Source for NEW VHB carbs...?

[moto]

I was wrong about the needle: it's not steel. On the other hand, mine is not much worn, especially compared to the difference just reported in the jet: 2.65 vs. 3.01mm! It's the annular space between the needle and the jet that counts.

I've got the dimensional specs for the V9 needle around somewhere. I'm going to measure my needles before buying new ones.

How did you measure the bore, by the way? Very impressive.

Just ordered two new atomizers.

Moto

[Antietam Classic Cycle]

I've got the dimensional specs for the V9 needle around somewhere. I'm going to measure my needles before buying new ones.

I posted a link with the dimensions of all the needles last night:
https://www.thisoldtractor.com/dellorto_slide_needle_specifications_for__vhb_motorcycle_carburetors_-v_slides-.html

[moto]

Thanks, Charlie.

It is possible to approximate how much excess flow the needle and needle jet will have with a worn jet.

First, the needle itself is a simple geometric object: a cylinder attached to a truncated cone. The cylindrical part for the V9 needle is 2.48mm in diameter. The needle maintains that diameter down to the point marked "C" in the diagram on the page that Charlie linked to. (It is not immediately clear, but still true, that the diameter given in the table for point A also applies down to point C.) Below that is the truncated cone, which terminates at a diameter of 1.80mm, the point marked "B."

As the Dellorto guide explains, the needle and needle jet combination become important in "high speed" use, which it specifies as about 1/2 throttle. I don't have a carb off my bike so I won't try to measure exactly where on the needle half throttle occurs. (If any one does want to measure that, please do.) I will assume first that half throttle is one half way down the truncated cone. This means the diameter of the needle that regulates fuel flow at half throttle would be half way between the point C and point B diameters, or (2.48 + 1.80) / 2 = 2.14mm. We are interested in how much difference in flow we get at this point when the jet is 3.01mm in diameter instead of the correct 2.65mm.

The flow through the jet should be approximately equal to the cross-sectional area of the jet minus the cross-sectional area of the needle at one-half throttle. This is a ring-shaped, or annular, area. I will calculate it twice, once for a new jet with a 2.65mm diameter, and once for a jet worn to 3.01mm.

A) The annular area for a new jet:

Area = area of the jet minus the area of the needle (at the specified point)
        = pi (2.65/2)^2  - pi(2.14/2)^2
        = 5.515 - 3.597
        = 1.918 mm^2

B) The annular area for a jet worn to 3.01mm:

Area = area of the jet minus the area of the needle (at the specified point)
        = pi (3.01/2)^2  - pi(2.14/2)^2
        = 7.116 - 3.597
        = 3.519 mm^2

C) Ratio of the annular areas, worn versus new:

Ratio = 3.519 / 1.918
        = 1.835

So a worn jet of 3.01mm diameter should pass about 83.5% too much fuel at high speeds (half throttle), even with a new needle. This was an eye-opening calculation for me.

I do have a needle removed from one carb. After cleaning it briefly with a Scotchbrite pad I see no signs of wear except some minor denting extending around the circumference about 41mm from the tip, or 15mm into the cylindrical section. I would guess this is the position of the needle that contacts the jet opening at idle. If so, a better calculation for the half-throttle position on the needle might be 3 + 38/2 = 21mm from the tip (allowing for 3mm that never leaves the jet). This would be 21/26 or 81% up the conical part, giving a diameter at half throttle of (.81*2.48 + .19*1.80)  = 2.351. Making the same calculations as before, with this new needle diameter, gives the area of the needle at 4.341, and the ratio of the two annular areas (worn vs. new) of (7.116 - 4.341) / (5.515 - 4.341) = 2.364, implying the over-fueling rises by 136% with the worn jet.

I did measure the needle's two specified diameters and found them to be within spec, to the limits of my instrument.

Summary: A worn jet (at 3.01mm diameter) is more than enough to wreak havoc on the fueling at high speeds, increasing it either by 84% or 136%, depending on the assumed position of half-throttle. My own needle is completely smooth in appearance except for marks at 41mm, which I judge to occur when the bike is idling, and which marks are well outside the range of the taper. I concluded that I will probably need a new jet (assuming mine is enlarged) but not a new needle. The calculations were so persuasive that I went ahead and ordered two new 265 atomizers from Harpers before taking off my carburetor!

The needle seems to wear appreciably only at its contact point at idle, which is not relevant to its function. But the same contact at that point ruins the jet.

Moto

[radguzzi]

moto,
The measurement for the atomizer bore was not great feat, simply a digital Vernier and accurate enough for this discussion to show that the ID is worn.   

