Lectron Carbs

[Propellor]

The more I read up about the Lectron carbs, the more excited i get to try it out! When I get it on ill make a post and say whats what. Im hoping it the Lectron 34mm will be healthier and more efficient then the Mikuni TMX 38mm thats on now.

Joolz do you know where I can get parts? There's a few bits missing i need and only american sites seem to stock parts.

Mackenzie

Good luck. Looking forwards to hearing of the results.

[Propellor]

............. CVs are a bitch to tune, often the problem with ditching the air box is that the air-corrector passageway is then too large. You used to be able to get jet kits (Dyno-Jet) for CVs, most of them required the air corrector hole to be drilled and tapped so a screw in jet could be fitted.

Ok. I see what you mean. The pressure difference across the air bleed jet will increase with the airbox off, I guess.

As the underside of the diaphragm is also vented into the airbox, the pressure acting on that will also increase. At first I wondered if it would need a different spring rate to compensate, but now I can't decide if the thing will self compensate anyhow. That's kind of what cv carbs do! Certainly a brain teaser, that one.

Anyone any thoughts?

[JOOLZ]

Spares for lectron carbs in the U.K  http://www.suzukiperformancespares.co.uk/product/yamaha-34mm-lectron-carbs/1196/

[Propellor]

A ha. Says here that the principle as used in EI and lectron was originally used by an Englishman, Ron gardner in 1970. Get in!

Also says that the gardner carbs were/are popular among classic racers for G50's and Manx nortons.

On the EI carbs it says that different needles were required for 2 strokes and four strokes and that only three needles were "claimed" to cover all adjustment ranges. Mmm. Strikes me that there may not have been sufficient choice of needle tapers available? His many do lectron offer?

The lectron carbs are apparently renowned for excellent part throttle response! Maybe that's a marketing claim.

[Propellor]

Spares for lectron carbs in the U.K  http://www.suzukiperformancespares.co.uk/product/yamaha-34mm-lectron-carbs/1196/

£500 for a pair. Could be worse I suppose. Maybe worth it, if they do the job.

Hopefully they're not now made in China......

[Furry John]

Spares for lectron carbs in the U.K  http://www.suzukiperformancespares.co.uk/product/yamaha-34mm-lectron-carbs/1196/

Gardner Carbs. are still made and used a lot in Historic racing, my Neville Evans/Molnar Manx Norton copy is fitted with one, they are very clean running and easy to tune, Ron still produces needles for most applications or will make one to suit once you know where and when you the mixture leaner or richer. Needles are about £15 each, I have one leaner than standard all through the range for high octane petrol, one standard for 5-10% Ethanol and one rich for Supermarket cheap. Ron himself still answers the phone and is delighted to talk to you about your application. Gardners only have the one fuel route, in the centre of the slide, the needle taper determines the mixture through the full range. Lectrons need setting up as was said, low range right, mid range right and then handover to the straight through pipe correct, it can be time consuming to get all the tapers on the needle correct.

2d

Furrry

[Propellor]

Spares for lectron carbs in the U.K  http://www.suzukiperformancespares.co.uk/product/yamaha-34mm-lectron-carbs/1196/

Gardner Carbs. are still made and used a lot in Historic racing, my Neville Evans/Molnar Manx Norton copy is fitted with one, they are very clean running and easy to tune, Ron still produces needles for most applications or will make one to suit once you know where and when you the mixture leaner or richer. Needles are about £15 each, I have one leaner than standard all through the range for high octane petrol, one standard for 5-10% Ethanol and one rich for Supermarket cheap. Ron himself still answers the phone and is delighted to talk to you about your application. Gardners only have the one fuel route, in the centre of the slide, the needle taper determines the mixture through the full range. Lectrons need setting up as was said, low range right, mid range right and then handover to the straight through pipe correct, it can be time consuming to get all the tapers on the needle correct.

