Yet another VHB carb part to find

[Missionguzzi]

First, if you want to retain your sanity, stay away from incomplete VHB carbs.  Components are becoming more and more difficult to source, which seems to have occurred over just the past year or two.
The latest pair I have were incomplete, missing float bowl, float bowl nuts and 1 accelerator pump (among others I may not have discovered yet).  Charlie Mullendore was kind enough to find me a pair of float bowl nuts (I had extra float bowls, but not the nuts/drain plug).  I THOUGHT I had a complete accelerator pump, but found it's missing the main jet holder, Dell'orto part number 7828.  Simple little screw-in brass piece with external threads to fit into the accelerator pump body and internal threads to fit the main jet.  Can't seem to find one in the U.S., and purchase/shipping from Europe is prohibitively expensive.  Anybody have a spare?  I hesitate to ask Charlie again because he's going to think I'm a pain in the rear.....    I'll post a picture in a short while.   THANKS for any help with this.  And I'll add that I don't know what other surprises I'll find and probably be begging for.

[Missionguzzi]

This is what it looks like, greatly enlarged.  The hex is 10mm, I believe.

[Antietam Classic Cycle]

I have a very limited supply of those, used. Could have included one with the bowl nuts that went out yesterday. See what else you need and let me know.

[wirespokes]

Looks like something that wouldn't be too difficult to make. Probably modify a brass bolt.

It used to be no one wanted the VHBs and they went really cheap. Not any more. My G5 runs fine with them, but if I ever have too much trouble with them, I'll switch to PHF36s.

Another difficult item is the floats. Since the new white ones are junk the alternative is good used black ones.

[Missionguzzi]

All of my early Guzzis have run fine with VHB c30 and c29 carbs, including my current 2 850Ts and 1 G5.  I experimented with a PHBH 30 and was not happy with the overall performance or fuel efficiency (but I didn't chase the issue with jets and needles, etc).  Also, they didn't fit well under the side covers due to a different intake manifold. 
I'm wondering if anyone has experience, information or opinion on VHB-A carbs.  They're different from the VHB-C carbs in having no accelerator pump and other details, and I hear they're a higher-performance carb, possibly more difficult to tune.  Thoughts?

[Antietam Classic Cycle]

All of my early Guzzis have run fine with VHB c30 and c29 carbs, including my current 2 850Ts and 1 G5.  I experimented with a PHBH 30 and was not happy with the overall performance or fuel efficiency (but I didn't chase the issue with jets and needles, etc).  Also, they didn't fit well under the side covers due to a different intake manifold. 
I'm wondering if anyone has experience, information or opinion on VHB-A carbs.  They're different from the VHB-C carbs in having no accelerator pump and other details, and I hear they're a higher-performance carb, possibly more difficult to tune.  Thoughts?

Not really "higher performance" since they're virtually identical save the lack of an accelerator pump. The A version does not work well on Guzzis, no matter how it's jetted.

[wirespokes]

Flat slides, like the VHBs, are a higher performance carb than round slides. I don't know why that is, but that's what I've heard and what I've experienced. If I was going to replace the VHBs, I'd probably mount some PHF 36 Dells.

[turboguzzi]

FWIW,

I omitted the fuel pump from the VHBs in my 1000 SP , worked super well, YMMV of course.

When i got tired form the stupidly heavy slide springs on long rides, I adopted the idea of our badly missed mtiberio, of using cheap PWK copies.

Well, it's another world, both in throttle response and effort at the throttle, to quote him: feels like a fuel injection throttle

Not bad for 50$ (for two carbs :) )

[guzzisteve]

Thanks Turbo, I was waiting for Charlie to mention it, Ha Ha . I was going to in another minute. PHF's are more performance than VHB's, why do you think they used them stock on performance models.

[Antietam Classic Cycle]

I've already mentioned the PWK copies to Missionguzzi in an email.