What is impressive is the calculation that you posted with a 3.01 mm bore and the effect on fuel consumption.  Just Wow...!  Indeed quite the eye opener...!

Thanks for that, a good sanity check that my issue Must be in that worn jet.  Or in the way that jwinwi stated "Hogged Out"
rad__

================ 

Charlie,
The chart that you linked for needle dims proves your point about the differences between the V9 and V5 needle.

Thanks,
Rob



One other possible issue showed itself when I removed the manifolds from the VHB carbs today getting ready for another ultrasonic bath...

The plastic insulators did not want to let go of the manifold.  At all, I finally had to gently vise the carb body with thick cloth buffers on the jaws to twist the manifolds off.

How on Earth will those go back on...?  Grease or light oil..?  Would that not help break down a plastic, oil based product...?  The fit is Very tight.

This concerns me, looking forward to reassembly.

Thanks,
Rob


 

[radguzzi]

Greg also shows this exploded diagram labeling the parts:

moto,
I found one purveyor of the parts I need and while looking through the list-o-stuff for VHB carbs I noticed they have a Mixture Screw Set  #17 on this diagram (oddly enough they list as an Idle Screw) WITH an O-Ring and washer... 

My carbs (VHB C models) did NOT have the O-ring or the Washer... 
 This diagram does not list the O-Ring or Washer either.

Thoughts...?

https://guzzino.stores.yahoo.net/idscsephfphm.html


Thanks,
Rob

[Antietam Classic Cycle]

17 is what I can an idle mixture screw. 90% of VHBs don't use the o-ring and washer, doesn't seem to make any difference either way.

[yackee]

Before measuring wear don't you need to know what the manufacturing tolerances were? According to one of my Vespa suppliers (German shop SIP), Dellorto main jets, at least, had pretty large tolerances, they claim "DELLORTO jets can vary up to +/- 0.05mm from the given value".

Not sure if this carries over to other components, or if it is valid for stuff manufactured back in the 70s.

[radguzzi]

17 is what I can an idle mixture screw. 90% of VHBs don't use the o-ring and washer, doesn't seem to make any difference either way.

Gotcha,
Thank you,
rad__

Before measuring wear don't you need to know what the manufacturing tolerances were? According to one of my Vespa suppliers (German shop SIP), Dellorto main jets, at least, had pretty large tolerances, they claim "DELLORTO jets can vary up to +/- 0.05mm from the given value".

Not sure if this carries over to other components, or if it is valid for stuff manufactured back in the 70s.

I guess however, the disparity between 2.65mm and 3.01 is huge.  The calculation that moto showed us talks directly to the additional amount of fuel consumed when the wear is greater than design diameter.

rad__

[Rich A]

Jet & needle: https://www.ebay.com/itm/183926668299?hash=item2ad2e23c0b:g:rZ0AAMXQ01tRTuYO

Rich A

[radguzzi]

Jet & needle: https://www.ebay.com/itm/183926668299?hash=item2ad2e23c0b:g:rZ0AAMXQ01tRTuYO

Rich A

That is a good price for a set.  I went with motoguzzino, they had both the V9 Needle and the 265 Atomizers. 

As much as I like to stay with the usual suppliers I also like to have a supplier to fall back on.   
As with Triumph vendors, I seldom shop around however, often one place will not have everything that I need and instead of making two small orders to two different vendors I will go to the one with all the bits.

I realize also that the V5 needles would have worked as well as the V9 but I just wanted to get the carbs back to stock trim and go from there.

This has been a great learning experience, I appreciate the input from you all.

Update in a week or so...

Best,
Rob

[Rich A]

That is a good price for a set.  I went with motoguzzino, they had both the V9 Needle and the 265 Atomizers.  ck trim and go from there.

This has been a great learning experience, I appreciate the input from you all.

Update in a week or so...

Best,
Rob

Curiously, you and I seem to be on a parallel track--I'm in the process of refreshing the carbs on my 77 'vert. I think I bought the last set of 265s from MGC, but that was a week ago.

It is a good learning experience--just hope it all works out well.

Rich A

[moto]

Before measuring wear don't you need to know what the manufacturing tolerances were? According to one of my Vespa suppliers (German shop SIP), Dellorto main jets, at least, had pretty large tolerances, they claim "DELLORTO jets can vary up to +/- 0.05mm from the given value".

Not sure if this carries over to other components, or if it is valid for stuff manufactured back in the 70s.

I doubt that what you were told is true, or at least was true, since Dellorto made both a 264 and a 265 atomizer, I believe for one of the round slide models. If the tolerance was plus or minus 0.05, that wouldn't have made any sense. For that matter, there are pages and pages of different jet needles for the round slide models, often differing by very small amounts. Again, that would make no sense if tolerances were as sloppy as your shop told you. The production of both the V5 and the v9 needle, previously discussed, is another point against the idea that tolerances were so poor.

