Hi. Long story short.... I have a Monster S4 project on the go. I'm replacing the tank with one from a 748 and need to lose the airbox in order to create clearance for the underside of the tank and also to relocate the battery and ECU etc. I will need to fit cones or some sort of pod filter over the velocity stacks. I can't find anything for an S4 but can find stuff for the 916. The S4 and 916 use the same engine but I don't know if the ancillaries, in this case the velocity stacks, are the same. If they aren't then 916 filters won't fit the S4 velocity stacks. Please could someone tell me the outside diameter of the flared end of the velocity stack on a 916? I think its 90mm, but I want to be sure. Thanks!
I know that the ST2\4 are shorter as this is a top end mod for tuned 748's. I am not sure if this helps at all but it may be a starting point.
Well, yeah, I took that picture in the dark, right, while balancing the full fuel tank on my shoulder and, like, oh my god, juggling the phone with my other hand and, like, the stupid casing of the iPhone 6 seems to be made of Teflon and is top heavy and stuff and, yeah, WHATEVAH, SO STOP PICKING ON ME!!!
As for dimensions; 916, diameter 90mm, length (overall) 58mm S4, diameter 85mm, length (overall) 47mm
Thanks for that info, although it's not parricularly what I wanted to hear. I really wanted them to be exactly the same diameter as that will make life a lot easier.
Follow up questions. How easy is it to change the velocity stacks? I can get a 916 pair effectively for free and so I may do this just to make things a bit more simple. Does a longer stack move the torque and power up or down the rev range and should I remap if I fit 916 stacks to my S4? Thanks.
They push/twist in/out a bit like a bayonet light bulb, so dead easy to swap but watch you don't pinch the 'O' rings. You could always take 5mm off the width of the 916 stacks? A longer stack should make more torque but less at the top end, some fit the shorter stacks to 916 for more top-end. I've got TPO stacks on my 916 which claim to give both more power and torque, however I'm not convinced but since I had it mapped for them (and it goes very well) I'm not changing them without remapping, besides (even though you can't see them) they do look nice;
Thanks. I may just fit the 916 stacks then as I prefer torque over power anyway in a street bike. It seems a bit counterintuitive though that they'd fit the Monster with stacks which make more top end and fit the superbikes with stacks that enhance torque? Perhaps it's a packacking thing as there isn't very much room under a Monster S4 tank
I think it may have been a space issue due to the fuel tank/airbox design that gave the S4 shorter stacks? (916 fuel tank is the top of the airbox and is shaped to give more room).
I think it must be that. Anyway, it's all good because I'll get a better looking bike AND more torque!* *hopefully
It's a larger airbox, the throttle bodies sit inside it to create more volume. The TB's & linkages are standard 916.
Thanks for all your replies chaps. They were very helpful and enabled me to come to a decision. I've now bought through fleabay these little filter pod thingies which sit on top of the velocity stacks. I can only source them in a fitment for a 916, and as the Monster stacks appear to be a smaller diameter, I'll replace the Monster stacks with the 916 stacks the seller is supplying with them. Not sure if they'll do that great a job of filtering and they might disrupt the air flow into the stack but they don't take up any space at all, which is ideal for what I'm doing. The foam looks very open, so I may rig up some sort of secondary filtering using one of my girlfriends cut up stockings. At only £45 for the filters and stacks together and as the (extremely helpful) seller has said I can send them back if they don't suit my application, it's worth a try. I'll see how I get on and post an update when they're fitted.
