Back to Dellorto carbs 2nd go

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Weg
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Joined: Tue Sep 25, 2018 7:30 pm
Location: Huntingdonshire

Back to Dellorto carbs 2nd go

Post by Weg » Tue Oct 02, 2018 2:28 pm

I've posted this again, copied from old forum, as the previous copy had sensitive information on it. Woops!

WestEndGuzzi
Edith is back on the road following her winter overhaul.
I’ve refitted the Dellorto Phf36 carbs, replacing the Webber DCOE40.
The main reason for fitting the Webber was to cure the problem of cutting out on bends etc. but I was not completely satisfied with the result.
Now she runs as she should, thanks to advice from muselermark and others.
The set-up. (Video here)
Phf36 carbs on splayed out manifolds, bought new when I built the car 13,000mls ago.
Now fitted with Anti Surge Washer PtNo.10428, fitted above the main jet holder (£4-20 ea +vat from Eurocarb) (link)
I believe this to be the magic component that has cured the fuel starvation on corners,. Thanks Mark.
Swill pot fitted to give gravity fuel feed to the carbs, return pipe taking pressure back to tank.
Carb vent pipes taken up to high level under bonnet, on top of breather box.
Exhaust balance pipe and expansion boxes removed, giving straight through pipes.
‘Progressive’ throttle linkage fitted, replacing the 2 into 1 cable thingey. (https://youtu.be/w01cMNfw8Vo)
This gives a much more relaxed start and smoother town running.
To conclude, I am thrilled with the improvement to the overall feel of the car. Well worth the effort.
And here is a short video of the result!

david
result,,,yes impressive..seems to go really well, loved the wheels gently rollin up and down…body stays flat or so it looked…

doverhay
Did you find any difference running the engine without the exhaust balance pipe? It certainly looked ok based on the video.


WestEndGuzzi
Yes.
I think it is a definite improvement. She even sounds like a Vee twin now!
You can get a 500 single tuned perfect, so why not 2 x 500s?
The cross pulse in the pipes would be early into one pipe and late into the other, Interfering with the smooth running of each pot.
I cannot see the logic for it being there, especially with twin carbs.
It’s possible that with a single carb there may be a beneficial effect,
A lot of the Pembly guys have a link pipe on small & large block Guzzis and the 602 2CV engine.
But why? Can someone explain?
I don’t recall Guzzis ever being run on a single carb, they have a link pipe/box so why is it there? Additional silencing perhaps.
Certainly saves a lot of expense and weight on stainless work.
So far, my trial has been a sheer delight, how much is result of reverting back to the Phf’s, gravity swill put, progressive throttle, exhaust pipe……… I don’t know.
The bends were done by slitting with 1mm disk nearly through and then tig welding back together.
• 08/03/2017

billdavies
Hi Tony,
Nice pipe work with complex bends. Folk do not appreciate the work involved and the disasters that occur.
My Trike is running on two carbs and other than the fuelling problems of last year it runs well and the engine appears to be in balance.
Your complex two to one cable set up is complex but looks good and appears to work well…but can you repair at the roadside if a cable breaks…I just used a simple bike part and carry standard cables as spares.
Hope to see you on some of the outings this year
Cousin bill
• 08/03/2017

WestEndGuzzi
Thank you Cousin Bill.
Good to hear that your motor transplant has turned out successful.
The layout for the cables gives them all nice easy sweeps with no kinks and no pulling at an angle where exiting adjusters etc. Hence the fulcrum. I was inspired by the very complicated linkages on the SU carbed Jaguar engines.
I make my own cables and they can all be changed easily at the roadside without fuss. I carry a spare lower cable and one second cable.
The botton cable has trumpet nipples rather than the small carb nipples, much stronger for the main pull. The second cables have the normal 3mm carb nipples both ends. I get all my cable supplies from Venhill (Web site)
Use galvanised wire not stainless. (can’t be soldered).
I did put some comments in a thread about soldering (here)
Best wishes
Tony