From Mike:

I have been posting about this on the loop list, but I should really spread the
news. I have been looking for a replacement for the old square slide VHBs for a
while. I found a chinese made Keihin carb knockoff modified to replace british
Amals. Mating a pair of those with a set of the Guzzi Amal manifolds (yes small
valve roundfins came with Amals for a while in 1974 I believe) is possible and
practical. Other than buying the manifolds, the carbs, and a pair of off the
shelf throttle cables, the whole conversion required no machine work or other
special fitting or cuttin (other than fuel line)...

I have never installed a totally different carbs on a bike and had them work as
perfectly as these carbs did tonight on my Eldovert. It all jelled when I got
some throttle cables in from MG tonight. I asked the guys at MG to measure the
freeplay of their throttle cables, and asked them to send me a pair of whichever
ones had the most freeplay. It ended up being their "no name throttle to VHB"
cables. I knew the Keihins ate up more cable than the VHBs so I
thought I'd start with these cables. As I was doing some measuring tonight
trying to figure out how much I was going to modify the cables, I realized they
would work with my Thom 2C throttle and the Keihins as delivered. Then I
realized I had everything I needed, and by 8:30 I had them installed. I went to
start the bike and it didn't even cough. Oops, I left the spark plug wires off
(I removed them to get them out of the way). Once I had spark, choke, the bike
started right up and settled into a decent idle. I rode off down the street, and
by the time I went 3 blocks, it was idling high, oops I left the chokes on.
Chokes off and it idled perfectly, and ran great in my residential neighborhood.
Quick to get home, finish buttoning up the tank bolts and put the saddle on, get
my jeans on and head out for a top speed run. Bike pulled cleanly to 100, and I
ran out of road. I'll have to watch the gas mileage, and do some plug chops to
get these carbs any better set up they are that close. I uploaded some pix so
you can see the sano install with the Guzzi Amal manifolds...



They have carb mounted chokes, but a cable kit is available, I might spring for
that. They take 1/4" fuel line, but since I was set up for filters that take
1/4" line, that issue was no sweat. I was using dual spigot banjos on my VHBs
for a crossover, I'll either have to "T" each line to do the same or use both
petcocks. I do have a set of Tonti petcock adapters, so that will give me a
reserve back if I don't go for a crossover. The inlets are about 2" dia, so I'll
probably pick up a pair of unifilter foam socks to handle the air cleaning
chores. There are no clearance issues between the float bowls and the bell
housing. In other words, a bolt on perfect fit as long as you have the Amal
manifolds... Oh yea did I mention the throttle pull is oh so much lighter...

More later...

The carbs are made by a Brit Bike specialist called JRC Engineering
(http://www.jrceng.com/). They are "Keihin PWK" oval bore (28/30) semi flat
slide carbs. They are big with the moto cross crowd. JRC doesn't do retail, and
has dealers. I used Specialty Spares 253/853-1420. They were $100 a pop plus $15
shipping. The manifolds were made by Moto Guzzi to allow mounting of Amal carbs
to Eldos back in the early to mid 70's (either Dell'Orto couldn't supply enough
carbs to Guzzi, or Guzzi didn't pay their bill!?!). No one ever liked the amals
on guzzis, so the manifolds are easy to find used. While a lighter throttle pull
is one reason to convert, I was hoping for more precise metering and
adjustability, together with a sense of lets do this because we can...


Dec. 5th, 2011

Still on the bike. All I did to jetting is go one smaller on idle to 35, and lean out the ims to 2.25 turns off seated. 37 to 39 mpg with my convert.

still occasionally pops, but then so did the vhb's. Bike does have 155000 miles, so I don't expect perfection. Throttle spring is soooo much lighter. Like FI. I recco this mod to anyone that has 29 or 30 mm vhb carbs...