2d

Furrry

Very interesting. Thanks. Sounds like a very clever fellow and no doubt a mine of information. One thing which struck me was that maybe, with extreme care, it might be possible to alter the taper yourself. With it being flat (3 flats, as I understand it). Maybe that's a bit ambitious!

Do the gardners still have a separate float chamber?

As I understand it, all three designs use basically the same (gardner designed) idea in that the needle has three different gradients on it and these determine the fuel slope. The American designs have the power jet also. Raising or lowering the needle will make it overall richer or leaner but won't affect the general slope. Getting the right gradients to suit your application is paramount. Is that about right?

Cheers

[Propellor]

............. CVs are a bitch to tune, often the problem with ditching the air box is that the air-corrector passageway is then too large. You used to be able to get jet kits (Dyno-Jet) for CVs, most of them required the air corrector hole to be drilled and tapped so a screw in jet could be fitted.

Ok. I see what you mean. The pressure difference across the air bleed jet will increase with the airbox off, I guess.

As the underside of the diaphragm is also vented into the airbox, the pressure acting on that will also increase. At first I wondered if it would need a different spring rate to compensate, but now I can't decide if the thing will self compensate anyhow. That's kind of what cv carbs do! Certainly a brain teaser, that one.

Anyone any thoughts?

I'm back to my original thought!

This is my current train of thought. The butterfly determines the airflow, the airflow determines the Venturi pressure. The Venturi pressure acts on the topside of the diaphragm and opposes the the pressure on the underside plus spring force. Spring force will vary according to preload and rate. Change the pressure source on the underside of the diaphragm and you'll need to change the spring force.

That sound right?

Next question us do we alter the spring preload and keep the rate the same or keep the preload the same and change the rate. Or both?  !!

Also this may need to be done in conjunction with a change to the air bleed jet.

Oh eck!

[Furry John]

Do the gardners still have a separate float chamber?

As I understand it, all three designs use basically the same (gardner designed) idea in that the needle has three different gradients on it and these determine the fuel slope. The American designs have the power jet also. Raising or lowering the needle will make it overall richer or leaner but won't affect the general slope. Getting the right gradients to suit your application is paramount. Is that about right?

Yes, a normal remote mounted float chamber is used, there are 12/24 places/stages on the needle that can be set, the junction between them gives the the smoothness of transition to the next stage. The screw on the end of the needle sets the start point of the stages, so yes you are correct. The main difference is that all moving needle carbs. use a needle jet which has air induced into it to emulsify the fuel at the needle prior to its entry into the combustion chamber which gives control for pollution, acceleration, smoothness etc. The moving jet carbs. just control the amount of fuel passed into the inlet tract, emulsion starts in the tract, so suit the competition type engine more. The earliest was the Wal Phillips injector which just used a rotating hole into the tract to give rudimentary quantity control. Fixed needle carbs. are sometimes called injectors because of the lack of an emulsion stage.

+ 2d

Furry

[Steve H]

My understanding was that emulsion tubes help to correct the WOT fuelling. The relationship between pressure differential and fuel flow is not linear throughout the rev range, if you have the correct WOT fuelling at 3000 rpm it will be too rich at 8000rpm. The introduction of air via the emulsion tube corrects this. A good example of this is a blocked emulsion tube on an SRX will cause it to run really rich and stutter at larger throttle openings.
That said the Keihin CR carbs I have fitted don't have emulsion tubes so I am not sure how they compensate for this.

[Propellor]

My understanding was that emulsion tubes help to correct the WOT fuelling. The relationship between pressure differential and fuel flow is not linear throughout the rev range, if you have the correct WOT fuelling at 3000 rpm it will be too rich at 8000rpm. The introduction of air via the emulsion tube corrects this. A good example of this is a blocked emulsion tube on an SRX will cause it to run really rich and stutter at larger throttle openings.
That said the Keihin CR carbs I have fitted don't have emulsion tubes so I am not sure how they compensate for this.