WestEndGuzzi
And another thing.
Changing a throttle cable with one of those 2 into 1 thingies is not easy.
You have to release the carb end of the cable before it will come out of the 2-1 barrel. With a strong spring in the carb and an accelerator pump actuator to contend with, it gets a bit ‘springy’.
So, I made the 1st end of the cable easily detachable from it’s actuator. This then gives enough free inner cable to take virtually all the tension from the throttle spring.
Similar principle on Daisy the Pembly, quick release of the ‘A’ end of inner cable, but without the progressive mechanism.
Or you could take the simple approach and have 2 cables direct from the throttle pedal……….
• 01/04/2017

david
I had a new -just msva’d guzzi JZR !!! a long time ago without a balance pipe and that performed really well and sounded good.. But i spent a year altering suspension and handling issues.different uprights/ built in some caster!!/guzzi brakes/machined splined hubs instead of bolt on adaptors/19″ wheels and avons..[.but then bought a mk 1 Triking which instantly handled far better…]
I might try removing the balance pipe..as I gather it helps extract gases from the other cylinder but as you mention,the beat is different so might interfere more than help…

WestEndGuzzi
Since taking off the cross pipe and 2 expansion boxes, the exhaust was much noisier.
So I reverted back to the original Guzzi silencers from the donor bike. That improved the exhaust note to a sensible level.
However, between 2500 & 3000rpm I was getting a very loud intake noise. This was at the critical cruising speeds of between 55-65mph.
The noise was metallic, throttle slides slapping back and forth.
The first thing to try to get rid of the organ pipe resonance was to put a metal slide in the inlet pipe, post carb. I tried it vertically and horizontally but that didn’t work.
Inlet eliminated, must be the long exhaust pipe before the silencer.
So I put an 18″ long home made baffle into the front of the long pipes.
Bingo. It works. Resonance eliminated!
o 16/05/2017

doverhay
I’m confused Tony, what is the picture showing, it looks more like the inlet pipe rather than the exhaust??
• 16/05/2017
WestEndGuzzi
Well spotted Dick!
That is the inlet pipe.
That’s the bit that didn’t work.
I have a couple of pictures of the baffles on my hard drive, but I can’t find them!
So you can either wait till I find them, or I extract similar items from Daisy’s pipes to reposition them, take new pictures and file them where I can retrieve them.
If you want to see the pictures, you have to loggin!
• 17/05/2017
WestEndGuzzi
By popular demand, here is the baffle, courtesy of Daisy.
30mm pipe (inside the 38mm side pipe) with slots cut in it, then one side of slot bent inwards.

BSA
Posts: 9
Joined: Mon Oct 01, 2018 8:11 pm
Location: New Zealand

Re: Back to Dellorto carbs 2nd go

Post by BSA » Mon Oct 08, 2018 9:33 pm

Hi Westendguzzi

I have phf36s on my 1100 California powered Type 3. This is a recently built car, and the one 'fettling' issue I have not yet resolved is fuel delivery.

The carburettors as removed from the donor bike had 270 float valve and needle (paperwork I have seen indicates 300?) and I have a low pressure Facet pump.

The car ran very well, but on tight right hand corners would cut out onto one, with a strong smell of petrol, presumably from the overflows from the carburettors, which are directed to run to the ground avoiding anything hot. It would clear after a few seconds. I am pretty sure that the float valves were not coping with the pressure delivered by the fuel pump, in conjunction with the cornering forces acting on the fuel in the float chamber.

I have fitted to 'anti surge' washers to the carburettors - but this doesn't seem to make a difference. I think that this is because it is not going lean round the corner, it is going rich.

I have tried fitting 170 float valves and needles as recommended by Eurocarb, and have also trialled a fuel pressure regulator. This resolved the cornering issue completely, but when driving on the motorway into a sustained head wind first one, then the other, side cut out - fortunately restarting presumably after the floats bowls had refilled.

I then tried 220 float valves and needles and things were better, but eventually I provoked the same symptoms.

I have been back on the 270 float valves now for about 500 kms and that seems to resolve the higher speed issue - but I am back to the cutting out onto one when cornering hard.

I am now going to try fitting a 1 litre surge tank/swirl pot which will be mounted in front of the firewall, just behind the breather catch tank, which I think is the solution you have adopted.

That should lead to gravity pressure feeding the carburettors.

Is that consistent with what you have done? Are you able to advise what size float valves are fitted in your float bowl? I think I should use either 270 or 300. Have you fitted a fuel tap to your 'swirl pot'. or does the set-up rely on the float valves/needles sealing even if the car is laid up for a while? Do hou have 5/16" fuel hose to and from the swirl pot and 1/4" to the carbs?