[moto]

moto,
I found one purveyor of the parts I need and while looking through the list-o-stuff for VHB carbs I noticed they have a Mixture Screw Set  #17 on this diagram (oddly enough they list as an Idle Screw) WITH an O-Ring and washer... 

My carbs (VHB C models) did NOT have the O-ring or the Washer... 
 This diagram does not list the O-Ring or Washer either.

Thoughts...?

https://guzzino.stores.yahoo.net/idscsephfphm.html


Thanks,
Rob

The oring sounds like an emissions control modification. I thought maybe I had seen a mention of this in Guzziology but a quick perusal of the chapter turned up nothing. I think Charlie gave you the most important information already.

Moto

[mtiberio]

Idle mix screws will WORK with just the screw and a spring, but they COULD leak a bit of air. They are supposed to have a washer and an oring outboard of the spring. The washer I assume is to protect the oring from the sharp edge of the spring, and the oring to prevent air leaks and to hold the whole assembly together during insertion/removal. If the screw comes out without this entire stack, I always go into the hole with a piece of safety wire bent into s short "ell" to hunt for the oring, washer and spring.

[moto]

Idle mix screws will WORK with just the screw and a spring, but they COULD leak a bit of air. They are supposed to have a washer and an oring outboard of the spring. The washer I assume is to protect the oring from the sharp edge of the spring, and the oring to prevent air leaks and to hold the whole assembly together during insertion/removal. If the screw comes out without this entire stack, I always go into the hole with a piece of safety wire bent into s short "ell" to hunt for the oring, washer and spring.

That also sounds reasonable. The exploded VHB parts diagram in the V7 Sport parts manual doesn't show the oring and washer, though, so I suppose they must have been added later on:





Moto

[Antietam Classic Cycle]

None in the VHBs of: V50 II, Morini 3 1/2, Benelli 650S Tornado, H-D Aermacchi 350 or Benelli 175 Enduro.

[mtiberio]

None in the VHBs of: V50 II, Morini 3 1/2, Benelli 650S Tornado, H-D Aermacchi 350 or Benelli 175 Enduro.

You know this stuff better than me. I believe... It works without.

[radguzzi]

Curiously, you and I seem to be on a parallel track--I'm in the process of refreshing the carbs on my 77 'vert. I think I bought the last set of 265s from MGC, but that was a week ago.

It is a good learning experience--just hope it all works out well.

Rich A

Great minds and all that Rich...    We do seem to have the same types of rides in the garages, Converts and Hacks.  You don't happen to be into Triumphs and MGBs do you...?

So the needles and atomizers are on order, update soon.

Cheers,
Rob

[Rich A]

Great minds and all that Rich...    We do seem to have the same types of rides in the garages, Converts and Hacks.  You don't happen to be into Triumphs and MGBs do you...?

So the needles and atomizers are on order, update soon.

Cheers,
Rob

I think we both had early 70s Triumphs (I had a 650 Tiger). As I recall, we both also had mid-60s Yamahas (I had a 250 YDS3). I also had an MGB, sold it a few years ago during a downsizing episode. Kinda weird.

Rich

[moto]

UPDATE/REVISION:

It turns out that the OP measured his jet's diameter incorrectly, at the edge of the top surface. The actual aperture is a millimeter or two down in the bore. I didn't recognize this until I received two new atomizers from Harpers and opened my own carb to compare them with a worn atomizer. I could have made the same mistake without the old and new atomizers side by side.

Being down in the bore, the aperture is hard to measure. I tried to pass two drill bits through the new and worn bits. The 3/32 bit (2.38mm) passed through both, but the 7/64 (2.78mm) did not. So my worn bore is less than or equal to 2.78mm. (The new bore is 2.65mm.) I asked the OP to repeat this experiment and he reported the same result.

Now that we know that his bore is not any greater than 2.78mm, I'll repeat my calculation with that figure instead of his initially reported 3.01mm.

I also removed my carb and measured the points on the needle that are level with the bottom of the main bore at idle, half throttle, and full throttle. That is about where the aperture sits inside the atomizer. These are the points I determined on the needle, measuring from its bottom:

41mm  -- mark on the needle where it meets the slide, when on the second notch. (Not the jet at idle, as I initially thought.)

