Ducati 916/VTR trumpet Carb jetting

[VTRDark]

& will hopefully be fitting VTR cams in the new year too.

You should ideally do the cams before getting the carbs tuned in as these will affect the tuning, therefore you will be playing with carbs again once the cams are installed and clearances set. The carbs on these bike have got to be the most sensitive finicky carbs I have ever worked on. The smallest of changes elsewhere, especially cams/clearances will affect the tune.

Have you adjusted the TPS at all yet? note that this will also go out of adjustment after changes in a carb sync and/or idle adjustment.
http://www.vtr1000.org/phpBB3/viewtopic ... 31&t=29429

(:-})

[lloydie]

No sorry I'm no longer doing the flywheels as I fell out with the engineer after he fecked up my swing arm .

[Varastorm]

& will hopefully be fitting VTR cams in the new year too.

You should ideally do the cams before getting the carbs tuned in as these will affect the tuning, therefore you will be playing with carbs again once the cams are installed and clearances set. The carbs on these bike have got to be the most sensitive finicky carbs I have ever worked on. The smallest of changes elsewhere, especially cams/clearances will affect the tune.

Have you adjusted the TPS at all yet? note that this will also go out of adjustment after changes in a carb sync and/or idle adjustment.
http://www.vtr1000.org/phpBB3/viewtopic ... 31&t=29429

(:-})

Hi, I don't mind fiddling with the carbs & its free, also as its my daily ride I have to get the fueling sorted as its painful high fiving the staff at the local petrol station every other day...

I adjusted the TPS when I first did the carb conversion, the connecting plugs on the bikes are different (rectangle v's round) & I had to make sure that it all worked & was set up right at the time. I also checked the balancing yesterday (connected the adaptors onto the inlet manifolds when the carbs where off) & it was spot on, but I will check the TPS next time I am under the tank

I've some low mileage Std VTR cams sitting in a Moriwaki cam box in the shed, just saving for some MCCT then do them both together

Local bike club night tonight, but the weather is crappy, so will have to postpone the test ride for another day

Thanks for the help BTW

[Varastorm]

No sorry I'm no longer doing the flywheels as I fell out with the engineer after he fecked up my swing arm .

Shame, What year Fireblade swingarm do you take the brace from? & what is the width & length of the arms?

I have an idea coming on.........

[lloydie]

92-99 width and length ? Unsure as the mrs thinks it's less than I do !!!

[Varastorm]

Hehe,

92-99 width and length ? Unsure as the mrs thinks it's less than I do !!!

[Varastorm]

Hi,

Update on the new carb settings, I ended up going to the club on the bike tonight. 40 mile freezing round trip on greasy salted back roads, so no heroics

Its pretty good as a bit of a stab in the dark setting & not slower in any way, just hope there's an increase in MPG too.

So, it now requires choke to start✓, ticks over at 800rpm✓, no popping surging during the ride✓. Drag start to red line through all but the top gears with no issues✓. Top gear 1000rpm @ 30mph slam the throttle open & it keeps on pulling with no issues at all✓, pretty good & better than I thought it would be TBH

Next will be plug chops through various rev ranges just to make sure the plugs are telling me the same as my butt.

Then I suppose it will have do it all again after the advancer is installed

[VTRDark]

So, it now requires choke to start✓, ticks over at 800rpm✓, no popping surging during the ride✓. Drag start to red line through all but the top gears with no issues✓. Top gear 1000rpm @ 30mph slam the throttle open & it keeps on pulling with no issues at all✓, pretty good & better than I thought it would be TBH

That all sounds very promising and close to the mark. I'd guess your on the leaner side of the AF now. Whereas these engines seem to prefer to run a little on the rich side. Saying that though, I'm on the leaner side myself right now, bike runs lovely in this cooler weather. Come Summer I will tweak the mixture, it's like there's very fine line between the lean and rich, which with these highly sensitive finicky carbs one can feel a difference. At equal speed and revs it should be smooth all the way through. I found low speed steady state cruise, say...at 20mph/2000rpm - 30mph/3000rpm a good low down test. Hopefully you should see a nice increase in MPG.

So, it now requires choke to start✓, ticks over at 800rpm✓,

I like the little ticks.

(:-})

[Varastorm]

Quick update on the fueling,

These runs are traveling back & fourth to the same place every day, mostly carriage way @ 80-90 MPH. He told me....

