Adding another F to Fast Fuel Flow Faucet

[solostax]

I have three Lambrettas all with 200cc rebuilt engines ,that is new cranks ,bearings ,oil seals top ends and 12 volt conversions etc. All run with distinct but different characteristics leading me to believe the variations are carburettor induced.However mere swapping of the carburettors hasn't necessarily correlated to isolating the differences.
Not wanting to get too involved in the “Black Art “ of carburettor jetting / tuning I have instead tried buying new Jetex carbs supposedly suitable for standard engines,with mixed results.

My GP ,on completion of 380 miles “running in” I decided to push the speed up and over 50 but after a few minutes at high throttle setting suffered loss of power and fearing partial seizure coasted to a slow speed but was surprised when releasing the clutch the engine restarted. With reduced speed I managed to limp home noting that the power fade was now more apparent whenever the throttle was opened to climb gradients.
As a strategy for diagnosing this particular problem and after LCGB forum research I began with investigating fuel flow. I tested the fuel feed rate with a container at the same level as the carb and despite the tap being supposedly rated as“Fast Flow” measured 280 mL (just under ½ pint ) per minute.
A further two (different makes) “Fast Flow” taps were bought both returning similar flow rates.
Being reluctant to modify an existing tap I have been searching for a genuine “Fast Flow” tap that specifies a given flow rate ,which I understand should give approx 1 pint per min. Even the advertised Youtube featured SIP demo (which is in German) https://www.youtube.com/watch?v=DvNHuXfCVGU shows an original, versus SIP fast flow tap discharging into calibrated containers BUT with no reference to time!
Is there a product on sale that clearly states a flow rate ?

[Tractorman]

If you are getting 1/2 pint per minute that's a gallon in 16 minutes so does your scooters only do 16 miles to the gallon? Or is my view on this wrong.

[solostax]

Tractorman, Thanks for the reply and the common sense way of looking at the fuel consumption. Whilst the obvious logic dictates very few Lambretta owners would suffer an engine that consumes petrol at a rate close to a pint every 2 minutes i.e. 16 MPG, I have wondered, like yourself why such emphasis is placed on Fast Flow taps, indeed there seems to be healthy demand for them. Somewhere, sometime I read the answer to this question but can't remember the reasoning.
Back to symptoms I suffered though, I feel temporary lack of fuel caused the sudden power sapping and suspect has resulted in damage to the piston /cylinder bore. I will confirm on strip down.

[Tractorman]

Are you sure it was not a seizure? Very often engines will start and run ok after a slight seizure.

[Warkton Tornado No.1]

Judging by comments on this Forum alone, there still exists a lot of optimism when it comes to 'upgrading' from standard OEM Lambretta components.

Many Lambretta owners still fit electronic ignitions, principally made in India, believing that reliability will be ensured.

However, there are still many that expect that they can fit any component without thoroughly checking it over first

Taps are just one example of an item that a full inspection is mandatory.

However, for my money, the Scootopia tap does comprise all the elements of a great component, not necessarily assembled correctly, from what other Forum user's have reported! Ironically, my purchases have all been good, but I disassemble them anyway, to check for burrs & swarf, modify the reserve etc.

Not much of an accolade, but the Scootopia tap is the best of the bunch IMHO, & a very sensible inexpensive upgrade that them allows complete concentration on all the other things that can go wrong......

[missing lynx]

380 miles "running in" on an iron barrel seems a bit short especially if they are Indian ones maybe you just haven't run it in enough or, (and I don't want to sound rude) properly

[Chadley]

On mine, using a standard OMG fuel tap, I measured a flow rate of 340ml per minute with a half full standard tank.

[solostax]

Gentlemen,thanks for your comments and suggestions
Following comments and advice I will be buying the Scootopia tap ,I believe the engine had partially seized, but as in line with my previous method of running an engine in from 400 miles extending the speed range in brief spurts to over 50Mph had been completed without mishap.

The nub of my original post was that there exists a market for fast flow taps ,whereby in the past, standard engines that were not run hard could cope with the existing standard flow rate taps.With the performance improvement provided by third party manufacturers I presume the standard flow rate then became insufficient.
Although obviously no expert on Lambretta engines ,I can follow and understand (and appreciate) the technical improvements made by very clever enthusiasts.It is that well of knowledge (freely given) on this forum that makes owning a Lambretta possible for me.

So whilst operating a “not as original spec 200cc” Lambretta I am confronted by unforeseen problems that logical thinking at first points to 3 possible causes.1/ A Not original manufacturers
but aftermarket Jetex carburettor (which some criticise, some deem OK).....2/ Conversion from points 6v system to 12v ignition........3/ Unleaded ethanol enriched petrol.

If nothing else has changed since owning my first LI (54 years ago) including riding style and method of running in then I am tempted first to look at the 3 possibilities mentioned above as a possible reason.
With my recent experience of Jetex inconsistency between carbs I am first tempted to look at the flow rate ,considering float bowl level and it’s replenishment.This then lead to my initial surprise that having fitted a “Fast Flow” tap (for no particular reason) I discover that the measured flow rate is half the recommended flow rate as advised in many tutorials. Until I reconcile this anomaly I cannot progress. Thus the subject matter of the post.

