Swapping out the VHBs for PHMs or PHFs?

[R1100purist]

Hello all,
I have an 79 Convert with some crusty VHBs as my next project bike. My aim is to keep things as stock as possible, however I hear that swapping for newer dellortos will lead to a. More midrange grunt b. Better fuel economy c. Lower throttle effort d. Easier access to rebuild parts.

That being said, I am open to hear what others have done to skin this particular cat. For what it’s worth I would like to keep the original air box, but I am a bit confused what will be required in terms of changing cylinder head spigots etc. in order to be compatible with later Dellortos.

Thanks,
Owen

[Idontwantapickle]

You could mount PHFs pretty easily with existing guzzi parts. Many bikes came with PHM or PHF so it's really just a matter of finding the parts from a later SP or CX100. They used very nearly the same engine as the convert.
A call to Harper's or any of the older suppliers should lead to a satisfactory outcome!

Hunter

[Turin]

IMO, there is nothing wrong with VHBs. I don't think your going to gain anything noticeable by switching to a phf or phm, at least compared to the cost. Clean up and rebuild what you have. I still run a set of VHBs on my ambo and they work great.

[R1100purist]

Thanks guys! This was the kind of conversation I was hoping to have. I guess I have been influenced by other posts and the wayword thought that somehow since VHBs are "obsolete" they were deficient. My original impetus for starting this line of inquiry was Dave Richardson in Guzziology stating that he got better fuel economy with PHM 40mm carbs than 30MM VHBs, unless I mis-read that.

[Turin]

That sounds familiar, and he did say that a small valve head can almost use up a 40mm carb. At the end of the day, any del'lorto is " obsolete". ( not that carb technology is advancing be leaps and bounds anyway). Mikunis might make a little difference, being a more modern design, but I find them temperamental compared to a del'lorto.

I did things kind of backwards with my 850T. First thing I did was fit 36mm phfs. I opened up the ports a tiny bit so there wasn't a lip. It made a little difference, but not enough to justify the cost of the bigger carbs. Only when I swapped the cam for something more aggressive did I really notice any significant gains. Get her running right, and invest in your suspension and brakes.
I've just started working on a 77 convert project. Checked the rubber, new battery, flushed the tank and brakes, and got here fired.

[Frenchfrog]

I made the switch from Vhb's to Phf 30 a long time ago but nothing was gained apart from making carb balancing possibel...the vhb slides were badly worn.

[R1100purist]

Alright! Sounds good, I will try to give the VHBs a good scrub and try them out. If I tap and drill the intake elbows is it possible to put a barb fitting so I can balance the two sides?

[Frenchfrog]

Yup...my manifolds already had this done.

[Antietam Classic Cycle]

Alright! Sounds good, I will try to give the VHBs a good scrub and try them out. If I tap and drill the intake elbows is it possible to put a barb fitting so I can balance the two sides?

I doubt a "balance tube" will have any real effect. But, if I were going to add one, I'd get some M6 banjo bolts, M6 banjo fittings with barbs and utilize the vacuum ports that already exist. No modification of original parts necessary.

[Simon_London]

I put PHF36s on my T4 with reducer manifolds from HMB Guzzi. Made a big difference   Adding a Le mans l / ll exhaust system and flywheel made a big difference too. I love the bike now. I would have sold it otherwise. Not cheap but worthwhile.

[moto-uno]

  I may have mentioned this in another post , the 29 mm carbs are not a bad setup . If the slides aren't badly worn and the rather rudimentary accelerator pump
is working they are fine within most riding conditions, no they're not high performance , but there's a subject that'll only drain your pocket book . Peter

[huub]

I put 36 mm PHF on a V7sport, because the VHB's were completely worn out. only to find out they were too big.
no way i could get them properly tuned .
after that i switched to 32 mm PHF's worked brilliantly, but as the VHB's were shot to begin with they should be....

So , recommended , if the VHB's are shot.
You can also consider VM mikuni's , dirt cheap nowadays , and easy to tune ( i've fitted those to my Lario)