Dellorto PHF ifo

1

1969mustang

New member
Location
Alberta Canada
1982 Jota 180 Series 2
Bike has been sitting for ages, the carbs were sticking so have stripped and cleaned carbs,looking thru the Dellorto exploded picture and parts list i realise i do not have the Throttle Stop Screw ?
There is the Mixture Screw and Pump jet and Holder. The location for the Throttle stop screw is plugged on all three carbs /
I am totaly new to Dellorto carbs, so if i am missing something obvious and this is a stupid question please humor me !, ive attached a pic of the carb, this is the left side carb from the intake end, but all three are the same
Thank You
c1.jpgc2.jpg
 
Damn you Piet. You robbed me of the opportunity to live up to my forum name!

1969mustang said:
i have the two adjustment screw on top linkage
Click to expand...

Mr Mustang: Two adjustment screws on the top linkage? :unsure:
They're not throttle stops. They're for synchronising the left and right throttle slides with the centre one, which the throttle cable actuates.

There's only one throttle stop (or idle speed) adjustment screw. It's on the steel frame that holds the carbs together and adjusts the rest position of the throttle cable bell crank. It hangs straight down between the centre and right hand carbs and has a knurled head on it so you can reach under the carbs and adjust it by hand while the engine is idling.
 
Dellortoman said:
Damn you Piet. You robbed me of the opportunity to live up to my forum name!



Mr Mustang: Two adjustment screws on the top linkage? :unsure:
They're not throttle stops. They're for synchronising the left and right throttle slides with the centre one, which the throttle cable actuates.

There's only one throttle stop (or idle speed) adjustment screw. It's on the steel frame that holds the carbs together and adjusts the rest position of the throttle cable bell crank. It hangs straight down between the centre and right hand carbs and has a knurled head on it so you can reach under the carbs and adjust it by hand while the engine is idling.
Click to expand...
Dellortoman Thanks for that, I have been reading a lot of your earlier post on Dellorto Carbs

Its becoming clear now, ive been reading every thread i can find on carb balancing and must have got confused with threads disscussing Twins, not triples where people are setting the throttle stop screws, thats my excuse and playing with Amal carbs.

So after rebuild on the bench i can check for leaks and accelerator pump working, put all three carbs back onto the Frame / rack initially setting the two outer carbs to get close to equal slide opening and closing as the centre carb.

Mixture screws set to 1.5 turns out.

Once back on the bike and running carry out final synchroning using the three mixture screws and two upper screws,

Set final tickover speed with the lower screw knurled head

I need to buy a set of vac gauges, Amazon etc have cheaper sets for approx $60 - $80, in your opinion are these good enough to set up the jota, apart from this bike i have no other use for them except rechecking now and again, so pretty much one time use.

Thanks again for the Info
Gordon
 
1969mustang said:
I need to buy a set of vac gauges, Amazon etc have cheaper sets for approx $60 - $80, in your opinion are these good enough to set up the jota, apart from this bike i have no other use for them except rechecking now and again, so pretty much one time use.

Thanks again for the Info
Gordon
Click to expand...
I bought a Morgan Carbtune Pro Vacuum Balancer 4 Gauge, last year, as the Davida 3 Gauges I had bought some years previously were useless.
I found it easy to use and it worked well.
If you dont need it, in the future, it's going to be a lot easier to sell than a 3 gauge.

Carbtune.jpg
 
I've just finished putting some new linkages bushes in, easier than I expected and using this forum as a guide I positioned them where there was no spindle wear. I'm feeling extra pleased with myself now. I'll look for something else I can break instead tomorrow.
 
While Carbtune, etc and decent quality vacuum guages work OKish, I'm really pleased with my relatively new to me SynX electronic synchronising gadget. Probably similar products on the market that work just as well.

Mercury columns are still sort of a benchmark imho, properly set up they're a joy to use. But, as the stuff is toxic and hazardous, it's banned almost everywhere. Still more than enough of it in the brazilian goldfields... :rolleyes:

The base model SynX is just about fool/idiot proof to use and a lot more sensitive and accurate than most anything I've used before. Expensive and more a professional than a hobby tool, but highly recommended if you have cash to burn.

piet
 
Thanks, I will have a look at that type of Synchroniser tool.

Definately dont have $$$$$ to burn, once the Jota is up and running again im not sure how much i will actually ride it but it needs to be in a running condition.

Another question regarding pilot Circuit, in Stevios hints and tips he lists the following checks.

