Carburettor Settings

[Rob B]

Evening all,

Does anyone have a list of carburettor settings, needles and jets please?

On my bikes past and present / V1000 and Vampire I have seen a fair range of set-ups and logged them all but I don't actually know what is best or what is right.

Needles - K1, K2 or K27?
Needle position?
Throttle Slides (cutaway and pump ramp) - 60/3 or 50/3?
Main Jets - 145, 150, 155, 160 or 165
Idle Jets - 55, 60 or 65?
Atomizers - AB260, 262, 264 or 265?
Pump Jets - 33, 35, 38 or 40

Other settings which seem to be standard are:
Needle valve - 250
Starter jet - 70
Float height 18mm

I have set-up the accelerator pumps to 2.5ml per stroke. I do this with the carburettor clamped upright on the bench and a 75ml graduated syringe body connected to the inlet banjo with a short length of pipe. 20 full strokes on the pump uses 50ml of fuel. I have no idea if this is right but it seems to work.

Any ideas or recommendations gratefully received!

Many thanks,

Robert

[Miti]

I only have experience with my own bike's carbs/settings Rob, but for what it's worth, here're the details:

Needles - K2 (recently replaced these as I found they were "pitted")
Needle position - Centre
Throttle Slides (cutaway and pump ramp) - 60/3 or 50/3? - Sorry... Not Noted
Main Jets - 150 - Seems very rich though
Idle Jets - 50
Atomizers - 265
Pump Jets - Not Marked (I did check)

Other settings which seem to be standard are:
Needle valve - 250
Starter jet - 70
Float height 18mm (Front was 19.5, but I reset it to 18)

[Rob B]

Thanks very much for this. Much appreciated.

Interested to note the K2 needle because they are a bit richer than the K27's I have fitted to the bike that I have which is weak on the Progression (1/4 throttle onwards). I was going to increase the slide cutaway from a 60 to a 50 but will first try lifting the K27's to the lowest (weakest) notch and if that doesn't work then try a set of K2's.

The current K27's are new because, like yours, the old ones looked like swiss cheese! but they were also K27 not K2.

Thanks again and all the best,

Robert

[Rob B]

Sorted! At least for the engine with bigger valves, stronger springs, KENT CPL2 cams and 70mm velocity stacks where I ended up today with:

K2 Needles, AB265 Atomisers, 603 Slides, 65 Pilot jet, 155 Main jet, float height 18.5mm, pump jet 35 and pump delivery 3ml. - It is running very nicely indeed now.

Tomorrow I will try this set-up on the standard (EN10'd) bike with air-box and filters and then work from there and report back on the best combination I can find for that one.

Many thanks

[Miti]

Hi Rob;

Just a thought... My V1000 has the following bits and pieces in the carbs:

Idle Jet - 50
Main Jet - 150
Choke Jet - 70
Needle - K2
Atomiser - AB265
Float Height - 18mm

Sorry, I don't know what the slide cutaway or accel pump jet size is...

The bike starts first time every time, but is running really rich... I recently made the mistake of adjusting the rear mixture screw to the same setting as the front and the richnessosity has increased dramatically...  So I don't have to be Sherlock Holmes to deduce that my mixture screws are too far out...

I think I've been maladjusting the mixture screws instead of readjusting the idle speed screws... Do you have an "initial setting" I could try? (EN10 bike, bog standard apart from hardened valve seats).  I'm planning on having a go with a colourtune this week to see if I can get better results... My 45mpg fuel consumption has gone down to 40mpg since my (unnecessary) tweaking and I want that 5mpg back!

Jeff

[Rob B]

Hello Jeff,

The idle mixture screw starting point is theoretically 1 1/2 turns out but in reality my bikes are about one turn out which is a bit less mixture being added downstream of the throttle valve, hence leaner. Remember the mixture screw is simply controlling the amount of pre-mixed air/fuel that is being added to the air hissing under the throttle valve when it is resting on the speed screw. So, if you open the mixture screw you are increasing the volume of fairly rich fuel/air being added to the air and so you are enrichening the combined mixture.

