Ducati 916 trumpets on VTR 1000 carbs

[Varastorm]

Hi, Quick update on the Stack mod.

Firstly, I stole a rolling pin from the kitchen & removed the handles, this left me with a perfect diameter tool that fitted into the aluminium trumpet. It only went down half way, then with a slight tap it was held firmly enough to work on as aluminium gets very hot, very quickly.

The idea was to reduce the Ducati trumpets original 5mm wall thickness to 0.5mm. Starting with a 4" grinder & roebuck flap wheel then use a belt sander held upside down in a vise to sand & turn the trumpet until it was a perfectly cylindrical 0.5mm wafer thin tube so it would fit into the carb's the same way as the Honda trumpets.

What I ended up doing was sanding the trumpet bases down to a 0.5 mm thick wall tube but came to the conclusion that it was a bit too thin for my liking, as it ended up Coke can thin.

I then looked at fitting them into the Honda short trumpets, the transition between the modified Ducati trumpet to the standard short Honda trumpets is practically non existent, the new height is now 5mm longer than the standard Honda longest trumpet but it is has the advantage of being fastened to the carbs properly.

So the hybrid stacks are ---- 80mm long with the top of the trumpet taper being 55mm diameter with a total flare diameter of 90mm.
The Std tall trumpets are --- 75mm long with the top of the trumpet taper being 55mm diameter with a total flare diameter of 67mm.
The hybrid trumpets sit perfectly on top of the standard air box internal pipe work & fit under the air filter, so no other mods are required.

Since looking into this modification, I have read most of the threads on the site & issues people have had with modified trumpets so was very aware that I might turn my daily ride into a pig, but this has not been the case.

I am running Hawks carb settings, Std air box & filter, Hybrid stacks & open race Renegade exhausts.

The test ride was impressive to say the least. It runs like a different machine, every gear & every rev range, it just keeps pulling. I thought it would be trying to buck me off or be flat somewhere in the rev range, usually two long stacks = poor top end, but this is not the case. It just keeps on pulling.

I am truly shocked that Honda never did this to the bike from the outset, such a simple modification with enormous results.

So all in all, £20 Ducati 916 trumpets sanded down using the glass blowing technique of spinning & sanding until you get it coke can thin then plop them into a pair of short VTR trumpets so they measure 80mm long top to bottom & glue them in! Enjoy.

BTW, 80mm is perfect for fitting them into a standard air box, any shorter = the pipe work in the way, any longer = touching the air filter.

Regards.

[AMCQ46]

sounds like a good test ride......... you got any pictures.

I use the DrHonda stacks on my bike and they are equal length and longer than the std long stack and did a back to back dyno test and couldn't see a difference!!!!!!! really confusing,
so I tried the std trumpets for the next 2 days and it was clearly slower accelerating so fitted the billet ones again.......... on the road it is like you said, the roll on performance is like you just dropped a gear compared to standard. oh and the induction noise

so I don't know what it is about the Wide Open Throttle nature of a dyno test, but is didn't reflect how the bike ran on part throttle on the road

[lloydie]

Any pics ?
Sounds like you had some fun

[Varastorm]

Hi,

Just been on the bike (another test ride) to the local bike club meet at the Anglesey circuit. Waste of time, blowing a gale & the low fuel light came on half way there......

Still impressive though, I am thinking that it might of been running a little rich before hand & this mod has sorted it?

I have pictures of them fitted in the air box but I don't do anything to upload pictures on to so I can post on here.

I can email them to anyone who is interested though.

Regards.

[lloydie]

Normally when you fit stacks to these they run richer , I know mine dose

[Varastorm]

Hi,

Are you sure? I am lead to believe that they improve the air flow & so makes it run leaner.

The engine sounds more gruff, it's not the intake roar because I can't here it through the sound proofing (baglux cover & bag full of
waterproofs).

The engine firing over just sounds louder, nastier when running. Quite hard to explain, I suppose it's because I am so familiar to what it did run & sound like, no one else would notice I suppose.

Also, I keep trying to hook another gear.... Not realising I am in top, I am having to recalibrate myself.....Second gear power wheelies on a Varadero, WTF.

