our low-revving bikes need long stacks, and the aftermarket stacks are all made for high-revving bikes that only need short stacks.

They do look cool, and give a racy appearance. Great for bike shows.  When riding with the stack, it would be best to avoid dusty and sandy areas. You won't kill anything by riding with an open stack like that, but over time you get some effects of the dust in the engine, which tends to make things wear out a bit faster.

I doubt you'd need to do any re-jetting, because I think the Ace Air Canister will flow just as well, and the rubber connector tube on the Ace Air Canister offers a stack-effect of about 3" as it comes, but it's still too short for any real wave-tuning effects at our rpm range.

Essentially, you're looking at just an appearance option, as far as technical aspects are concerned.  But losing the filter can cause some accelerated long-term wear, so I'd use the stack sparingly, just when you want the appearance effect of it.

I like the looks of a stack on there too. It's cool.
But for normal riding, a good filter will be better for engine longevity.

It doesn't say anything about being compatible with the AVL, so I'd check with CMW about that when ordering.

[xStevex]

Ace!
Thanks for the advice- I knew you'd have some good tips to offer on this subject.

Would the stack have any usefulness if it was mounted on a tube of some length that attached to the carb, rather than just bolting directly to the carb? Or, if the carb was farther from the intake manifold, with the stack attached directly to it?
I think I sort of have a basic grasp of velocity stacks/intakes from some of your previous posts, and was wondering if there was a way to get a bellmouth to serve more of a purpose than just appearance for a Bullet, though I'm content with 'looking cool' in small doses, and for selected uses, if that's the reality of it.

thanks again,
xSx

[enfield freddy]

if you are going to get one ,, get a good un



note the difference between a ram pipe and a velocity stack?

spot the little air holes at the bottom?

[ace.cafe]

Ace!
Thanks for the advice- I knew you'd have some good tips to offer on this subject.

Would the stack have any usefulness if it was mounted on a tube of some length that attached to the carb, rather than just bolting directly to the carb? Or, if the carb was farther from the intake manifold, with the stack attached directly to it?
I think I sort of have a basic grasp of velocity stacks/intakes from some of your previous posts, and was wondering if there was a way to get a bellmouth to serve more of a purpose than just appearance for a Bullet, though I'm content with 'looking cool' in small doses, and for selected uses, if that's the reality of it.

thanks again,
xSx

Yes, there's a way, but it entails having a stack that's probably between 6"-8" long, for rpms that our engine will see.
That's why that stack you see on Chumma's bike in the photo above is 6" long.
That's tuned for around 5200 rpm, but it has some effects at rpms a bit higher and a bit lower than the tuning center.
Lower rpms than that will need a longer stack, and higher rpms need a shorter stack.
The actual wave tuning can vary from bike to bike, depending on the cams, the rpm range, and the actual length of the entire inlet tract from the back of the valve to the outer edge of the bellmouth.
And it is of most use with wide-open throttle, and gets less useful as the throttle positions get smaller.

[xStevex]

Gentlemen,
Thanks for taking the time to repsond and enlighten me- I'll have my Bullet 'clubman' ready for Brands Hatch or Brooklands someday!

I'll be doing some more research into this, but you've got me off to a great start: the relationship between RPM's and velocity stack/intake.

thanks!
xSx

[cyrusb]

Another thing that should be mentioned about the stack and K=N style filters is the noise. Pretty loud chuffing. Also without a stock style filter there is no flame arresting,(should the need arise).

[geichal]

I run a 5" stack on my 34mm flatslide.  I dig it, it could be longer as Ace noted.  It has a very distinctive sound!  I think the combo makes good power, just poor fuel economy.  I'm still in the process of optimizing, but am happy with the progress!  I'm looking forward to an alloy jug and ACE piston!
geichal

[Ice]

I run a 5" stack on my 34mm flatslide.  I dig it, it could be longer as Ace noted.  It has a very distinctive sound!  I think the combo makes good power, just poor fuel economy.  I'm still in the process of optimizing, but am happy with the progress!  I'm looking forward to an alloy jug and ACE piston!
geichal

 Just curious, do you think the poor fuel economy could be due to using the extra power a bit more often ? 

[xStevex]

As a follow-up to my question:
I did a quick little experiment this weekend, after getting the fluids all changed in my clubman Bullet.
Did a quick run with the stack installed, and another run with the Ace unit installed. The bike ran better, much better actually, with the Ace unit than with the stack.
A guy I work with builds and races racing cars, and i asked him his take on velocity stacks, as he also rides a carbed, HD-motored Buell. His 2 cents were that on an RE, a velocity stack might make sense when it's hot humid, not somuch when it's still cool and dry.
thanks again for all your help and input guys.
xSx

[xStevex]

Enfield Freddy,
is that an Amal Monobloc you're running on your bike?

[chumma7]

Enfield Freddy,
is that an Amal Monobloc you're running on your bike?

xStevex
That is my bike pictured with the velocity stack. It's a 6 1/2" custom stack made by cjayheff who can be contacted via the yahoo forum. The carb is a 1 3/16" monobloc. Videos of my bike running at a local dyno can be found here: http://www.youtube.com/user/EnfieldTuning

Attached is a picture of another stack cjay made for me after I lost the first stack (shown in freddy's post) while cruising on the highway. His work is pretty damn good.

[geichal]

Just curious, do you think the poor fuel economy could be due to using the extra power a bit more often ? 

I average about 40 mpg, I probably ride it a little more enthusiastically now that it has good power!  I've noted before that my buddy with a morgo'd Triumph and all the go fast goodies didn't believe that it was just a primitive 500 single!
geichal

[chumma7]

I average about 40 mpg, I probably ride it a little more enthusiastically now that it has good power!  I've noted before that my buddy with a morgo'd Triumph and all the go fast goodies didn't believe that it was just a primitive 500 single!
geichal

Ouch Giechal, 40 is kind of low but if you're having fun...who cares! I blame the 34mm carb.  When i was experimenting with a 34mm roundslide mikuni I was getting about 45mpg with a fairly stock engine setup (not stock exhaust).
 
With the 1 3/16" (about 30mm) monobloc and the stack i avg 50-55mpg with spirited driving. This is with my current hopped up setup. I could probably touch 60mpg but I've never managed to drive that way for an entire tank haha. When i fit ace's mondello head and magnum cams for dyno testing I will be switching over to a mikuni tm32.
I didnt notice much loss in mileage with the addition of the stack on the amal, maybe just a hair of difference if that. I think the stack actually gave me a more efficient combustion since I would have expected to lose a lot more mileage considering I did have to go larger on the main jet by a ridiculously large margin. The improvement in power across the rev band was huge.