There is a lot of talk about the fine passages in the PHF but in reality the only critical one is the brass calibrated idle air metering passage which you can just see if you look down the idle air inlet. I have no idea what size this is but it is tiny and the first thing to block if you run without air filters, which results in a very rich and uncontrollable idle. Don't be tempted to stick a needle down it because it is very accurate. Better to squirt carb cleaner through it.   

So, On H1 (My original V1000) I run with a 65 idle jet and more importantly a 165 Main Jet because I have junked the air boxes and replaced with 70mm velocity stacks but with reworked heads, bigger valves, Kent CPL2 cam profiles etc. etc. Therefore the settings on this bike are irrelevant for you.

H2 (Vampire) is now running on K&N filters so I have fitted 260 main Jets and 60 Idle

On H3 (The EBay V1000) I still have the twin air boxes and it is a basic EN10 bike so this is more relevant with:

155 Main
55 Idle
K27 Needle
264/262 Atomizer

I think the clue is the atomizer and needle combination because all of the above bikes run with smaller 264 Atomizer on the rear cylinder and even smaller AB262 on the front and the thicker K27 needle (middle groove) front and back. Hence weaker than yours on the rear and much weaker on the front.

Personally I find that the 50/3 throttle valve cutaway gives smoother progression than the 60/3 cutaway so it is worth checking that too.

I hope this helps,

Robert

[Miti]

All good info Robert... Thanks

I had a quick muck about last night with a Colourtune... Blooming hopeless!!  The ambient light levels have to be near pitch black for anyone to read the flame colour correctly and i'm buggered if I'm locking myself away in a darkened garage with a machine that is deliberately trying to hydrocarbon me off the face of the planet..!!

I went back to 1st principles... I set the idle screws for a fast idle of about 1,500 rpm and set the idle mixture screws 1¹/₄ turns out...  Then I "tweaked" the mixture screws, listening (and feeling) for the smoothest pulses from the exhausts...  AS the pulses smoothed out, I reduced each idle screw by an equal amount... I ended up with a hot engine, an idle speed at about 1,100 rpm and the air mixture screws 1¹/₈ out on each carb...  I think that the overall mixture will still be too rich, but I'll go with this as an interim setting...

I completely understand why anyone would want to junk the original airboxes... They're a NIGHTMARE to work around!! But I want to keep the bike relatively original, so they're staying (for now, at least).

Jeff

[Rob B]

Hello Jeff,

A Morgan Carbtune - http://www.ebay.co.uk/itm/morgan-carbtune-11-unused-/190860858169?pt=UK_Motorcycle_Parts&hash=item2c70319339

is also a good idea for balancing the throttle-stop screws but more importantly the throttle cables.

I also agree with keeping the airboxes for originality; on a shelf in the garage :-)

Cheers,

Robert

[Miti]

I have a Carbtune II... I've had great success with it over the years, but the V1000 steadfastly refuses to "play the game".  I can't get the bugger to read vacuum on the front cyl... I've done compression checks (185psi on both), rebuilt both carbs, removed/examined both inlet manifolds and spacers/gaskets... No apparent defect (now) but no difference to the Carbtune, front cyl is always low on vacuum... I even tried replacing the throttle cables and swapping the "channels" about on the carbtune... No difference...

The rear cyl readsno problem, but the front just dips down and then rises a few seconds after the rear, so synchronisation is a non-starter... I'll get to the bottom of it, but not tonight...

Jeff

[Rob B]

Just a thought, have you checked for leakage at the inlet manifold joint where it connects to the head? As it doesn't have a gasket or an O-Ring then it is hard to imagine why it would ever seal unless you use copious amounts of silicone snot....

[Miti]

My bike has two gaskets and an insulating spacer twixt head and manifold castings...  Whenever I have them apart, I grease the gaskets prior to reassembly...

