Dellorto floats

[Garry]

The RGS drives me crazy sometimes...
I have/had the problem that after driving for about five minutes, it would run on two cylinders and sometimes on just one. Because I’ve completely restored it and replaced or modified all sorts of things, I didn’t know where to start looking...
Eventually I got round to the Dellortos, where I replaced all the brass parts (jets etc.) and the throttle needels, as well as the floats.
The black 10g ones were no longer available and were replaced with the equivalent type 7450-01 in white.
When fitting them, I didn’t compare them with the old ones, only to discover that these are actually the right ones.
I swapped the floats back to the old black ones, and only then did I notice the differences.
Looking at the photos, does she get too much fuel with those white ones?
Which might explain why she then runs on just 2 or 1 cylinder?
After a short test drive, she does indeed run better and the exhaust headers are turning more brownish-blue.
A longer, more thorough test drive will show whether this was indeed the problem.

Does anyone have any experience with these white floats?

 

[Paul Marx]

If you set the fuel level in the float bowls, what matters the colour of the float.
The weight can come into play in some situations.
But why the hell did you change perfectly good floats in the first place?
If it ain't holed, it floats.
Paul

 

[Garry]

I replaced the floats because they’d already been adjusted a few times in the past…
and because I thought: while I’m at it, I might as well replace the rest as well….

 

[TeddyG]

As mentioned above, check for proper height of the float needles regardless of which you use and properly synch the carbs and check the gas levels that’s squirting from each of the brass nozzles protruding near the slides. I believe the black floats are solid but others can chime in to verify this. What do the plugs look like after a high speed test ride?

 

[sfcpiet]

If it ain't broke, fix it till it is...

I can only echo Pauls' comment. Colour has nought to do with it as long as the weight is the same as the originals. The height can then be set to stock spec, even if the tab differs from the original. If the floats differ in weight, required height will differ from stock spec.

There are only 2 major wearing parts in the carbs that require routine replacement, needle jet and jet needle. Slides take pretty long to wear out completely. Float valve can wear eventually, as does the throttle linkage of the triples. During long lay-ups, the pump diaphragm will harden/crack and the non-return valves of the accelerator pump circuit are prone to failure.

Corrosion does other nasty things...

piet

 

[henrywillms]

My limited personal experience with this sort of issue is ignition. What ignition system do you have?

 

[Garry]

That white one is supposed to be the replacement for the 10g black one. The white one weighs 8.5g, but that still doesn’t explain to me why the tab is in a different place, and it’s no longer adjustable either.
I still need to give it a proper test ride, but I’m already feeling more confident about it.

Piet, yes, you’re absolutely right

If it ain't broke, fix it till it is...

 

[Garry]

My limited personal experience with this sort of issue is ignition. What ignition system do you have?

Moto Witt DMC 2

 

[gpzkat]

A couple of my floats were damaged from many years sitting with the taps open. They appeared to have dissolved or melted on the bottom. I found white 8.5g replacements on eBay. They were listed as PHB but looked identical to PHF, and had the same part number, so I got them. The floats stuck due to the width of the plastic at the hinge pin. I filed them down, and they are fine.

 

[Exmoor beast]

Black floats are supposedly ethanol resistant- I’m running ‘69 floats and they still float.

 

[henrywillms]

My RGS would often "fall asleep" running at constant highway speeds. It became very sluggish when you accelerated and felt like one cylinder was not getting spark or fuel. It worked fine under other driving conditions.
By downshifting and accelerating and getting up the revs it would come back to life and would be good for awhile again.

Eventually after checking and trying new plugs, carbs, wiring, I changed the Witt box out and it fixed the problem.

Years later had another ignition issue with a cylinder cutting out. It occurred at certain RPM range while accelerating and only with headlight on. Turned out to be a broken wire to a connector at a coil (vibration related) combined with only one phase of the regulator working (low amps). The combined low amps and flakey connector caused the coil to cut out.

Lots of info on testing the Witt and Witt and other and ignition issues...use the Search to find them.

 

[Garry]

Lots of info on testing the Witt and Witt and other and ignition issues...use the Search to find them.

Personally, I don’t find the site’s search function very easy to use. I use Google and search for ‘Laverda forum’ and, for example, ‘RGS floats’.
It works perfectly, and that’s how I’ve found a lot of information on this forum.

 

[Paul Marx]

The weight of the float will have little influence on a road bike unless you do moto cross or scrambles with them, in which case the bounce factor must be taken into account.

Paul

 

[sfcpiet]

The weight of the float will have little influence on a road bike unless you do moto cross or scrambles with them, in which case the bounce factor must be taken into account.

Paul

A lighter float will float higher on the fluid surface, therefore closing the valve earlier and possibly causing fuel starvation. Far more influence on a road bike than off-road.

One millimetre difference in fluid height at WOT can decide over life or death of a combustion engine.

piet

 

[Paul Marx]

A lighter float will float higher on the fluid surface, therefore closing the valve earlier and possibly causing fuel starvation. Far more influence on a road bike than off-road.

One millimetre difference in fluid height at WOT can decide over life or death of a combustion engine.

piet

Yes.
Anybody riding a Laverda at WOT these days is an anomaly and looking for trouble anyway.
In fact, anybody riding a Laverda is an anomaly.
Tolerance on fuel level in the float bowl is 1mm.
Paul

 

[MotoJouni]

Strange conversations once again.

Are you all above sure there isn't any other difference than the weight on the earlier and latter type of floats that Dell'Orto have sold with the same part numbers? The latter type is a bit lighter, but I suggest it has some other differences too. There can be, for example, differences on the shape, volume, density and mechanical dimensions. Therefore the latter lighter float can have practically similar response than the earlier type despite the differing weight. Therefore the weight comparison would be valid only for other way similar floats. Dell'Orto sells these with three different part numbers.