Thanks for your time (and anyone else who has grappled with this)

Regards

BSA

Archie
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Joined: Sun Sep 30, 2018 8:55 am
Location: UK

Re: Back to Dellorto carbs 2nd go

Post by Archie » Tue Oct 09, 2018 6:32 am

Fitting a return line to the fuel tank should cure this . It will allow you to use a higher constant fuel pressure and also remove any vapour locking.
Fit a Tee piece in the fuel line after the pump with a return line to the top area of the tank. The return leg of the Tee piece will need a restrictor in it which can be made up with an old carburettor jet pressed into the return leg of the Tee piece. There will probably be a pipe already welded into the top of the tank to accommodate a return line for the injection models that you can pick up on. This system has been around for a long time and is commonly used on sidecar outfits and Carb. Aero engines to releave this problem.

Weg
Posts: 808
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Location: Huntingdonshire

Re: Back to Dellorto carbs 2nd go

Post by Weg » Tue Oct 09, 2018 6:58 am

Take the vent pipes up to a higher level, cable tie to the top of the oil catch tank is a good place.

My swill/header tank (home made 3mm ally with spiggots welded in, about 500ml), is located where you suggest, bottom fed from pump and through a pressure regulator, left and right lower side outlets to carbs. 5/16" pipes in all cases.
The return pipe that Archie details, I've taken from the top-rear of the swill pot back to top of the petrol tank. The restrictor is a pilot jet, size not important, screwed into the outlet spigot. M6 thread I believe so easy to tap in.

Hope his helps
Tony

BSA
Posts: 9
Joined: Mon Oct 01, 2018 8:11 pm
Location: New Zealand

Re: Back to Dellorto carbs 2nd go

Post by BSA » Tue Oct 09, 2018 11:24 pm

Thanks to you both. I will post when resolved.

riccardogale
Posts: 7
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Location: Larkspur

Re: Back to Dellorto carbs 2nd go

Post by riccardogale » Wed Oct 17, 2018 11:14 pm

WestEndGuzzi-

Would you be able to provide the links you reference here (where you wrote "video here" and "link"?
...The set-up. (Video here)
Phf36 carbs on splayed out manifolds, bought new when I built the car 13,000mls ago.
Now fitted with Anti Surge Washer PtNo.10428, fitted above the main jet holder (£4-20 ea +vat from Eurocarb) (link)...

I have a Type One and it has always run on one cylinder following fast, tight corners. It seems like installing the Anti Surge Washer solved that problem for you, is that correct?

Thank you! Riccardo (from California)

Weg
Posts: 808
Joined: Tue Sep 25, 2018 7:30 pm
Location: Huntingdonshire

Re: Back to Dellorto carbs 2nd go

Post by Weg » Thu Oct 18, 2018 9:03 am

Hi Riccardo, good to see you on the Triking Forum.

Firstly, here's the link to the anti-surge washer https://www.dellorto.co.uk/shop/dellort ... ge-washer/


The short video looking round Edith is here
https://www.youtube.com/watch?v=e9K30LA ... e=youtu.be

The 'progressive' throttle linkage ----
https://www.youtube.com/watch?v=p3MLPTu ... e=youtu.be

And finally the test run-----
https://www.youtube.com/watch?v=JdNbpkE ... e=youtu.be

The throttle linkage video gives a clear view of the swill pot.
Hope this helps.
Tony

BSA
Posts: 9
Joined: Mon Oct 01, 2018 8:11 pm
Location: New Zealand

Re: Back to Dellorto carbs 2nd go

Post by BSA » Tue Feb 25, 2020 5:06 am

I should have posted long ago my thanks to Archie for his suggestion.

It transpired that the fuel starvation (at touring speeds) was cured by replacing the fuel pump and filter, and the ‘fuel surge’ leading to cutting out when cornering hard was resolved by fitting a return line downstream of the pump, with a restrictor.

The fuel filter (carb model with low pressure pump) is a service item which no doubt should be replaced at regular intervals.

I thought perhaps every 20,000 km.

Any thoughts?

Weg
Posts: 808
Joined: Tue Sep 25, 2018 7:30 pm
Location: Huntingdonshire

Re: Back to Dellorto carbs 2nd go

Post by Weg » Tue Feb 25, 2020 12:35 pm

Good idea. We really should replace the inline filter before we breakdown!
The anti-surge washer really was the one tiny item that cured the loss of power on fast cornering for me.

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