I've sprayed the joints with easystart to check for leaks (makes the engine rev if it gets sucked in) but no signs of a leak...

I'm wondering if the carbs were so far out of balance last time I use the gauges that synchronous readings were never going to happen... I'll try again...

Jeff

[Miti]

Tried again... No change... I've now tried a Mk II Morgan Carbtune (all 4 channels in almost every conceivable combination of pairs) and a pair of bourdon type gauges with neat little adjustable dampers in the vacuum lines... Same symptoms persist...

At idle:

Both cylinders read about 10 mm/Hg with an idle speed of about 1,050 rpm (on bike's tacho).
I can adjust idle screws, mixture screws and cables... All affect idle speed/stability as you would expect and the bike has a stable tickover as soon as it's properly warm...

When revved:

The bike revs quite freely, but gives different readings on the gauges... The rear vacuum rises as you would expect, but the front vacuum dips down, only rising when the engine is on the overrun.

I was experiencing horriffic backfiring and thought that the carbs might be so wildly out of balance that the vacuum readings were actually "out of phase" (if that's possible..??) so I adjusted the cables mechanically (set for point where both slides are exactly in line with top of carb venturi) and then tried again... Exactly the same...!!

I've covered over 2k miles on the bike this year, mostly on A-Roads and it's been totally reliable, always starts and (up to 75 mph) it's great... It totally runs out od steam at 80 mph and the plug colour (and smell of unburnt fuel) suggest it's running really rich (so no air leak..?)

One thing I haven't considered is the exhaust system... The RHS silencer appears to be a Motad one - there is a baffle end plate visible about 2" or so down from the tail end of the pipe, but the LHS one is different and doesn't have this plate (or the Motad stamped numbers).

Would uneven back pressure cause the problem I'm having with balancing the carbs perhaps..?

And... During a chat I had with Colin Evans this week, he retold the tale of the DellOrto folk comimg over to set up a pair of PHFs on a V1000, so that the carbs for the production bikes could be preset prior to delivery... Apparently, they turned up, only to find that there wasn't a bike available to test and setup the carbs... So... Hesketh took delivery of all the PHFs with factory settings being the Dellorto folks' "best guess", loosely based on the settings they had used for the Ducati 900SD (864cc, 74bhp, 32mm PHF carbs).  It's a wonder any of them run right..!!

Anyway... It'll be back off the road as soon as the salt goes down (another month or so) and those carbs are going to be 100% checked over again...

Jeff

[Miti]

I'm revisiting this thread as it's become relevant once again...

My V1000 is BOTR after the winter workover... I've re-shimmed the heads, re-timed, the cams, reset the ignition timing and readjusted the idle speed...

I took her out for a spin yesterday and there a number of notable changes in the way she runs...

• Definitely more power from about 4k rpm up...  Really pulls hard now...
• Hesitation from idle, through 1/4 throttle.  It appears that one cyl is "stuttering"
• More "stuttering" during slow speed overrun... causes transmission "rattle"

The MPG was well down too... She went onto reserve at approx 130 miles (ish) which is NOT good...  Although, in the bike's defence, I was seriously enjoying the extra oomph and some spirited riding through some of Perthshire's finest roads will never produce the best fuel economy...

I didn't get around to fettling the carbs over the winter, but I reckon it's overdue now...

Jeff

[Miti]

After three fouled spark plugs (not easy on a twin..!!) I made some time to look at the front carb (all three plugs fouled in the front cyl).

I removed the carb, stripped all the jets out and cleaned everything with carb-cleaner and an airline...  Once reasembled, I checked the float height... 25mm..!! 

I set the height myself last year... 18mm with the same steel rule...  I figure that the solid carb mounting allows engine vibes and road bumps to be transferred, and that this jolts the float height out of adjustment... 

Bottom line is that the front plug hasn't fouled since and the hesitation at about 1/4 throttle is albeit gone...  I'll make some time to check the rear carb too and then set about balancing the buggers again...

Jeff