[missing lynx]

You say non std 200 what barrel are you using? Also what have you set your timing at? And what oil petrol mix are you using? Personally I think the mileage running in in insufficient if it's an iron barrel. When I first started riding lammies over 40 years ago 1000 miles was a std riunning in period so I still think you opened it up a little to early, for to long or in the wrong place(on hil etc)

[rossclark]

The usually quoted figure for a good FF tap is 1 pint a minute which wil always mean that the tap/tank cannot lead to fuel starvation and that the float and float valve will meter the flow to the bowl. On standard engines with standard carbs standard taps should be adequate but if you're replacing a faulted tap why not fit a fast flow? I'd be surprised if you can find OEM or NOS taps now so you're almost always going to end up with after market / pattern ones.

My 225s get about 10 miles / litre so even at a steady 50 mph that would be max 5 litres / hour or 83ml / minute

I've used the Scootopia tap a couple of time but as WT1 has said take it apart and check it carefully before fitting. On one the rubber part inside was out of line and I was getting about 100ml a minute - I'd put 5 litres in the tank and it took near an hour to drain to take the fecker back out and fix it. Lesson learned. They have a nice positive feel about them in each position.

[solostax]

OK missing lynx,and rossclark thanks for your interest,
My definition of non standard engine was limited to the only departures from factory specification being a Jetex carb and 12v electronic ignition .In all other respects it is standard SIL 200cc .I am reluctant to enhance its performance by any other modification and confirm the timing set at 19 and running 3% Petroil ..
I seem to have been lucky in not seizing previous engines when "Running In " but will heed your advice when I replace barrel /piston (If found necessary)
Much obliged
regards

[missing lynx]

The sil barrels are very tight and require extra care when running in. It may be worth getting a light hone on it for peace of mind. Ps no need to shout lol

[Warkton Tornado No.1]

From your own responses, I feel sure that any fuel tap issue is obviously something that you will be able to rectify & easily tailor the amount of reserve to suit your own preference.

Some of us that have never been without Lambrettas since first getting motorised transport will be more aware than others of some of the potential issues to be avoided.

Reading through this Post, I would remind anybody that some common assumptions should be avoided. Potentially, any long term car driver, or perhaps somebody not familiar with a fan cooled two stroke, should forget common practice associated with such other vehicles.

Debates about ignition timing & petroil mix often occur on this Forum, but you need to figure out what it is you would like to do & try & stick with it, otherwise you will having nothing consistent.

Ignition timing of a fairly standard engine will probably be best retarded from OEM due to the fuel. How much is really anybody"s guess, but it's fair to say IMHO that any safety margin is commonly applied & then some! Recently, I have witnessed examples where the ignition has been set as OEM with no apparent detriment to the engine. I am just saying that the reasoning for retarding can often be over stressed & it really is not an exact science unless analytical equipment is available.

Petroil mix & the brand of oil is another topic often discussed. Whilst I am on record for what I use, it won't suit certain engines, say, like a reed valve engine where big end lubrication may not be so liberally available. However, in a ported Rapido Suzuki TS piston 71 x 61 that pulls TV200 top gear ratio (no doubt torquey then...) I use Exol Optima with the best Super unleaded that I am aware of. Currently, that appears to be Tesco's @ 99 Octane rating, but I stand to be corrected. That engine runs very happily on 2%

I would imagine that just by reading what I have thus far said, may cause some consternation, but I am merely trying to express how the variables are so......variable!

Some things are consistent though.

I wouldn't mind a pound for every time I have read of extra oil being added to the tank whilst running in & the practice of keeping RPM low.

Both are detrimental! Adding oil weakens the petrol/air mix.

Not revving an engine means less fan cooling, thus over heating! I am not advocating caning a fresh bore, but with the increased friction as the consequence, low revs are potentially more dangerous than high! Riders used to car engines have been known to roll off the throttle after a high speed blast. Easily done, but the consequences are less oil & cooling. That has been enough to cause @ least one owner of an MQ engine to need a replate of the bore.

Gasp! Despite my often out spoken views, I hope you can enjoy ownership of your Lambretta & not be put off by what may be judged as the complexities.

Lambretta in it's purest form is as reliable as any vintage motor scooter, taking into account the need for adjustments due to changes in legislation, the most likely of which is fuel. A big part of the problems brought about is that in particular, we in the UK tend to tinker & I confess to being guilty of that. Hopefully, some of my experience may help others avoid making some of the mistakes that I have.....

[solostax]

Yo (modern greeting) missing lynx and WTno1
Thanks for the further enlightenment ,info taken on board and apologies for shouting…(I presume shouting=submitting large text?) .Because I struggle to read text due to the small tablet screen size I use I like to opt for “large” so as to read what I’ve written! LOL and all that!
I’m back on track having ordered a scootopia fff tap and might be sourcing another from a fellow member. Because I’ve been given the benefit of sound advice I intend to document what I find with the view to sharing whatever might be learned.
Best regards