36mm -- point on the needle passing through the bottom of the bore at idle (as set recently by me)

26mm -- transition from the cylindrical to the conical part of the needle (as specified in the table)

22mm --- point on the needle passing through the bottom of the bore at half throttle

 8mm --  point on the needle passing through the bottom of the bore at full throttle

The travel of the throttle slide from the throttle screw resting position to the point where it leaves the bore at full throttle is 28mm.

From the above I see that the needle is only 4mm into the conical portion at half throttle. Calculating the diameter at that point I get (22/26)*2.48 + (4/26)*1.80 = 2.38mm. So the area of the needle at that point is pi * (2.38/2)^2 = 4.449mm^2. Using that figure with my original formula for the annular areas for a new atomizer and one worn to 2.78mm I get:

A) The annular area for a new jet:

Area = area of the jet minus the area of the needle at 22mm from its bottom:
         = pi * (2.65/2)^2 - pi * (2.38/2)^2
         = 5.515 - 4.449
         = 1.066

B) The annular area for a jet worn to 2.78mm:

Area = area of the jet minus the area of the needle at 22mm from its bottom:
         = pi * (2.78/2)^2 - pi * (2.38/2)^2
         = 6.070 - 4.449
         = 1.621

C_ Ratio of the annular areas, worn versus new:

Ratio = 1.621 / 1.066
         = 1.521

So, with the worn jet aperture set to 2.78mm and the position at half throttle identified as 22mm from the bottom of the needle, the degree of over-fueling is about 52%. That's still big, but it is only an upper limit since the actual aperture may be less than 2.78mm.

Using a #36 drill bit could establish an aperture upper limit of 2.71mm, but I don't have that bit.

This calculation is much less interesting without a reliable measurement of the aperture. I regret that I didn't check the value the OP reported before using it.

I gave a half-hearted try at an alternative measurement by timing the flow of a known amount of water through my new and worn atomizer jets, but couldn't detect a difference, probably because my water reservoir was only 60ml.

Moto

 

[radguzzi]

So I received the bits from Moto Guzzino ( www.guzzino.com) today and stuck them in, runs great, a slight popping at idle so I will mess with mixture screws and all that. I had no time for a ride and a plug chop as I had a prior commitment so I'll get to it tomorrow.  The two minute running time gave me a sooty plug.

Thinking that just lowering the needle from the stock middle position might be do it but again, I'll test it all out.

On the road to recovery.

rad__

[moto]

The measurements I made the other day finally showed me why the needle jet has no effect until nearly half throttle. The tapering part of the needle is still below the aperture until that point, so the needle's taper can have no effect at all until then.





So as the Dellorto manual has always said the procedure is to start with the idle mixture, then the pilot jet and cutaway, and only after that the needle and needle jet. The main jet is for the mixture above that. Good luck, and report your success.

[radguzzi]

The measurements I made the other day finally showed me why the needle jet has no effect until nearly half throttle. The tapering part of the needle is still below the aperture until that point, so the needle's taper can have no effect at all until then.


So as the Dellorto manual has always said the procedure is to start with the idle mixture, then the pilot jet and cutaway, and only after that the needle and needle jet. The main jet is for the mixture above that. Good luck, and report your success.

Correct, I will start with the idle mixture and go for a test blast.  The idle is slightly higher than I recall previously, all the adjusters are bottomed out and there is no issue with the cable routing.

I can get back to the test in a day or so and post the results.  I like your term "report your success"  Will do.

Thanks,
rad__

[chuck peterson]

Ha! I’m stealing this to make a tshirt..

[moto]

Ha! I’m stealing this to make a tshirt..

I'll have one in gray, XL, please. 

Moto

[radguzzi]

I have not been able to make a good run with the Vert due to a prior commitment yesterday and rainy periods today.

There was a short window for a quick blast of about a mile this early afternoon, the mixture screws were inadvertently set at 1 turn out and not 1-1/2 turns out to start with.

Slight popping was present from idle through about quarter throttle and from there, wow, it pulls so clean and strong, more than I recall previously. 
 
I checked plugs when I got back, not a real plug chop. Not too badly blackened, more dark brown to light-ish black.

As soon as the rain clears up I can do more testing with the 1-1/2 turn setting.


==========

@moto,
Your previous comments regarding the taper of the needle being still in the aperture discounts Any possibility that making adjustments to the needle would make a significant difference.

Is it your conclusion that a clip change to lower the needle would that not help lean the mixture any at all...?

More later,
Rob


===============

Chuck,
I'll take a large tee please... 

Thanks,
rad__


 

[moto]

I have not been able to make a good run with the Vert due to a prior commitment yesterday and rainy periods today....

@moto,
Your previous comments regarding the taper of the needle being still in the aperture discounts Any possibility that making adjustments to the needle would make a significant difference.

