Ducati 916 trumpets on VTR 1000 carbs

[Varastorm]

Right then, I have been reading up lots on velocity stacks! Long & short, big & small, different edge radius for the mouth section etc.

There are many variations & more specifically, where the owner/tuner requires the torque & horsepower to be in the rev range.

I am not very knowledgeable on the subject but what I have gathered is that the standard VTR 1000 inlet trumpets can be improved upon.

So here goes.

My initial plan was to save up & purchase some Dr Honda/Moriwaki designed & copied (via CAD drawings) trumpets from EBay (US) £160 - £190 Quid…….. Plus import duties etc.

So I hatched another plan.

Use the lower half of a VTR trumpet & mating it to a Ducati 916 bell mouth.

Think about it, all the hard work has already been done on the velocity radius & we all know it works well, very well.

•Find a set of similar standard OEM trumpets that are already manufactured to a superior design & get them to fit the carbs.

•The Ducati 916 trumpets seems to fit the bill, similar 1 litre’ish engine, 115 HP so must gulp around the same amount of petrol & air as the VTR.

•First problem, 916 trumpets are 54mm. So that means they are way too big to fit straight on to the carburettors via lathe work.

•54mm does sound quite large compared to the standard 48mm Honda VTR, but the VTR trumpet is a conical 47mm long tube/trumpet, which starts off life as 48mm & increases to 56.5mm diameter before it starts the small bell mouth radius top edge.

• I am looking into using two standard long VTR trumpets, & modifying them both above the securing/mounting plates. The mounting of the trumpets to the air box remains the same, but you need to cut/remove the external webbing above the mounting flanges to accept a rubber pipe to slide over & join the two modified trumpet sections together.

•The VTR trumpet length is 47mm; you need to remove the top 21mm to get down to the required 54mm internal diameter (the same diameter as the Ducati 916 trumpet). Remember the further you cut the smaller it gets.

•Then the Ducati trumpets need to be cut down to whatever length you want, 10mm+ it’s up to you, just make sure you have enough to jubilee a hose on.

•Finally, after deciding what length trumpets you want, make sure that when the two half’s of the trumpets are butted together they are a good snug fit. Then all that is required is to slip some rubber pipe over both ends & jubilee clip them together, the same way the carburettors are attached to the cylinder head.

•BTW I have read that the Ducati ST4's have slighter smaller 50mm trumpets, which would allow you shorter trumpets..... just some ideas guys.

•Please remember this is an idea & I have not done this mod yet, just waiting for all the parts to arrive from EBay, £15 so far for the Ducati trumpets.

•Wish me luck & will update.

•If it does work I might buy some proper Dr Honda ones.

• Regards.

[VTRDark]

You wont find Moriwaki stacks on eBay.

Tony had a go at this with SP velocity stacks attached to the base of a VTR stack. IMO you may as well stick with the standard long and short or two long two short stacks. The bell part wont have that much of an effect unless it has been designed for the bike, right curve, the right height and perfectly smooth. There some extremely advanced calculations made when designing stacks. Sticking one to another is going to introduce imperfections which will mess with the airflow. What you want is the airflow that flows over the edge to fall more evenly alongside the airflow that shoots straight down through from the top.





You could always try to make some
http://www.vtr1000.org/phpBB3/viewtopic ... honda+copy

Still not as good as the real macoy like I have now though.

(:-})

[Varastorm]

Hi Carl,

There are some Velocity stacks made from the same Moriwaki CAD dimensions on the US eBay.

eBay item number: 121451472377

I Mailed the guy & asked if they were the same as the ones Dr Honda had made for some members on the US Superhawk forum & he agreed!

I know that my above mod will not win any prizes but it has to flow better than the stock items, all I am really using is the bell mouth from the Ducati!

Anyway, the parts are purchased £28, so will update.......

Thanks for the link, excellent work btw.

[lloydie]

Hi Carl,

There are some Velocity stacks made from the same Moriwaki CAD dimensions on the US eBay.

eBay item number: 121451472377

I Mailed the guy & asked if they were the same as the ones Dr Honda had made for some members on the US Superhawk forum & he agreed!

I know that my above mod will not win any prizes but it has to flow better than the stock items, all I am really using is the bell mouth from the Ducati!

Anyway, the parts are purchased £28, so will update.......

Thanks for the link, excellent work btw.

Not MORIWAKI they are Dr honda/hrc
These are moriwaki

[VTRDark]

Cough coup......mori copies

Somebody is having a clear out. I wonder if the tank bra's come in different cup sizes.

(:-})

[lloydie]

Cough coup......mori copies

Somebody is having a clearout to finance the next project. I wonder if the tank bra's come in different sizes.

(:-})

Well the pic is a copy of a copy of a copy !! :-)

[Varastorm]

Sorry guys, I stand corrected! HRC copies they are...

How well did the SP1 modification work? Also how did those beautiful fibreglass stacks work out?

[VTRDark]

I've been searching for the pics but have given up now. Got bored searching. The man himself will be along shortly no doubt, and he can tell you all about it.

(:-})

[MikaelJ]

They are HRC/Dr Honda copies that I have for sale on ebay.

I had a run of these done and got some extra left over.

If anyone one wants a set PM me and I'll see what shipping would be, also the price will be lower.

It is ebay after all, might as well see how much I can get for them

[VTRDark]

It is ebay after all, might as well see how much I can get for them

I like your style

Well done on offering a forum discount

(:-})

[NZSpokes]

It is ebay after all, might as well see how much I can get for them

I like your style

Well done on offering a forum discount

(:-})

Thats where I got mine from. Seem to work well.

[mik_str]

They are exact replicas of the HPower long stacks........

[tony.mon]

My cobbled-together experiment is posted on here somewhere, with before and after dyno charts.
They worked, and fairly well, too, but then I got another step up in torque and top end when I fitted the ones i currently run. You can see mine in the airbox mods thread.

I just grafted the tops from some SP1 stacks onto the std Strom ones, but used less exclamation marks.

[Varastorm]

Hi Tony, All fixed.

I had a good read of your work on the modded stacks & am quite looking forward to having a go with the Ducati items.

You have got my alarm bells going with the height issue though, that never occurred to me.

Like I mentioned above, this project is still in the resourcing all the parts stage at the moment & I will be stumped if I have to look into raising the tank because on the Varadero the fairing bolts on to it.

[Varastorm]

I have been looking up bits about trumpet design & found this good read.

http://www.profblairandassociates.com/RET_Articles.html

Might be of interest to someone...