Here you have a table:
Dell'Orto Part number, weight of the older type (black), weight of the latter type (white):

7450.1 10g 8.5g
7450.2 14g 12.5g
7450.3 7.5g 6.5g

To my limited experiences these latter white floats with same part numbers work similar way in practice. Of course it is possible to make a comparison, for example, by using transparent float bowls and compare the fuel levels.

To my understanding the latter white type is for eliminating the need to adjust the float heights, and secondly it is the suitability for ethanol fuels.
To my understanding either types are not indestructible. To my understanding very first production batches of the white ones were reported to have problems with ethanol fuel, the latter ones seems to last. I have found new white ones use to have burrs on the shaft hole. I use a loose around 5mm metal drill to remove the burrs, carefully rotating the drill by hand, a turn or two, and final inspection that all of the burrs are removed and new ones are not created. The metal parts are not indestructible on the black ones. I'm not sure if long use of ethanol fuel may harm the black floats, and I'm not saying that all Dell'Orto black floats have necessary the same materials. In Finland we have had ethanol fuels since 2007. I had two black floats that eventually failed such way the carburettors were just flooding, and the black surface possibly looked a bit strange on them. I was not able to find any mechanical issue on them, I did various inspections and tests for them and used a lot of time, but replacing these floats to any other similar floats immediately solved the issue.

-Jouni

 

[sfcpiet]

In my experience, up to 10% ethanol content has no ill effects on anything within the old Dellorto carbs.

German/EU E5 petrol has had at least 5% ethanol content for around the past 15-20 years, during my trip to the North Cape I was forced to use E10 with 10% ethanol content because there's nothing else available up there! I experienced absolutely no difference in performance or consumption with the GTL. I was expecting the worst having forgotten to drain the float bowls of the GTL for the winter lay-up, but it readily spluttered to life after standing for close to 5 months. I had even neglected to charge the battery! Based on this experience,I have now decided to use E10 in all my petrol-fuelled vehicles and garden appliances. Even my 55-year-old Gutbrod lawn tractor runs happily on the stuff. The Mazda has clocked up 270000km with it with absolutely zero issues, the RGS, 500 and the old Matchless thumper seem to be very happy as well. Even the 100 ran excellently on E5, been off the road for a while... No trick materials or any precautionary measures taken in any of the mentioned carbs. When I get around to flogging the 3C around a bit, it'll be getting a couple of tank-fulls of E10 as well.

In all the years working on bikes, I have come across only a single holed Dellorto float, it was one of the newer white examples. I have found a few physically damaged/bodged, but never through normal use. I have also never had any issues with the plastic floats in the Amal Monobloc carbs. The brass Amal GP floats are a whole different matter though.

In regard to float weights... physics ain't that hard to understand. I like to think Dellorto, as well as all other carb manufacturers, put a lot of thought into which floats are suitable for particular applications. Shrugging off a couple of grams here and there... well, it's not my pistons and valves on the brink of expiry.

All adjustments, especially within a multi-cylinder combustion engine, will make all the difference between mediocre or crisp performance, be it valves, carbs or ignition. Slob around with all manner of adjustments, you can't possibly expect anything near peak potential. Putting a bit of effort in getting everything as close as possible to spot-on rewards you with a sweet and reliable engine, irrespective of marque or engine configuration. It's not fuckin' rocket surgery...

piet

 

[piranha-bro2]

Of course it is possible to make a comparison, for example, by using transparent float bowls and compare the fuel levels.

-Jouni

What i was thinking - it has always been an alternative method for measuring fuel height. Are you serious that the new float bowls have no adjustability???

And yes, a very small discrepancy in float height can indeed spell 'bad things' DAMHIK.

As for WOT, why in hell wouldn't you be able to operate a Laverda at WOT??? I must be one seriously anomalous gent. In fact, I think I must know quite a few anomalous Laverda owners. The bikes didn't just suddenly become allergic to WOT throttle because a few decades had passed FFS.

 

[motoddrob]

Fuck me my Motodd has done 12 days on track over the last couple of years at wide open throttle bouncing off the rev limiter.
Collectively that computes to around ~1500 kays flat out.
Apart from oil changes I haven't had to do any maintenance on the motor. Recent valve clearance check the 3 exhaust had closed up to .23 and inlets 2 x .20 and 1 x .18.
When checking the clearances one 8mm exhaust cam block stud had pulled and a second one pulled reinstalling the exhaust cam. Probably would have happened without the track days putting it down to a 46 year old head having had many heat cycles.
The only other changes I've had to do is go up 2 sizes on the Mikuni main jets. Pretty damn reliable Id say.

 

[chrisk]

Fuck me my Motodd has done 12 days on track over the last couple of years at wide open throttle bouncing off the rev limiter.
Collectively that computes to around ~1500 kays flat out.
Apart from oil changes I haven't had to do any maintenance on the motor. Recent valve clearance check the 3 exhaust had closed up to .23 and inlets 2 x .20 and 1 x .18.
When checking the clearances one 8mm exhaust cam block stud had pulled and a second one pulled reinstalling the exhaust cam. Probably would have happened without the track days putting it down to a 46 year old head having had many heat cycles.
The only other changes I've had to do is go up 2 sizes on the Mikuni main jets. Pretty damn reliable Id say.

My son was aghast when his Holden car pulled a head bolt thread when replacing its head gasket.

I reminded him it is 61 years old, and the head gasket probably failed due to the dicky thread in the first place.

Time takes its toll.