Is it your conclusion that a clip change to lower the needle would that not help lean the mixture any at all...?

More later,
Rob

Hi Rob,

Lowering the needle will make the mixture leaner, but only in the range above nearly half throttle, where the taper begins to become exposed. (Lowering the needle will also delay the effect of the taper by a small amount since more slide travel will be required to begin to expose the taper.)

Until you reach nearly half throttle, lowering the needle will have no effect at all in making the mixture leaner, since its taper is still concealed below the jet aperture. The taper's effect is constrained to the range above nearly half throttle.

The effect of the tapering part of the needle ends near full throttle when the area of the annular aperture between the needle and jet becomes greater than the area of the main jet (down below, in the float bowl). When that happens, there is no more mixture from the main jet to be passed by increasing the annular area.

The non-tapering, cylindrical part's diameter also affects the mixture before the taper is exposed at nearly half throttle, but lowering the needle does not make the mixture leaner in that range.

This can all be understood by referring to the diagram I posted with the added markings showing where the needle disappears into the jet at 1/4, 1/2, and full throttle, and then comparing those with the marking at 26mm above the needle's tip, which is where the taper starts. Also by reflecting on the admonition of Dellorto to make sure the annular area exceeds the main jet area at full throttle. I don't think I can make a very clear explanation of the diagram without flailing my arms, which doesn't translate into a small amount of text. I'm happy to try to answer specific questions about it.

I think I have this nailed down, but don't forget I'm no specialist. The transitions I just described are simplistic deductions from the positions of the needle and its taper, and from the cross-sectional areas of the main jet and the needle jet annular area. I believe the actual transitions are less precise than this analysis suggests, because of the highly dynamic state of gas flow in the mixing chamber. It's not as precise a science as I make it sound, from what little I've read.

Best,
Moto

[radguzzi]

Well I geared up for a test ride of the changes in the Convert carbs,  I had planned to burn up an entire tank to see how things had improved, trying to be positive here.   

As  headed out the Gen light in the dash came on...  Never had previously.  Instead of the possibility of being stranded some miles from home I turned back to investigate. The only electrical component that I had touched while playing with the carbs was the Vetter wiring harness connector, simple plug and play however, I checked it.   There is no way to connect those two parts incorrectly so I moved on to the headlight, fuses, battery terminals etc...  Headlight was inop, both beams.  

New H4 bulb installed, I hit the left hand control switch with a Hi beam Flasher / Horn rocker switch, when I hit that the horn weakly sounded and the headlight flashed... odd.  

All other lights work as they should, everything, dash lights included so I am thinking that the tin foil innards of the left hand control has finally given it up.  

MGCycle (and others) have a really neat replacement that I like the looks of so I guess that is next.  

I was looking forward to a decent ride to test the carb changes but that will have to wait for a bit...

More later, hopefully soon.
rad__

[Antietam Classic Cycle]

Well I geared up for a test ride of the changes in the Convert carbs,  I had planned to burn up an entire tank to see how things had improved, trying to be positive here.   

As  headed out the Gen light in the dash came on...  Never had previously.  Instead of the possibility of being stranded some miles from home I turned back to investigate. The only electrical component that I had touched while playing with the carbs was the Vetter wiring harness connector, simple plug and play however, I checked it.   There is no way to connect those two parts incorrectly so I moved on to the headlight, fuses, battery terminals etc...  Headlight was inop, both beams. 

New H4 bulb installed, I hit the left hand control switch with a Hi beam Flasher / Horn rocker switch, when I hit that the horn weakly sounded and the headlight flashed... odd. 

All other lights work as they should, everything, dash lights included so I am thinking that the tin foil innards of the left hand control has finally given it up.   

MGCycle (and others) have a really neat replacement that I like the looks of so I guess that is next. 

I was looking forward to a decent ride to test the carb changes but that will have to wait for a bit...

More later, hopefully soon.
rad__

Sold my (fully functional) original switches for $300 and installed this one:
https://www.mgcycle.com/index.php?main_page=product_info&cPath=37_140&products_id=183
Greg Bender sells a "plug & play" adapter harness for it.

[radguzzi]

Sold my (fully functional) original switches for $300 and installed this one:
https://www.mgcycle.com/index.php?main_page=product_info&cPath=37_140&products_id=183
Greg Bender sells a "plug & play" adapter harness for it.

That is the one I have ordered Charlie along with the right hand side, just because.  I have installed this very same switch on another Guzzi previously, wicked easy wire up.

I'll have to contact Greg about the plug and play adapter although I have that pesky Vetter harness to deal with so I do not know if that will be a factor or not. 

Thanks,
Rob