delorto carburetor

If you are talking about the PH style round slide Dellortos that were sometimes used on Nortons a few decades ago, it might be because new ones suitable for a Norton are not so easy to find. Ron Wood used to import them in sizes to fit Nortons, but I couldn't find anyone selling them now, except used or some very limited NOS. I haven't seen anyone fit the newer flat slide styles to a Norton, but I'm sure someone, somewhere, has done so. :)

I used a pair of 34s on my 750 Norton road racer,

delorto carburetor


and Ron Wood used them in 36 and 38 mm sizes on his flat track bikes.

delorto carburetor


delorto carburetor


Ken
 
British Bike magazine December 1994 featured a 920 'flat track' replica build fitted with a single 38mm accelerator pump equipped Dellorto using an: 'APS grass track specialists' manifold.
Built as a road bike, they were impressed :)
 
Haha I have that mag in the garage! Loved that bike. I have a manifold & a 36 & 38mm carb to fit to my Flattracker. All because of that article.
However back to Seattles question. On my road bike I fitted 32mm Dellorto phf pumper carbs. Dellorto were helpful & gave me a setup based on the Ducati GT860. Well bike ran well, I never did adjust the pump screws. My mileage was awful but small tank, big smile, it's easy to ignore. The settings are a mile off. They are an expensive carb, good quality but you are on your own setting them up. They are often clip fitting which puts people off. I fitted 30mm non pump Dellortos to my 500 Daytona & they were fabulous. Lots of help from the off road guys with settings. If you see some the right size & reasonably cheap, then buy them but be prepared to fiddle.
 

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The carbs are very expensive, I was thinking about running a single 34 or 36 VM on my Atlas. I installed an AFR gauge trying to fine tune the single 34 Mikuni and discovered that there is a big lean-out under acceleration and de-celleration. It looks like an accelerator pump would fill in the hole. I have not investigated the more modern Mikunis or Keihins, I imagine one of them also provides an accelerator pump.
Are old Delortos as bad as old Amals?
 
How do you know if the afr gauge is giving you an accurate reading? Did you compare it against another method of reading the gas/air mixture?
At low engine revs up to 3500 rpm it's safe to use a Colourtune.
If using Amals , some Mikuni needles will also fit giving a wider range of ajusting mixture .
 
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I have no way to double check the AFR gauge. It recalibrates each time I use it. Some trust is involved.
I was thinking about also using a Color tune but I have a question. If you have one perhaps you have the answers.

Jim Comstock recommends an AFR between 12.3 and 12.5. I will accept his recommendations.
It has been difficult to get easy to read instructions for the colortune but the desired color is bunsen blue which is 14.7.
12.5 would give me the yellow-orange color.
**Which color should I go for? Which one do you use? I would like to use the color tune up to 3500. Would the color change under load? Obviously the bike must be stationary .
 
I was keen to try the older SS1 models on my 500 twin race bike years ago but never managed to find any. They would need to meet our pre 1963 rules so modern ones are not allowed.
 

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seattle##gs said:
I have no way to double check the AFR gauge. It recalibrates each time I use it. Some trust is involved.
I was thinking about also using a Color tune but I have a question. If you have one perhaps you have the answers.

Jim Comstock recommends an AFR between 12.3 and 12.5. I will accept his recommendations.
It has been difficult to get easy to read instructions for the colortune but the desired color is bunsen blue which is 14.7.
12.5 would give me the yellow-orange color.
**Which color should I go for? Which one do you use? I would like to use the color tune up to 3500. Would the color change under load? Obviously the bike must be stationary .
Click to expand...
The Colourtune would need the engine running at a constant revs to give a reading.
As it shows up what is actually happening inside the combustion chamber as each spark occurs, you can tell from the colour whether you are rich/ weak or the correct blue - I stress that I only use mine in the dark, in bright sunlight they are useless!
The only really accurate way of determining you have the correct mixture is to run engine under load, going on a slight uphill road at a determined number of revs and do a plug chop. It can be a long tedious process.
 