The old benchmark was 100 miles = £18

The new setup is doing 120 miles = £20

I know there is a difference in test mileage, but that's just because of a lack of attention to detail & looking at the mileage.....

There is a slight increase in MPG, but I have noticed the idle slightly erratic, fluctuating 100-200 RPM, so I followed the advice from Cybercarl.

I found low speed steady state cruise, say...at 20mph/2000rpm - 30mph/3000rpm a good low down test. Hopefully you should see a nice increase in MPG.

Whilst doing the low speed cruise test, I noticed that also is erratic. Its not bad, but it is noticeable, like a small hunting feeling.

So, it looks as if the carbs are coming off again this weekend for another fiddle

Quick ask, I have seen some pictures of lengthened air screws with knurled ends floating about on the site, any clues to what they are off & how much they are?

Thanks in advance.

[VTRDark]

120miles is bloody good.

Whilst doing the low speed cruise test, I noticed that also is erratic. Its not bad, but it is noticeable, like a small hunting feeling.

I would try a 1/8th to 1/4 turn out (richer) on the fuel mixture screws.

Quick ask, I have seen some pictures of lengthened air screws with knurled ends floating about on the site, any clues to what they are off & how much they are?

They came from the States.
http://www.superhawkforum.com/forums/mo ... rew-31449/

Great idea but you still have restricted access unless you relocate the coolant bottle. Try getting you fingers in to turn them with a hot engine running, count turns while listening to the engine idle and exhaust note.

This is what I use. It's still a little awkward on the rear carb but it gets easier with practise.
http://vtr1000.org/phpBB3/viewtopic.php ... 35#p254323

(:-})

[Varastorm]

Hi,

fuelling update again , been for a ride around Snowdonia today. Betws-y-Coed, Blaenau Ffestiniog & Bala, really cold & greasy roads dictated the smooth & easy pace.

Filled her up after 103 miles £14.50...

I pulled the front plug half way through the day for a quick look & it looked darkish grey around the thread base with grey strap & electrode. I am a little concerned, so will strip her down tomorrow & richen the pilot & maybe lift the needles slightly.

It runs really well, the best it has ever been TBH. I can't hear any pinking at all, but the exhaust is quite loud though. I'm getting paranoid with it costing just £14.50 to brim her after over 100 miles. That's too good in my book detonation?

Any help regarding what colour plugs Dr Honda or similar velocity stacks produce with various jetting would be gratefully received.

Thanks in advance.

[Phil_H]

Wouldn't it be more accurate to compare miles/litre or miles/gallon?
Fuel cost has reduced quite a bit over the last few months making miles/£ wholly innacurate!

You are the first person I've come across who isn't happy with reduced consumption (cost)

[Varastorm]

Hi Phil,

I know I should do the maths but it never crossed my mind, in Betws it was £1.22 a litre IIRC so £14.50(to fill her) ÷ £1.22(cost per litre) = 11.8 (litres bought) so 11.8 ÷ 4.5(litres in a (UK)gallon) = 2.6 UK gallons bought with £14.50, so 103(miles) ÷ 2.6(UK gallons) = 39.6 to the gallon

I just don't want to melt a piston by running her too lean, that's my main priority & worry when playing around with experimental engine bits because its my daily ride

I am just trying to get a good base setting so that if anyone tries this (very cheap) modification they can adjust the carbs and it works straight away.

I had the carbs off over the weekend & have adjusted the front pilot to 1 turn out & rear pilot to 1 1/4 turns out, I have swapped the plugs for some new ones & taken pictures of them but no means of posting. Will update soon.

[sirch345]

Hi Phil,
I have swapped the plugs for some new ones & taken pictures of them but no means of posting. Will update soon.

You can post any pic's you have onto me Phil, I'll post them up as before. I'm enjoying reading this thread

Chris.

[VTRDark]

I just don't want to melt a piston by running her too lean, that's my main priority & worry when playing around with experimental engine bits because its my daily ride

A little lean at lower revs is not a bad thing but as long as it's not heavily lean at higher revs I wouldn't worry too much. It's low compression pistons and as standard everything I suspect (being a road bike) is on the conservative side allowing room for error and Honda would have designed the engine with engine reliability and longevity in mind. Also be aware that if your using Iridium plugs they are not as accurate to read as a traditional standard plug. Plug chops IMO are not always the best way to go when judging things. Personally I think your at that stage now where a Dyno run would be most beneficial to see where things are at.

(:-})