PILOT BLOCKAGES. The easy way to check the progression galleries with carbs built and on the bike is remove pilot jets and mixture screws. Open the throttle. Use a can of carb cleaner with extension tube fitted. Put the tube up the hole where the pilot jet goes; cover the mixture screw hole with finger and squirt cleaner while looking for a stream coming up into the venturi, just in front of the back edge of the slide. Then put the tube in the mixture screw hole, cover the pilot jet hole with finger and squirt cleaner whilst looking for a stream coming out between the slide and the engine. Finally put the tube into the little air hole under the carb intake (not the "middle" one - the other drilling) Squirt and look for cleaner in the venturi.

Both of the first two checks are good im getting fluid as per the post.

The last check is not spraying into the carb Venturi,,, as in the above in bold, if i understand his post correctly, in the attached picture, is he refering to the drilling on the left side of the carb intake ?
C3.jpg
 
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Whichever passage you're checking, the key is to block all other escape routes bar the one you want to check (usually the tiny hole in the venturi. You might like to consider ditching the accelerator pump system while you're at it - some will argue they work, but many others will report zero problems and a lighter throttle after tossing them.
 
1969mustang said:
Dellortoman Thanks for that, I have been reading a lot of your earlier post on Dellorto Carbs
Click to expand...
Don't be misled by my forum name. I'm not a Dellorto guru.

I called myself dellortoman when I first joined this forum many years ago, not because I consider myself an expert on Dellorto carbs, or because I think they're the dog's bollocks in carburettors, but simply because I had a bunch of old Italian bikes of various makes (Laverda, Ducati, Benelli, Moto Guzzi) and the one thing they all had in common was Dellorto carbs of one type or another. As a consequence of that commonality, I couldn't help to become intimately familiar with them. But I'm sure there are people on here who know a lot more about them than I do. Especially as far as Laverdas are concerned.

As for Amal carbs, I started my biking life in the mid 60's when British bikes still had some cache. I began at the age of 17 with an AJS 350 single, then hit the big time a year or two later when I "graduated" to a 1967 Triumph Bonneville. The thing I learned about Amal carbs from those days is they're the work of the devil. Well, they were probably OK when new, but as a teenager I could only afford high mileage used bikes with worn out Amals. After failing miserably to get my Bonnie to run well enough to not be an embarrassment, I put a pair of Mikunis off a Suzuki 500 Titan on it and it transformed the bike into something approaching user friendly (if you ignored its other faults). It actually started first kick, idled nicely, accelerated without flat spots and made more HP at full throttle, and I didn't get fuel-soaked gloves from tickling the damn things - a revelation! I could reliably drag off other Bonnie owners while they were still spluttering and backfiring at the traffic lights.

I also have to confess that I've become a traitor to my forum name by fitting a set of Mikuni flat slide carbs to my Jota. They didn't make the bike go any better but they're much better at metering fuel than the Dells, so the fuel consumption reduced considerably.

Good luck with your Jota. You can get a reasonable carb balance by measuring the slide heights with a drill bit as a substitute feeler gauge, or by eye. Look at the slides to make sure they all open from the same rest position and reach the full open position together. If you want to use vacuum gauges, you might be better off borrowing a set if you don't think you'll ever use them again.

Cheers,
Cam
 
As Pat/pf1 has pointed out earlier, all this effort will turn out pretty much wasted if the throttle linkage shows excessive slop. You might end up with a nicely working idle circuit, but synch will go flyin' out the window on the first lap of the block.:eek: Your pic shows the carb mouth has been re-worked at some stage, the carbs have been apart at least once and chances are they've probably covered more miles/km than imagined...

In my experience, almost all bushes are worn well beyond service limits by now and very often, the linkage shafts are damaged through lack of lube (hardly any of them have seen any lube since passing the Breganze factory gate). It's not terribly difficult replacing the bushes with wider/longer examples allowing the shafts to bear on un-worn areas, new shafts are mostly unobtanium by now. Stock bushes are 10mm ID x12mm OD x10mm L, pre-oiled sinter bronze bushes are readily available in 8x12x12,16,20. These just need to be bored/reamed to 10mm ID. The felt seals and metal retaining caps are available as OEM spares. Won't last as long as a new shaft, but will probably out-last most of us if a drop or 2 of oil is applied every blue moon... I have ready-to-fit bushes, felt seals and retaining caps in stock if required.

When sychronising, it pays to check the tightness of the screws fixing the slide bell cranks to the linkage shafts. These are ALWAYS loose if they haven't been tightened after leaving the factory!;)

piet
 
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Dellortoman said:
Don't be misled by my forum name. I'm not a Dellorto guru.

I called myself dellortoman when I first joined this forum many years ago, not because I consider myself an expert on Dellorto carbs, or because I think they're the dog's bollocks in carburettors, but simply because I had a bunch of old Italian bikes of various makes (Laverda, Ducati, Benelli, Moto Guzzi) and the one thing they all had in common was Dellorto carbs of one type or another. As a consequence of that commonality, I couldn't help to become intimately familiar with them. But I'm sure there are people on here who know a lot more about them than I do. Especially as far as Laverdas are concerned.