I have abandoned the Dellorto idea. I discovered the UFO in the single 34mm Mikuni has made quite an improvement in my Atlas. Pilot jet is now 17.5 and the needle jet is P-0. Quite an improvement. Starting and idle is very good. Well worth the $70.
 
seattle##gs said:
I have no way to double check the AFR gauge. It recalibrates each time I use it. Some trust is involved.
I was thinking about also using a Color tune but I have a question. If you have one perhaps you have the answers.

Jim Comstock recommends an AFR between 12.3 and 12.5. I will accept his recommendations.
It has been difficult to get easy to read instructions for the colortune but the desired color is bunsen blue which is 14.7.
12.5 would give me the yellow-orange color.
**Which color should I go for? Which one do you use? I would like to use the color tune up to 3500. Would the color change under load? Obviously the bike must be stationary .
Click to expand...
Stick with the afr
It's light years away from a colour tune
 
baz said:
Stick with the afr
It's light years away from a colour tune
Click to expand...
You pays your money and make your choices.....
A little used Colortune on flea bay is about £25.
The cheapest AFR is about £45, but if you have 2 exhaust pipes you need a least 2 senders, both welded into somewhere .....so........
 
Bernhard said:
You pays your money and make your choices.....
A little used Colortune on flea bay is about £25.
The cheapest AFR is about £45, but if you have 2 exhaust pipes you need a least 2 senders, both welded into somewhere .....so........
Click to expand...
For me it's not about the money
It's about the way each system works
The colour tune will get your idle circuit about right
The afr doe's the whole lot ,no plug chops etc
You mark your throttle drum and take note of the afr "while are riding" at every throttle position
You adjust the needle possition , change the slide cutaway and jets and your done
Yep you have to weld a bung into your downpipe within 200mm of the exhaust valve
I welded one into an old down pipe
You only need to weld one in one down pipe
Just make sure you adjust both carbs the same etc
 
baz said:
You only need to weld one in one down pipe
Just make sure you adjust both carbs the same etc
Click to expand...
Sorry, but this smacks of a shortcut.
You cannot make assumptions here, each cylinder might NOT be getting the same ingition advance, or the best jetting for optimum performance!!!
It's just possible that one carb will require a bigger main jet than the other.........
 
Bernhard said:
Sorry, but this smacks of a shortcut.
You cannot make assumptions here, each cylinder might NOT be getting the same ingition advance, or the best jetting for optimum performance!!!
It's just possible that one carb will require a bigger main jet than the other.........
Click to expand...
As long as the engine is in good fettle ,carb wear,valve clearance, compression etc then YES it's a huge shortcut
In the past I have spent forever doing plug chops , changing jets etc etc
Nowadays I look at the afr
When was the last time you used an afr Bernhard?
 
I use my AFR gauge often, have a set of test pipes for commandos and one set for Atlas. Now, in all of creation, does anyone have a spare pipe for an S model ?
 
The one I have is a Spartan 2 wide band, dual Bosch sensor with a dual read out gauge (for each cylinder)
The recommendation with it was the sensor/s two feet from the exhaust port (it has temperature LEDs though)

John F doing the round the world on a Commando posted his AFR settings and they were rich compared to anything modern.

For oldies there are all manner of modern things worth exploring (but not necessarily purchase) and an AFR was worth it to me even if it takes effort to install.
The threaded fittings are only $10 a pop so not even worth machining yourself.
#
I have a colour tune somewhere, I read the other day they want to fly to the moon and one day telephones will have no cord.
Sure they will.
 
Time Warp said:
The one I have is a Spartan 2 wide band, dual Bosch sensor with a dual read out gauge (for each cylinder)
The recommendation with it was the sensor/s two feet from the exhaust port (it has temperature LEDs though)

John F doing the round the world on a Commando posted his AFR settings and they were rich compared to anything modern.

For oldies there are all manner of modern things worth exploring (but not necessarily purchase) and an AFR was worth it to me even if it takes effort to install.
The threaded fittings are only $10 a pop so not even worth machining yourself.
#
I have a colour tune somewhere, I read the other day they want to fly to the moon and one day telephones will have no cord.
Sure they will.
Click to expand...
A mate of mine uses an afr gauge on all his bikes
He has made a universal data logger from a ford throttle position sensor that attaches to the twist grip
But don't tell anyone!!!!!
 
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