[Missionguzzi]

Thanks for the input on the VHB A-type carbs.  Interesting that they can't be jetted to work adequately well on Guzzis.  I see some practically being given away, and thought they might be a "plug and play" for the VHBC type, but I guess not.  And I like the recommendation of the PWK copies.  The price is right and they're simple, as long as you have the manifolds for Amals.  Maybe next time I build a bike, I'll chase down a pair of these.  For now, I'm still trying to get this set of VHBCs together, and scrounging parts from Charlie Mullendore.  I wish I'd had the foresight over the past few decades to save critical parts like carbs.

[Antietam Classic Cycle]

Thanks for the input on the VHB A-type carbs.  Interesting that they can't be jetted to work adequately well on Guzzis.  I see some practically being given away, and thought they might be a "plug and play" for the VHBC type, but I guess not.  And I like the recommendation of the PWK copies.  The price is right and they're simple, as long as you have the manifolds for Amals.  Maybe next time I build a bike, I'll chase down a pair of these.  For now, I'm still trying to get this set of VHBCs together, and scrounging parts from Charlie Mullendore.  I wish I'd had the foresight over the past few decades to save critical parts like carbs.

It's possible to use PWKs without Eldo/Amal manifolds, you'd just have to do a bit more work. VHB manifolds could be modified, or possibly those from a later model that used PHFs. PWK copies are super cheap: https://www.amazon.com/Carburetor-100cc-Engine-Motorcycle-Scooter/dp/B0G13BMT9K but would require jetting changes to work as well as those that Mike used.

[wirespokes]

Do they make the PWKs in left and right hand versions?

[Moparnut72]

I have a pair of those that I was going to put on my T3 project. I I can be somewhat assured that they will work I have a pair of VHB-C's that you can have for a very modest amount, just trying to recoup a little for my project. I am reluctant to mess with them as they have spent who knows how long full of water and old fuel. I cleaned up one up as best I could but it is still sketchy. The pin that holds the float has been driven in so far into a blind hole that there is no way to remove it to get to the float valve. When I started on the second I found that it was worse so I quit and got these aftermarket ones. They also came with pod filters. For what I paid for them not much to lose considering the cost so far. The brand I got are apparently very popular with off-road racers. I also am very impressed with the quality, the most nicely finished carbs I have ever seen. The slides are so well polished they are like a mirror. They should mount up to the manifold I have fairly well with a piece of stiff hose, the diameters are almost identical. It is going to be a while before I get to test them.
kk

[Antietam Classic Cycle]

Do they make the PWKs in left and right hand versions?

Probably so. There's a bump on the side of the carb where one could drill and tap for the idle speed screw, but I don't see the same for the air screw.

If anyone else is looking for that jet holder, they're not as "rare" as it might seem, Harper's has 91 of them in stock.
https://harpermoto.com/products/jet-holder-17939400

[Missionguzzi]

Charlie M - When I searched for the main jet holder for the VHB at Harpers, using Dell'orto p/n 7828, nothing showed up.  The only "main jet holder" that showed was for the PH-type carbs.  I couldn't find elsewhere the specific Guzzi p/n, as all the carb diagrams I could find only showed the Dell'orto part numbers.  Interesting.  Same story at Bevel Heaven.  MG Cycle doesn't even carry the main jet holder.  Anyway, thanks for the part number reference.

[Antietam Classic Cycle]

Charlie M - When I searched for the main jet holder for the VHB at Harpers, using Dell'orto p/n 7828, nothing showed up.  The only "main jet holder" that showed was for the PH-type carbs.  I couldn't find elsewhere the specific Guzzi p/n, as all the carb diagrams I could find only showed the Dell'orto part numbers.  Interesting.  Same story at Bevel Heaven.  MG Cycle doesn't even carry the main jet holder.  Anyway, thanks for the part number reference.

I found the part no. and part using Harper's parts diagrams.

[Missionguzzi]

 Thanks, Charlie.  The exploded diagram with Guzzi part number references is very helpful and supplements the diagram with Dell'orto part numbers.  I printed the diagram and the parts list for future reference.