As for Amal carbs, I started my biking life in the mid 60's when British bikes still had some cache. I began at the age of 17 with an AJS 350 single, then hit the big time a year or two later when I "graduated" to a 1967 Triumph Bonneville. The thing I learned about Amal carbs from those days is they're the work of the devil. Well, they were probably OK when new, but as a teenager I could only afford high mileage used bikes with worn out Amals. After failing miserably to get my Bonnie to run well enough to not be an embarrassment, I put a pair of Mikunis off a Suzuki 500 Titan on it and it transformed the bike into something approaching user friendly (if you ignored its other faults). It actually started first kick, idled nicely, accelerated without flat spots and made more HP at full throttle, and I didn't get fuel-soaked gloves from tickling the damn things - a revelation! I could reliably drag off other Bonnie owners while they were still spluttering and backfiring at the traffic lights.

I also have to confess that I've become a traitor to my forum name by fitting a set of Mikuni flat slide carbs to my Jota. They didn't make the bike go any better but they're much better at metering fuel than the Dells, so the fuel consumption reduced considerably.

Good luck with your Jota. You can get a reasonable carb balance by measuring the slide heights with a drill bit as a substitute feeler gauge, or by eye. Look at the slides to make sure they all open from the same rest position and reach the full open position together. If you want to use vacuum gauges, you might be better off borrowing a set if you don't think you'll ever use them again.

Cheers,
Cam
Click to expand...
Interesting, We have a similar background, i started out around the same time with British bikes being born in the UK, i still get to play with Amals, i have a 500 Daytona that has a good set of Concentrics on it, but still get the gas soaked gloves.

When i get it running i will see how it is, if i need vac gauges to finish it, i will set it up initially with the drill bits as suggested.

I am going to modify my air blower nozzle tip to fit better into the carb mouth drillings as i cannot seem to get air thru either drilling way, I assume that i should be able to ?????
Thanks
 
sfcpiet said:
As Pat/pf1 has pointed out earlier, all this effort will turn out pretty much wasted if the throttle linkage shows excessive slop. You might end up with a nicely working idle circuit, but synch will go flyin' out the window on the first lap of the block.:eek: Your pic shows the carb mouth has been re-worked at some stage, the carbs have been apart at least once and chances are they've probably covered more miles/km than imagined...

In my experience, almost all bushes are worn well beyond service limits by now and very often, the linkage shafts are damaged through lack of lube (hardly any of them have seen any lube since passing the Breganze factory gate). It's not terribly difficult replacing the bushes with wider/longer examples allowing the shafts to bear on un-worn areas, new shafts are mostly unobtanium by now. Stock bushes are 10mm ID x12mm OD x10mm L, pre-oiled sinter bronze bushes are readily available in 8x12x12,16,20. These just need to be bored/reamed to 10mm ID. The felt seals and metal retaining caps are available as OEM spares. Won't last as long as a new shaft, but will probably out-last most of us if a drop or 2 of oil is applied every blue moon... I have ready-to-fit bushes, felt seals and retaining caps in stock if required.

When sychronising, it pays to check the tightness of the screws fixing the slide bell cranks to the linkage shafts. These are ALWAYS loose if they haven't been tightened after leaving the factory!;)

piet
Click to expand...
Piet, Thanks
I will have a closer look at he linkages and bushings as you recommend and also the bell cranks.

The Jota is very low miles, its spent the majority of its life parked up in a heated shop, total miles coverd are now around 13,000.

I purchased the bike from a Forum member when i lived in the UK, it belonged to Roger Brownless ( Roger GB ) who was i believe a regular poster on this site, past annual MOT certificates support the speedo reading, not yet sure how much i will use it but i want to get it up and running.

The picture i posted of the carb mouth was to get info regarding the drillings, at the moment i cannot seem to get air to blow thru either passage, I assume that i should be able to do this, all other drillings are clear ??

Thanks
 
Only one of the drillings at the mouth actually leads anywhere, to the pilot jet boss, follow the casting on the "roof" of the float chamber. The other is blind.

13000 miles and someone's found it necessary to mod the carbs? A racing past? Also more than enough to wear out the linkage bushes if they haven't seen lube.

piet
 
sfcpiet said:
Only one of the drillings at the mouth actually leads anywhere, to the pilot jet boss, follow the casting on the "roof" of the float chamber. The other is blind.

13000 miles and someone's found it necessary to mod the carbs? A racing past? Also more than enough to wear out the linkage bushes if they haven't seen lube.

piet
Click to expand...
Thanks ! thats great info, im going to have another look / blow thru
 
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