My understanding is that you are absolutely right with what you say. The air pressure reduces as the square of the air speed. In other words if we look at a throttle position at low rpm and then look at the same throttle position at high rpm the pressure will be vastly different (but the needle position the same).

But my understanding is that furry john is also right. Arguably more right. The air bleed jet is there to compensate for pressure differences and it happens to feed air via the emulsion tube. The emulsion tube is designed specifically to allow this air through whilst atomising the mixture more thoroughly.

So in a nutshell, the air bleed jet decides how much air is bled, whilst the emulsion tube decides how this bled air is mixed with the petrol.

That's my take on things anyhow. That said, I'm not claiming any credentials on the subject, just a strong curiosity.

[Propellor]

Do the gardners still have a separate float chamber?

As I understand it, all three designs use basically the same (gardner designed) idea in that the needle has three different gradients on it and these determine the fuel slope. The American designs have the power jet also. Raising or lowering the needle will make it overall richer or leaner but won't affect the general slope. Getting the right gradients to suit your application is paramount. Is that about right?

Yes, a normal remote mounted float chamber is used, there are 12/24 places/stages on the needle that can be set, the junction between them gives the the smoothness of transition to the next stage. The screw on the end of the needle sets the start point of the stages, so yes you are correct. The main difference is that all moving needle carbs. use a needle jet which has air induced into it to emulsify the fuel at the needle prior to its entry into the combustion chamber which gives control for pollution, acceleration, smoothness etc. The moving jet carbs. just control the amount of fuel passed into the inlet tract, emulsion starts in the tract, so suit the competition type engine more. The earliest was the Wal Phillips injector which just used a rotating hole into the tract to give rudimentary quantity control. Fixed needle carbs. are sometimes called injectors because of the lack of an emulsion stage.

+ 2d

Furry

Reading the lectron blurb (I read it last week), I recall that they claim that the way air passes over the metering rod at the vicinity of the fuel outlet, it somehow aids fuel atomisation, doing the same job as an emulsion tube I suppose.

How these carbs compensate for air pressure differences, as pointed by steveH, I don't know.

[themoudie]

Aye,

Used to great effect on a racing Ducati 350 desmo tuned by Andy Farrer, with a Swallow pilot, in seasons past.

Link to set-up instruction sheet: Gardner_carb_setup

Link to Classic Racer article on Ron Gardener and his carb: Classic Racer article on Ron Gardner This link may prove tempromental! 

Quote from CRMC website in 2010:
" #4 : August 22, 2010, 04:51:36 PM »
Alan,
Best person to speak, without doubt, is Ron Gardner himself (note correct spelling !) . Ron's phone no is 01444 233485, available between 9am and 8pm. Ron offers advice on all problems re fitting and tuning his carb's, and also has spares available for all the models he has manufactured from 1947 to the present day. He has recently started to remanufacture replica's of the original 1947 B series range for anyone competing in early classes around the world.
Andy Farrer."

Link to comment/conversation of Tony Foale: Tony Foale conversation Gardner carbs

Please check before bombarding Ron with queries as he is in the business of selling carbs, even though he may enjoy a technical blether, health permitting. Ron's son now runs the business.

My regards, Bill.

[Propellor]

Very interesting info there themoudie, thanks.

The link to classic racer article is actually the same as the carb setup one. On my device anyway.

In the setup guide there are repeated warnings about opening the throttle with the engine off. This suggests a float chamber level at or near the level of the bottom edge of the Venturi. Weird! I assume the float chamber is vented? Or is the model described the one with a separate chamber and the instructions are covering for the worst case. Or is there a fundamental requirement for these carbs to run with a high level?

Cheers

[themoudie]

My understanding is that all models of the Gardner carb require a remote float chamber, unless running alcohol for speedway.

Link to site selling Gardner float bowl kit: Gardner_float_bowl_kit

My apologies for the incorrect link to the 'Classic Racer' article, this has now been sorted! 

My regards, Bill