Dellorto PHF rebuild

[Mike_P]

I’m needing to strip and rebuild the Dellorto PHF 32 carbs on my 79 Jota 180 after a 30 year lay up. My question is….are these easy enough to strip & work on or am I better off handing them over to an expert. I’m reasonably mechanically competent having rebuilt many cars/bikes/engines over the last 40 years but I’ve never stripped a Dellorto carb
Mike

 

[Rob]

So possibly 16 years of wear. This may mean the spindle shaft bushes are worn - they're seldom lubricated.
An ultrasonic tank is highly desirable to clean the bodies. Everything else is simply check, clean, replace.
A lot depends on who the expert is - there have been some mixed experiences reported.

 

[IAG]

Yes, you can do it. Basic tools & picks, one at a time in case you forget placement/order of bits, ultrasonic cleaner & blow out orifices w/ compressed air before reassembly. Be sure to remove small O-ring on idle screw, pump jet only fits in one way & consider taking notes on screw positions (how many turns out from bottom) for each carb.

 

[Paul Marx]

It's easy.
Ultra sonic tank though it's not guaranteed that you'll unblock the idle circuits.
New slides
New brassware and needle
New gaskets and seals.
Make sure everything is straight. Linkages and mounting plate can be bent.
Paul

 

[Schurminater]

Yes go for it Mike,follow the advice as given above,doing it yourself is a good way of getting to know your bike and its workings.
Definitely a good idea to change the brass wear and seals as a minimum and obviously check and adjust if necessary the float heights and base settings that you are running with or that the carbs are fitted with.

Base setting idea can be found here also.

TECHNICAL – uk.laverdamania.net

uk.laverdamania.net

 

[TeddyG]

As above, yes you can do this yourself (just as I did)-buy a complete del orto rebuild kit and carefully remove and replace all the internal gaskets, along w new slides if they are badly scored. replace the cables if they,re worn and buy a syncher. I,ll post a good instructional pdf. shortly. And of course make sure the tank internals are clean, along with fuel spigots and lines.

 

[Vince]

The only thing I found tricky is identifying what O-ring goes where; a few are similar to each other. Do one carb at a time so you have a complete carb to compare with. So many simple carbs are so similar that you will end up getting good at it. BTW, it's always blocked idle jets and passages; they sit about, and the fuel ends up congealing into sludge.

 

[Ian Short]

I've found that a package of heavy gauge guitar stings can be quite handy when cleaning the small circuits during a carb clean/rebuid. They're budget friendly as well...... unless you buy another telecaster while you're there

 

[Mike_P]

Thanks so much for all the good advice and help folks, you’re a font of knowledge, all very much appreciated !!

 

[Paul Marx]

For the O rings.

 

[Ernesto]

If the slides need to be replaced, note that only the
newer type might be available. To adapt them you'll have
to modify them to make sure the gap is 28,5 mm wide.

Ernesto

 

[Paul Marx]

If the slides need to be replaced, note that only the
newer type might be available. To adapt them you'll have
to modify them to make sure the gap is 28,5 mm wide.

Ernesto

Yes, but surely not on a triple where the slides won't be bottoming?
Paul

 

[sfcpiet]

Yes, but surely not on a triple where the slides won't be bottoming?
Paul

Ernest is correct, Paul.

Has nought to do if the slides actually bottom, but they must be able to! Otherwise you'll end up with a 2500rpm idle...

The 32mm carb mixing chambers are internally the same as the 36mm type in regard to dimensions and shape, just that the slide-stop screw is missing (triples! 500s have the stop screw, same basic carb). The later carbs were re-designed to accomodate the more sophisticated stop screw that better protected the slide stop, hence the different slide base. The new type slides MUST be altered for use in the older carbs.

piet

 

[Paul Marx]

Ernest is correct, Paul.

Has nought to do if the slides actually bottom, but they must be able to! Otherwise you'll end up with a 2500rpm idle...

The 32mm carb mixing chambers are internally the same as the 36mm type in regard to dimensions and shape, just that the slide-stop screw is missing (triples! 500s have the stop screw, same basic carb). The later carbs were re-designed to accomodate the more sophisticated stop screw that better protected the slide stop, hence the different slide base. The new type slides MUST be altered for use in the older carbs.

piet

Yes, but do the slides on a triple go low enough once set for that ramp to intervene?
Paul

 

[CLEMTOG]

listen very carfully Marx, I will say this only once.
curent/later/the only type available new slides MUST be modified or they wont work in PHF's.
as my learned friends above correctly state.
no buts other than the one you sit on.
CLEM

 

[sfcpiet]

Yes, but do the slides on a triple go low enough once set for that ramp to intervene?
Paul

An un-modified PHB/PHF slide will sit at about 2mm open in an older carb, results in an idle rpm of at least 2000. Give it think, Paul. Just look at the "bulges" at the bottom of the mixing chamber, the slide needs to clear them, not sit atop. The bulges are a lot smaller/lower in later carbs, they no longer extend as far to the sides of the chamber as in early carbs.

At idle, the trailing edge of the slide is about 0.3-0.6mm open. It passes just enough air to provide vacuum for the idle circuit to work. Not just Laverda triples, on any carburetted bike, for that matter...

piet

 

[Paul Marx]

An un-modified PHB/PHF slide will sit at about 2mm open in an older carb, results in an idle rpm of at least 2000. Give it think, Paul. Just look at the "bulges" at the bottom of the mixing chamber, the slide needs to clear them, not sit atop. The bulges are a lot smaller/lower in later carbs, they no longer extend as far to the sides of the chamber as in early carbs.

At idle, the trailing edge of the slide is about 0.3-0.6mm open. It passes just enough air to provide vacuum for the idle circuit to work. Not just Laverda triples, on any carburetted bike, for that matter...

piet

Yes, I gave it a think.
You need to get the Dremel out with new slides in old bodies.
Paul

 

[sfcpiet]

Yes, I gave it a think.
You need to get the Dremel out with new slides in old bodies.
Paul

Chuck it in the lathe, 20 seconds per slide job and a lot safer, quicker and more precise than hand-carving with a Dremel.

piet

 

[TeddyG]

Disclaimer- these 2 PDFs are for PHF36 carbs from twins, but they should be helpful, along with the info in the Green Book. Just take your time and you'll get those carbs working better. Crucial to get the float levels correct and proper synching of the 3 carbs. If you need to get new slides and they don't fit correctly, be careful trimming the ramps, but I'm not sure that your carbs will have this issue that the twins have. Steve Allen of Bevel Heaven is THE dell orto expert-

 

[Mike_P]

Huge thanks everyone, it’s amazing how much I’ve learnt just from this 1 post !
Much appreciated…Mike