I have done many, many modifications to this bike & this one is shockingly easy & shockingly impressive, 10/10.

Regards.

[Jscobey]

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

not exact replicas. i can tell just by looking at those that they are different from the HPower stacks that i just sold in more ways than one. similar though.

[NZSpokes]

Hi,

Are you sure? I am lead to believe that they improve the air flow & so makes it run leaner.

The engine sounds more gruff, it's not the intake roar because I can't here it through the sound proofing (baglux cover & bag full of
waterproofs).

The engine firing over just sounds louder, nastier when running. Quite hard to explain, I suppose it's because I am so familiar to what it did run & sound like, no one else would notice I suppose.

Also, I keep trying to hook another gear.... Not realising I am in top, I am having to recalibrate myself.....Second gear power wheelies on a Varadero, WTF.

I have done many, many modifications to this bike & this one is shockingly easy & shockingly impressive, 10/10.

Regards.

As the flow is improved over the needle so it runs richer. I had to back off needle with the stacks.

[VTRDark]

Normally when you fit stacks to these they run richer

Agree.

Are you sure? I am lead to believe that they improve the air flow & so makes it run leaner.

If only it was that simple more air = more fuel or more fuel = more air. Have you ever considered that more air can draw more fuel. Carb tuning can go against all logic sometimes. It seems on these bike that the more air that is introduced the smaller the jets required.

(:-})

[AMCQ46]

The engine firing over just sounds louder, nastier when running. Quite hard to explain, I suppose it's because I am so familiar to what it did run & sound like, no one else would notice I suppose.

Also, I keep trying to hook another gear.... Not realising I am in top,
.

same with the DrHonda ones............ the noise when you roll the throttle full open at mid revs is like orchestrated industrial carnage with steam hammers pounding out sheet metal and you keep changing up to find out you are in top gear already.

take them off again, and it is all civilised and you need to change down when you want to accelerate in the same conditions

[Varastorm]

Hi,

I am quite impressed with the running, but I suppose I will have to do some plug chopping to see if what my ass is telling me & what is really going on are the same.

These iridium plugs are a pain to read as the ceramic is quite long & the main body of the plug is shrouded like inside of a Budweiser bottle...

I did a lot of this when the VTR carbs were first fitted, I bought a DynoJet & K&n. What a waste of time & money.

Hawks setup if Excellent, but you must use a standard filter. Like he states, free flow filers allow the slides to lift too quickly & the result is a Rich & crappy mid range.

[NZSpokes]

Write up I found on reading plugs below from ages ago if you dont already know it.

http://honda-tech.com/forced-induction- ... *-3063102/

[VTRDark]

These iridium plugs are a pain to read as the ceramic is quite long & the main body of the plug is shrouded like inside of a Budweiser bottle...

Yep definitely not as reliable to read, I though about buying some standard NGK's for that very reason. It's also a pain to plug chop the higher speeds/revs. I usually go with by butt and then verify with a dyno run when I think I'm there.

(:-})

[Varastorm]

Hi,

For the high speed runs I wind it up to the required speed/revs & hold it for around 5/10 seconds then cut the engine clutch in & free wheel to a planned parking area on the dual carriageway.

Remove the front plug (Fairing & tank removal for the rear one....) & pop in a fresh one to get me home.

Once home, I cut the threaded section off & sit in front of the computer reading various dragster forums, mouse in one hand & plug in the other..... Those dragster guys are like gypsie fortune tellers when it comes to the black art spark plug reading. They only have around 6-7 second runs! no dyno time for them.

If it needs any jets changing I will be surprised, saying that I had sparks flying out of the right exhaust last time at the track. I put it down to the red hot wadding coming out of the baffle.

That's what I told myself any way, so I could sleep at night. Hammering your daily ride on track till you kill it is a very stupid thing to come to terms with.....

It's behaved since though, so next job on the list is to repack the exhausts. Either EBay or pop down to the tyre & exhaust centre with an extension & angle grinder & cut open some old silencers for some second hand wadding.

Regards.

[sirch345]

Very impressive Varastorm, keep up the good work













Chris.